Blinkered energy efficiency focus brings death and dispair

This tragic fire has been attributed to a faulty fridge freezer and the cladding that was put onto the building. So how could a simple electrical fault cause the deaths of so many and strike fear into many more living in and around tower blocks in the UK?

We have been on a drive for the past few years to reduce carbon emissions. This is laudable as climate change is bar far the biggest threat facing the natural world. However, this drive has been blinkered. We have dumbed down the issue to one of carbon and carbon alone. Governments and industry like this, as they think that it can be a. measured and b. profitable. However, when you are purely focused on cutting carbon emissions you miss out on the beautiful complexity of life and the systems that surround, and are embedded into, it.

At Grenfell, the problem that was overlooked was fire risk. What happens when you cover a building with a flammable covering and you don't fit fire breaks? Well, we all know what can happen now. So what went wrong? Well one of the key issues, that underpin so much of the construction industry, is that or testing and specification. Many of our testing regimes are old, tired and not fit for purpose. They are rarely updated or questioned as entire industries are built on them. Companies have developed products that meet the basic test levels and they don't want to go through the cost of having to change these and make better ones. The complexity of the industrial structure also allows these factors to get lost. Main contractors, sub contractors, system suppliers, building control, planning etc all have their say and it makes it very easy for key things to be assumed rather than checked and insisted upon. The focus in the process is money and time, not quality. We await to hear the findings and recommendations, but one can predict that pinning this onto one party will be difficult / impossible as really it is the whole capitalist system is in the dock and no-one in power wants to find that guilty!

This can be seen to full effect in Fishwick, Preston. Never heard of it? Not surprising as the whole debacle is being covered over by the Government and Industry. 387 homes had External Wall Insulation (EWI) fitted, again for all the best intentions. All have failed. 100% failure. Now each of these homes has mould and damp problems.

In this instance it appears (believe me you have to know how and where to dig to get any information on this whatsoever) that the EWI used was one of the standard products. However, against all the advice of groups like the STBA and the BRE (i.e. those people who know about this stuff), they slapped this EWI onto traditional solid walled properties. Now on paper this is fine. The whole industry thinks that this is standard practice and they even offer a 'warranty' to go along with it (this is of course a complete waste of time and not worth the paper it is written on - ask CIVALLI (http://www.civalli.com/)).

The trouble is that the moisture test that the whole industry is based on is fundamentally wrong! The standard even says that it will not work in in-situ conditions. It only looks at water vapour in a one dimensional manner. Last time I looked water came in liquid and solid form as well as vapour. Water also appears to have the ability to go both in and out of a structure. It even has the audacity to move sideways. So the whole industry is based on a one dimensional world with only one state of existence. I think that even the least enlightened know that the world is not quite like that. However, all the technical decisions about insulation is based on these tests. No wonder that Fishwick went wrong. They must have three dimensions, water and ice up there! Who is going to pay for this? Well, I will let you make up your own minds whether it will be the contractor, the 'insurance' industry or the tax payer.

So, if you have 3 dimensions where you live and / or it rains or freezes at any time then you too might face similar issues.

If we are to avoid Grenfells and Fishwicks (and the many others that exist - these are just the biggies) then we have to be smarter. We have to use the right tests to get answers that might actually happen in the real world. We have to realise that the world is a complex and interlinked place. What we do in the name of carbon reduction has other implications. It can cause fire spread, it can cause mould and damp issues, it can cause structural failure, it can cause health problems....... It also can have its benefits, of course, in many cases we are able to reduce emissions and make homes warmer etc, but there is not much point doing this to the properties where we ruin them in the process! This is very much the situation for solid walled and narrow cavity properties (these make up around 35% of our building stock!)

The STBA and others have been saying for many years now that we have to look at things in the round; holistically. We also have to understand how products work in the REAL world, not just on a bench in a testing laboratory. we have to take this knowledge and apply it to each individual case. One size fits all is blatantly false. We have to use our skills and experience wisely, not just follow outdated and inappropriate testing regimes. Unfortunately this goes against the common thinking that the construction industry needs to be dumbed down so that even the least educated can get jobs in it. We should celebrate the fact that our building stock is varied and complex and train our crafts people and professionals appropriately. Some people have the knowledge on how to do this right (and hence do it once), but do we get a look in? The inertia and power of the mainstream industry is enormous and they don't want any boats rocked thank you very much.

So, we know how to avoid Grenfells and Fishwicks, but Government doesn't want to listen to the voices of reason and truth. It wants easy solutions that address the needs of now, so it turns to Industry for answers. The whole of the Each Home Counts review (that references Preston / Fishwick) is being run by Industry. It doesn't fill one with joy and hope. We really do need to wake up to see how the system works and who it actually works for.

I am not a do-nothing type of person, I agree that we need to do the right things and address the issues like climate change, BUT we have to be clever and learn from mistakes, not cover them up. We need to make it easy for people to use their homes in a less carbon intensive manner, this might be using EWI, but we need to use the right materials in the right way otherwise we are just going to have to do it all over again in the future. That is a waste of time, money, resources and carbon!

I might have a rant now about modern buildings: It is accepted that ALL new homes (yes the ones that the House Builders are building now) will all need retrofitting for energy efficiency in the future. What are we doing people???? Can't we see that Redrow, Wimpey, .... all need to be told to build carbon negative homes NOW? Trouble is Government is too weak in the face of big business. It would be laughable if it weren't so serious.

Knowledge is power. We need to get the answers to Fishwick out in the open. We need to ask questions of our politicians, we need to question the integrity and focus of industry, we need to demand proper recompense for mistakes in the construction industry, we need to act within the constraints of fairly allocated planetary resources. We are effectively been trodden on by uncontrolled capitalism in pursuit of the free market. Well the free market only seeks profit. We need to demand proper controls from the Government (who are after all elected by the people for the people) so that we and the planet are put on a level par with profit. Only then can the three pillars of sustainability truly start to exist.

Economics, Environment and Society must all be treated equally.

Maintenance Matters

Rhyd-y-car Terrace in St Fagans Museum of Welsh Life

For those, who have not been to St Fagans in Cardiff, it is worth the trip. Great place and an ideal way to start to understand how buildings have changed over time.

One of the key elements of the museum is Rhyd-y-car Terrace. It illustrates how one style of property (in this case a Welsh terrace of houses) has been altered over time to address the cultural needs / desires / aspirations of the residents. (click on the photo for a link to discover more)

The original terrace house is represented by the home on the left and the team has made alterations to each subsequent house to reflect the changes to terraces in Wales. So when you reach the last house it has a covering of render on the walls rather than limewash, tiles on the roof rather than slates, modern casement windows rather than sash, large window panes rather than small etc. The internal layouts and services have also changed. Fascinating, but intuitively we sort of know this. However, what is not really explained on site is whether these changes were positive or not.

