Concrete slab -- 1930s semi -- damp proof practice

[rlx]

Hi all,

building an extension and moving the kitchen has allowed me to add the space of the old kitchen to the living room and increase the floor area.

Pulling up the vinyl tiles in the kitchen (which had been there since the 60s I reckon) showed the concrete slab beneath. Not sure if this is the full thickness of the slab visible from outside (about 30 - 45 cm) or not.
The slab is covered with some BLACK STUFF which is now coming off. Am I right in thinking that that was how they damp-proofed in these days? Laying the slab and painting it with bitumen or something on top? The reason I suspect this is that when the interior wall (non-load bearing, but made of brick) came down the bricks were sitting on a bed of slate (just like the damp proof in the outside walls).

How do I deal with this? There is a very very faint smell of damp, but no visible dampness, so I suspect that it could be a problem at some stage.

Can I just paint the whole thing with a bitumen-based sealer and lay carpet?

Or what...?

[ultimatehandyman]

How thick is the black stuff?

Is it thin like it has been painted on or is it thick like 10mm or so?

If it is thick it is probably asphalt, which is poured on hot from buckets and then flattened and allowed to cool.

If it is thin itis most likely bitumen paint.

[rlx]

Hi,

it is thin like paint and most of it has come off with the tile adhesive...

Should I just paint it with some W*ckes liquid damp-proofer or is there something better?

[ultimatehandyman]

Hi,

it is thin like paint and most of it has come off with the tile adhesive...

Should I just paint it with some W*ckes liquid damp-proofer or is there something better?

If it was me I'd get it asphalted.

Or you could at least get a price for having it asphalted and if it is too expensive you could go for the other option of painting it with the liquid damp proofer.

[rlx]

Asphalting might be a problem since it will raise the floor level. I was hoping to carpet the whole old kitchen living room in one piece without a step.

If I use the liquid damp-proof is there anything to be done before laying carpet?

[ultimatehandyman]

Asphalting might be a problem since it will raise the floor level. I was hoping to carpet the whole old kitchen living room in one piece without a step.

If I use the liquid damp-proof is there anything to be done before laying carpet?

Best check with the people supplying the carpet and see what underlay and anything else they suggest.

The last thing you want to do is fit a carpet and then have it shrink a few days later

[izalarfin]

I'd line it with building paper or something like that so your carpet don't stick to it.