Skillion roof calculations

Skillion roof calculations.
Model drawn in Sketchup free

[@Darrenholmes]

Is it best to have the highest side of the wall facing the prevailing wind or have the lower side facing the prevailing wing? Just thinking of the angle of the roof and how the prevailing wind passes over it with uplift. Cheers

[@mattthechippietrainer]

If the sizing and connections of the members is correct then it wouldn’t matter. I would say however that having the low side towards the wind would produce less uplift force.

[@markfletcher4964]

I believe the heel of both birds mouth should be on the outside edge of each top plate. That will prevent the walls from being forced outward.

[@rm4305]

Exactly what I was looking for , thanks

[@acadian101]

what is the maximum span on the roof one can having using 2x10s or 2x12's at a 30 to 45 degree angle? cheers

[@mattthechippietrainer]

Allowable spans will depend on the building code in your area. Every country will have their own way of regulating that.

[@natej6671]

It depends on a number of factors. What is the species of the wood. Will the roof be subjected to high wind loads. Will the roof be subjected to snow loads. What will be the spacing between the rafters. What's the weight of the ceiling and other roofing materials. What do the local codes allow in your area. Ironically, the slope or the angle has very little effect on the maximum span.

[@andrewdarnley4608]

Is the actual length of the plumb cuts different to the span ie the plumb cuts are found by using the length of the hypotenuse rather than the span ?

[@mattthechippietrainer]

The length of the plumb cut will be determined by two measurements; the height of the timber and the plumb angle.

[@mrtrader4628]

How do size the rafter to get 17ft run?

[@mattthechippietrainer]

In Australia we have strict span tables to abide by or an engineer can size building elements. You will have to refer to the building authorities in your area.

[@arturoramos9509]

Thanks. This helps me a lot.