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I'm adding a roof to a derelict (but strong) old shed.

The image below shows the simple plan. 152x38mm rafters, upon which there will be 76x50mm purlins at 1,000mm spacing. IBR roof sheets will be fixed to the purlins.

Plan showing roof timber construction

What I'm wondering is:

  1. Do I need to have wall plates on the load bearing walls? (so long as each rafter is fixed by a wall tie)
  2. What is the best (rudimentary) way to connect the rafters together at the apex? Circled in the image below. I'm hoping to avoid nail plates because of my remote location and their unavailability.

Shed showing rafters resting on apex wall

  1. What prevents the rafters falling over before the brick fill between them is added?
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    I presume from the apparent rafter spacing that you're in an area where snow load is unlikely or unknown? Ah, Zimbabwe! Snow load seems unlikely to be a concern....
    – Ecnerwal
    Commented Oct 3, 2023 at 12:45
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    Zimbabwe may have limited snow, but the possibility of uplift due to wind ought to be considered. Tie downs are the solution. Note that the uprights on the open (left, as shown) side need to be tied down at the bottom end as well as the top.
    – HABO
    Commented Oct 3, 2023 at 15:14
  • Observant people! :D Impressed. Indeed, we do not get snow here but strong wind and torrential rain are common. I'd use galvanized wall ties (hoop irons) on the rafters at apex, each under 2-3 brick courses and skewnails at the opposite end on the open side. Hurricane brackets/clips would be ideal but availability is a problem.
    – Jimbo
    Commented Oct 4, 2023 at 4:52

1 Answer 1

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You can use plywood gussets attached with glue and nails or screws to join the rafter peaks. You can also use plain wood, but plywood is a bit tougher if it's not too hard to get.

I would suggest shifting the join point from where it is drawn (left rafter unsupported by wall) to the right enough that both rafters bear on half the wall at the peak.

The boards at the rafter tails, and the purlins should hold the rafters until you fill in between them.You may want some additional blocking or x-bracing between them at mid-span to prevent twisting under load, though. That would also help to hold them.

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  • Thanks! Yes, the join point of left and right rafters at apex was based on my original idea of simply lap-joining them (instead of butting with gusset). I would shift it to center of wall if using gusset. What do you think of the lap joint idea?
    – Jimbo
    Commented Oct 4, 2023 at 4:56

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