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Double Girts v.s. Knee Braces? #7932 07/20/01 09:30 PM
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I am currently looking at building a two-story colonial style timberframe house in the Indianapolis area. One of the 'design philosophies' that we are pursuing is that of a small, but well desinged space, meaning that we are looking to build as small a house as is still comfortable for our family and lifestyle. The challange has been interesting, as it has forced us to be creative

However - one problem we are finding is the placement of furniture, doorways, and appliances with regards to the knee braces. According to Tedd Benson's book (or one of them :> ), knee braces should be roughly 1/2 the length of the timber they are supporting. unfortunatly, with our tentative design (3 bays, 4 bents - 14 foot span on both bay and bent - two stories) the knee braces are a _significant_ problem. It's not east to place kitchen cabinets, appliances, etc. working around the knee braces.

However - we seem to have spotted a possible solution - and one we are quite excited about from a decorating point of view - as it allows us to incorporate Japanese shoji screens into the design.

We noticed in some of the work by Cascade Joinery of Wasington, that knee braces can be eliminated - at least in part of the frame - by the use of double girts. By raising the first floor from 8 feet to 10 feet, and by creating a two foot 'panel' at the top (the gap filled with the aforemention shoji screen panels), it would be possible to eliminate the knee braces, we hope.

Now - all dimension are 'wild ass guesses' from non-timberframe designers, and have not been checked with any engineering software - they are just reasonable guesses based on what we have seen.

What we're looking for right now, is some 'educated' feedback on how practical such an idea might be. Is is possible to double up _all_ the girts in this manner? With knee braces being 1/2 the length of the supported timber, it doesn't seem like simply adding a second timber will add that many b.f to the design (apart from the girt-to-girt supports).

It is a strategy that doesn't seem to be used much, and we're wondering if there is a _reason_ for this? A reason apart from the fact that the resulting frame has a definate non-traditional look that is.

Feedback anyone?

Are there any local (Indianapolis-to-Bloomington) timber frame companies out there that have done any design like this?

Thanks for your attention

Re: Double Girts v.s. Knee Braces? #7933 07/21/01 11:34 AM
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Can you tell me where, and in which book of Tedd Benson is the reference to making knee braces 1/2 length of timbers they are supporting? In a book of his that I have, I can't find any reference to this. I'm concerned with this, also. Thanks, Jim

Re: Double Girts v.s. Knee Braces? #7934 07/21/01 06:02 PM
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Ok - now I'm doing this by memory as I have loaned out that copy of that book - but I THINK it's on page 39 of "Timber Frame-Home : Design, Construction, Finishing" (not 'Timberframe : The Art and Craft of the Post-And-Beam Home' which is basically a photo-essay of the beauty of timber frames)

In any case, it's easily located in the index - you have to hunt around on the page for it - but he mentions the 1/2 figure.

He also notes, much to my amusement, that since the engineering fomulae for knee-braces really don't exist, he designs his frames to be stable _without_ them, and then adds the knee braces as extra contingency stability.

Which I found to be encouraging, as it meant there might be a way to elimate the suckers after all!

Also - if you check out the website for Cascade Joinery, you'll see a lot of double girts in their photos and a lack of knee braces around those trusses.

STILL - if there are any knowledable designers/engineers/builders who have a comment on this matter, I'd much apprciate it.


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