Wall to cold roofspace junction crack

[WWilts]

New build in progress.

 

Cold roofspace. Plasterboard wall & ceiling. With scrim and skim at wall/ceiling junction. At stud wall/ceiling junction, a crack has appeared in the skim. 

 

Concern: crack will let air through into cold roofspace. 

In hindsight many things should have been done. But now the question is, what will reduce the risk of air leaks at the stud wall/ceiling junction?
Especially at internal stud walls that run perpendicular to timber joists. That is where the crack has appeared at junction with ceiling. Stud walls top plate fixed to roof trusses, bottom plate fixed to timber joists.

 

Considering airtightness paint (which goes black but can then be painted over with white to match the rest of the room)
Considered also plaster coving fixed with expanding foam adhesive, or Contega Solido tape (later painted over). Contega might not adhere to the powdery paint
Considering also anti-crack acrylic sealant
Or even OB1 sealant/adhesive

What would be most cost-effective? (Have Blowerproof paint, and OB1)

 

Edited November 25, 2022 by WWilts

[ProDave]

What is the build standard of the rest of the house?  i.e. standard, or all air tight membrane and service void?

 

A cold loft is the hardest thing to detail as not only cracks like this want sealing, but EVERY penetration, every light fitting, everywhere cables drop down into a stud wall etc etc.

[WWilts]

5 hours ago, ProDave said:

What is the build standard of the rest of the house?

Fair bit of attention to detail, incl tonytray for first floor void (joist space), airtight taping around all door/window frames, cables & pipes care to not penetrate Celcon (airtight) blocks, sealed first floor pendant light penetrations, ducting through external walls sealed. 

Weaknesses: ground floor to plasterboard wall junction, not taped. Used expanding foam to reduce permeability
first floor ceiling to roofspace: some PIR inserted later but no airtightness sealing so far. Electrician swears the PIRs don't let air through. Not convinced. Will need to think of a way to seal the perimeter of the round ceiling PIRs that jut up into roof space.

What solution for cracks in first floor ceiling though? And potential cracks?
Frontrunner emerged: Acryrub SWS (Soudal window system). Advantage over airtight paint is the white colour. For all studwall/ceiling junctions


 

[Radian]

16 hours ago, WWilts said:

Stud walls top plate fixed to roof trusses

Access from above?

[WWilts]

18 minutes ago, Radian said:

Access from above?

Only for some. Mostly 400mm loft insulation roll covering everything.

Edited November 26, 2022 by WWilts

[Radian]

10 minutes ago, WWilts said:

Only for some. Mostly 400mm loft insulation roll covering everything.

Just wondering if you could get at it from above and lay-in some Illbruck FM330 along the joint between ceiling and top plate?

[WWilts]

4 hours ago, Radian said:

lay-in some Illbruck FM330 along the joint between ceiling and top plate?

Good idea but not enough access. Will probably try "caulking" the wall/ceiling junction from below with Acryrub SWS

[Radian]

28 minutes ago, WWilts said:

Good idea but not enough access. Will probably try "caulking" the wall/ceiling junction from below with Acryrub SWS

I suppose if you use a profiling tool designed for caulking baths etc. you could get a neat concave bead at the junction. It would give it some decent contact area. Better than a big coving unless that fitted in with the rest of the property.

[WWilts]

Yes, that's the plan