Blinding sand in concrete slab

[colinh]

I'm about to lay a concrete floor in an old barn. I've had it specified by an architect and he has specified 150mm hardcore, 50mm sand blinding, 1200 gauge polythene, one layer A142 mesh, 150mm RC30 concrete

Having dug out the barn and layed the hardcore I would prefer the finished floor level to be a bit lower (measure twice!!).

What is the sand for and could I leave it out.

Cheers
Colin

[Mikey_C]

others who in the trade may correct me the purpose of the sand is to level the hardcore perfectly and to protect the DPM from puncture omitting it all together, I would think is acceptable, both from a technical POV and from the fact your are no longer following the architects plans. Negotiation in to a reduction to 1/2-1" might be acceptable.

[Tony McC]

Yep: Mikey has it. The sand blinding is a fine regulating layer and cushion for the Visqueen (or other approved damp proof membrane) so you can get away with 10-12mm. If you need further height reduction, you could reduce the sub-base to 100mm.