Treating damp behind kitchen unit in semi-basement

[DiAiWei]

I have a kitchen unit with cupboards and drawers which is fixed to an external wall, and the kitchen is in a semi-basement, so the top of the unit is just below the pavement outside. (It’s at the end of a terrace.) Not very surprisingly there is damp behind the unit, which is causing mould in the cupboards and drawers. Either side of the unit there are tiles, and no damp or mould is evident there; behind the unit is plastered brick. I am wondering what to do about this damp problem. One possibility might be to remove the unit, hack away plaster, instal a damp-proof membrane or apply a damp-proof paint (which?), then replaster. I wonder if it might also be worth fixing with plugs going into brick a rigid sheet of something like pvc (to prevent the membrane or paint perhaps eventually being loosened by damp) before reinstating the unit; but I’m not sure how worthwhile this would be. I’m also not sure if it’s worth removing and replacing plaster rather than just applying the membrane or paint to the existing plaster. Obviously a limited treatment like this would leave damp elsewhere behind the tiles, but it’s the kitchen unit which is the urgent problem, and I’m certainly not going to remove all the tiles. Any ideas?

 

[Blagard]

Any basement condition can be a problem for dampness. However a kitchen in that situation gives rise to further problems due to the relatively high humidity you get.

I suspect that the mould is in fact a result of condensation which damp proofing is not going to solve. Mould would find it difficult to establish itself on the face of glazed tiles, with only the grout giving a surface where mould may establish itself. If the tiles are not showing any signs of falling off It suggests to me the wall behind is not actually damp.

You could consider tiling through behind the unit after removing mould affected plaster, but as noted without cleaning, mould would eventually establish itself on the grout. Your idea of a sheet of PVC might actually work.

 

[DiAiWei]

There certainly is plenty of condensation in the kitchen. But as I said, there isn't any evident mould on the tiles (nor for that matter on the grout), just where there is untiled plaster behind the kitchen unit, so I'm inclined to think there is damp coming through from under the pavement outside, which wouldn't be surprising. Should I do more than fix a pvc sheet though, eg applying damp-proof paint like Synthaprufe?