Money where mouth is moment!
I have long been an advocate of treating old solid walls correctly. This means allowing them to breathe using a lime based render (where render is needed of course).
Anyway my house has been suffering from damp for a while and so eventually we have managed to get enough money together to start to put it all right. So we are taking the correct approach of getting the outside done first before moving inwards. So, first part has been to remove all the old cement render from the solid walled parts of the building. Note that we are not taking off the render on the already lime renders timber frame walls, or the newer block cavity walls, that form the end extension on the property.
|Front of house is stone, behind door is solid brick wall, next extension is early cavity, still rendered is block cavity at ground level and timber frame above|
|Front door separates different materials|
|First floor timber joist exposed. Southern side of building is suffering from rot due to trapped moisture from cement render|
I have long been a follower of Harry Cursham at Traditional Technologies (http://www.tradtech.net/) and Welsh Lime Works (http://welshlimeworks.com/) and so I have been very specific about the type of render that will be used. I have chosen the following:
1:3 Mix of Lime Putty (from Limestone NOT Chalk) and Aggregate (and this is one of the keys!)
As you may have read in some of my earlier posts, I see aggregates as being the vital, but often overlooked, element to renders. The aggregate mix that I have chosen is:
1:1 Limestone (3mm to dust) with Sand (50:50 mix of coarse and fine)
The key ingredients are the limestone dust and the limestone putty with the sand acting as a filler. The limestone and lime will do all the work in the render as it is these two elements that will carry the water in and out of the wall. Getting consistency of material, avoiding weak points and ensuring that de-lamination is avoided mean attention to detail!