After breaking through an old external double skin wall in to a new extension I have a problem with a damp smell coming up, usually only a day or so after a hard rain shower. I therefore think its something to do with the water table and the fact that there used to be an old external drain there. The drain and all the pipe work has all been removed (I did that myself so I know 100% its all gone). However, I can't figure out why this smell still shows itself when its damp outside. I'm guessing the soil around the drain contains contaminent or something.
Anyway, the brick opening was chopped down to DPC level and I've put floorboards on battens (on new DPC) across from new extension to meet tiles in the original house. Is there a preferred way of 'sealing' this old cavity to prevent any smells coming up? Its probably not the cavity itself since the bricks/blocks were built off the solid foundations, but it must be something, some hole or other around this area. I've used expanding foam below DPC to try to seal it up but its still coming through; my next thought it to use liquid DPM (never used it) to try to seal up the bad smells.
Any other ideas? I'm hoping that once the plasterboard is on and skimmed/painted it might help, but I'd rather solve this now so I don't have to rip down the plasterwork afterwards to solve it.
Anyway, the brick opening was chopped down to DPC level and I've put floorboards on battens (on new DPC) across from new extension to meet tiles in the original house. Is there a preferred way of 'sealing' this old cavity to prevent any smells coming up? Its probably not the cavity itself since the bricks/blocks were built off the solid foundations, but it must be something, some hole or other around this area. I've used expanding foam below DPC to try to seal it up but its still coming through; my next thought it to use liquid DPM (never used it) to try to seal up the bad smells.
Any other ideas? I'm hoping that once the plasterboard is on and skimmed/painted it might help, but I'd rather solve this now so I don't have to rip down the plasterwork afterwards to solve it.