Of course, we do not want to live in houses anymore that have open coal fires, draughty doors and windows etc. However, neither do we want to live in houses that suffer from trapped moisture in the walls, rotting timbers and poor internal air quality. Unfortunately, some of the 'improvements' that are illustrated in the terrace have caused problems like this in the real world.

In time you could add another cottage to this terrace, with its original stone walls now clad in polystyrene (EPS) external wall insulation. This is a reflection on where we are blindly heading without due regard for the original structure. Again we shall then have a warmer property that is at high risk of overheating and likely to suffer rot and mould issues from penetrative damp and condensation.

Designing improvements to buildings is important, but we must get it right. So again, I urge you to read the STBA documents and guidance on retrofit of older houses. See www.stbauk.org

However, this article is about maintenance. So where does this fit in with the retrofit agenda?

Well, when you read all the underpinning documents about retrofit, they all say that any building should be in a good state of repair and stable before any work starts. So before even contemplating any improvements the house should be damp free and well maintained.

This is where much of the trouble has started. Organisations like the Government have targeted their initial efforts on those properties that were in urgent need and these tend to be the ones in a poor state of repair. So they started putting a load of retrofit measures on properties that weren't ready for it. Putting a load of non-breathable cladding / insulation over a wet wall, just seals in the damp. This would be bad enough, but putting a load of non-breathable cladding / insulation over a wet wall badly so that more water can get in, well, you can guess what has been happening!

So, we need to ensure that our buildings are in a good state of repair first and then we need to ensure that we do any retrofit works well. The second element is starting to be addressed (slowly and still with little real knowledge of the characteristics and pathology of traditionally built houses), but the issues of maintenance is less attractive to business.

Large companies delivering large scale projects are not really interested in minor works, or leaving buildings to become stable over time before starting with the big tools and toys. They just need to crack on, come rain or shine, cold or heat and get the job done ASAP and as cheaply as possible.

So we need to take a step back. Assess what we have, understand it, fix it, let it settle and become stable and then start to improve it sensitively and with the right amount of care and caution so that we don't mess it up.

So the first rung on this retrofit / improvement ladder for traditional buildings is not EPS wall insulation, it is Maintenance and Building Pathology.

CADW have produced some guidance on maintenance, but people see this as being for conservation areas and heritage buildings. We need to make maintenance relevant to the 34% of buildings in Wales that are traditionally built. This means all the terraces and stone / solid brick built homes that litter the landscape that we are so familiar with and proud of. After all it is these buildings that define the character of our inner cities and valleys.

Maintenance in itself is relevant to the retrofit agenda. A wet wall is 1/3 less efficient than a dry wall for example.

Building pathology is equally important. The recent Each Home Counts report for the UK Government highlights the recent case in Preston where the race for energy efficiency and the lack of understanding of older houses has left a trail of catastrophe. The details are being repressed by those concerned inc the Government as it really is a tale of woe, but suffice to say the underpinning issue was the lack of knowledge on traditional buildings within the mainstream construction and retrofit industry.

So we need to understand our homes, their history, how they work. This means getting to grip with material science and building dynamics. A good surveyor should be able to tell you these things, but most just refer on to 'specialists'. Unfortunately most of these are not really specialists, just glorified sales people. So we need 'Power to the People'. These are your homes and you are the ones paying for works to be done. So I urge you to understand older buildings and look after them well. Most of the things that I see when visiting homes are simple maintenance issues that can solve many ills.

As a starter for ten, have a think about the following:

A hole in the junction between a window and a sill. Water running down the window above the hole will go into it. What then? Well generally a damp patch and potentially a rotten floor joist. Solution? Fill the hole with some silicon sealer. Cost? 10p in silicon? 10 minutes in time. Potential savings? £350 for a damp report, £1,000 for DPC injection and replacement plaster, £2,000 for replacement joists,....

A crack in render on a west facing wall. Water above the crack will flow down into it. It cannot get back out if it is a modern cement render. So a damp patch. Rotten timbers maybe... Solution. Fill the crack. Cost? DIY solution, maybe £10. Contractor, maybe £100. Potential savings? Well, see above.

Dislodged guttering pouring water down and into a wall. Replacement bracket cost, maybe £1. Cost of leaving it? Easily into the £1,000's of pounds.

So check things like seals around doors and windows, leaf build up in the gutters, cracks in render, mortar and stonework. Make sure external ground levels are kept 15cm below internal floor levels, that extracts are working properly, that floor vents are not blocked by litter and dirt, that pipes through the wall are sealed up properly, that slipped tiles are replaced quickly, chimney stacks are in a good state and that any repairs are made with lime mortars etc etc.

I could go on. But I hope that you get the message. Preventative maintenance is cheap, relatively easy and essential both in terms of keeping you and your home healthy both now and into the future.

Do you need a new damp course?

3 injected damp proof courses in this house, courtesy of Heritage House

When we buy a house a surveyor will often find high readings on their protimeter ('damp meter'). This then leads to a recommendation to have a 'damp proof specialist' do a report. The mortgage company will insist on having the damp treated. This will mean that the damp specialist will almost invariably diagnose 'rising damp' and a recommendation to have an injected DPC (Damp Proof Course) and the removal of the 'damp' plaster internally up to a meter high.

This is the common practice that is accepted as industry standard. IT DOES NOT WORK (in many properties)!!!

The picture above shows where a house has been injected 3 times at different periods. When will we learn that it doesn't work?!?!?!?

Surely just seeing that a wall has been injected three times might indicate that the solution is wrong, but no, we just blindly go on doing the same old thing. Wasting your time and money!

If you have an old house (or even a new one!) use a damp specialist that does not have a DPC to sell you.

There are solutions, but generally DPCs are not one of them. Save your efforts and money for getting a proper solution that works permanently. Happy to assist if needed.

Beware the "Damp Meter"

This is the tool of choice for damp proofing companies

The Protimeter is pretty much ubiquitous in the damp and building surveying world. The meter is used to show owners how damp their homes are. This is also invariably 'rising' damp that 'will require' an injected DPC. However, is this tool an actual damp meter?

The short answer is NO!

