Garage and DPM

[BoltonSte]

I've currently got a block garage on a slab that leaks like a sieve through the walls (think they used thermolite). There's a 4' wide path down the side of it.

The current plan, is to drop the garage and extend it to the full width (claiming the path), I'd have to build a base to lay a second slab, but I want to raise the floor height over the whole garage so it would end up with a single floor.

But where do I put the DPM?

1) Do I build the new slab, DPM the total floor then concrete to raise the floor
2) Do I DPM the current floor then down under the new slab (but wouldn't that be too low to have any effect)
3) Do I lay the new slab, then DPM the total floor whilst the new slab is wet and pour the common floor on top?

I was intending to get the concrete delivered and poured, to save time/effort and make sure it's mixed correctly, but doing it myself may be possible.

Ste

[Owenski]

Normally speaking you wouldn't Dpm a garage floor as it's class as an un-inhabitable building. However if your reconstructing from the ground up then a Dpm is possible a good idea (I used one doing mine).
If your problem is seapage due to the floor level of your garage been below that of the adjacent land then your looking to 'tank' the construction and a Dpm isn't the only/best way of doing this.
If the floor level is to be above the ground level outside then typically you bring the Dpm in through the block coursing at 150mm above ground level, you then take it down inside a cavity then run it under the floor construction (in your case slab) and mirror it on the adjacent wall.

The depth of Dpm is irrelevant in relation to the floor construction as once the barrier is there it's function is performed regardless, provided obviously either end of the Dpm finishes above ground.

If your floor level is below ground and you need to tank it then it's prob best you pm me and I can explain it all better.