Sand/Cement between DPM and DPC!?

Discussion in 'Building' started by uhf, 2 Nov 2020.

  1. uhf

    uhf

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    Location:
    Hertfordshire
    Country:
    United Kingdom
    I've just had an extension room renovated and we had damp problems on the wall.

    We've had the exterior ground lowered and drainage put in, we also found that the cavity had been filled with mortar above the DPC so we had that cleared out (was accessible as we had a set of french doors out and also a floor to ceiling window and the room isnt that large).

    We were also advised by a damp specialist to knock off 1.2m of bonding and replace with hardwall (something that others now tell me is incorrect and it should have been sand/cemented).

    Anyway, we were about to have to flooring installed and i mentioned the previous damp issue so they wanted to install a floor hygrometer which did and it read 81-86% RH which we're told is unacceptable.

    The room has a DPM under the screed which looked like it lapped into the inner DPC, however closer inspection reveals there is a sand/cement (mostly sand!) filled gap between the two which appears to run all the way around the room on 3 external walls!

    This stuff is damp to touch and I've tried excavating it to see if it goes all the way through and so far it appears to which means its dragging in moisture form below the DPC into the interior wall below the DPC and above the DPM.

    I'm assuming the screed is then just soaking this up in the odd place it touches or just brought it into the internal atmosphere which its then soaked up. 20201101_162644.jpg

    I'm assuming this is not normal or correct? It seems they went block, mortar, dpm, mortar, dpc, mortar, block from the ground.

    Edited to say: the bonding used to come all the way down to the screen with zero gap! It doesn't any more, is it possible this is just still damp from before and just hasn't dried?
     
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