Damp smell near front door.

[Andrew]

I live in a 1976-built semi with halls adjacent and a small porch at the front, also semi-detached with neighbour. The inner front door frame is the original Boulton and Paul 33inch software frame with hardwood cill.

The cill sits on a strip of bitumen dpc and there is a vertical dpc each side that folds inside the cavity. All fairly standard. The front garden slopes gently towards the house and is sandy soil.

10 years ago I dug out the ground floor screed and applied another 1000 guage dpc ontop of the slab, with 3x2 battens screwed into the slab with concrete screws and each hole given a squirt of oil-based mastic before inserting the screw. In between the battens is 70mm Quinn Therm PIR and wickes 18mm hardwood flooring on top.

The area butting up to the front door was tricky, the original screed overlapped the inner leaf and the cavity which had no special dpc, just a couple of cement bags scrunched up !. I had to extend my

2ndary dpc up to the door frame after clearing out the cavity which was noticibly damp at the time, so I pushed some celotex down as far as I could and tried to seal the 2ndary dpc to the cill of the door frame, as this diagram shows

DD <- door frame cill == <- bitumen dpc under cill |xx <- top row of outer leaf ===|xx <- 2ndary dpc ontop of slab extended to cill xxIxx <- I= celotex inside cavity below door and floor level. xxIxx

Today I was trying to finish it off, because the section around the hall/lounge doorway did not meet at the same level and there is a distinct smell of damp immediately next to the outer door cill. This will be the damp I noticed when I cleaned out the cavity immediately inside the front door, so my attempt to seal the 2ndary dpc hasn't worked. The area at each end of the cill is tricky to seal properly. Spiders are getting in so that means water vapour molecules can also rise up from inside the cavity into the area immediately inside the door.

What next ?. Would expanding foam, filling the cavity in place of the scraps of celotex that I pushed down there make an effective dpc ?.

The wickes 18mm hardwood flooring was glued to make planks 240mm wide by 2400 mm long and are fixed with ordinary spax countersunk wood screws through the tongue so taking up the section immdiately inside the front door is easy, albeit laborious (amazing how much dust and fluff accumulates after 10 years).

Andrew