draughty floor - seal it up

[Carrerahill]

Hi All,

 

I have a cupboard on the ground floor of my house, house is a suspended floor which has 50mm EPS between all the joists which helps but it was a bit draughty, not an issue in 90% of the ground floor now as all rooms and hall I laid rolls of underlay all taped and up the walls at the skirting which I then laid a 22mm engineered floor over with glued joints, the kitchen has 9mm ply, screed and tiles so the house is pretty airtight on on the ground floor. Good ventilation exists under the house from the original brick vents.

 

The last remaining draughty area is the cupboard under the stairs, this is no longer a cupboard but rather 2 large drawers and a cupboard as I built a custom storage system into the space. I clearly wasn't thinking it all through because at the time with it wide open and easy access I should have laid ply to seal it all up but rather left it bare boards, the issue now is that with the storage system framework installed it would be difficult/impossible to lay in sheet material, since the drawer and door fronts have gone on last week I have realised just how draughty this cupboard is and the drawers and cupboard and always freezing.

 

Now the frame for the storage system means I have effectively tanked this area and it got me thinking. Do I simply mix up a sand/cement screed and pour it in to a thickness of 10mm to act as a one piece seal? If I did this should I put some DPM so the moisture from the screed doesn't soak the timber too much. 

 

I know it would not be recommended method for a floor, but it will never be trafficked. I did contemplate resin but could not cope with the idea of stinking fumes for weeks on end and the constant off-gassing.

 

For the record it would not be easy to seal from the underside of the floor because there are intact dwarf walls to 40% of the underside of this cupboard which would mean breaking through to get access - not keen on that and secondly because joists sit on this wall it would mean loads of custom cuts to make up some sort of sealing system.

 

Thoughts please ladies and gents.

Edited February 26, 2018 by Carrerahill

[dpmiller]

papier mache was the old way of dealing with this kinda thing?