Suspended Wooden Floor Over Concrete Subfloor

19 Nov 2010
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United Kingdom
Hi Everyone
My son has just bought a house that needs a new dpc. As part of this job we will be replacing the ancient concrete floor in the kitchen with a suspended wooden floor supported on pillars from a concrete subfloor. We have already started digging out the old floor to the same depth as the subfloors in other parts of the house. The subfloors are below dpc level and the kitchen is about 3.2m x 3.4m. We assume the subfloor will incorperate a plastic sheet DPM & my questions are as follows.

1. thickness of sand under the DPM
2. thickness of sand over the DPM
3. thickness of concrete required to support the pllars for the joists
4. minimum temperature to lay the concrete

any advice would be helpful
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Not sure if this is the best idea i've heard of !!

If you are going to break up existing concrete floor why not use kingspan insulation and sand/cement screed ?

You are basically laying two seperate floors here, twice the work and twice the cost.. plus you still have to incorporate the suspended floor at dpc level in existing walls tructure..

If you dig out some of the soil you can then lay a hadcore, sand blinding, DPM, kingspan then screed finish for a level, insulated floor where the DPM (damp proof membrane) is incorporated into the DPC (damp proof course).

If this sounds like what you're after come back to us and i'll help with dimensions.

Doing it the way you plan means quite a step up to the kitchen as you will also need to leave @ 100mm void between concrete and suspended floor and will have no insulation.. and new dpc that sounds like it will be a bit on the high side ?

Don't mean to change your idea, just thought this advice would help !!
Hi mac
thanks for your reply

The suspended wooden floor will be level with the existing wooden floors and the void under it will be about 300 to 400mm just as the rest have. We will insulate between the joists.
There are a few reasons we decided to do it this way even though it is a bit more work. The void will make it easier to run services. Even though the rest of the house has under floor voids due to the location of the old concrete lump air flow to some parts was severely restricted so we hope to get these areas to dry out abit. The boards will be sanded & varnished to finish.
I suppose we will need to lay some dolomite as a first layer ?


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