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How to fabricate attic truss intersection

How to fabricate attic truss intersection

How to fabricate attic truss intersection

(OP)
I'm building a fairly simple shop (24x32) and planned to put in attic trusses (14' clear space). Then I thought of putting in intersecting attic trusses (i.e. perpendicular to each other) so that the clear space in the attic would be in the shape of a cross (or Tee). However, I can't figure out how to accomplish the intersection without going to floor trusses as the bottom joist of the attic truss. Intersecting the attic trusses create an unsupported joist span of 19' (Tee) or 24' (Cross). Is there a way to do this without going to "stick built"?

I also considered putting in a wide shed dormer, but run into the same issue. BTW, can can prefabricated tusses be made with shed dormer profiles?

I'm looking for ideas. Thanks
Dan

RE: How to fabricate attic truss intersection

Why do you want to "T" the attic trusses.  Just make it a straighforward gabled end roof and be done with it.

Dormers can be done....

Get with a good truss manufacturer in your area and they can work out the details.

RE: How to fabricate attic truss intersection

Agree with Mike.  Just have the truss manufacturer design dormers into the roof.  It will be partially attic trusses and partially stick framed.  

RE: How to fabricate attic truss intersection

Starting with a straight run of attic trusses 24"oc, take the two trusses at center and spread them apart till they meet adjacent truss making it a 2-ply unit: you now have a 6' opening that can be ladder-framed between bottom chords to create a floor. Ladder frame between the top chords to maintain the roof slope and/or ceiling inside. Eliminate the top chord ladder framing in the area of a dormer or perpendicular room expansion.

For more attic room space, take the 2-ply truss units and spread them apart to adjacent trusses to make 3-ply units and a 10' opening dormer/room each perpendicular direction.

The 2 & 3 ply units are multi-ply girder trusses. Spreading the 3-ply units to create 4-ply's and a 14' dormer/rooms requires some special bolting to make the 4-ply act as a unit. The ladder framing hanger load needs to distribute evenly into each ply of the unit. For this opening and larger, most fabricators will 'special design' that girder unit with increased member/connector sizes, which may dictate the size for all trusses (even floor & ceiling).

For larger than 14' room widths, ladder framing with trusses and special girders may be used. Strategically providing a post/wall bearing support at girder locations will drive truss costs down quickly.

Using this preliminary design method, a single truss calc can be designed to accommated these systems; just add the weight of any dormer/wall framing to the top chord. Remeber to divide that weight by the number of plys in girder.

RE: How to fabricate attic truss intersection

(OP)
Excellent !!! I never thought of doubling (tripling ..) trusses and building a ladder frame between.

Thanks for the replies.  I now have several ideas/designs to take to the truss manufacturers.

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