Fixing insulated plasterboard on roof.

[joncooper27]

Hi
I have a roof on a holiday let conversions am fitting insulated plasterboard to the roof which also has Velux windows. As the boards are quite heavy with 50mm Kingspan and 12.5 mm plasterboard is it recommended to use a washer so the screws don’t pull through the board something like below?
https://amzn.eu/d/eGnVwcU

I have put 100mm insulation between the rafters @ 400mm centres with 50mm gap above then I’m planning on installing roofing lats then superquilt insulation then lats the other way and 62.5 insulated plasterboard.
Does this sound okay?
Has anyone any tips or help doing this.
The Velux are the old type without the insulation, what’s the best way to insulate around them ?

 

[Sachakins]

Doing all that work, then I would think replacing the old Velux with a new insulated triple glazed unit at the same time would be of benefit.

 

[ChaiLatte]

Kingspan have a well-staffed and knowledgable technical department who would be glad to advise you if you call them.

They will also have technical literature on their website.

If you do not like speaking to the King, ring his German brother at Knauf as the fixing requirements will be common to the type of board.

The horses's mouth will give you far better information than a load of ignorant wafflers (myself included) on a forum.