These meters measure electrical resistance between the two prongs. That is not necessarily the same as the amount of water between them. Originally they were developed for timber to check how dry it was. In timber the only real thing that will conduct electricity is water and hence they were quite useful. However, this is not the case in masonry.

So what else could they be measuring?

Well, there is another factor that can give a high readings on a protimeter:

Carbon content. As you may be aware some old mortars were made using dust from industrial waste. This is especially true in areas like Cardiff where we have black mortar. This mortar is high in carbon and hence conducts electricity well. So high readings may well be to do with the mortar, not moisture.

So, if you have a high reading in a house without old mortar / plaster, then a high reading is probably indicative of dampness. However, the key question is then; What is causing the Damp?

Well this opens up a range of options (however, the majority of the damp industry only looks for 'moisture' along the base of ground floor walls).

The damp could be caused by:

Hygroscopic salts. These are actually very common in walls and are often the cause of high readings. Salts can be introduced by the building process, water ingress and from the combustion processes associated with fireplaces. So if you have high readings around the base of the fire place / hearth this may well be salts not rising damp. The salts are 'hygroscopic' and that means that they attract moisture to them. So this moisture might be linked to condensation, being located in high humidity areas like kitchens / bathrooms, etc. So the moisture is probably associated with salt not 'rising damp'. So just keep dusting off the salt residues until they disappear and lo and behold you will have cured the damp. Simple.

Condensation. Virtually all external walls have a cold bridge along their base and this attracts moisture to condense there. This is natural and nothing really to worry about unless it is causing some mould issues. This condensation can also be caused by a lack of ventilation. So again you might need to look at ventilation / insulation rather than jump straight into a potentially unnecessary damp proof course. Note that thermal bridging can occur in a number of other places (ceiling edges, around window frames etc) where the wall is cold for some reason so again check issues like insulation cover and building defects.

Leaks. Old or current leaks can show up on the meters, so this is a case of fixing the cause, or just allowing the wall to dry naturally.

Material incompatibility. Old houses have walls that allow moisture to pass through them, however most modern materials are designed to resist moisture movement. Commonly you get a combination of materials that don't like each other in terms of moisture and a lot of problems stem from this. Gypsum plaster is particularly prone to becoming hygroscopic when it has been placed over old lime plaster.

Penetrating damp. This is the likely cause of most damp issues. The industry tends to recommend injecting more DPCs into the wall rather than addressing the actual problem. This tends to be simple and cheap maintenance issues like sealing around windows, cracked render, repointing etc.

So if you see a 'damp' meter, make sure it is attached to something that has an inquisitive brain and also nothing to sell you!!

Home Report Video from Profiad Ni

Thought that this might be of interest as it shows the types of advice given when we do a Home Inspection Report. The winners of the Profiad Ni competition had visits from us for around 2 - 3 hours each followed by a written report that re-enforced the messages about damp, energy efficiency, maintenance, ventilation, structure etc.

It was a great couple of days (if a tad tiring) so many thanks to Bethan from Profiad Ni for arranging it all.

Happy watching.

Killing mould naturally

Mould commonly appears where walls / surfaces are cool and damp

How to treat mould? Well it is commonly assumed that the best way of doing this is using bleach. However, if you do use bleach you will experience several things:

• The mould will return quite soon (bleach only works on hard surfaces and so will not kill the mould 'roots' in any porous material)
• It will smell terribly
• You will have to get out the gloves to protect your hands
• You will have to be very careful to ensure that you don't bleach anything else

So are there any better and safer alternatives? Thankfully the answer is a resounding YES.

You can buy products like the Auro Anti-Mould System (that we supply) or you can make some mixes yourself.

Systems that actually work and are safe include:

• Hydrogen Peroxide (this is the main ingredient in the Auro product)
• Tea Tree Oil
• Borax
• Baking Soda
• Vinegar
• Grapefruit Seed Extract

The best are those that are not just alkaline (Baking Soda and Vinegar) but also naturally antisceptic, antifungal and antibacterial. So the Hydrogen Peroxide, Borax, Grapefruit Seed and Tea Tree Oil (ensuring that it is from Melaleuca Alternifolia) provide the best solutions. These work on porous surfaces as well and so kill the 'roots' as well as surface mould.

• Tea Tree Oil use a spray in a 2% solution
• Hydrogen Peroxide use a spray in 3% solution
• Borax use a spray in 6-7% solution
• Grapefruit Seed Extract use a spray in 0.5-1% solution

I would recommend that Hydrogen Peroxide is sprayed on and then left for around 10 mins before being wiped off. The rest can be sprayed and left on to act as a longer term inhibitor.

I would also suggest that you need to deal with the root cause of the mould in the first place. This might be making the surface warmer (potentially by using insulation), making the material drier (by increasing ventilation around the area, using correct materials, eliminating water ingress etc).

Home Buyer Report - The Journey

This is what the Home Buyer Report (HBR) looks like that you will probably make a lot of decisions by when you buy your new home. One of these will cost you around £450 - £700 depending on the level of investigation requested. Most people opt for the cheaper version.

So what do you get for your money?

The report is designed to look in detail at the condition of the house and make recommendations as to any course of remedial actions required. This is of course important for you to know as there may well be some major issues like subsidence or damp.

The majority of the report is basic tick boxing and space for some additional comments. However, mostly what goes into the comments box is something along the lines of: damp noted in such and such room, we recommend that a damp proof specialist provides a report. Quite often 'rising damp' and 'injected damp proof course' are mentioned. This is odd given that most truly independent damp specialists suggest that only around 5% of damp houses are suffering from 'rising damp'. So why is it put in those specific terms when the rest of the report is otherwise quite generic?

The answer seems to be this all pervasive thought that damp only occurs at ground level and is always caused by rising ground water. This is so common that many houses, that I have been to where a HBR has been shared with me, surveyors have not even tested for damp above the ground floor (unless it is blindingly obvious). It is almost that penetrating damp doesn't exist for some surveyors. I have not seen reference to orientation of the house or exposure levels in any HBR to date.

So, the next step on your house buying journey is to get a damp specialist in. Having spent £450 on a report and found that there is damp, you are starting to have doubts about buying, so having a free report from a damp proofing company seems like a good idea. What little we know.

The reports from a damp proofing company virtual all say - you have rising damp and require a damp proof course (DPC). This will in turn cost you between £3,000 and £6,000. Not so free now is it! Then you haggle over prices, it comes down a couple of thousand if you are lucky and the 'required improvements' to the house come to £2,000 - £4,000 net. Plus you have a guarantee! Sound OK?

