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Damp Proofing
Sodden (90%) concrete extension floor
Anonymous user 29 August 2019 - 1.05 PM
Hi all, We moved into a 1950s house about 18 months ago. We have recently discovered that two drains have been leaking underneath the concrete extension floor - presumably for a very long time - as most of the concrete floor is showing as 70 and 90% damp. Both drains were fixed about 6 weeks ago, and a drying company have had a de hum going since then, but the floor has only dried marginally. We have had to move out of the property whilst this is all going on. The drying company are going to keep the dehum going for another 8 weeks - but it doesnt look like its going to dry as it is so sodden. The insurance company have suggested putting a liquid dpm over the top and 'tank' the extension. I am concerned that this will leave permantely wet concrete underneath, and make it difficult for us to sell the house in the future. Does anyone have any recommendations whether 'tanking' is appropriate, or should the insurance company dig up the concrete floor, and completely relay it? We are desperate to get this resolved and I am non the wiser...
5 answers from MyBuilder tradespeople
We would recommend taking up the floor screed and laying a new DPM Then a new fibrous floor screed to finish. We have recently completed a job with the same problem with great success. Kind regards Rodney
Answered
29 August 2019
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Good afternoon, We wouldn't recommend laying a liquid DPM to such a damp floor slab, it would be better to lay a specialist platon membrane to the floor which would allow the slab to breathe and continue to dry out naturally beneath, this would however need to be covered, most commonly by a caber flooring. Then any remedial works required on the walls would depend on the extent of the damp but a similar method can be used on the walls, as with the floor, with a membrane system. With all the excess moisture that will be within the property as it dries out, it is possible you may find a significant condensation build up to which an iPIV unit installed in the loft space would adequately deal with this problem. Hope this helps! Mark Dare C.S.R.T
Answered
29 August 2019
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Application of a new DPM over a wet floor will mean the concrete will never dry. (Trapped moisture) the drying time will depend on thickness of concrete, typically between 10cm and 25cm . I would recommend a new floor be laid. An insurance company is more likely to stick with dehumidifier's for 12 months. If there are areas where mould is visible you can use the potential of health conditions as encouragement to resolve the issue quickly.
Answered
29 August 2019
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Not really you need to find the source. So you need to dig up whole floor and see what's going on and take it from there. Putting a dpc on floor and tanking just covers up the problem and might solve problem for now it will be a very cold floor.i think insurance company are trying to get a cheap fix. Ok Colin
Answered
1 September 2019
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Concrete wets or dries at about 1.0mm per year if it is structural quality . From the length of drying time you’ve mentioned, it’s probably poor quality concrete . A simple SBR and neat cement paint on DPM is sufficient to stop floor damage and the moisture will slowly dissipate back into the ground over many years. The render on the walls surrounding the slab must be cut away by 20.0mm to isolate it and allow slow evaporation , this may be covered by cupboards or skirtings for aesthetic reasons .
Answered
1 September 2019
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