Newbie needing to sort damp in bay window - current render is mix of lime, multi as well as a bit of cement tanking

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diogrwydd

New Member
Hi

This bay window in a Victorian built terraced house has been having a few damp issues.

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After investigating, removing the skirtings showed multi finish skim going right down to the floor, so I've started hacking that back given that it probably was wicking moisture up (there was green in the centre of some of the plaster around the damp areas - what is that?). It is also evident that there are sections plastered in original lime (the lovely black ash found often across South Wales), as well as indications that it has been tanked in cement at some stage, up to the usual 1.5 meters I would presume.

The tanking is a bit of a strange one, as I can't see any evidence of a liquid DPM having ever been drilled into the bricks either side. There is a gutter downpipe outside that is just dumping on the bottom of the wall of the property, so that is probably at least on source of moisture that is getting sorted. Looking under the floorboards, I've cleared out the air vent that was full of dirt. There is also what appears to be a bitumen DPM in there somewhere, but this is a few courses of brick below the external ground level, which doesn't make sense to me except for the fact it somewhat protects the floor timbers sat on those bricks, but giving limited protection to the rest of the wall (plus no cavity). Would this be expected in properties built at the turn of 1900, or some kind of retro fitting?

I'm thinking the best course of action would be to remove the cement tanking (at least the level of the window sill) - hack this back to brick and then render it properly in lime in keeping with the original build and retaining breath-ability in key areas below the window. With the exception of about a foot of angle beading that is showing through with rust which I may cut our or treat, I'm hoping to keep costs and effort down to retain the rest (including the pink skim the rest of the way up). Is patching between lime based plaster and pink skim like this possible and going to work, or will it likely lead to more problems?

Thanks
 

ChrispyUK

Well-Known Member
Hi

This bay window in a Victorian built terraced house has been having a few damp issues.

View attachment 51218 View attachment 51219 View attachment 51210 View attachment 51211 View attachment 51212 View attachment 51213 View attachment 51214 View attachment 51215 View attachment 51217

After investigating, removing the skirtings showed multi finish skim going right down to the floor, so I've started hacking that back given that it probably was wicking moisture up (there was green in the centre of some of the plaster around the damp areas - what is that?). It is also evident that there are sections plastered in original lime (the lovely black ash found often across South Wales), as well as indications that it has been tanked in cement at some stage, up to the usual 1.5 meters I would presume.

The tanking is a bit of a strange one, as I can't see any evidence of a liquid DPM having ever been drilled into the bricks either side. There is a gutter downpipe outside that is just dumping on the bottom of the wall of the property, so that is probably at least on source of moisture that is getting sorted. Looking under the floorboards, I've cleared out the air vent that was full of dirt. There is also what appears to be a bitumen DPM in there somewhere, but this is a few courses of brick below the external ground level, which doesn't make sense to me except for the fact it somewhat protects the floor timbers sat on those bricks, but giving limited protection to the rest of the wall (plus no cavity). Would this be expected in properties built at the turn of 1900, or some kind of retro fitting?

I'm thinking the best course of action would be to remove the cement tanking (at least the level of the window sill) - hack this back to brick and then render it properly in lime in keeping with the original build and retaining breath-ability in key areas below the window. With the exception of about a foot of angle beading that is showing through with rust which I may cut our or treat, I'm hoping to keep costs and effort down to retain the rest (including the pink skim the rest of the way up). Is patching between lime based plaster and pink skim like this possible and going to work, or will it likely lead to more problems?

Thanks
Sort out the cause. Penetrating damp form the down pipe.
 

diogrwydd

New Member
Sort out the cause. Penetrating damp form the down pipe.
That has been repaired already. I’ve also sorted some issues that could be factors, including lowering levels outside as well as clearning a pretty much blocked air vent in the centre.

The space between the original plasterwork and the floor had previously been filled with what looked like carlite bonding, which again would have been a major factor.

My question is more about the reinstatement. I could easily hack out and patch affected areas before skimming in multifinish, but thought having two or 3 feet of lime render at the base of the wall would be better for preventing future damp issues. Just not sure how well patching in lime would be against existing gypsym work
 

martinemj

Well-Known Member
Patching with lime finish is going to stand out like a sore thumb
Lime finish needs to be left an open texture (no steel trowel to finish) we use a sponge float and then a sponge to finish

For a patch it Does not blend into surrounding plaster very well because it contains silica sand
 
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