Frame is complete and I'm starting the enclosure. The plan had been to put the roof on first (OSB + I-Beam + OSB) but I'm a little concerned that it's just going to act as an enormous sail.

To paint a (hopefully) clearer picture, the frame is a primary purlin design, 4.5m wide with a ridge beam and 2 wall plates (The ridge is off centre, but that should haven't any affect - Check the link in my sig to see photos). The house is 14m and parallel to the valley making the gable ends face the normal direction of the wind (A better way might be to say that the wind if normal E-W / W-E and the gables are E + W. Spanning between the purlins are very light rafters, loosely nailed to the structure. These are non-structural and serve only to provide bearing surfaces for the I-Beams which are actually supporting the roof.

My concern is that if I fix the OSB and I-Beams in place before the walls, they'll only be attached to the light rafters and so there'll only be a few centimetres of nail resisting uplift.

I would normally just put the walls on first, but I have some assistance on site for a few days and getting 2.5m x 1.25m sheets of OSB onto the roof is going to be considerably easier with two people, at least to get everything started.

If consensus is that the walls should go up first, then we'll concentrate on that. The accumulated thickness of I-Beam, OSB and rafter will make the alternative solution of lag bolting it all down somewhat tricky.

Thanks in advance,

Jon (who's finally stopped cutting joints and now has a fighting chance of being watertight before winter!)

I have never had a problem putting on roof surfaces first. I usually attach my roof surfaces with Headlock screws aka panel fasteners. They come in lengths up to 18". It would be nice to be able to attach the roof assembly through the rafters into the timber plate. How much time will pass between the roof structure going on and the walls?

In theory, once the roof is in place, the walls will follow pretty quickly. I'd like to say 1-2 weeks... but this is a self-build and I'm often alone on site so nothing is guaranteed. Having slept on it, I'm inclined to put the walls up first. The winds have been picking up here (we've had 50mph gusts running along the valley in the last few weeks) and another week or two without a roof covering is preferable to having to recover my rafters from the neighbours property and put them all back on the roof.

Thanks for the reply.