General Category > OT Knowledge
Solid wall buildings part elebenty - alternatives to lath and plaster
Mrs Pingu:
No, I am not proposing to get rid of any existing lath & lime plaster wall!
So, back to the saga of my damp gable wall and chimney breast.... when the renovation team come to hack out the cement pointing and replace it with lime, I also asked if they would poke holes in the damp interior walls, remove any debris which might be causing damp bridging and then make it all nice again.
As mentioned previously, I had this wall skimmed in gypsum 12 months ago, (before I became a damp solid wall traditional building bore and realised the error of my ways). I've just spent the last few days scraping said gypsum skim coat off this wall in preparation.
What I have found is that most of the chimney breast is old L&P, but the edge of it, and the sides of the alcove abutting it are not. I assume it's some sort of gypsum plasterboard, but it's not the stuff with a paper surface.
It might help if I post a photo at this point:
2015-12-30_04-52-13 by The Pingus, on Flickr
So you can see on the LHS the problem alcove. The point above the left of the mantelpiece where the 'white' wall stops is the interface between L&P and the other stuff.
If you look at the back of the alcove there is a large stain round where the light fitting is. This has now been stripped of gypsum back to the original lime plaster. And yet creating the alcove itself, strangely is all modern board. This appears to go up as far as a wooden bead I found embedded in the wall about 6 inches below the cornice.
At this point I stopped stripping the skim coat as I figured I might as well get rid of the plasterboard, given then it doesn't breathe.
So my current plan, when the pointing and other exterior works is done and the guy starts work inside, is to suggest they rip out the plasterboard and replace it with something more sympathetic to an old building with solid walls, which is a bit more forgiving to damp.
My initial thought was replace with lath and plaster, but I suspect that will be ££££, so I wondered if there was anything else out there I should consider.
I've been reading some Historic Scotland case studies today where they used calcium silicate board as a hygroscopic, capillary, vapour permeable insulator, but it was basically plastered on the hard (directly onto the stone wall) as insulation with lime plaster affixed to a mesh on top of it.
Given that the problem wall gets a fair bit of prevailing wind and rain i'm not sure that the moisture would go from the inside to the out rather than the other way around!
If you've made it this far, thanks for reading :thumbsup:
My plan is to paint this wall with claypaint so it's nice and breathable, BTW.
So, any old building owners used alternatives to L&P? I tried Googling but it's mostly people getting rid of L&P, not the other way around ;)
Canardly:
Presumably the inglenooks/alcoves are formed within what were existing recesses either side of the chimney breast? If so, I am bit intruiged as to how could be damp unless there is something else going on apart from external pointing. You could remove the falsework altogether and reinstate the recess/es?
Mrs Pingu:
I think that 'new' alcove is a replacement for an old alcove, judging by what I've seen in similar flats for sale on my street. Current suggestions for the damp there are a) from roof, b) from wall, but either way the damp refusing to budge suggests there may be debris bridging between the outer and inner surfaces, not being able to dry out with current cement pointing trapping the water.
Also a possibility is c) water coming down my downstairs neighbours flue. Don't know exactly where that runs, but it must be up there somewhere.
I.e. lots of reasons :(
ETA - I was wondering about wood wool board to replace lath, with lime plaster on top (I assume it would be quicker and therefore cheaper to install than a load of new laths), but not sure how forgiving to moisture it would be.
Mrs Pingu:
Lots of new damp patches today :(
Took a look in the attic - water running down the wall, and then soaking into the floorboard which have been butted right up to the wall.
Suppose the next DIY job will be trimming those back if I can manage it. I assume that the big bit of wood lying across the top was only there as a frame for the plasterboard, and it's not going to make anything fall down if I chop it up... :-\
Canardly:
The water is coming from somewhere particularly in the light of your last post. I doubt it is simply rain penetrating a 9" or above solid wall no matter how naff the weather is. Likely suspects are flashings, loose copings, missing dpc, missing or damaged cavity tray where applicable, broken water/waste pipework, leaking gutter or water not going into gutter from roof therefore cascading down into the wall, blocked rainwater pipe or some such. What is the roof detail above this wall?
Is this wall the weathered side? (prevailing wind etc)
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