Well actually, as you may have picked up, most damp is not rising damp. So the money spent will probably not cure the damp. In fact it can make it worse in the long run. But the guarantee? Unfortunately it is not worth the paper that it is printed on. It is a chocolate teapot. Looks great, makes you feel like you can have a cuppa at anytime, but make one and whoops!

So, be aware that if you do have damp picked up on your HBR, it may just be worth your while employing an INDEPENDENT damp specialist who will not just go through the motions and come to the conclusion that you need an expensive (and ultimately potentially dangerous) (DPC). S/he will look at the whole house holistically, assess the pathology of the building - what has been done, when, how well, using what etc. and should then be able to provide a much better and more appropriate set of recommendations or comments.

This can be fraught with difficulty as most of the time you have to use little physical clues, an eye for detail, years of experience, knowledge of the real world building industry and some imagination. Houses have years of history associated with them. We don't keep records of who did what and when, we don't have pictures of the work being done etc. Experience is key. A qualification is good, but really it is the experience of seeing large numbers of houses, noting common faults, listening to owners and tenants and getting their stories etc that really provides the knowledge to be able to diagnose buildings well. Afterall the only real way of knowing what is actually going on is to take the building apart, so given that this isn't going to happen the best solution is to rely on the experience of a truly independent specialist.

Just to add a bit of paranoia into this (because it is warranted), Estate Agents want to sell you the house. It is their income. They want you to buy the house with blinkers on. 'Lovely location', 'Close to a good school', 'Good transport links' etc. Similarly Surveyors don't want to take the risk of doing a diagnosis as it is frought with unknowns, better to take the money and pass the buck onto a specialist in damp. The average 'Free Survey' damp specialist comes from a company that wants to sell you a damp proof course, .......

Knowledge is power and it is important when making the biggest financial decision for your family that you get it as right as you can. Getting information from a reliable, independent source that will explain what's going on, the physics and material science behind it etc is really important and worth the money.

What is the point in spending £ thousands on a DPC when actually the damp is due to some pointing issue, or a failed window seal, something that might cost you a couple of pounds.

I know that this sounds like a sales pitch as we provide this independent service, but whoever does it, the principles hold true. People like me, who understand damp and materials, will be able to give you a much better, much more detailed idea of the issues that face a house and hence will allow you to make a much better decision.

Rising Damp

From Yorkshire Times article entitled 'Rising Damp in Old Houses - It's just a myth'

I have been to two houses in the past couple of days, both of which have had damp proof courses (DPCs) injected into them. These new DPCs and associated work are now actually causing more damp problems than were there before!

One house has evidence of approximately two injected DPCs and the owner was being recommended to have another one. I bumped into a neighbour who had seen the original plans for the houses in the Glamorgan Archive and guess what, it turns out that it has had a DPC since the day it was built!! 

What are we doing believing damp proof 'specialists' from commercial damp proof companies? Their 'free' surveys might not cost anything, but the recommended treatments that they come up with with see thousands of pounds leave your account. So much for being 'free'.

So in the first house, there was a lot of damp all around the front bay and along the west facing wall. The damp 'specialist' failed to identify that there were a number of large cracks in the render, or that the render on the bay was blown. Neither did he mention anything to do with the lack of ventilation in the house, .......

In the second house, the damp was now appearing over a metre from the ground. No doubt that there was damp in the floor of the house, but sealing up the wall as a cure, really?? That is just trying to hide the damp, not to actually deal with it. Now the owner will have to remove all the hard waterproof render and start again with a proper solution. More expense, disruption and hassle. Why?!

If you are serious about solving a damp problem, rather than causing one we would recommend that you use a good independent damp specialist in older buildings. We could save the 'hard working families' of the UK lots of un-necessary expense and also help to preserve our built heritage rather than introducing ridiculous ineffective modern quick fixes.

For a good rant, have a read of the Yorkshire Times article here

Measures working, but still more to do

Last year we spent a lot of time getting the walls of our home sorted. I dug a trench around the house and installed drainage to make sure that rainwater was taken away from the plot as quickly as possible. The walls were also stripped of their cement render and a lovely new render from Welsh Lime Works was applied.

So where are we now?

Out of the red and into the green

Well I went around the house yesterday to check moisture readings in the external walls and I am happy to announce that the levels are down from the mid 20% to around 10-13%.

So the external walls are drying out even now, despite have amount of water that was allowed into them after the cement render was removed and then the application process associated with the lime render. So great news!

However, the internal walls where concrete replacement floors have been installed are still wet. The lower part of the wall, where the waterproof render and plaster has been fitted is around 10%, but above the 1m mark where the original lime plaster is still intact is wet through (mid 20%s). I have been hoping that the silicon treatment that I installed would have had an effect by now, but it seems as if there is still water being sucked up by capillary action between the waterproofed render on the walls.

I think that I will have to inject more silicon cream into the mortar at the base of the walls to see if I can reduce the amount of water being drawn up. The water pressure that is created by replacement floors is amazing, but I have little choice as to the action I can take, bar cutting out the mortar and installing a physical DPC - lots of dust that the rest of the family might not appreciate!

So, good news on the main piece of work on the house, but still a little more to do to remove the issues created by blindly following the conventional damp industry and mortgage providers.

I can't afford lime render!

Lime rendering done by Welsh Lime Works in Cardiff

Lime rendering is a specialist trade (not to be confused with lime plastering or cement rendering!) and as such it takes time served craftspeople to do it well and it also takes more time to do. These two factors mean that many people who need to have their houses re-rendered choose the cement route. Using cement, of course, represents a higher long term cost. The render will crack and, most likely, damp will be re-introduced to the walls. This will need to be addressed again in the future, whilst a lime render should last the lifetime of the building.

A customer of ours choose cement render over lime due to the cost, however within 8 months the cement had failed, the wall was still wet and she has had to do it again. So the difference in price has already been negated due to failure.

However, this article is about what to do if you cannot afford at the moment to replace the cement with lime.

My recommendations (in general) would be as follows:

• Keep the existing cement render on
• Regularly check the walls for failed render (tapping the walls will audibly indicate where the render has become separated from the wall)
• Repair any cracks (even the small ones, especially if facing the prevailing winds and rain) and any blown areas of render
• When replacing blown areas, it is better to cut around the render to be removed so that the process of removal does not dislodge any of the surrounding render
• Use cement render to replace / repair
• Check for failure of seals around doors, windows, pipes etc and repair as necessary
• Save up and when you can afford it, replace the cement with lime.

