Damp proof membrane

[mwkenna]

Hi Guys

I am erecting a small ish shed/workshop/garage and I was wondering about the damp proof membrane and whether it would be OK to lay it and concrete over chippings. I have flattened them really well using a punner and I would like to avoid having to raise the level any further with sand. I am confident that I can get the DPM down and fill it with concrete without causing any tears or damage, have some really big beams I can use to work above the DPM. Building reg's aside (because I am just re-doing an old shed), are there any technical reasons why this is not acceptable?

Any insight would be appreciated.

Thanks,
Mark.

 

[tony1851]

The purists say you should put sand blinding down before the sheeting, but if you are careful in pouring the concrete, you shouldn't in practice have a problem.
Its only a shed, after all, and in anycase reasonable-quality concrete will often keep the damp down itself.

 

[theprinceofdarkness]

have you considered what happens if any rain falls on your concrete base, which is above the membrane? in the worst case, if the concrete is dished , then any rain falling on the edge will run into the centre of you nice dry shed?
Frank

 

[dalio66]

I'm new to this forum and appear to be unable to create a new topic - so I'll pop my query here and maybe someone will see it.

Situation: I'm renovating an end terraced house that is about 115 years old (9 inch brick) . The kitchen extension is made of stone, built by the occupants in about 1940.
The kitchen floor is quarry tile, laid directly on top of earth.
The floor slopes off towards the door and to the back edge of the room.
I don't want to dig up and do the floor to building regs.
I have built a stud wall around the room to hold insulation and dry line onto (Celotex 50mm).
I don't want to self level the entire room (i.e. under where kitchen units will be) - only the area to be walked on.
Up to 40mmm of self level will be required in places.
Room is about 3 x 4m in total.

So here's my plan:
Visqueen laid around 500mm perimeter of room and to go up stone wall about 1 meter. (between stone and stud wall)
Visqueen is trapped to stone by 2x1 roofing batten screwed down.
The roofing batten serves to: Trap the visqueen to the floor and to create a barrier to self level up to. The batten basically marks out where the kitchen units will be and I am now only self levelling the area of floor the will be walked on.

The following will only be applied to the floor up to the point where the battens are trapping the visqueen to the tiles (by screws)
Roller on acrylic self leveller. (to cover contaminates and provide a "seal" rather then to actually level.
Prime quarry tiles with P131.
Lay Screedmaster one coat DPM. A thick coating.
Prime over DPM with P131.
Complete self level with level flex (water based) self level compound.
Lay 3mm Acoustic foam underlay (screw fix)
Lay 10mm laminate.

The cavity between the stud and the stone wall will be vented by the way.

Any thoughts on my radical plan?