Is plasterer taking the piss???

[Sam9769]

We have hired a plasterer to insulate our kitchen ceiling with celotex and board and plaster it. He installed sheets of celotex but didn't tape up any seams or apply an expanding foam to the gaps and is proceeding to board it?
Is he taking the piss and cutting corners?
It seems to me that what he is doing is a waste of time if he isn't going to fill the gaps as the insulation won't be effective.

Can you tell me what you think please?

I thought you weren’t supposed to use expanding foam any more? When we bought our house last year there was a big thing in the news about how expanding foam made houses unmortgageable? I think it was something to do with a fire risk? I’m not sure if anything has been brought out to replace it yet. Can you not ask him about it?

If he isn't inserting the insulation into frames (presumably not if it's being applied to an existing ceiling) he should have sealed the joints with insulating tape and then added a moisture barrier.

I don't know whether the moisture barrier's optional. I'm paranoid about condensation, so would never have skipped it.

How-to guides:
https://www.insulationsuperstore.co.uk/help-and-advice/project-guides/insulation/how-to-install-celotex-insulation-boards/

It's the 'spray foam' that can make a proporty unmortgageable because of the effect it has on the rafters. Celotex is a solid sheet of insulation board.

OP was expecting him to fill gaps between the Celotex boards with foam. There shouldn't be any gaps in need of filling. The boards should be flush and the joints sealed with insulating tape.

“Can I just say I’m curious as to why….
it seems to me that without….
Is this the latest thinking when fitting…?”
This seems the kind of conversation you need with the plasterer before it goes too far. Take photos before it’s covered too.

We’ve never taped our sheet insulation. If you’ve cut it to fit snugly in the wall cavity you don’t need to. Once it’s in and boarded and plastered it’ll be spot on. We did our upstairs rooms with king span and they are noticeably several degrees warmer than the rooms not yet insulated.

expanding foam would be a terrible idea. You need some air movement in the cavity to prevent damp.

The OP is talking about using a small handleld can is spray foam to fill any minor gaps round the end when fitting the celitex board in the ceiling. Fairly normal practice.

What you are talking about is completely different. Coating the entire underside of the roof in the loft with a thick layer of foam. It can cause rafters to rot and makes any roof repairs very difficult. Often necessitating a complete roof replacement where normally a small repair could have been done. That is why mortgage companies don’t like it.

Is there a room above or is it a flat roof?