Enlarging cracks allows for a better repair as the new render will fit into it

The rationale behind this recommendation is that where you have a structure that has been altered to try to keep water out then as long as this philosophy is being maintained then it will have a better chance of working than when it is not. Cement render and masonry paint is designed to keep water out and as long as it is doing this then it will provide some protection from wind driven rain, however it needs to be uncompromised. So maintenance of its integrity is really important. The more water that gets behind it, the worse the wall will perform and the more likely damp issues become.

This patching and maintaining is really important to allow the wall to perform as well as it can before the ultimate solution of the lime render is applied. So don't waste your money on putting a new coat of cement render over your pre 1919 solid wall house, repair what you have and save your money up so that you don't waste it on an unsustainable, and still quite expensive, piece of cement based sticking plaster!

If you have a 'rising damp' problem (this is rare to occur in most untreated houses, but can be caused by the introduction of cement based renders and plasters onto a breathable wall) then another cheaper option is to remove the cement render up to around 1m above ground level. This wall might then need to be repaired using lime mortar (re-pointing) or it could be lime rendered. Doing this at ground level means that there is no need for scaffolding and the area involved is much less, thus keeping the costs down. You will need a good drip above this so that any water running down the upper wall is not fed directly into the lime or onto the exposed wall.

If you need to put up expensive scaffolding to do the repairs then this brings an extra dimension as the lime rendering becomes more cost effective in the longer term. So any initial repairs to the cement are best done off of a tower scaffold or ladders.

I have written at length before about lime rendering, but it is worth re-iterating at this point the things to remember when looking for a good lime renderer.

• Use a company that both supplies and installs the render (this can get over the issue of where, if there is a problem with the final work, you are not inbetween a rock and a hard place where the installer blames the manufacturer and the manufacturer blames the installer!)
• Remember that rendering is not the same as plastering. So use an experienced renderer.
• Ask for references and a good portfolio of completed works
• If it is new company then you will need to ask about the experience of the tradespeople and where they served their time. You can then investigate this company.
• Read up about lime from trusted sources like CADW, Historic England, Historic Scotland etc (depending on where you are)
• Ask about the mix that they will use and the finish that will be applied. I am a believer in aggregate being really important. I think that the aggregate needs to be a mix of sizes and also that it contains a high proportion of permeable stone.
• The finish needs to be appropriate. So a lime putty and permeable stone mix can be easily covered with a lime wash, a less breathable combination of NHL lime and sand will probably work better with a mineral paint.

Forget Energy Efficiency think Health!

Readers of this blog will know my views on lots of the energy driven 'improvements' that we are blindly doing in the UK at the moment.

We are making so many mistakes due to the fact that we are using more than useless techniques, materials etc in a slap dash manner. All of this is being done with the best intentions, but we are storing up many problems for the future by our haste and lack of underpinning knowledge.

In years to come we shall look back at this period in our history and hang our heads in shame, I think that in the worse case scenarios it will be regarded as a modern day 'asbestos' story.

So how can we change and do this better?

Well, a very easy way would be to think about it all in a very different manner.

At the moment all we can think about is energy bills, carbon reduction, fuel poverty and regeneration. None of these things are bad, but they do drive us into solutions that are not fit for purpose. For any readers not up to speed here there are fundamental flaws with how we measure energy efficiency in buildings (especially older ones), how we measure thermal efficiency in walls and also more importantly how awful we are when it comes to moisture. Have a look at the STBA reports on thermal and moisture measuring for more info.

Now DECC know all of this stuff - the STBA have told them, but it takes a long time to change Standards, Conventions, a whole industry! And then there is the political fallout! So basically we will have to wait a long time before we manage to make things better, so in the meantime we shall continue to make lots of mistakes and install lots of inappropriate measures.

So, as a proposal, should we not think about Health.

To have a healthy internal environment we need to provide:

• Fresh clean air
• Stable Relative Humidity (around 50-60%)
• No mould or damp
• Comfortable internal temperatures that are not prone to overheating
• Sufficient natural light
• Low toxicity in materials
• No off-gassing from materials
• A long term solution that maintains these conditions

To do this we need to have items like:

• Breathable walls (where they were designed to breathe)
• Insulation that is suitable
• Good ventilation that is controlled by Internal Air Quality systems
• Natural materials used
• Low / Non toxic materials used
• Good quality installers / builders

So the basic idea is that, if we can create safe, comfortable and healthy internal environments then energy efficiency comes as a by-product of this process / specification. So we would create good internal environments that are suitable for human beings. Isn't this the point of a building in the first place - to create a safe, sheltered and nice place to spend time with loved ones?

Won't it be great to look at a building and think 'how can I make this a really great place to live?' The satisfaction in making a house a home that you would want to live in and enjoy. After all someone has to live there and shouldn't we make it as healthy, homely and safe as possible?

However if we work within our current unrealistically blinkered parameters we shall just produce internal environments that help to burden the NHS and also provide people with poor quality of domestic life.

So lets start to put people first and I wouldn't mind betting that we shall be able to not only provide high quality space, but also save more money in the long term and reduce CO2.

Wales is in an ideal place to make this happen, but we need to drop using dangerous tools like rdSAP and also BS5250, especially for older buildings.

Getting solid walls to meet Building Regs

Building Regulations in the UK have been interpreted for years as demanding that refurbished walls need to meet a U value of 0.3. Products have therefore been designed using BR443 and BS5250:2011 to comply with this.

Unfortunately, BS5250:2011 states that it is no good at modelling 'in service' situations. The whole model is based on water vapour only, no account for liquid water at all. Not so good when you are dealing with moist walls (AKA virtually all walls built before 1919!)

BR443 is the calculation matrix that gives us U values. This, though, has been shown in virtually all cases to be very inaccurate when assessing solid walls. Caroline Rye's work has clearly shown wide discrepancies with measured in-situ U values with predicted ones from common U value calculators. DECC is taking this very seriously and the STBA has been affecting Government thinking thanks to this key research.

So, given that the tools that we have to use to calculate solid wall U values are, in effect, useless and that the unintended consequences of using non-breathable insulation materials can be as severe as structural failure, what can we do?

Well there is a little used get-out clause in Part L1B of the Building Regulations.

Part L1B states:
Dwellings Exempt from Energy Efficiency Requirements
3.8 Historic and traditional buildings where special considerations may apply
c. buildings of traditional construction with permeable fabric that both absorbs and readily allows the evaporation of moisture

It goes on to say that you should aim to improve the energy efficiency as far as is reasonably practicable and it should not increase the long term risk to the building fabric. It also states that you should make provisions to enable the fabric of the building to 'breathe' to control moisture and reduce the decay problems.

