damp concrete floor and tiles

12 Jan 2005
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United Kingdom
we have a small back kitchen with a concrete floor - originally this was the washouse so i doubt it has a DPC. later they built an extension next to this room and must have filled in the gap between the new room and old room with concrete - doubt this has a DPC.
Both areas are about a 1 1/2 foot from ground outside.

The concrete in the kitchen is totally sloping to the outside wall and is wet (it has thin plastic and lino over it at present).

What is best mode of action if i want to tile this floor.

1. Lift floorcovering and let concrete dry out - how long?
2. do you think it is condensation or water from below making it wet?
3. How do I level it if it doesn't dry out
4. will tile adhesive stick to damp concrete.
5. would i be better to use a hydraulic lime screed and put a natural floor tile down so moisture can slowly be released and not trapped or shoved up walls ( I think walls a brick cavity).

Many thanks
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We've just had an old scullery/workshop/coal store/WC knocked into one room and extended to the front. The new extension has a dpc in the floor but the old part (90% of the room) does not.

The building inspector asked us to give the floor two coats of a rubberised bitumen solution and spread kiln sand on the final coat whilst still tacky. This left us with a sandpaper like texture to the finished floor which has given the floor adhesive a key.

We're now tiling the floor with slate tiles on a waterproof thick bed tile adhesive. The floor was uneven but the tiles aren't uniform thickness so we started at the high point with a medium tile and have worked toward the lowest point with the thickest tiles. All is going well (but slow).

Once the rubberised bitumen was down the damp from the room disappeared and we had no condensation even when it was bitterly cold outside. We used Cromaprufe as it was cheap, cheerful and was recommended for floors.

In answer to your questions:

Our floor was exposed to the elements whilst we had our flat roof changed to a pitched roof. It poured and poured with rain but as there was no damp proof course it took about two weeks until it was dry enough to coat with Cromaprufe.

We had a combination of condensation and damp from the earth below but now have neither.

Not sure about the levelling but slate tiles are working for us and you can do some levelling with tile adhesive if it says it can be used in a thick bed.

I don't think tile adhesive will stick to wet concrete but I could be wrong!

We asked about leaving the floor damp as my father-in-law lives in France and they don't have dpc at all. Our building inspector said we had to have the damp remedied to use the room as a kitchen/diner but our neighbour two doors away put their floor straight down on the concrete in the same room (they too have had it knocked into one and extended but some years ago). They, however, still suffer with the damp on the walls.

Hope that's helpful.
I just read this post - and was wondering which option you went for in the end? Your situation sounds like it was very similar to my curent one!


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