Thanks a lot Ray. It's been a lot of fun doing the research. Any idea if the limestone tiles can be sealed without ruining the breathability? I've seen a few manufacturers who claim breathable but would hate to ruin all that hard work on a sealant
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Limecrete - Is there any point?
- Thread starter tvrulesme
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- breathable concrete damp limecrete
raytheplasterer
Well-Known Member
Thanks a lot Ray. It's been a lot of fun doing the research. Any idea if the limestone tiles can be sealed without ruining the breathability? I've seen a few manufacturers who claim breathable but would hate to ruin all that hard work on a sealant
I'm not sure so wouldn't want to give any dodgy advice, but I imagine they would be sufficiently aged before being sold to you for the floor and probably come ready prepared/sealed, best to ask the company you buy them from. The only tiles I know that need sealing are sandstone/soapstone tiles ??
I realise this is an old thread and the decisions have already been made, but for anyone finding it later:
It doesn't seem to have been made very clear that the moisture is coming up through the ground under the building, and originally would have come up through the earth or lime floor, and any tiles etc on top and would then have been taken away up the chimney by the large airflow caused by open fires. If the floor is sealed by a DPC, concrete slab, or non permeable floor coverings, then the floor will get damper, and as it connects to the walls, which if they have no DPC are also getting moisture from below, then there will be more moisture to lose and it will tend to make it's way further up before evaporating.
Assuming you have already sloped/french drained outside, and removed any non permeable exterior finishes then the moisture will escape, and if the interior is soft lime with permeable finishes it wi also escape there, but obviously the floor surface area is large compared with the exterior bit of wall below floor level which it otherwise has to escape from, but digging out internally (with suitable sloping to support the walls) to put in a full limecrete floating floor, lowers the water level that the walls have to deal with.
Unfortunately, anything that gives you a modern, hard, easy clean surface is inherently going to reduce evaporation and increase the amount reaching the walls. This is why the report you refer to shows only minor improvement using lime, as to give a hard floor they are using NHL5.
As with lime plasters and renders, the harder you go, the less it breathes, so use the softest you can, which is why stone slab or brick/unglazed tile flooring is good as it can sit straight on a floor made of kiln ash just bound with weak lime, or even straight on earth but give a hard surface, but if making a floating limecrete floor slab you need the stronger lime (plus fibres) to hold it together.
Good limecrete floors reduce the amount of moisture coming up by using foamed glass insulation with a low capillary finish, so the water isn't drawn up, but still have to deal with the moist air, so still have to be permeable.
Any floor finish will reduce permeability, but unglazed terracotta tiles with lime pointing are probably the best bet. The Victorians went in for encaustic tiles (the mosaic like ones found in Victorian hallways) as they were slightly permeable themselves, but the large number of joins between the small tiles gave a lot of quite weak lime pointing to let the moisture out, while producing a hard easy clean surface.
If you really need to seal tiles or stone then natural linseed oil is probably the best bet, but that will certainly reduce permeability. I just use a linseed based floorsoap (ecover) on unfinished tiles, as it gives a slight, but not solid, finish.
Any sort of lino or modern laminate will just trap the moisture at floor surface.
There are also some indications that underfloor heating increases the capillary action of solid lime floors, but given the anti capillary layer of foamed glass aggregate, this shouldn't be an issue for properly constructed limecrete floors.
It doesn't seem to have been made very clear that the moisture is coming up through the ground under the building, and originally would have come up through the earth or lime floor, and any tiles etc on top and would then have been taken away up the chimney by the large airflow caused by open fires. If the floor is sealed by a DPC, concrete slab, or non permeable floor coverings, then the floor will get damper, and as it connects to the walls, which if they have no DPC are also getting moisture from below, then there will be more moisture to lose and it will tend to make it's way further up before evaporating.
Assuming you have already sloped/french drained outside, and removed any non permeable exterior finishes then the moisture will escape, and if the interior is soft lime with permeable finishes it wi also escape there, but obviously the floor surface area is large compared with the exterior bit of wall below floor level which it otherwise has to escape from, but digging out internally (with suitable sloping to support the walls) to put in a full limecrete floating floor, lowers the water level that the walls have to deal with.
Unfortunately, anything that gives you a modern, hard, easy clean surface is inherently going to reduce evaporation and increase the amount reaching the walls. This is why the report you refer to shows only minor improvement using lime, as to give a hard floor they are using NHL5.
As with lime plasters and renders, the harder you go, the less it breathes, so use the softest you can, which is why stone slab or brick/unglazed tile flooring is good as it can sit straight on a floor made of kiln ash just bound with weak lime, or even straight on earth but give a hard surface, but if making a floating limecrete floor slab you need the stronger lime (plus fibres) to hold it together.
Good limecrete floors reduce the amount of moisture coming up by using foamed glass insulation with a low capillary finish, so the water isn't drawn up, but still have to deal with the moist air, so still have to be permeable.
Any floor finish will reduce permeability, but unglazed terracotta tiles with lime pointing are probably the best bet. The Victorians went in for encaustic tiles (the mosaic like ones found in Victorian hallways) as they were slightly permeable themselves, but the large number of joins between the small tiles gave a lot of quite weak lime pointing to let the moisture out, while producing a hard easy clean surface.
If you really need to seal tiles or stone then natural linseed oil is probably the best bet, but that will certainly reduce permeability. I just use a linseed based floorsoap (ecover) on unfinished tiles, as it gives a slight, but not solid, finish.
Any sort of lino or modern laminate will just trap the moisture at floor surface.
There are also some indications that underfloor heating increases the capillary action of solid lime floors, but given the anti capillary layer of foamed glass aggregate, this shouldn't be an issue for properly constructed limecrete floors.
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