Lime and Steel

The difference can make or break (literally) your project

These products do the same job. 

They also look very similar

One will work, the other will not

Fixings are used a lot in the construction industry. My render job on the house is no different. I shall have the following types of metal in my wall:

Expanded Metal Lath (EML)

Stop Beads

Screws

Washers

The EML will be used to tie together those parts of the wall where there are junctions (points where the risk of movement and cracking is most acute).

The Stop Beads will be used around the base of the wall

The Screws and Washers will be used to hold the Beads and EML in place

The important thing is that they are ALL stainless steel. Lime (and cement) attack steel and galvanisation is only a thin coat of zinc over the top of mild steel, so any slight removal of this protective covering will allow the moisture in the render to rust the steel. The galvanised steel will also slowly react with lime and this will cause the structure to fail as the rust expands and cracks the render.

Using galvanised and stainless steel together also creates a electrolytic reaction between the two and this will also lead to the render failing.

So when you are using a lime product it is vitally important that you use ONLY stainless steel (and / or plastic) in your fixings. Don't think that you can get away with using good quality beads and EML and then fixing them with some ordinary screws / nails. It will not work.

Stainless is a bit more expensive than galvanised, but in the long term it is very much cheaper! No point having work done only to need it redoing in a couple of months / years.

It is also worth noting that on a recent visit to a newly built school they had the same problem. All the drip beads had failed and had 'blown' the cement render. So it is not just old buildings where care needs to be taken with regard to material selection and combinations thereof.