uneven slightly damp sandstone slab floor - levelling compound/tiles/carpet?

[tez]

Hi

I have just moved into a house where the kitchen floor is made up of sandstone slabs which appear to be layed directly on the soil beheath. The house is on a steep hill so the kitchen is the only room where the floor is on solid ground - there is a cellar at the front of the house with floor boards for the hall and lounge.

The stone slabs are uneven and not very attractive. They would be lovely if it wasnt for 3 cement 'channels' containing pipes criss-crossing the floor. Most of the pipes are redundant, just a water and gas pipe running arount the edge of the room to the cooker and sink.

What I would like advice with is what to do with this floor. I dont have enough money to lift, level, relay and buy extra stone slabs in order to have a tidy stone floor.

The previous owner had levelling compound covering two thirds of the floor and then just a carpet on top. I lifted the carpet to redecorate teh room and noticed lots of black spots on the underneath which may be mould. The floor is a little damp in places particularly towards the wall backing onto the hillside, and the next terrace above. The plaster is also damp on the wall where next doors kitchen floor level is about 20 inches higher than my floor. This wall is going to have the plaster removed and then cement/tanking/lime plaster/finishing plaster applied to a height of 1.5m

When I first moved in I intended have the floor asphalted which I thought would level and waterproof the floor at teh same time. THe asphalter said I had to remove the levelling compound before he could start. I smashed the compound off the floor with a small hammer 8) But started to read on teh internet that asphalting a damp floor was not a good idea and could cause the damp to move towards the walls instead.

What I would really like to have is a flat floor with carpet or tiles that breathes. Do all levelling compounds waterproof the floor? Apparently the tile adhesive is waterproof also so a levelled, tiled floor would effectively do what the asphalt would have?

I went to a carpet shop to ask about just laying a natural fibre carpet like a seagrass carpet straight onto the slightly uneven floor. The carpet man said putting a carpet on a damp floor would cause the glue in teh carpet to begin to smell.

Please could you give me some advice on what to put on the kitchen floor? I would probably just leave it as it was with a rug in the middle of the room if the stone slabs hadnt been so spoilt.

[Rick Dipper]

You really need to lift it, and do it properly, in the long run it

*WILL* be cheeper.

If you do most of the work yourself, a few hundered quid will see a concrete level floor in place, just get a guy in for 1 day to help level it. Micro digger = 60 quid a day Concrete = 60 quid a cube Visqueen = 30 quid a sheet Insulation = 16 quid for an 8x4 of 100mm ploysterine guy for a day = 120 cash

For a bodge, I'd put the following layers down :- Sand (5mm) Visqueen Concrete or Screed (50 mm min) Of cource I should have put insulation in there somewhere, but its a bodge.

Rick

[Ian Middleton]

I am afraid lifting it is the only solution. A friend of mine had similar in his kitchen, damp blistering plaster in places, mould under carpets as well as ants occasionally popping up between the flags. Oh also rusts the underneath of washing machines, cookers, tumble dryers as well as making chipboard kitchen units swell and collapse.

He got it all lifted, dug out, and proper base + damp proof membrane + insulation installed + levelling etc. Got a nice flat and dry kitchen floor. As a side effect the damp plaster all stopped, implying the damp was coming up through the earth of the old floor. Only his kitchen floor was like this the rest of the house being conventional floorboards.

[Ian Stirling]

If you could find a few extra slabs in a matching or contrasting colour, then might simply chopping out the concrete with a diamond saw, and then filling in the gap with those work. (if it goes 'around the room', then you'd probably want to continue the cut around the other edge, so it's a feature.)

[Anna Kettle]

There is no point in using lime plaster if you are then going to put an impermeable layer on both sides of it. Use cement instead, its cheaper. Or don't put the impermeable layers in place, just use lime plaster and paint with limewash to let the wall breathe so it doesn't trap damp

I disagree with the people who say that lifting the stones and putting down a damp proof membrane is the only way to go. That is one way, but the other way is the traditional way of allowing the moisture to escape (what you now have ... levelling compound and a carpet does not allow moisture to escape as you have discovered). Reverting to the traditional way will be cheaper too which is important to you

How about making some of your own 'stone' slabs from cement and sandstone dust and use them to replace the nasty bits of your floor, then put the rug down. It will be habitable and pleasant and the floor will breathe and so not trap damp

Sandstone slabs are worth good money and are a definite plus when selling. Maybe they wouldn't add much to the value of your house in the state your floor is in now, but it would be a pity to pour gunk on them so they are lost forever

Anna ~~ Anna Kettle, Suffolk, England |""""| ~ Lime plaster repairs / ^^ \ // Freehand modelling in lime: overmantels, pargeting etc |____|

01359 230642

[Pete C]

Hi,

Can the slabs be lifted and the damaged ones turned over or replaced? Also natural flooring can be had without a backing and edged to create a large mat. Would have thought the backing is damp proof anyway, it's usually rubberised or something like that.

Maybe have the better slabs and a bare floor by the cooker and sink etc then a large mat elsewhere.

Sisal is nice stuff and if treated with Scotchguard is easy to clean, it might be possible to take outside and blast any stuff off with a hose.

If you're on a budget coir matting can be had very cheaply and cover the whole floor, and replaced when funds allow.

See also:

cheers, Pete.

[The Natural Philosopher]

I would say that you don'tt have enough money not to frankly.

If you do it yourself, its not that expensive.

