How do I seal this ?

[Spinny]

Looking to prepare the junction between walls and ceiling structure ready for plaster boarding.

How should I be finishing this area adjacent to the steel ?

The silver PIR insulation across the end of the steel is the top of the cavity insulation in the wall. I am thinking somehow I need to seal it so that warm air in the ceiling doesn't contact any cold air squeezing through the top of the PIR where it meets the plywood deck. Thinking I should somehow put some more insulation around the steel and the top of the inner leaf it sits on ?

(Have rockwool but that wouldn't be vapour/air tight)

[Nickfromwales]

You could use Illbruck fm330 (closed cell) foam. That's airtight and won't bridge damp / moisture, plus will help insulate the beam.

 

I think just stopping airflow through there would be suffice, so the foam should be a good option imho.

 

 

[Spinny]

Thanks Nick, looks like good stuff although not on the high street it seems. But how do you use it for ceilings though when the can has to be inverted ?

[Redbeard]

1 hour ago, Spinny said:

But how do you use it for ceilings though when the can has to be inverted ?

 

You *may* get away with using an extension tube (flexible brewer's/wine-maker' tube is what I have used. I say *may* because the extra length slows the flow and if the first 'hit' is not fast enough nothing sticks and you just end up with a foam floor. It has worked for me, and also it hasn't...