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Concrete floor for cellar - Advice required.

Postby kevinpsw » Mon Nov 12, 2007 12:01 pm

The cellar of my Victorian house was built as a coal storage area, approx 2.5 x 3.5m dimensions. The walls are brick but the floor is compacted earth. There is the musty smell of damp coming from the floor but no sign of damp on the walls. The height is barely adequate and I have no desire to raise the floor level. I know that to dig down more than a few inches would necessitate expensive under-pining so I can't expect to increase the cellar height.

I intend to dig down just 6 inches (but not under the base of the walls), in approximately 1m bands across the floor, lay 2 inches of ballast, a damp proof membrane and then 4 inches of unreinforced concrete. The finished level would be as the earth floor is now. I intend to lay the concrete in bands in order to work in manageable bites and to ensure that, if there is any strain put on the wall foundations during construction, it is only a fraction of the cellar at any one time. Once the 3-4 bands of concrete have been laid, I would then level the floor with self-levelling screed.

Any advice/comments?

Surely, if anything, the cellar wall foundations would be strengthened by a concrete floor over compacted earth?

The cellar will only be used for storage and I expect to paint the walls with damp-proof paint just in case some of the mustiness does come from the walls.
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Simply Build It

Postby scooty » Thu Dec 13, 2007 9:43 pm

Yo Kevin , i am in excactlly the same position as you and would appreciate some advice to .I would have written the same post as you. I am going to plaster my cellar walls with limelight waterproof render.
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Postby mattdiy » Sun Jan 13, 2008 8:26 pm

Hi, I am in the same situation, I am under the impression though (which I want to confirm) that it is perfectly ok to dig down to the bottom brick and replace with concrete, which can be on a dpm directly on the soil, therefore it might be possible to increase the head room
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Postby thedoctor » Sun Jan 13, 2008 8:34 pm

See the projects section and the project ground floor slab. Exactly the same principle applied. Concrete floors need to be laid on firm solid gound and the only way to ensure this is to compact it properly. The DP membrane needs to be turned up the sides of the wall and sealed as otherwise any damp under the slab can squeeze up between the slab and the wall causing damp on the floor. Its very dangerous to just excavate down the sides of what are effectively foundation walls and we would suggest very strongly you sought advice from an architect or at least the building control officer of your local council.
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Postby smuglilal » Thu Jan 17, 2008 7:27 pm

just done my cellar floor lifted slabs up to find a french drain in bad repair
could be were your musty smell comes from concreted mine now smells good if you have earth retaining walls i would use more than a paint. seeker render or that bubble membrane stuff
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