The single block wall of the shed is letting water through the mortar joints. O.K., some of the pointing isn't perfect but the shed is fairly sheltered and the walls have two coats of Sandtex exterior paint on, which claims to be waterproof.
Any suggestions as to how to increase the water resistance? Any other treatment will have to be compatible with the Sandtex paint already on there.
Cheers
Dave R
Repoint and remove paint. Waterproof paint stops evaporation as well as ingress, causing damp. Lime paint doesnt.
NT
Repoint and remove paint. Waterproof paint stops evaporation as well as ingress, causing damp. Lime paint doesnt.
******************************************However the current issue is that the waterproof paint ISN'T preventing ingress. I can cope with evapouration on the internal wall for any moisture within the wall, but I don't want rainwater penetrating from outside. Hence the 'waterproof' paint. Which isn't. Hence the question.
The pointing isn't perfect but it doesn't look terrible. It makes me wonder if I should have mixed some waterproofing stuff into the mortar.
I am really looking for something that is more waterproof than the current paint but which can be applied over the current paint. Trying to remove paint from concrete blocks is not a trivial exercise.
The paint *is* waterproof on smooth or semi smooth surfaces, but it's not going to stop water coming through cracks
Don't think it would have made any difference, blocks walls have a tendency to split along the beds - this is where the water gets in, regardless of how waterproof the mortar is
Just give it a coat of 'Thompsons concrete roof seal' - it's grey and it's water based but sets like rubber, you can put it on with a roller and it's guaranteed for 10 years - I've used it on loads of rooves and never been back to any of them, I'm sure it will last longer still on a masonry wall. Whether you can paint over it with sandtex I don't know but is it that important what colour the shed wall is?
Coat the inside with synthaprufe? Dilute first coat(s) to get good penetration and finish with full strength. Blind with sand if you like.
Bob
You said all that at the start.
People often fondly imagine thatacoat of paint will stop rain getting in, and thus the wall will stay dry. Neither of those is really the case, as I explained. Nothing will keep water out, so you need evaporation in order for it to be dry.
If its not perfect, its letting rain in.
No point
As long as you go down that path you will fail.
Pressure washer. Repointing will also remove some.
NT
What about silicone water repellants? Might sort out the capilliary action problem. There was something (Thomsons?) which had a lot of advertising a while ago, but I've never used one.
Don't disagree with all the other advice, but a silicone spray might be worth a punt before going to the aggro of repointing.
Cladding.
Nobody has mentioned render yet (although applying over paint would probably require that metal mesh stuff to make it stick). If I did it all again I think I might use a lighter, cheaper block then render. Discounted this originally because I thought it would be too much work but easier block cutting and laying would probably justified the extra work of rendering.
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