The document also points you towards your local conservation officer for advice. So I would recommend sending them the STBA report on Responsible Retrofit first!

Dr Jo Hoppers work on thermal insulation seems to suggest that the thermal bridging associated with wall insulation is such that even the best detailed Passive House refurbishments will be hard pressed to reach U values much below 0.3, so standard installations will be virtually impossible to achieve these types of figures.

However, within this doom and gloom is there a ray of hope?

Yes!

The U value research by a growing number of people and orgs (inc BRE) show that the U value of these old solid walls are radically better than predicted, so you might already have a well performing wall! The U value of your wall might correspond to the types tested by the STBA / SPAB by Dr Rye, so it is worth checking your wall structure against the research findings. You can then use this to show your Conservation Officer as well.

Using breathable insulations like wood fibre on walls is a lower risk option, but all this depends on the existing wall structure, how it has been altered over time, etc etc. So managing risk is difficult, but certainly using materials that have been assessed and labelled using inappropriate tests raises the chances of 'unintended consequences'. This subject is one that BRE has been looking at for years and will soon publish its research into.

This post was originally published in 2013, but this is an updated version.

The importance of a good overhang!

In Wales we have had a tendency to design our houses with the minimal amount of overhang on the roof. The tiles sit very close to the walls. This has meant that anything else that we add to the depth of the walls loses precious protection for the wall plate. So rendering and over cladding often has the unintended consequence of making the inner wall more liable to water ingress. Where the over cladding is water proof this can easily trap wind driven rain / overflow from blocked guttering into the structure.

I was in a house last week where the fascias have been twisted and are now potentially channelling water into the building. Another building around the corner from the centre is also suffering after the owners installed external wall insulation. Here the builders had put one of those awful plastic covers over the top of the insulation to 'provide protection' against rain. Surprise, surprise a few months later they were back extending the roof to do the job properly! Wind and rain are a potent force in Wales!

The junction between roof and wall is one of the weakest in a house and so we must be very strict about how we protect walls from the elements. Extending the roof line may seem like a costly addition to any work on the external walls, but if you are doing work on them it may actually save you money if you get it done at the same time. Certainly it would have saved the people around the corner a pretty packet on their scaffolding costs!

If you look at houses on the continent, most have large roof overhangs. This helps to protect the building fabric, provides shading against the summer sun (and with climate change we might even get some of this at some point!), gives additional shelter for windows etc. Learning a lesson or two from the near continent is always a good idea.

Note: this post was first published in 2013. Check through our whole blog for other interesting articles.

Vapour Control Layers in Insulation

From RIBA

The pressure for energy saving in solid walled buildings is real and tangible. Green Deal and rising energy bills are encouraging us to insulate our walls. Where we have external features / facades that we want to keep we are forced to choose internal wall insulation (IWI).

BS5250 (the British Standard) for moisture control in buildings recommends a series of potential interventions (but crucially it also says that this is NOT a recommendation for breathable walls - which are virtually all the solid walls). One of the main recommendations (and hence common practice) is to install a Vapour Control Layer on the warm side of the insulation.

If there is no water in the wall then this works fine, but it is now becoming common knowledge that virtually all the UK's solid walls must be seen as 'moist'.

This is starting to create problems for the vast majority of the solid walls fitted with VCLs or non-breathable insulations due to Reverse Condensation (or Summer Condensation). This is a phenomenon that occurs when external temperatures and hence humidity levels are greater than the internal environment. Higher external pressures associated with temperatures forces this moisture laden air into the wall and when it cools and hits a water proof membrane or insulation the vapour condenses and runs down the back of the barrier. This concentration of moisture deep into the wall structure also means that joists and other wood is more at risk of damage.

The answer is to carefully read BS5250 and listen to what it says, which is, for breathable walls take professional advice from specialists. The best to provide this are bodies like National Trust, CADW, English Heritage and Historic Scotland. Thankfully all these sources of specialist advice are members of the STBA (as indeed RDE is) and their advice / case studies etc are available from http://www.stbauk.org.

The best advice recommends using a fully breathable insulation (wood fibre for example) with a lime / clay plaster and a breathable paint finish (like our Earthborn Claypaints or Auro Lime Paint). 

So beware of advice and common working practices that are based on half-true information. 

Cabling and pipes into walls

Walls tend to have a lot of 'punctures' through them

In the UK we build walls and then make holes in them. This is a bit strange when you think about it, but in older houses we are forced to drill through walls in order to install our modern conveniences and technology. So old houses have a range of holes for soil pipes, TV aerials, washing machine drains, phone lines etc. We have also drilling into walls to inject cavity wall insulation, chemical DPCs etc. Take a look at your house and see how many times it has been drilled through.

Surely drilling and placing a cable / pipe through is a simple matter with few risks?!

Oh how wrong we can be. Having just been to a house where incorrectly installed cables and pipes are potentially causing a lot of damp (even on the cavity wall extension).

So where does it go wrong?

Well the most obvious problem is where we encourage water to track into the wall by:

1. Drilling down at an angle rather than horizontally / slightly angled up. A downward slope encourages water to run into the hole especially if it is not properly sealed.

2. It is almost impossible to adequately seal holes / around pipes etc. Most of the time contractors don't even bother trying to seal around holes.

3. Cabling is not looped around so that all cabling enters from below (if cabling goes down the wall and straight into the hole, water will track down it and into the structure).

4. Many holes are drilled into walls that face the prevailing wind rather than exploring another less risky option of an East or North facing wall. This means that the weak spot of the hole is exposed to the worse of the weather.

Sometimes it is difficult to access the best place on the wall for a hole and this is especially the case with Damp Proof Course injections. These tend to be fitted on the external face of the wall and need to be as close to the ground level as possible (generally). This often means that the drill holes are sloping down into the wall due to the body of the drill being next to the ground. The trouble with this is that rainwater running down walls will enter these holes and put water above the DPC! It is vital therefore that these holes are sealed completely and in a long lasting manner, However, more often than not I see holes unfilled, ill fitting plastic plugs pressed in or a dot of mortar placed roughly over the hole. In the long term these will all let water into the structure and cause damp.

So when faced with having to drill through a wall, remember:

• Keep the drill level (or sloping up slightly)
• Seal around the cable / pipe using a good quality sealer and press into the wall as much as possible
• Ensure that the cabling does not encourage water into the wall
• Put as much cabling through the lee side of a building (rather than facing the prevailing winds)

Shoe missing in street

This could be titled: 'How to get a roof load of water into your floors and walls'.

