Hi all cutting a roof this week straight forward gable on extension problem is its 6.5 metres between wall plates with no supporting walls inside was going to put ceiling joists at right angles to rafters shortest span 3.5 metres putting purlins in and collar ties but do I need to have bottom of rafters braced in some way between wall plates thanks
Big span that. What depth are your ceiling joists? If you do put them at right angles I would keep them from the wall a couple of feet and run shorter joists alongside the rafters tying into the ceiling joists. Is it a possibility to run an rsj down the centre across the short span, built in with timber bolted into the web both sides, then run ceiling joists from that timber off joist hangers alongside the rafters? That way the rafters are tied into the centre and both sides of the roof,the joists are acting like a double floor with the span reduced, and with the rsj built in don't think there would be any possible spread of rafters, but then I'm no structural engineer. Fixing 11mm osb sheeting to the outside of the rafters covering the entire roof will strengthen and brace the rafters considerably too.
Even 6.5m bracing across wall plates. No weight-bearing, so not hefty depth needed, surely. Mr. HandyAndy - Really
Ceiling would sag over that span with undersized timbers unless you fixed hangers and binders to rafters, then you can't utilise the space afterwards, fella didn't mention if roofspace to be converted at later date so..... Plus, difficult to get readily available timber over 5.4m lengths these days.
Hi guys had a word with a builder about problem he said that in these situations in the past he has put the ceiling joists at right angles short span and braced across 4 off them to each rafter screwed on every joist using 100x50 says that's the way to do it suppose it makes sense the ceiling joists are 150x 50 @ 450 centres
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