Schoolmarm
Member
- Messages
- 1,894
- Location
- edgworth, lancs
:lol: :lol: :lol: :lol:
- Thread starter jaykayem
- Start date
By way of flogging this long-dead horse, I wondered if I could ask a question about flooring? As you can see from the photos, there is a plastic membrane with concrete on top, but neither the sheet nor concrete meet the wall. Ought they? Between the extremity of the sheet and the brick is bare and very damp earth. I imagine this will make it very difficult for the lower bricks to dry out, which the upper ones are doing well.
I can't do anything without serious difficulty about ground levels internally or externally. So my question really is about flooring types, screeds and the like. Can anyone suggest how this little scenario ought to look? Thanks again.
I can't do anything without serious difficulty about ground levels internally or externally. So my question really is about flooring types, screeds and the like. Can anyone suggest how this little scenario ought to look? Thanks again.
Matt Green
Member
- Messages
- 671
If the Damp Proof Membrane of the floor were tied into the wall beneath a Damp Proof Coure in the brickwork any water trapped under the membrane and entering the base of the wall would not rise up it very far if it could not evaporate through to the external surface because it would be blocked by the DPC.
Now I'm guessing that your wall doesn't have a DPC meaning the bricks at the base of the wall will remain wet indefinately unless the external ground levels are reduced (to allow evaporation through the external surface). Originally (when built) your floor would have been more breathable than it is now and the ground levels would have been lower. The retro-fit DPM and DPC approach to period properties can work and give you stable internal decorations but it has to be perfect and it usually causes irreversible damage to the bulding fabric. Are those chemical DPC holes in the picture...?
You can either try another attempt at retro-fit DPC with cement plaster to go with the water-exclusion model of a damp-free home that will eventually blow off the walls, or put in a limcrete or brick floor to go with the breathable model with equally breathable plaster....that will spoil decorations at low level because of the ground levels allowing water through the base of the walls. Currently your arrangement falls between the two models and ripping up a floor is no mean feat.
Time to either grab the nettle and lower the ground levels or dry line the interior surface (you can use laths on battens for a period finish or panelling, but isolate the battens from the brickwork with strips of DPM).
Sorry, no easy answer. Nice example of how these approaches differ and the results/problems when they are mixed.
Matt
Now I'm guessing that your wall doesn't have a DPC meaning the bricks at the base of the wall will remain wet indefinately unless the external ground levels are reduced (to allow evaporation through the external surface). Originally (when built) your floor would have been more breathable than it is now and the ground levels would have been lower. The retro-fit DPM and DPC approach to period properties can work and give you stable internal decorations but it has to be perfect and it usually causes irreversible damage to the bulding fabric. Are those chemical DPC holes in the picture...?
You can either try another attempt at retro-fit DPC with cement plaster to go with the water-exclusion model of a damp-free home that will eventually blow off the walls, or put in a limcrete or brick floor to go with the breathable model with equally breathable plaster....that will spoil decorations at low level because of the ground levels allowing water through the base of the walls. Currently your arrangement falls between the two models and ripping up a floor is no mean feat.
Time to either grab the nettle and lower the ground levels or dry line the interior surface (you can use laths on battens for a period finish or panelling, but isolate the battens from the brickwork with strips of DPM).
Sorry, no easy answer. Nice example of how these approaches differ and the results/problems when they are mixed.
Matt
Matt is far more an expert in this than I (but I would have said what he did :wink: )
We had a similar situation in that we have some old walls with no DPC (which would have been wrecked if we tried to fit one) but otherwise modern construction for the rest of the house. The question was what to do where the concrete + DPC floor met the old wall?
The route we chose was to leave a 300mm gap between the old wall and the new floor. This has been filled with limecrete made from leca to give an area where the moisture can evaporate from. (We have a high water table being next a stream and on clay so the ground under the house is always damp.) So far, there are no signs of any damp though we have also lowered the ground level on the outside to well below inside as well.
No simple solution I am afraid.
We had a similar situation in that we have some old walls with no DPC (which would have been wrecked if we tried to fit one) but otherwise modern construction for the rest of the house. The question was what to do where the concrete + DPC floor met the old wall?
The route we chose was to leave a 300mm gap between the old wall and the new floor. This has been filled with limecrete made from leca to give an area where the moisture can evaporate from. (We have a high water table being next a stream and on clay so the ground under the house is always damp.) So far, there are no signs of any damp though we have also lowered the ground level on the outside to well below inside as well.
No simple solution I am afraid.
Matt, MDB, thanks for these comments, looks like lowering the external level will be the lesser of two evils. How far should it be lowered? I've dug a trench on the other side of the kitchen and that really seems to have helped that wall to dry out, so I'm convinced that floor levels are crucial! Yes, the wall has been treated to a chemical dpc or two. I do like the idea of filling in the margin between concrete and brick wall with limecrete. is 300mm the recommended dimension?
I would aim for 150mm to 200mm below inside floor level but don't undermine the wall. It is unlikely to have any foundations.
Inside, I would rake out what you can in the gap you currently have and then fill with either limecrete or lime mortar depending on how big a gap you have. I wouldn't bother removing any of the concrete initially. I would then leave it 6 to 12 months to see how it goes. If you still have a problem then consider a wider gap but you may find you don't need to bother. Sorting out the ground levels will be the best thing you can do.
(you can get small bags of (fairly expensive) leca at garden centres though it is normally all the same size. Ideally you want a mix of different sizes)
Our limecrete sections. The yellow buckets are standing on the concrete.
Inside, I would rake out what you can in the gap you currently have and then fill with either limecrete or lime mortar depending on how big a gap you have. I wouldn't bother removing any of the concrete initially. I would then leave it 6 to 12 months to see how it goes. If you still have a problem then consider a wider gap but you may find you don't need to bother. Sorting out the ground levels will be the best thing you can do.
(you can get small bags of (fairly expensive) leca at garden centres though it is normally all the same size. Ideally you want a mix of different sizes)
Our limecrete sections. The yellow buckets are standing on the concrete.