Double Girts v.s. Knee Braces?

Just a question I had about engineering/design that I posted to the 'Timber Frame Design' section of this discussion board - but thought it probably should be here as well for all the engineer types - rather than reposting it here, I thought I'd just draw your attention to it

Dear Charles,

You don't say if you have appointed a timber frame designer or if you are attempting to do this yourself. Either way its not easy or maybe even fair to compare the approaches adopted by various companies or designers regarding bracing or frame stability in isolation from other relevant factors. It is really necessary to look at the whole approach taken to building to determine what is and isn't acceptable. For example the use of SIPs will probably reduce the action of braces once they are firmly attached in position.

If you email me a sketch of what you are trying to build then I can offer you a better opinion on whether you are about to take a "wrong turn".

Check out the design section on our website at :- http://www.clik.to/WorldofWood which features a number of frame designs by me all of which are braced.

Ken Hume P.Eng.

To your question about a timberframer - the answer is: Both.

While I am studying as much as I can about designing timber frames, in order to determine what is and is not 'reasonable', we are looking at taking our initial ideas to a professional to be re-worked and 'vetted'.

I'm not sure I agree 100% with the comments about the SIPs. While I agree that they _would_ have a 'firming' effect - I'm of the 'purist' opinion that the elements of the house (masonry, frame, shell, foundation) should be independently 'complete' and not rely on one another. The frame might be able to last for 300-400 years, the paneld for only 40-50, etc. They should function independantly as well. This doesn't mean that they cannot support one another - but that support should be supplimentary, not essential.

As to the actual design - it's _very_ simple in my mind so far - a 28x42, 2 story colonial frame - no dormers, no ornamentation, and whichever roof system is simplest. Three bays, 4 bents - bents are three posts wide on the main floor, a simple king-post with struts truss design on the second. The only irregularities being the possible double-girting in place of the knee braces, and the shifting of the bent-to-bent support in the middle of the bent-frame, between the 2nd and 3rd bents 4 feet north (making a catwalk).

I have checked out your website, and the style I have in mind is most like - Large 4 bay American Aisled Threshing Barn (40 x 60 ft)