Insulating subfloor

[geraldthehamster]

I need to raise the level of the floor so it meets the door threshold and need some kind of air gap underneath to keep the council happy.

You certainly need to maintain ventilation of the void under the Celotex, from the air bricks - is that what you mean?

Cheers
Richard

 

[drpepe]

I've used tape along every edge, to further hold the already wedged insulation, and also to stop drafts. I used expanding foam around the walls, and screws or battens for extra support where i was concerned there might be issues.

Worked well in 2 houses.

 

[kennydies]

I am assuming that the foam around every edge of the PIR is a lot more air tight than friction fit?

 

[theprinceofdarkness]

The foam I have used is remarkably floppy until it goes off. poking the tube into any sort of hole will result in a great deal of foam falling straight down, which in your case is wasted. I would fill all gaps with rolled up newspaper tamped down to give a 3" gap over the top of it.
Battens are good, seals the gap and provide decent temporary support and in the longer term stops the whole foam bit dropping out as foam shrinks over time.
Frank

 

[geraldthehamster]

I am assuming that the foam around every edge of the PIR is a lot more air tight than friction fit?

It is. And with careful application the foam will grab the sides of the narrow gaps and won't fall through.

Cheers
Richard