insulating floor of flying spur

[gustygale]

hi all

I have a bedroom that is built over the underpass that goes to a parking area. the room is freezing cold at night. the other day i took some of the floor boards up and there is no insulation between the joists.

attached are some pictures, the one from underneath shows a crack in the flooring, what would be the recommendation to fill this gap?

what would be the best insulation to use in this case?

thanks and stay safe
Justin

[PeterW]

How long has it been built ..?? If there is nothing there in the gaps and it’s been built in the past 10 years it should have a warranty. 

 

That should have a fair amount of insulation in there - what is your budget ..??

 

The crack looks superficial - could be caused by the joists moving about as you pull the boards up. I’d tape it from above with a reinforced foil tape then get a DPM between the joists and get them fully insulated. 

[gustygale]

Hi Peter

 

Thanks for your reply. it was built in 1982. nothing in the gaps at all and in winter it is like sleeping outside!

 

Budget is whatever is needed to be honest, what would you recommend to fill the gap in the joists? do i have to worry about leaving a gap around the edges or anything? Forgive me, DPM?

[PeterW]

OK
 

DPM - Damp Proof Membrane. Will also stop any air blowing up through the boards. 
 

How deep are the joists..?? That may dictate what you use, but it sounds like anything is much better than nothing ..!

 

Got any internal photos ..??
 

 

[gustygale]

ok, so is that put on top of the insulation between the joists?

 

not 100% but i'd say 25cm deep each? what i use rockwool stuff or slabs etc?

 

no, although i could take up the flooring tomorrow if that would help? 

[PeterW]

I would try and lay the DPM between the joists and stick insulation into the DPM “valleys” as it will also keep it dry. 
 

Are you able to take the whole floor up in one go or have you got to do it in sections ..? Is it floorboards or chipboard ..?

[gustygale]

ok, so you mean lay the DPM and create like sagging between the joists and fill with insulation? yes can empty the whole room and take all floorboards up

[A_L]

I would use airtight breather membrane rather than dpm, less risk of interstitial condensation. Support it from underneath to produce a small cavity. You could then fill with loft  roll insulation. You could add polythene across the top of the insulation.