Roof window collars

[cdbe]

I'm fitting 2 keylite CP08T roof windows in my new extension. I'm not finding the instructions particularly great and they show pictures of felt collars and (separately on the keylite website, vapour collars) which I don't have.

Do I need either or both?

It's 40 degree pitch, vaulted, roofshield membrane, Marley modern tiles, DTRF flashings.

I saw one you tube video where a commentator said he cuts out roof membrane to form a collar - is this possible as it would help in the current situation?

And one other question, the windows are 1140mm wide, how is the window support batten supposed to span this if it's located above the trimmer?

Thanks for any assistance.

 

[noseall]

Do I need either or both?

Not necessarily no. A lot will depend upon how robustly you complete the whole roof build (including insualtion, venting, VCL and plasterboard fitting) and how well you understand the relationship between the tiles, felt and how best to mitigate any water ingress that is interrupted by the roof window.

And one other question, the windows are 1140mm wide, how is the window support batten supposed to span this if it's located above the trimmer?

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The lugs on the window fall upon the support batten at the same point as the (doubled up) rafter beneath.

 

[cdbe]

Thanks noseall, I'm not 100% on the top side so I've order the felt collars as keylite is still operating, I'm more confident with the vapour control side so I'll leave that for now.

Regarding the batten, it's this that's got me confused:

Unless this is just for illustrative purposes it shows the tile batten and the window support batten above the trimmer - to allow for the splay?

Thanks.

 

[catlad]

I splay the trimmers when I have this issue.

 

[cdbe]

I did wonder if that's acceptable, otherwise I thought a triangle support fixed to the trimmer would be ok:

I think I need to get one of the frames up there next to see how everything fits.

 

[noseall]

Set up your roof window and support battens, temporarily drop your widow in place, then go below and have a slice of plasterboard handy. Place the strip of plasterboard (9.5mm works best for the narrow groove) into the dedicated slot and fathom a way of fitting the trimmers to best suit the light ingress angles they suggest.

You cant always achieve the angles they suggest, but one strives to.