Retrofit Concrete Floor

Martee

Hi folks, I'd be grateful for opinions on two details I'm grappling with at present.

I am looking at replacing a 1970s suspended timber ground floor with an insulated concrete slab. A complicating factor is the existence of a concrete slab on which the sleeper walls for the joists sit. I'm wondering if this would need to be removed or could it be integrated into the new build up of the floor. There is 400mm between the current floor level and the top of the existing 'slab'. From what I can see the void is bone dry. I'm reluctant to investigate the make up of the slab in case I damage an existing DPM.

The second aspect is that the existing DPC is 200mm below the internal floor level (and just 130mm above the footpath outside). There are no existing damp issues that I'm aware of. Based on the levels of the floor and the DPC, the DPM from the floor would be running up between the wall and floor construction to isolate the floor. If it was adhered to the DPC it would stop well below the floor level. If it continues up it's not adhered to the DPC. Is it essential for the DPM and DPC to have a physical bond or overlap or is it sufficient for them to be pressed together (albeit edge of DPC to flat of membrane) to manage risk of damp?

I'm not sure if that is clearly described but thoughts most welcome. Thanks.

Calahonda52

is it the wall DPC you are referring to at 200/130etc?

Martee

Hi, yes. The wall DPC is below internal floor level. I think this protects the timber joists by keeping them on the dry side of the DPC, presume this would have been a standard approach.