I am renovating a lower ground floor flat from ~1870. It has a solid concrete floor which has been partially dug up to lay new pipework for the plumbing. This has now been filled with concrete, and I intend to somehow level the floor. I ideally want to minimise moisture being directed towards the wall. Should I bother treating the floor as porous at the moment? And if so, what would be levelling compound which could maintain permeability?
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Itchinfilth
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In my experience of concrete floors, moisture was trapped underneath and travelled to the walls causing issues. I believe it may be porous to some degree but not very. As it already had a concrete floor, is there any signs of issues with walls at the moment?
The key question is whether you have a plastic DPM under the concrete?
If not it will probably be fine, it’s not as bad as everyone makes out. Polished it can look good…
Even with DPM, it may not be terrible.
Do you have damp issues?
We had a previous concrete slab laid on plastic, but it was on such dry ground it caused no damp issues at all.
If not it will probably be fine, it’s not as bad as everyone makes out. Polished it can look good…
Even with DPM, it may not be terrible.
Do you have damp issues?
We had a previous concrete slab laid on plastic, but it was on such dry ground it caused no damp issues at all.
No DPM, just earth. With regards to existing damp, I could only see some evidence on exterior facing walls, but likely due to gypsum plaster being used.
I was thinking of laying down newton 601 slimline membrane with fold ups at the edge to allow the floor to breathe. Do you think there is any point, or should I just put down liquid membrane?
I was thinking of laying down newton 601 slimline membrane with fold ups at the edge to allow the floor to breathe. Do you think there is any point, or should I just put down liquid membrane?
stuart45
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If the floors are dry and it's the walls that contains a bit of damp, I wouldn't bother with a DPM.
Cubist
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The suggestion that concrete is impermeable to water is an old wives tale. It can and will absorb water from any available source. If there is no DPM beneath the slab that water will ultimately migrate toward its surface. Any water in the ground beneath the DPM material will migrate to arrear at the DPM edges and continue its transfer into any surrounding materials. Applying a surface coating that is less permeable than the concrete itself will overtime, result in water migration into the walls - always assuming its doesn't break up the less permeable surface coating material or perhaps delaminate it from the concrete.
It's best, frankly, to leave well enough alone other than perhaps to improve ventilation to in turn accelerate water transfer to atmosphere.
It's best, frankly, to leave well enough alone other than perhaps to improve ventilation to in turn accelerate water transfer to atmosphere.
Cubist
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By the way; what plumbing has been buried in the new concrete?
If you’re fortunate enough to have no membrane, do not do the wrong thing and introduce one. Newton products are the devils work.
Treat your concrete floor as a porous one, allow it to manage moisture from its surface and it won’t track up the walls.
Treat your concrete floor as a porous one, allow it to manage moisture from its surface and it won’t track up the walls.
If you install Laminate, you’ll quite possibly create yourself a damp problem on your perimeter walls. It’s unlikely a sensible plan.
Put a plastic bag on the floor with something heavy on top, leave it there a night or two and see how moist it is in that area when you remove it. That will give you a feel for how much moisture is being evaporated through the existing slab, and to understand what will happen if you effectively apply that plastic bag to the entire floor area.
Put a plastic bag on the floor with something heavy on top, leave it there a night or two and see how moist it is in that area when you remove it. That will give you a feel for how much moisture is being evaporated through the existing slab, and to understand what will happen if you effectively apply that plastic bag to the entire floor area.