HI,

I'm new to the forum and am planning my first structure to be built this summer.

It will be a small (16x20) barn with no interior finish or insulation, clapboard siding, metal roof. Likely three bents if I can get a crane in there or find enough muscle.

I've been studying Steve Chappell's "A Timber Framer's Workshop". There's a lot of information in there but he doesn't get much beyond the frame, all his designs/examples have the rafters end at the walls. I would like 12-14" eaves. I'm GUESSING that extending the roof sheathing that far with out support won't work.

Suggestions? Also, suggestions for other good basic reference materials would be appreciated.

Thank,

Carl

I'd suggest a more traditional design. Jack Sobon's books feature a lot of traditional timber frame details. I especially like "Historic American Timber Joinery", which shows many examples of how to frame an overhang. It is available here from the TFG as a free download (http://www.tfguild.org/joinery/joinery.html) or in print form here as a booklet (http://tfguild.stores.yahoo.net/tifrbo.html) along with his other books.

Regards,

Creating a step lap rafter tail will give you overhang you want. As mentioned it is in the rafter joinery section of the Historic American Joinery series.

Or you could just add a sprocket, shown in the same section.

Thanks for the references, there're a big help.

Thought I should mention why I hope to use bent construction. For the most part I will be alone on this project. There will be a couple weekends with a lot of help but otherwise I'll be chiseling and sawing in the Adirondack boonies by myself. My thinking is that I can get the three bents jointed and assembled on my own and then when help arrives use those "resources" to get the frame erected. Once it's up I hope to be able to do the rest on my own. Make sense??

Looks like the rafter to post joints with be either, housed birdsmouth rafter with through tail (#7 illustration), or step-lap (#10 illustration) from the Graphic Guide. The tie beam in the bents will be joined to the posts with a wedged dovetail below the rafter and intermediate plate joints.

I have no idea yet for the size or number for rafters of the 8/12 pitch roof. Besides the three rafters in the bents I'm thinking two more between each bent for a total of seven (7). I'm thinking collar ties and queen posts in the bents and just collar ties on the extra rafters. What do you think, is this overbuild/under-built?

Metal roof--I had planned on dovetailed purlins every 4 feet. I've been told metal roofs attach every 2 feet. Should I instead use a larger # of small purlins, continuous purlins in notched rafters, plywood, or planking under the metal?

That's enough questions for now, I'd appreciate any help,

Carl

I think you should stop what your doing and read several more books on Timber Framing before you cut anything do any joining. I don,t mean to sound harsh but that's what I think based on your questions. Start small with you first frame like a wood shed or a garden shed. You will then look though different eyes on your second frame.
Just my $0.02

Thane

I would use continuous top plates, skip the CG's which is how I read your post. By using the continuous top plate your rafters are independent of the post, simplifying the work and raising.

Also note/read that #7 has a tricky aspect which can be overcome by using the rafters in #9 and alluded to by Jim Rogers, I believe.

Rafter spacing on a 20' building and only 16' wide you could use 2' but I would fall on the 4' side, nice, neat and half the work. Full 1" boards and roof top guard with the metal on next. No purlins needed. That is what I am doing and commencing cutting in the morning.

If you use collar beams will you have enough head clearance on a narrow building, have you drawn it yet? Might as well use the space. How far below the eve line are you planning on placing the tie beam?

I don't see this as all that big of a frame, a nice starter to learn on. Now you have $.04 worth in debt notes, not silver or gold, btw.

Tim

Carl,

Your use of purlins on 4' centers implies that you're using principal rafters. And principal rafters and step lap rafter seats don't often work out well, because you have to take too much meat out of the plate.

Like Tim said I would stick with continuous top plates, common rafters, and nail 2x4 purlins over the rafters, metal roofing over that. I like the purlins at 20" OC because it's a little easier to crawl around the roof.

If you want to use clapboard siding, you may want to consider a Dutch frame, with smaller bents spaced closer together. That way, you don't need any studs, just claps right on the posts. Or use girts if you want vertical siding.

I have plans for a little 3 bent 16x20 if you're interested. I could send you a picture as well.

Brad

Question:

How much stiffness does a metal roof alone add to a surface? In the case of 2x4 purlins atop common rafters, will the metal roofing adequately prevent racking? Or, should some additional wind bracing be used?

I ask the question because I'm putting on a roof similar to what Brad describes. The utilitarian buildings that I've looked at with metal roofing on 2x purlins don't seem to have wind bracing, so I've assumed that the attached metal skin will stiffen it up on its own. Is this a correct assumption?

Kevin, the ordinary metal roofing is not a means to a strong diaphram. The roofing is weak in structural connection and is easily crumpled and torn. Wind bracing is required for better assurance of stability. Compare the fastening schedules for roofing and plywood decking.

Roger,

Thanks. While I understand that it is by no means a substitute for plywood, diagonal planking, etc., I was curious to what incremental amount metal roofing might bring to the structure's rigidity.