Note the crack between the wall and the pavement

This is a very common sight in urban areas. Downpipes have had their shoes kicked off / removed and so all the water from the roof is being poured into the base of the wall rather than angled off into the main road drain.

In this particular location there was a large gap between the council's pavement and the wall. This has meant that for years the wall have been subjected to way more rainwater than it can cope with. No wonder there was damp in the wall inside.

The simple solution is to re-fit the shoe and get the system back working again. There will still be runoff entering the gap, but at least the volumes might decrease to a level where the wall can cope again.

Oh, for those who were wondering a 'shoe' is as follows:

Damp proofing a typical Welsh terrace wall

Typical streetscape in Cardiff

Can you stop stone and brick walls from getting damp?

The simple answer is YES, but there are a range of issues surrounding the question and the answer!

The main issue around whether a wall is damp or not is that diagnosing damp is an art not a science per se. Common damp meters use electrical resistance to measure damp and this is fine for timbers, but for walls it requires a lot of interpretation. High readings can come from salts in mortars, old lead based paint etc, so not always water. So where you take measurements can radically affect the advice that you are given. So some companies who are trying to sell you damp proofing measures can use these meters to show that you need treatment when you might not.

So that's the issue with defining whether you have damp, but assuming that you do actually have a damp problem the next issue is where is it coming from.

We have all heard of rising damp, but many houses in Wales suffer from penetrating damp. This is water that is blown, or diverted into the structure. This can be through cracks in pointing, cracks in render, leaking rainwater goods, blocked guttering, failed seals around doors and windows, ...

Damp can also be caused by condensation. This might be due to poor heating, ventilation, high humidity from indoor activities. Again this needs to be assessed by looking at heating and ventilation strategies and infrastructure. Do the windows have trickle vents, have the chimneys been blocked??

Rising damp might be due to a range of factors including external ground levels, the presence of replacement concrete floors, blocked under floor ventilation, ... 

As you can see, damp can be difficult to diagnose. However, it is really important to ascertain where the source of any unwanted water is coming from.

Once you know what the problem is, you can start to find the cure. However, the cure will be influenced by the history of the building and the materials that were used to built it in the first place. This means the make up of the basic structure and also the materials used to repair, maintain and develop it over time. This building pathology work is key to refining the diagnosis and will hence help lead to an appropriate solution being found.

I cannot go into any great detail here as each building is different and requires specialist individual advice. However, the question was is it possible to damp proof these old buildings. The answer you might remember was yes, so what are the solutions?

1. Rising damp

If you do indeed have rising damp then you might need to:

• Lower the external ground level
• Re-instate ventilation under the floor boards
• Remove cement render from the outer walls
• Re-point the bricks / stone with a lime mortar
• Re-render using a lime render

All of these are potentially permanent solutions, however they are fairly major bits of work, so most people just want to inject something into the wall. This is potentially possible and it depends on a range of factors, one of which is whether the wall is made from solid brick or stone. These walls are fundamentally different in their nature and it is easier to apply modern injection treatments to brick walls. 

Damp that is rising in a brick wall can be treated quite effectively using creams like DryZone. However even here you see companies injecting the damp proof cream into the bricks rather than the mortar. So with care this type of product can be part of a solution (but not if your damp is due to condensation or penetrating damp). However it won't work in stone walls (unless you have an even mortar bed at the correct height - like in ashlar walls).

Stone walls are fundamentally 'moist' in nature and so need a more holistic approach that is based on material science. The solutions here are much more likely to follow the bullet pointed measures above. It might also need to be combined with addressing ventilation issues, as stone walls need to dry out by the movement of water from the water to the outer and inner surface. 

2. Condensation

This tends to be more due to high humidity in the building and so a balance needs to be found between energy efficiency, ventilation, insulation and behaviour. It may be that a house needs positive input ventilation, or that the old chimneys need to be unblocked and vented, trickle vents on windows need to be opened, humidity controlled extractors fitted, or just a clothes dryer installed in the garden / room with an extractor fan. 

3. Penetrating damp

Penetrating damp is generally caused by issues around poor maintenance of a property. However, it can be down to the use of inappropriate materials like cement render. Seals like silicon around doors and windows fail over time and rainwater runs down the surfaces and straight behind the sill. Cement render (is fundamentally inappropriate, but nevertheless covers the majority of stone and brick houses) cracks due to its brittle nature and traps water behind it. Gutters and downpipes need to be clear otherwise they can easily poor high volumes of water against (and into) walls. Poor drainage around the building can lead to water sitting against walls,  I could go on.....

As you can see, diagnosing damp and finding the correct solution is a bit more involved that just pumping in a load of chemicals. However, pumping in chemicals and using water proof cement is what we do in the UK to the vast majority of our solid walled houses. In fact many mortgage lenders insist on this type of damp treatment. What a shame, it is generally a complete waste of money and resources. A typical damp treatment costs around £4 to £5,000. Don't be fooled by guarantees and assurances, many are meaningless. A recent customer had a injected DPC installed and when it failed dismally she was told that it had been installed correctly and so she couldn't claim against the warranty!

We would always recommend that you use your money wisely and this means that it is better to find a permanent solution to damp. This requires time and knowledge to get to the correct diagnosis, It is not a quick trip around with a damp meter and a bill of £5,000. The answers are there, but you will generally need some independent guidance to find the right ones for you and the house.

Chimney Problems and Solutions

Chimneys are a potential source of water ingress and it is quite common to find damp areas around the chimney breast. So what's going wrong?

Well there are a few key factors to bear in mind.

1. Failed pointing. This is quite common as the chimney gets a lot of wind driven rain and this can easily get behind the mortar if cement has been used and where the old lime mortar has been eroded away. When repointing remember to use a breathable mortar (a lime based one). Whilst this does allow moisture into the mortar it also allows it to dry out again. So ensure that the mortar joints are scraped out (to a depth of twice the height of the mortar bed) and then get it moist and repoint using the lime mortar. This should be finished in a flush manner to the bricks. Make sure you replace any broken bricks as well.

2. Cracked flaunches. Flat surfaces are not good for waterproofing as rain can settle onto the flat surface and soak in. Maintaining an angle / slope on the flaunch is really important if it made from a porous material. Cracking here is very common (again when cement is used), so either use a lime based mortar (and paint it with a mineral paint for a long lasting breathable finish) or look at a replacement option with a impervious capping material. This will help to reduce any water ingress into the stack.

