Loft roll & moisture

[WWilts]

New build in progress. Cost is a serious consideration.

 

First floor ceiling spec:
12.5mm foil backed plasterboard
150mm Crown wool tight between ceiling joists & spilling over wall plate
250mm Crown wool above ceiling joists

Low pitch hipped roof. For various reasons, masonry outer leaf about 150mm shorter than inner leaf. 75mm PIR insulation fixed externally to outer face of inner leaf. Roofshield membrane (completely air permeable) below Cambrian tiles. No eaves to ridge ventilation needed.

 

Ceiling plasterboard starting to go on.
BUT 
a) Not foil backed pb 
b) Only 150 + 150mm loft roll (Knauf loft insulation)

c) Loft roll not spilling over wall plate

 

Which of a) b) and c) is worth insisting on? Need to pick my battles wisely.

Edited May 18, 2022 by WWilts

[ProDave]

1 minute ago, WWilts said:

Ceiling plasterboard starting to go on.
BUT 
a) Not foil backed pb 
b) Only 150 + 150mm loft roll (Knauf loft insulation)

c) Loft roll not spilling over wall plate

 

Which of a) b) and c) is worth insisting on? Need to pick my battles wisely.

ALL of them.  They will all compromise the building from it's original design, and in an extreme case building control could refuse to issue a completion certificate if they are not happy.  They are all easy to correct, some at no cost (item C for instance, that is just poor workmanship)

[JohnMo]

If they are building and priced to your building spec, they have a contractual obligation to build to your drawing spec. and to a good standard.

 

The foil missing from plasterboard will allow moisture to pass through the plasterboard, where vapour could condense to water and cause issues.

 

Insulation missing will affect your long term heating costs for the worse.

 

Spilling insulation is poor workmanship.