RSJ to support rafters

[garyo]

Thanks Oldun.

I'm going to have a play around with the position of my internal partition walls to see if I can absorb the RSJ into those - it may make it an easy decision to put the RSJ underneath the wall plate then.

Can I ask about the comments in your earlier post:

you can use a lay board on the right hand side where valley gutter runs up, but not on the left hand side where roofs join into one and other. on the (hopefully) same plane.. You will not get a straight run from ridge to HAP with a layboard underneath jacks.

I can't quite picture why this would be a problem. I'd set the layboard away from the existing hip by 50mm or so, so that the new fly rafters were in the same plane as the existing jack rafters going in to the hip. I can see there'd be a small gap that the battens would need to fly over (rather than trying to birdsmouth over the edge of the lay board and still finish 10mm proud of the top of the ridge plate in order to keep it in the same plane)

Is it that this will be impossible for me to measure/cut accurately? I can't picture why the measure/cut process will be that different from your suggestion 2):

2. If existing rafters deep enough, drop layboard down onto noggins between existing hip jacks and then fly jacks from this to ridge. .
To know your dead loads what tiles are on existing roof.

Thanks

Gary[/quote]

 

[theoldun]

Gary. As this will be a long post, to avoid boring everybody else sh*tless will PM to you all you want to know. Give us another couple of days as mince pies are in bad way again.
Regards oldun

 

[theoldun]

Gary,
Read your meesage box.
Regards oldun.