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Andrew Smith
Andrew Smith, Plumber
Category: Home Improvement
Satisfied Customers: 3941
Experience:  City and Guilds Qualified plumber
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I have a problem with the concrete Floor slab in my kitchen

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Hi There,I have a problem with the concrete Floor slab in my kitchen
The floor has dropped on the outside 1.7 mtrs by about 15mm
So I have an area of about 1.7 x 3.3 mrts dropped in a kitchen about 3.3 x 4 mtrs
Are there any likely problems in breaking up the concrete using it as hardcore and re-laying the base and screed
That should be ok, but bear in mind you will need space for DPM and insulation now. Has the subfloor dropped by much?
Customer: replied 1 month ago.
Hi The subfloor has dropped by about 15mm at one end, there is a small crack across the room approx 1.7 mtrs in from the outside wall. What spec do I need to do now and would I need to do the whole floor or just the bit that's dropped. I have read that new floors have to have cellotex insulation above the slab would that be needed here?
Customer: replied 1 month ago.
I would like to discuss but I can't do it now as going out
If you dig out enough then you can get the cellotex in below the slab.
I assume it has dropped over time and eventually cracked the slab rather than a sudden drop from subsidence bearing in mind the weather?
Customer: replied 1 month ago.
it has dropped over the last 10 years and I think it had dropped about 5 mm before that
Customer: replied 1 month ago.
Is the spec 150mm hardcore then DPM then 100mm concrete then 100mm Cellotex and chipboard
Ok, you should be fine then.
When you use the DPM over the cellotex allow some slack at the edge so if you do end up digging out the other side then you have enough to lap and tape the joint.
Customer: replied 1 month ago.
Hi Andrew I am sorry I couldn't complete the questions last night had to go out, can you confirm if the specification for the new floor would be as I put above, i.e. finishing with the Cellotex and the wooden floor on top and would this apply to doing just half of a floor the part that is faulty ,or would I likely have to do the whole floor. OR would I do the floor to the original spec as it is a repair?
Better to replace with the new current spec with Cellotex, but it us up to you.
If you don't want to do that have you thought about a self-levelling screed over the top to repair the existing floor?
Customer: replied 1 month ago.
Applying a self levelling compound was my first option, but I am concerned that the floor has dropped a few mm in the last 10 years, and if I just put the screed over it may drop again. It is still the easiest option just not a certain one, and whilst the house is pretty much in pieces (we aren't living in the downstairs at the moment) it seemed the permanent fix was more appropriate. I am thinking of digging a hole in the floor for an inspection and if the undermatter has indeed settlled and compacted would it be appropriate to then just put down the self levelling compound.
Ok, if it was me then I would take the whole floor out while you're not using it.
New DPM, new insulation and floor slab after compacting
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