Rigsby
TPF Special Forces
I went to look at a job today where the rendering on two extensions built at separate times have blown. The client has told me that he has had the original render took off and renewed and that has also blown.
Both the walls in question face south although the kitchen extension has 2 sides still intact. The walls are built out of concrete block and the render which has blown is two coat and hard, not the usual dusty render on failings. It has blown off the face of the blocks. The wall also faces the Derbyshire moors but the render on the house which was done at the same time is on 30's clay common bricks and has had no problems.
This client wants a no quibble guarantee but I have said 2 years if it is down to faulty workmanship. That led to if I know my job it cant fail can it? Well that has got me thinking why the renderers work has failed because the mix looks right and the blocks are right so what could go wrong?
I suggested a sbr slurry with a scratch coat with mesh embedded fully and the mesh pinned back to the wall. Allow the scratch to cure hard and then render top coat with stress patches around the openings. There is of course the usual rend-aid and the like with ocr or the like with mesh.
So any idea's why it should blow of in sheets. I thought at first too hard a mix but it has only failed on the south facing walls. Now I am thinking perhaps the heat? The extension walls will have cavity wall insulation so could the heat cause this?
I am not frightened to do the job but want to get it right. If my work fails I wouldn't have a clue where I went wrong.
Any suggestions?
Both the walls in question face south although the kitchen extension has 2 sides still intact. The walls are built out of concrete block and the render which has blown is two coat and hard, not the usual dusty render on failings. It has blown off the face of the blocks. The wall also faces the Derbyshire moors but the render on the house which was done at the same time is on 30's clay common bricks and has had no problems.
This client wants a no quibble guarantee but I have said 2 years if it is down to faulty workmanship. That led to if I know my job it cant fail can it? Well that has got me thinking why the renderers work has failed because the mix looks right and the blocks are right so what could go wrong?
I suggested a sbr slurry with a scratch coat with mesh embedded fully and the mesh pinned back to the wall. Allow the scratch to cure hard and then render top coat with stress patches around the openings. There is of course the usual rend-aid and the like with ocr or the like with mesh.
So any idea's why it should blow of in sheets. I thought at first too hard a mix but it has only failed on the south facing walls. Now I am thinking perhaps the heat? The extension walls will have cavity wall insulation so could the heat cause this?
I am not frightened to do the job but want to get it right. If my work fails I wouldn't have a clue where I went wrong.
Any suggestions?
