The Forestry Forum

I'm building a 26 by 42 frame, four bents, three frames with a 10:12 roof pitch and principle rafters. The wall plate is above the tie, about three feet. I started to worry about wall spread and came up with five ways to help prevent it. I'm using four. The TFG green book had an article by Ed Levin on using struts or in the French Jambe the Force. So I decided that the strut would work for me as one of the ways to prevent wall spread.

Below are the steps I used to build the struts but I'm wondering if there is a better method that someone knows about. I haven't seen struts in any of the books I have or read.

The strut at first to me just looked like a brace, but not going between the bottom of the cross tie and post, instead running between the top of the cross tie and the botton of the collar ties used in each bent as Ed Levin diagramed in the green book.

But Ed didn't show the details....   Ah, the details, framing is based on; the details. I soon came to realized a strut is different from a brace in that the bearing surface at the one end is not on the same side of the strut as the bearing surface at the other end! At the bottom end of the strut where it fits into the cross tie, the bearing surface is on the outside ,toward the post and plate. At the top end where the strut fits into the collar tie the bearing surface is toward the inside of the buiding, much like a brace going into the bottom of a cross tie.

As I don't have a CAD computer program I started making big drawings to determine just how long my struts had to be and the angle of cuts for the tenons and bearing surfaces and mortice housing. I finally decide to test fit the entire bent as I finished it and build the left and right hand struts last based on the measured distance between cross tie and collar tie. The cross tie and posts are braced together but I had to make a couple of short "plates" so that the principle rafters would have a place to go.

After a couple of false starts I finally decide to measure the struts based on the distance from bearing surface of the cross tie mortice to bearing surface of the collar tie mortice. It's kind of a diagonal distance and I used similar steps that Jim Rogers talked about for brace layout. The distance is very sensitive to how well all the other joints fit together. I started using a couple of come alongs to pull the rafters/collar tie down on the plates just to get everything tight. Along the way I've made one pair of struts three times - wrong angle and a little off on the length. Did not peg the post and tie together at first so things moved on me. The short ones I plan to turn into braces as I'm using the same size wood for braces. Now I drill and peg everything before I measure.

I did a google search on jambe de force and got a hit. It had some  pretty interesting pictures but no how to info. Anyhow, is anyone familiar with building struts?

What page or story in the green book are you referring to?

It's Frame Engineering starting on page 54. Figure 19 on page 58 is what I've made. I have two internal short posts whereas Ed shows one in this figure.

Here are a couple of pictures of the bent and a little better view of the strut (looking from the rafter peak side) (https://forestryforum.com/gallery/albums/userpics/16609/BENT_A.jpg) (https://forestryforum.com/gallery/albums/userpics/16609/Strut_Close-up.jpg)