Steel reinforced lime

Stainless steel EML screwed into place over areas with different materials / old cracks

I have been busy on the house preparing it for its new coat of lime putty render. One of these jobs has been to mesh over any major cracks in the sub-structure and where there are different materials exposed. This is because the movement in the house may crack the new render. Whilst this is not catastrophic for the render, it is always better to have an uncracked surface aesthetically.

So I have been using stainless steel EML (Expanded Metal Lath) AND stainless steel screws and washers. So I have been drilling into bricks, mortar and an occasional stone to ensure that the mesh is tight to the wall.

The high spots of the dubbing out had to be rubbed back (using a nasty looking studded float) so that the EML would sit quite flush to the wall.

The only major issue was that I was doing this on my own and the EML is really sharp, even on the main surface, so I have managed to cut my fingers quite a lot!

So the EML now covers the main wooden lintel at the front of the house, a thin brick pillar that was constructed to make the door opening narrower, the zone between an old extension where the bricks were not tied in very well, a wooden strip that runs horizontally along the first floor and the junction between a brick element of the house and an infilled concrete block area (an old door way).

So the wall is getting there for being ready for the render. Welsh Lime Works starting today!!

Dubbing Out

Haired lime putty render thrown into deep holes in wall

One of the jobs associated with re-rendering the house has been to make good the walls before the main render coat is applied. This involves getting hold of some lime putty render (same as the top coat) and throwing it into the main holes that were left by the removal of the old cement render.

The walls were quite a mess after the initial removal. The cement render is far too hard for the walls and so it takes off lots of the underlying mortar and also breaks bricks etc when it is removed. The removal process also involved fairly heavy equipment in the form of breakers and if they are not used carefully then they too can remove parts of the wall. If using breakers then it is advisable to use lower powered ones rather than being all macho about it. So medium breaker, with a wide chisel end, used in as parallel an angle as possible is the way forward.

Anyway the upshot of the job is that rather than expecting some areas of render to be 10cm deep and others 2cm it is best to 'dub out' the holes to make the surface more even.

The process I have used is to throw the mix into the holes as this gets more air into the mix and hence it cures quicker. I have also had to replace some half bricks. Any exposed wood has been treated using Osmo 4005 and the windows have been insulated into any void reveals. Next will be to sort the various joints in the wall so that any variety in movement of the walls does not crack the new render.

Tracking down lime sources

A limestone quarry

What a palaver! Being a bit of a fuss pot over lime I wanted to check the lime credentials of the lime putty that is being ordered for my render. I seem to have been around the proverbial mulberry bush, but at last I feel at ease with the source that shall adorn my walls.

The lime putty that shall be used will have come from Cheddar (an Oolitic Limestone) as a Quicklime and then slaked in Brecon (at Ty Mawr Lime), left for a minimum of three months and then mixed with an aggregate including limestone from the Cotswolds.

I feel it is really important to know the source of lime as some limes are made from chalk. I think that an external render needs to be made from a limestone base rather than a chalk one. Ultimately it will be harder and more durable. Chalk derived products are fine for internal applications, but I am not so convinced with being exposed to the winds and rains that we can get (only occasionally mind) in Cardiff.

The limewash will also be a limestone based product as well.