DPM In garage base

[andyb85]

Hi all,

Laying a concrete base for a concrete sectional garage which I bought. Our garden is very damp, not investigated the cause yet but we're in a clay area so it seems like water is retained in the top soil for a while after it rains. There is a concrete slab in a different location in the garden which seems to suck water up through it after heavy rainfall.

Debating whether or not to lay a DPM in the slab because I don't know if it will be of any use - where do I dress the DPM to?

Do I have the DPM coming out of the side of the slab, then dress it up the side, under the sectional panels and then fix it to the internal wall of the garage?

Or do I have the DPM coming straight out the top of the slab, if I do that won't it create a hollow square of non-attached concrete all around the perimeter of the slab?

I'm just concerned I won't know where to finish the DPM to create a watertight floor, and if there's any concrete exposed to water, will the DPM just trap the water in the base?

Any thoughts or advice greatly appreciated!

 

[r896neo]

Its worth putting a dpm in to stop the concrete drying too quick, it will make a stronger base.

If you want a truly watertight building you need a proper garage.

Its always a compromise trying to build off a raft, you can never totally waterproof the joint between raft and building.

A bench of mortar and some liquid dpm is about the best you can hope for.

It is possible to angle the concrete that projects outside the building to provide a fall for the water but you need to be very accurate.