Double up joist

[trevorbayliss]

when fitting roof windows do you bolt together the rafters doubled up or just use long screws?

 

[John D v2.0]

They just screwed ours, don't know if that's right but it hasn't collapsed!

 

[bobasd]

its the doubling up that counts most.
the trimming rafters on either side and the trimmers top and bottom of the window should be doubled for best practice.

 

[bobsuerita]

depends on size of velux 550 do not need even with 400cc
remember they are roughly the same weight in tiles only normally need doubles if carrying more than one rafter

 

[trevorbayliss]

These are the fixed roof lights about 1000 x 1000. Approx 60kg. Will be doubling up. Just thought i might bolt rather than screw as have a few bolts left over. The extra time is not an issue for me.

 

[bobsuerita]

bolts or structural screws are fine

 

[^woody^]

Strictly, as with any structural timber beam they should be bolted as have a timber spur connector between the joists, and this provides true load sharing performance .

But for a Velux, large 6mm screws, or better still coach screws would be OK every 400mm or so.