How much bow is acceptable?

[Jim_Rogers]

Ok, well maybe we should go over this again.

Bow is a deviation from a flat plane of the wide face of a piece of lumber from end to end
Crook is a deviation from a flat plane of the narrow face of a piece of lumber from end to end.

You're telling us that you have a "crook" timber. That means the narrow face is higher on the ends then in the middle if crown is down or lower on the ends if crown is up.

If you want the rafters to sit on the timber all the same then you either cut all the rafters the same and shim the ones that sit on the low spots or cut the rafters to match the crown so that they all sit at the same elevation for a flat roof.

Now, you have a bow and the middle of the beam is either further away from the ridge or closer to it, then you may have to custom cut each rafter to fit.

What I have done, in the past, to test fit all my rafters to my plates before they are up in the air is to put the plate on the foundation/floor system in the exact spot where they will be except not up in the air. Basically remove the elevation of the posts. Check that they are true and square. And then sit the rafters onto the plates to ensure that the seat cuts are right and the rafters will sit correctly when they are up in the air.
I don't know if you can do this as you are using a ridge beam as well. You'd have to "mock up" the elevation of the ridge beam in between the plates to make sure it will all go together once up.

Good luck with your project.

Jim Rogers

[oe_alex]

Thanks for the further clarification Jim. As a matter of fact, I have a little of both on them. I think the best way to go about this is to cut each one individually like you said.

Thanks