[Shop-talk] Corrugated fiberglass panels. How many screws?

[pethier at comcast.net]

I am putting corrugated fiberglass panels up as a cover over a deck.  I bought the thickest white ones my local Menard's carries.  The finished roof will be about 17 x 8 feet.  This is a simple shed-style roof, with water draining down the corrugations at a 16-degree angle to a (wavy) drip edge.

Each panel is 8 feet long, and covers 2 feet wide when overlapped one wavelength.  I have corrugated strips of wood which purport to match the shape of the fiberglass.  The concept is that one drills a hole through the top of the wave and put a pole-barn screw (with built-in rubber washer) through the top of the wave, through the corrugated strip and into the wood crosspiece below.  I have four such crosspieces.

My question is:  How many screws do I need across each panel?

If I put them three across, that would be a dozen screws through each panel (the overlap section would mean that two panels share the four screws on the edge).  Is this enough?

BTW, I don't intend to cut any of these panels.  The panel length should be correct, and I will make the width come out correct by overlapping more than one wavelength. 

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Phil Ethier  West Side  Saint Paul Minnesota  USA
1962 Triumph TR4 CT2846L, 1992 Saturn SL2, 1993 Suburban,
1994 Miata C package
pethier [at] comcast [dot] net    http://forum.mnautox.com/forums/
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I decry the textmessagization of the American-English language.