3. Chimney pot not covered. Cowls are really important as we need to stop rain water getting into the main structure. Depending on whether the chimney is being used or no, there are a range of options to help reduce the amount of rain that are able to enter the pot.

4. Flashing. It is quite common for flashing to be fixed with cement. This again cracks easily and hence should not be used. Flashing needs to be set into the brickwork properly, not just abutted to the chimney. The flashing should be a lead one rather than the modern 'fix' that is glued on. Where mortar has been used, again it should be a lime mortar should be used rather than cement.

5. Vegetation growing out of the stack. Roots from plants like buddlia allow moisture into the structure and so these must be removed and the resultant holes filled with lime mortar.

I would warn against using cement renders, water proofing paints etc as they are much more likely to trap moisture behind them in the long term due to the effects of wind driven rain. So using materials that breathe and also have some movement potential in them makes them more suitable for these high exposure elements of our homes.

If the chimney has too many problems to mention (and this can happen when cement renders pull off the finish on bricks) then you may have to render / re-render them. Oddly enough I would recommend the use of a lime render. Make sure that the render has a good cap though as even lime renders require protection from above, so the flaunch /capping is really important to get right.

Be Positive on Ventilation

From http://www.housebuildersupdate.co.uk/ the illustration shows air being drawn into the house from the eaves and then pumped around the 'whole' house and the warm moist air being pushed out of the building envelope 

Positive Input Ventilation (PIV) systems are now starting to be much better known. This may well be due to the profits that the companies are making from the installation of these types of systems across the UK by the social housing sector.

Many problems have been encountered by this sector and the private sector by the installation of energy saving measures. Sealing up houses with draught proofing, insulation, double glazing, new doors, removal of chimneys etc has meant that the warm moist air that we generate in our homes gets stuck inside. This high humidity means that the excess water has to go somewhere and this tends to be onto cold spots in the fabric of the building. The levels of condensation have radically increased and this leads to mould issues as well as potential rot etc.

So, the industry have come up with a technological fix in the form of PIV.

Basically the simplest form of PIV is where fresh air is drawn into the building using a fan and then pushed out (generally from a single point) into the house. The fans are designed to run constantly and so are low energy consumers and quiet (but I would always check their wattage and db levels before making your final choice) The lower humidity (and cooler air) then effectively 'waters down' the higher humidity air constantly by forcing it out through any cracks / trickle vents etc that are in the building.

Having a lower humidity in the house means that walls can dry out slowly and condensation problems can be eradicated. Lower humidity area is also easier to heat and so perversely the house can become warmer by having fresh air pumped into it. However there are some potential issues. The cool air has to come in somewhere and this immediate area will be cooler due to this. So it is important to locate the input vent well. The higher pressure created by the fan will force air out from the easiest locations (out through extraction fans, trickle vents, ill fitting windows etc.) and so the benefits of installation might not be felt throughout the house. This is especially important when one thinks that most of these are installed through the first floor ceiling and many houses have most of the humidity in the ground floor kitchens, bathrooms etc. Having doors open creates better air flow but might not be practical where noise, smells, privacy etc require doors to be closed. So care is required when assessing the suitability of the product to your particular situation.

PIVs can be fitted as a DIY project, but there are a few horror stories where people have found that it is better to bite the bullet and get one of the manufacturers to install it for you. At least then you get piece of mind, a guarantee / warranty etc.

Whilst I see PIV as a potentially viable sticking plaster for homes, I would always aim to tackle the fundamental causes of damp / mould by using appropriate materials and ventilation strategies. However, in an imperfect world, the cost of installing a PIV system (around £700 - £900 fully installed price or £300 just for the machinery) may well be sticking plaster that you need.

There are, of course, variants within the PIV world, so you can have multiple output vents, integral heaters, automatic controllers, etc, etc. Of course, the more you pay then the better the controllability of the system, etc. So again you will need to assess which system suits you best. The specifiers / engineers from the various companies should be able to assist with this choice.

The best well known PIV systems come from Nuaire and Envirovent, but all the main ventilation companies produce their own versions.

Good luck.

Cavities not immune from damp

Cavity walls were designed to keep damp out of homes

Cavity walls have been the standard way of building for the past century. They are designed to have two walls (bound together by wall ties) with one acting as the external face that can get a little wet and the inner one that is protected by the cavity from this potential moisture ingress.

The cavities were vented to allow air to circulate in them to help dry out any moisture that did make it through to the cavity.

All sounds grand.

However, the system has some issues with it on a number of levels.

1. Initial Build - many cavities were not well formed as cement mortar etc would fall down the cavity during the construction period. This can cause a bridge to be formed across the cavity from the outer wall to the inner.

2. Maintenance - the wall ties that were used to bind the two walls together were mild steel and this rusts. So slowly the failure of the ties can cause cracks to appear in the walls and this requires the home owner to replace the ties when needed. Cracks in render also tend to go un-repaired and re-pointing is not undertaken when needed. These issues mean that water gets trapped in the outer wall, thus making the chances of water ingress across the structure more likely.

3. Improvements - many cavities have been insulated over the past couple of decades. This fills the cavity with material that can cause a bridge to form between the two walls. Some materials that have been used in the past have also failed (mostly foams) and these have slumped to the bottom of the cavity in a bit of a mess. It should also be noted that many houses are not fully filled - companies do not like filling around doors, windows, pipes etc as their products can escape through cracks etc and they don't want the hassle of tidying up, so many cavity walls are not very well insulated.

I have come across a number of houses recently where the wall ties and the use of cement renders has caused damp to find its way into what should be a damp free house. Basically what has happened is that the cracks associated with ties and lack of regular maintenance have let water into the outer wall and trapped it there. On mainly westward facing walls this moisture has then either tracked across ties, through or across the top of the insulation, thus reaching the inner wall. The lack of ventilation in the cavity means that the inner wall then gets wet and stays wet (only drying to the internal space).

So just be aware that cavity walls can be damp and that the fundamental remedies to problem might involve:

Re-rendering or at least repairing the 'blown' render

Re-pointing where required

Removal of old cavity wall insulation and potential insulation replacement once outer wall has been repaired

Replacement wall ties (with new stainless steel ties)

So if you are looking to buy a house make sure that you test all the walls (including upper stories) for damp.

There are of course other issues like insulation at wall plate levels, tying in ceiling and wall insulation etc.

Please remember that we can provide an independent damp report for you that will highlight areas of damp, their root cause and appropriate remedies rather than the standard tick box approach that is taken by the more mainstream industry.