Can scrim & skim make these junctions airtight?

[WWilts]

New build in progress.

 

With cold roof space. Includes central attic space in hipped roof.

Pics of first (top) floor wall ceiling junctions, plasterboard. Pics of worst gaps. No poly membrane above.

Old school plasterer, with a reputation for quality skim. Never used tapes, very suspicious/resistant.

Can scrim & skim make such gaps airtight? 

 

PS  Not looking for advice on what should have been done earlier, just trying to make the best of it moving forward.

Edited June 10, 2022 by WWilts

[Russell griffiths]

How airtight do you want it. 

You have trickle vents in windows and an extractor fan in the wall. 

Just scrim the joint and plaster it. 

Nothing else needed here. 

[nod]

They need filling before they are taped 

[WWilts]

4 hours ago, Russell griffiths said:

How airtight do you want it. 

You have trickle vents in windows and an extractor fan in the wall. 

Just scrim the joint and plaster it. 

Nothing else needed here. 

Closable trickle vents
Heat exchange extractor fan

[nod]

Anything more than three mil needs filling prior to skim

Or it will crack through