Damp on concrete floor

ST1991

Hi!
I am currently redecorating a room downstairs and there is a patch of concrete floor which appears to have some damp. It's not a part which is against an external wall. The house is approx 300/400 years old so the entire downstairs is concrete.

Is there anything i can seal this with, which is easy to buy from b&q or the likes?
it's a small spot. I painted it with some ronseal damp-paint, and it has made that bubble.

I will be laying floor, and putting down a DPM beneath the new flooring (underlay with aluminium foil on the back) - would that also work there? i'd prefer to treat it, rather than just cover it...

JimmyChanga

You can't treat it as such because the water has to come out somewhere. You have to treat the reason it's getting there. Are there any pipes that are buried in the concrete?

ST1991

Thanks for the reply. I don't think there are any pipes buried at all - as far as i know the floor is pretty old, and it'd in a very small patch (maybe 10x10cm?)

There are no radiators on that side of the room (or that side of the house, actually) and the central heating pipes are not channelled into the walls, they run along walls/through the walls in a short horizontal way, and then under floorboards above.

Unless it's not an issue just to ensure appropriate underlay is used before laminate goes down...?

FreeBear

ST1991 wrote: »

The house is approx 300/400 years old so the entire downstairs is concrete.

Are you sure the floor is concrete ?
Chip a little off and pop the crumbs in a jam jar. Add a bit of white vinegar - If it fizzes, it will be a limecrete not concrete.

ST1991

hmmm.. good point...
I had assumed concrete as that's exactly what it looks like...

I'll have a look when i get home - would that make a difference to treating/covering it?

When i pulled up the carpet (and grippers....) the nails from the grippers took chunks out of the concrete so i could easily test it.

FreeBear

ST1991 wrote: »

I had assumed concrete as that's exactly what it looks like...

I'll have a look when i get home - would that make a difference to treating/covering it?

It does make a difference. Concrete is pretty impervious to moisture (bad for a property that has solid brick/stone walls). Limecrete allows moisture to permeate through, helping to keep walls dry. If you slap a waterproof layer on top (foam, DPM, bitumen, etc), the moisture has nowhere to go and promotes mold growth under the floor covering and up the walls.

A limecrete floor should ideally be covered with cork (without any glue) and/or wool underlay and topped off with a hessian backed carpet. Simple rugs work well too.

ST1991

Thanks for taking the time to reply - that makes sense!

I'm not keen on carpet/rugs tbh which is why i was planning on laying laminate (which i've already bought... )

I'll test the flooring when i get home. It wouldn't surprise me if it 'is' concrete... as the whole house is also rendered in something not-300yearold-friendly - but it's a terrace of 4 and that's another matter i think...!
(I had no idea how old the house was when i bought it, as she said '1990's'. The old owner popped over a few months after completion asking if we'd like the old deeds and low and behold.... a huge pack of A2, handwritten deeds later... we realised it's not 1990...