Damp Concrete Blocks in 3 Storey Side Extension Ask questions and find answers on a range of subjects relating to self build projects

[Tossviscount]

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Hi

I’ve built a 3 story side extension which has been recently made watertight.

The walls are double skin concrete block with cavity filled with rock wool insulation battens. Recently I’ve noticed damp blocks on the first floor wall which seem to follow the laying order... the damp blocks are quite specific in layout but I can’t work out why they are damp... I’m assuming that if there was water ingress there would not be a defined pattern - which I am seeing. Does anyone have any ideas on this...can batches of blocks have a composition that can draw moisture from the air and exhibit this type of localised damp?

Any help would be most welcome

Thanks