Damp solid floor

11 Aug 2006
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United Kingdom
Hi Everyone

I'm just renovating an old 1906 house. I've recently taken the kitchen out and replaced it with a new one.

When I ripped out the old kitchen I found that the plaster behind it was damp, this wasn't surprising because we had damp in other parts of the house. What confused me was that the plaster went all the way down to the floor and onto the concrete floor?? I always thought that you needed a gap between the floor and the plaster to prevent damp bridging the damp proof course.

Could anyone advise me with whats best to do with this? Could I just strip the damp plaster off and re-plaster with salt retardant plaster leaving a gap for a skirting board? Other parts of the kitchen are plastered to the floor in the same way but have no damp. Also the concrete floor seems to be an addition as we found the original floor tiles in most of the kitchen.

I'm loathed to ask a damp specialist in because in my experience they say you need a new chemical damp course no matter what! :confused:


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Chop off about 2 inches to the floor and keep an eye on it for a few days, if this is the problem it should dry out ;)
Sonic1981 said:
I always thought that you needed a gap between the floor and the plaster to prevent damp bridging the damp proof course.

A 1906 house probably won't have a dpc so bridging won't apply.
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could be that there is no damp proof membrane under the floor or that the one there is teared. Also maybe the gorund outside the kitchen is banked against the wall. Maybe best to rip out the floor and start again.


Ok.....We have a damp proof course, its slate. Am I right in saying then that if there is a waterproof membrane under the solid floor then having plaster to the floor is not a problem??
Slate dpc is common in walls of older houses, bur was not used under floors.

If the old solid floor was dug out and relaid in the last 20 years or so, it may well have had a polythene sheet damp proof laid under it... but if a concrete screed was just added to level up an old floor, then it might not. In which case the solid floor is going to be damp.

To test a solid floor for damp, tape a piece of clear plastic (e.g. polythene bag) tight to the floor and leave it a few days. If condensation appears on the inside surface of the plastic, where it is against the floor, then the floor is damp.

It is an advantage not to take plaster all the way to a solid floor anyway. You might be able to see the slate dpc somewhere above floor level, in which case you would not want to bridge it with plaster.
The solid floor is new becasue we found that most of the kitchen has the original quarry tiles. Thanks for the advide it sounds like a good plan.

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