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Gable End Attic Truss with Structural Outlookers

Gable End Attic Truss with Structural Outlookers

Gable End Attic Truss with Structural Outlookers

(OP)
I am trying to figure out gable end trusses for the attic trusses. The reason this is stumping me is the complication of dropping the top chord for structural outlookers where the attic truss has a spliced top chord. Below is an example of a attic truss with a dropped top chord that I have encountered in the past but I don't know if this is the best method of handling this situation. Looking back through the shop drawings (3 years ago) for attic truss drawings I actually don't see an example of a dropped top chord so I may have come up with this detail on my own



Any thoughts or suggestions or examples of similar configurations are very much appreciated.

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

RE: Gable End Attic Truss with Structural Outlookers

(OP)
To further clarify the framing details with regards to attic trusses and structural outlookers I've created a sample model with a proposed dropped top chord gable end attic truss:



Please download and review the model here:

https://3dwarehouse.sketchup.com/model.html?id=u8c...

I've also included the infill wall framing to help put everything into reference (light green).

Is this the appropriate way to frame an attic truss (gable end) with structural outlookers?

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

RE: Gable End Attic Truss with Structural Outlookers

Not sure about the answer to your actual question but... I would wonder if the end truss really needs to have the full attic opening.
Maybe just some accommodation for a door or window (or some combo) would be more adequate.
Also, seems that the end truss could (might) be bearing on the wall anyway so...not as great of structural requirements.

RE: Gable End Attic Truss with Structural Outlookers

(OP)
The reason I provide the full attic opening at the gable end truss is so that the framed in wall can be the nominal ext. wall thickness of 5.5 inches and allow for R-21 insulation. I've had some truss plants provide the typical vert. webs for nailing off the sheathing over this space but then one has to fir it all out anyways to get the appropriate wall thickness for the insulation.

If the wall below the gable end truss is sufficient for bearing on then the gable end truss really does not need to have any structural capability so your observation is correct. One could probably get away with a 2x4 dropped top chord with the stacked top chord at the eaves as shown. It would make sense to have the same depth at the bottom chord though so that the floor sheathing has a convenient nailing surface right to the edge of the building.

Alternatively one could do away with the gable end truss entirely and just balloon frame the wall from the ground floor or from the attic floor up.

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

RE: Gable End Attic Truss with Structural Outlookers

(OP)
To clarify I should point out that the gable end truss shown is a "structural" gable end truss. A large garage door opening beneath the truss at the end of building is then possible with this configuration, without the penalty of an extreme garage door header.

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

RE: Gable End Attic Truss with Structural Outlookers

I'd like to address what HouseBoy said: "I would wonder if the end truss really needs to have the full attic opening."

If the attic room is small, and the room is unheated and just for storage - Maybe not.

If the room is for occupancy, the wall needs to be insulated. That's difficult to do in a wall that's only 1.5" thick.

But probably the biggest reason is wind. I know of a house near here that had the whole gable wall break. It was a rather large and tall attic room. (I don't know the exact dimensions) The wind simply broke the 1.5" thick studs and pushed the whole mess back into the attic room.


In my experience, the wall below has never been an issue. A gable doesn't add much weight to the wall. So beams below the gable truss aren't typically very large.

RE: Gable End Attic Truss with Structural Outlookers

If the roof overhang is more than 12" then I always insist on a dropped top chord and overframe the outlookers with a cantilever. Too much torq on the top chord if you don't. Also truss manufacturers fine print prohibits it even if the truss designer doesn't know it and does it anyway. Gotta make the builder happy and all that BS. If there is a window I'll sometimes have them hand frame the wall but easy enough to put the RO right into the truss too. Still need to insulate that wall and get some real studs into it. There is never a right answer so it pays to know the contractor doing the job and hope you get the shops before they are manufactured.

______________
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