Thats what happens 'on the cheap'

take a pick to it, remove the lot, inject the walls below damp level, dig down, lay smashed up floor back in, and blind with sand to get it roughly level, lay plastic DPM all over and up the walls a bit too, lay

2" of polystryene over it, screed the lot to 3" at least (preferably with UFH in ) and re-plaster lower walls.

Now what was the question?

[Rick Dipper]

My architect has told me that injecting stone/lime walls is not going to do anything usefull, so take some advice on this, as I guess if your floor is that old, so will your walls be.

[The Natural Philosopher]

A lot depends on the path the damp takes. If its coming upwards, then eventually it evaporates - outwards or inwards depending on RH and permeability.

If you e.g. inject inner surface up to a few feet and slap waterproof render on it, then it as more chance of evaporating outwards before it gets past the barrier. If the whole floor is coming up there is a chance of e.g. nailing battens over DPM and dry lining the walls up to a sensible height, and making a bowl out of the DPM to keep floors and lower walls dry.

Some damp is not a problem, but damp that gets into plaster or woodwork is.

Its just a question of where its going to be able to evaporate out, and making sure the bulk goes outwards

[tez]

Thank you all for your advice. I have dropped the idea of putting levelling compound and tiles over the stone floor.

If I go with levelling the sandstone slabs - would it be better to let the floor breathe rather than put an impermeable layer beneathe the stones. One wall is going to be tanked to a certain height as it is a earth retaining wall on a slope, and I cant remove that earth as the house above is sitting on it! The other 3 walls have old lime plaster which has been thinly skimmed to make them level.

What do you think of this approach - raising the slabs, clear the concrete bits, lay lime mortar on the earth, relay the good slabs on the lime mortar (?) to level the ground and let it breate and fill in the space left with new slabs. Would I seal the stones to stop them staining and let the stones breathe through the mortar or not seal them at all?

A surveyor suggested digging down a bit and laying the the stone slabs on concrete pods. Has anyone had experience of this? I think it is with the intention of having an airspace below the floor.

Should I install air bricks on the wall which leads down to the cellar (below the kitchen floor level) which would allow the ground to breate into the cellar (beneath the lounge and hall) and put a couple of air bricks at the end of the cellar which would allow air to exchange with outside air, or put airbricks on an external kitchen wall above the kitchen floor which would allow moisture to escape once it has come up through the floor?

THank you for your help

T.

[Rick Dipper]

Sir

You have to decide, what approach you want to take, there are 2 basic ones, each cam will argue that theirs is best, bith will work

1) Conservation - The walls "breath" You follow the same design ideas that the guys that built the place in the first place did, you get all the same benifits and issues they got

2) Modern - You build a huge tank, and live in it. You use plastic and concrete and you remove all the issues you have in (1) above, but do a certain ammount of damage to the bits of (1) that do actually work, and you fix this with more concrete/plastic.

To a certain extent the finished look can dictate the use of option(1).

I had this very dilema, and I went for choice 2, becuase I had to do so much repair work, also it seamed a whole lot easier to DIY it. So im my house, the floors will come up, I will dig down a bit, and bottom up lay this stuff :- radon sump sand visqueen radon, (bonded into the wall waterproofing when that goes up), I am in a radon area. concrete insulation UFH slate slabs set in concrete / screed.

On the walls, I'll use a plastic product, you "nail" up, and plaster over with normal plaster. Where the walls have voides, they will be filled.

While you have the floor up, if you are in a radon zone, fit a radon sump, it will cost you 20 quid as a DIY fit.

There is very little technical element to this procees, except for the plaster, and getting the screed right, its all DIYable, if you can get a good plasterer to help with the finishes.

If you live neer leeds, Pick Quick Service are great for the plastics, and the prices are the best I found in the whole country.

Rick

[Pete C]

Hi,

How about laying the sandstone slabs on... sand? Also try taping a 4' square sheet of plastic to the walls and floor, that will give some idea of how much damp comes through over time.

If you put an impermeable layer down the risk is that water will build up behind it and seep out round the edges in an unsightly way, having less opportunity to dry out naturally.

It might be that the earth retaining wall doesn't really need tanking, whether the house is on well drained or impervious soil will make a huge difference.

A stone flooring specialist will be able to advise on a foundation and sealer for sandstone, lithofin stainstop has been recommmended on here IIRC. It won't make the sandstone vapour proof, just stop liquids soaking in.

The best way for damp to escape is through the fabric of the rest of the building, so ensure the walls are painted or papered with something breathable. Airbricks that can allow damp air into a cold place won't be much good, but a kitchen extractor or cooker hood can help keep steam from building up when cooking.

cheers, Pete.

[The Natural Philosopher]

Rick has put it very well.

Damop in the ground has to stay there, or evaporate somewhere.

Its your choice as to wheher that is inside the house or not.

Damp damages plaster and tinmber, but if you don;t hae any of it, then so what?

The gret scare stories teh conservationist go on about damp proofing, are to do with teh fact that if there is a strong water movement through brick and stone, and you stop it in one area, its likely to get worse in another.

DPM work HAS to be caried up high enough so that there is enough external area of wall to evaporate rising damp without it coming through the walls internally. If you are not able to do that DPM'ing the floor will just make the walls worse.

Personally I think the modern way is better, if you can achieve it without comromising apprearance.

Me, I like the old look but the modern feel :D

If you don't mind slightly damp floors, lift the stones and lay back on mortar.

You CAN use dry sand, but my experience of layng irregular slabs is that its esier to get them level in very wet sand,which flows, and throwing in a bit of cement (or indeed lime) makes for a slighthly more stable approach, and allows you to 'grout' the joints.