Rough openings for Windows in Timbers...

I am designing a Garage/Workshop/Barn Frame and want to set windows directly into timber openings. (No panels $$$) Is there a preferred method or material to put between the timber and the window frame to accomodate twist, shrinkage, etc?

Thanks,
Mike Beganyi

Unfortunately, I have no experience on this one. Try Rudy Christian under the "Old Timberframe" heading. I expect Rudy can help you.