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Attic Truss with Raised Heel

Attic Truss with Raised Heel

(OP)
I've been looking at a number of garage designs recently that employ an attic or storage truss. I'm finding that a lot of them tend to use raised heels to allow for more head room while having a lower roof pitch (ie. 6/12 - 8/12). I've been thinking about adding in raised heels for the attic truss type in the plugin I've been working on.

A quick mock up would look something like this:



View model here:

https://3dwarehouse.sketchup.com/model.html?id=u20...

Ignore the unbalance in the panel lengths, in practice and in the plugin they will be properly balanced.

What I do have a question on is the use of a top chord splice as shown in the above image so that the overhangs do not have to be as deep as the top chord in the non-triangulated region of the truss. I have never seen a splice used on a attic truss with a raised heel, I don't see why it can't be done but it is always nice to have a confirmation that someone else is doing this sort of thing in practice.

A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com

RE: Attic Truss with Raised Heel

I've seen top chord sizes reduced, as shown in your example. Although I'd say it isn't done frequently. Attic trusses tend to be fairly short spans, so the top chords are one piece.

I do have a suggestion. The small kingpost right under the peak does absolutely nothing. If the collar tie is less than 10' long (which is rarely the case) it's totally unnecessary.

RE: Attic Truss with Raised Heel

In my (limited) experience, I would say that the main advantage for raised hell is that it allows of the top chord to have more depth over the "non-triagulated" zone. That is to say, the weak link is likely to be that section of the top coord that is above the attic space and not having the triangulation effect. I would expect that it will need to be larger (deeper) than a 2x10 and so, having depth available there is helpful.

Common spans for garage attic trusses (where I usually see them in use) would be 24 or 26 feet with 12 feet of attic width. Your example sketch looks like it might be a bit longer than that so I really expect the top chord demand to be significant.

I don't see a big problem with the top chord splice but for that purpose, maybe simply scabbing a tail onto the side of the truss would be adequate.

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