How to attach panels to the roof?

[rabascal]

Hello,
I am installing some 2X12 sungrabber panels.
In the instruction it is said that I need to use three mounting straps to hold the panels in place; one 3" down from the top header, one in the center of the panel, and one 5" up from the bottom header. The question I would like to ask is why is not recommended to use pipe clamps with screws to secure the panels from the top and bottom headers? In my opinion, the headers are the strongest parts of the system.
I also would like to as your advice regarding the roofing mastic. I need to drill some holes to attach the mounting straps with 2" screws and it is needed to apply roofing mastic in the drilled hole before inserting the screws. I went to Home Depot and got Elastomastic 209 by Henry. Is this a good product for this application?
Thank you for your support,
Rodrigo.

 

[dayhiker]

On mine, there are clamps at the headers. The straps are there to hold the panels down between headers. If they aren't present, you have this thin plastic spanning 12' when the wind trips to pick it up. Basically, they will belly up between the header hold down locations.

I'm a structural engineer. When I read how mine were to be held down I didn't think it sounded too great. When I actually installed it and saw it in place I felt much better. That strapping has a metal core.

 

[JohnT]

The straps keep the wind from making the panels flap, which would wear them out rubbing on shingles in no time. You also can't clamp the headers down too tight or the shrinking of the panels when cold will cause problems.

 

[rabascal]

Thank you for the feedback.

May I ask you what roofing mastic did you use?

 

[JohnT]

Thank you for the feedback.

May I ask you what roofing mastic did you use?

Someplace I found a good recommendation as to the type to get. I'll check the tube next time I'm in the garage.

 

[lborne]

You can secure the top header with clamps, but leave the bottom free as the panels contract and expand quite a bit.

 

[dayhiker]

Thank you for the feedback.

May I ask you what roofing mastic did you use?

Mine came with the panels. It was in a tube like caulk but was an asphaltic type of material. I need to dose up the fasteners again just for good measure.

Oh, and I spilled about half a jar of the plubming glue on my shingles. Don't do that.....luckily it's over a deck roof.