Question on Insulating Suspended Floors

SachaJ

Been reading about insulation of suspended floors and I have a question.

We're doing a refurb of a 1950's house that has around a 2 foot drop under the floors. I've had to rip up part of these floors as there's damp around the bay window which we have to fix. I also notice woodworm in places so I'm considering ripping up all the downstairs floors to treat the joists.

While I'm at it I might put some insulation in. The general consensus is the following:

1. Tack chicken wire beneath all the joists
2. Fill with fibreglass or rockwool insulation around 5mm thicker than the joists
3. Lay a waterproof membrane over the insulation and joists
4. Lay plywood (12mm to 18mm thickness) over the membrane
5. Put new floors down

(Putting in concrete floors is not really an option due to very limited budget)

My main question: when laying the plywood, do you screw it down to the joists? If so, does that not break the waterproof seal?

Another question while I'm at it..... Is there any value in ripping up the upstairs floorboards and insulating between the ground and first floor?

BryanF

SachaJ wrote: »

1. My main question: when laying the plywood, do you screw it down to the joists?
2. If so, does that not break the waterproof seal?
3. Is there any value in ripping up the upstairs floorboards and insulating between the ground and first floor?

1. yes
2. its not a 'water proof' layer your after, its a 'Vapour barrier' (essentially a fancy sheet of plastic, taped and sealed at all junctions and to the perimeter walls) - this reduces the risk of water vapour entering the floor timbers BUT even better than that it stops drafts entering your house! do note that its essential that the external wall vents remain active to the under floor space. to answer your question, the ply screws are OK to break the vapour barrier
3. no