Rafter spacing and valleys

[Digmixfill]

I have three gables in my roof, and ridges run from them to a pair of valleys. I'm playing around with rafter spacing to see what fits. If I try a centre spacing of around 592mm and space off from the gable rafters toward the valley junction, I can get equidistant spacing, but the valley jacks are irregular. If I start from the valley junction and space outward from it, I get regular valley jacks but have additional gable rafters at the ends.

 

Any thoughts/preferences?

 

In the images grey = internal block, yellow = PIR, pink = ridge beams, blue = valley rafters and green is cut rafter. Gable outer walls and internal dividing walls are 9 inches thick, and corbelled eaves extend around 12.5 inches.

 

 

 

 

[JohnMo]

Bottom one looks the prettiest.

 

But not really the point, your roof needs to be designed for wind loads etc. You structural engineer may decide 592mm is too far apart.

[dpmiller]

Will there not be gable ladders anyway? Surely you can loose the difference there...

[Digmixfill]

10 hours ago, JohnMo said:

Bottom one looks the prettiest.

 

But not really the point, your roof needs to be designed for wind loads etc. You structural engineer may decide 592mm is too far apart.

 

I'm working with timber span tables and using the ".75 but not more than 1kN/m2" column. 600mm spacings are acceptable for the span I have using 44x145 C24.

 

I can get 453mm to work with equidistant spacing, but I still have the irregular valley jacks.

 

10 hours ago, dpmiller said:

Will there not be gable ladders anyway? Surely you can loose the difference there...

 

We don't have any gable ladders. Just a lump of tile as undercloak and a wet verge. I'm thinking of using a kytun verge when it all goes back on, but with the same 50mm overhang.