DPC Levels

14 Sep 2011
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United Kingdom
I'm not sure I truly understand the DPC level.

I'm building a garage. Should the DPC level be the same level throughout, ie inside floor and in the concrete wall? From what I have read, if this is the case then, the internal floor would also have to be 150mm about external ground level which does seem to make much sense!

Can anyone help?
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dpc is a plastic strip preventing moisture wicking up the wall, the concrete slab has a damp proof membrane ( a thick sheet of polythene that goes under the concrete and returns up the wall before being trimmed off afterwards).

but then if the garage isn't a habitable structure then i don't know if this would be essential. it certainly won't do any harm anyway and is cheap enough - it'll stop moisture coming up from below in your lovely new garage :)

the slab can be above or below the dpc, as is convenient to your situation.
Thanks for that!

Then I supppose insulation is merely a luxury in a garage....? Do you know of any insulation sheets which I can simply lay, to cut down on costs?
Why do you want to keep your car warm in a garage?

In fact, the principle of insulation is to keep heat in, so unless you are heating this garage, and insulating the walls and roof, then insulating the floor has no point on its own
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A garage, when attached to a house would typically have a finished floor slab that is 150mm lower than the main dwelling.

This lower floor level does two things:
Firstly; it deals with the step down into the garage which is a regulations requirement.
Secondly; External ground levels are typically 150mm below dpc therefore dropping the garage floor the same amount means that you are able to drive into the garage without the need for a speed bump.

What all this means is (regards dpc) is that you can either have the dpc at all the same level as the house but show the same amount of engineering bricks or have a double dpc (one at dwelling and one 150mm lower) thus countering the splash effect from outside as well as dealing with things internally.

The dpm however will have to be cut off in the garage at slab level.

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