I have S.E details for my ongoing loft conversion which have been approved by B.C. But the more I read into them, preparing for the next stage and so on, the more a couple of things worry me. Any S.E's out there or experienced bodies care to give me an opinion I would be grateful.
Firstly, the roof is a conventional 40 degree apex, purlins with bearers onto a central supporting wall which runs parallel below the ridge line, where the joists meet to triangulate the rafters. New steels will run under the line of the purlins to support the stud wall which supports the roof to enable removal of these bearers and so on, pretty routine stuff. However, I am wondering what will happen when the stair opening removes the triangulation between some joists. I don't want to over complicate this, but suffice it to say only one side of the roof is affected. What's to stop the roof spreading as the six or so affected joists will effectively be free standing on the central wall?
Is there sufficient 'keyed in' material along with the deck and the galvanised strapping supporting each joist from the steel running above that this is not an issue? How is it not an issue if I open up the stairway before I fit the steels, lay the floor etc? I should add that there are 50x75 collars bolted to each rafter set up at the apex, but these are for the whole run not just the area of concern.
Secondly, regarding this galvanised strapping, my S.E has specified winding around the steel, nailed into packers, continuing down onto each joist and 'wound underneath'. These are designed to carry some floor load mid-span. Now perhaps I'm being thick here and missing something, but how the hell are you supposed to nail into the underside of a joist in close proximity to the ceiling below? Would nailing into the side of the joist be sufficient? (Beams are 147x50 SC3, max span from wallplate to supporting wall 3.7m, supported under steel resulting in a max free span of 2.1m.)
My designs are getting on a bit now and I think the S.E has retired, so a quick call in the morning is no longer the obvious option, hence my request for assistance, if only to put mind at rest!
Many thanks.
Firstly, the roof is a conventional 40 degree apex, purlins with bearers onto a central supporting wall which runs parallel below the ridge line, where the joists meet to triangulate the rafters. New steels will run under the line of the purlins to support the stud wall which supports the roof to enable removal of these bearers and so on, pretty routine stuff. However, I am wondering what will happen when the stair opening removes the triangulation between some joists. I don't want to over complicate this, but suffice it to say only one side of the roof is affected. What's to stop the roof spreading as the six or so affected joists will effectively be free standing on the central wall?
Is there sufficient 'keyed in' material along with the deck and the galvanised strapping supporting each joist from the steel running above that this is not an issue? How is it not an issue if I open up the stairway before I fit the steels, lay the floor etc? I should add that there are 50x75 collars bolted to each rafter set up at the apex, but these are for the whole run not just the area of concern.
Secondly, regarding this galvanised strapping, my S.E has specified winding around the steel, nailed into packers, continuing down onto each joist and 'wound underneath'. These are designed to carry some floor load mid-span. Now perhaps I'm being thick here and missing something, but how the hell are you supposed to nail into the underside of a joist in close proximity to the ceiling below? Would nailing into the side of the joist be sufficient? (Beams are 147x50 SC3, max span from wallplate to supporting wall 3.7m, supported under steel resulting in a max free span of 2.1m.)
My designs are getting on a bit now and I think the S.E has retired, so a quick call in the morning is no longer the obvious option, hence my request for assistance, if only to put mind at rest!
Many thanks.
