No fasteners were visible to fasten the upper trusses to the lower trusses, any concern?
My guess is that there may be a few nails under the roof sheathing used to hold them together but that does not seem enough…
Those are piggy back trusses and not installed like I normally have seen.
I like seeing them with purlins attached:
Click on “Piggy Plate” in Marcel’s link.
Or:
Larry beat me to it.
No purlins or 2x4’s between the trusses. If spans are long enough, I have seen trusses separate horizontal or bow outwards from lack of supports.
2 X __ X 4’-0" SCAB, SIZE AND GRADE TO MATCH TOP CHORD OF
PIGGYBACK TRUSS, ATTACHED TO ONE FACE, CENTERED ON
INTERSECTION, WITH (2) ROWS OF 0.131" X 3" NAILS @ 4" O.C.
SCAB MAY BE OMITTED PROVIDED THE TOP CHORD SHEATHING
IS CONTINUOUS OVER INTERSECTION AT LEAST 1 FT. IN BOTH
DIRECTIONS
Thanks Marcel, Larry and Sean for your prompt replies, excellent info as usual!
When something doesn’t look right, it usually isn’t…
It really depends on the engineered drawings that came with the trusses, but I have always done this with purlin bracing between the two trusses as mentioned above, and flat strapped the ends together.
Brad
I have only seen one set strapped here due to no wind load issues. I’m guessing most if not all are required to be strapped in your area?
I have an engineers drawing (titled Piggy-Back Detail) that clearly says the strapping down the top chords between the piggyback and base truss (called lumber scabs on the drawing) are only required in wind zones of 110+.
When required, the lumber scabs are actually an option to using metal straps or plywood gussets as shown on the drawing also.
The drawing did not mention the location of the roof sheathing joints at all which surprises me. I have always looked at joints within 12 inches of the truss joint as a need for the straps…
I see the lumber scabs very often but the drawing also indicates that these are often used to help line up the trusses for installation.
The CLB or continuous lateral bracing under the piggyback is required on all installations (which is missing in the original post pictures).
One interesting note is that I had a seller hire an engineer for some crawlspace issues once and while he was there he was asked to sign off on the lack of the straps that I had written up. The engineer said they were needed and the seller had them installed. So the final answer is up to someone other than home inspectors so be careful what you write up as a defect. It looked like I was right on that one but there are new homes out there that have documentation that says its not needed.
Not sure I am allowed to post the drawing on here. If you need a document, contact a local truss supplier and ask for it.
Most of our roofs in the area are 8/12 or better and most are piggybacked because of the height. In every drawing I have ever seen they call for purlins. The purlins help to keep them from racking or twisting at the joint. Due to past experience I would call up what I see in your photo every time. It would be almost impossible to nail that properly as well without splitting the crap out of that 2X2.
The problem is that those upper trusses are bearing on their tails, not on the bottom chords, as they should. The metal connectors shown in Marcel’s link are actually to transfer the structural loads to the bottom chords, not to prevent uplift. Recommend an engineer on this one. It should be fairly easy to transfer the structural load to the bottom chords by installing the correct hardware.
Longitudinal bracing is totally up to the truss designer, and it’s not uncommon for a truss roof to have little or no bracing, although there’s usually at least one down the center on top of the bottom chords, just to keep the bottom chords straight for drywall.
Is that what you mean by “purlins”?