Roof attachment through strapping into rafters?

[Cliffs]

Search didn't turn up anything - my house (built in the 60's, southern US) has a roof arrangement where there are 2x6 rafters every 20", then 1x3.5 strapping, with 5.5 inch spaces between boards, then plywood decking on top.

I'm attaching with flashloc Duo mounts, attaching to rafters https://unirac.com/wp-content/uploads/bsk-pdf-manager/2022/06/FlashLoc-DUO-Installation-Guide.pdf. Seems this would apply with any mount though. I guess strapping is uncommon these days.

Has anyone run into this? I'm wondering if there is any special consideration for going through the strapping, or going through the gaps between the strapping? The strapping eats up 3/4" of screw engagement in the rafter.

I'll inquire with Unirac but figure I'd ask here too.

 

[zanydroid]

Is that basically skip-sheathing with full sheathing on top?

I have 2x6 then skip sheathing (for old roof type) then MDF (new) then composition (new), and I installed Unirac SM into it. I informed them of the roof type when I ordered the plans and assumed they vetted it. I also told my AHJ

The Unirac plans I got had a minimum lag embedding length in a cross section showing how the screws worked, which was satisfied despite losing some depth to the skip sheathing

 

[Cliffs]

Do you have the unirac plans showing that minimum embedded lag length? Flashloc duo doesn't have that in any of the documentaiton.

 

[zanydroid]

These first two attachments were copy-pasta'd by UniRac into my plans:





And if you want to see the length you can eyeball it here from the CAD drawing from UniRac (not included in my plans): If it is to scale the shank easily clears the roofing material.

 

[zanydroid]

I took a quick look at FlashLoc Duo's CAD and the screws are not the same.

Probably need to ping UniRac, I'm not sure how popular UniRac, let alone FlashLoc, actually is on this forum. Lots of IronRidge fanboys.

 

[Cliffs]

I did, thanks!

 

[zanydroid]

OK, good luck.

I was a little scared to use FlashLoc as a noob to both solar and working on the roof. There's more room to recover from error with a standard flashing solution.