I’m going to replace the current ?plastic? roofing panels in the roof of my shop. To match the current panels, I’m going to use ridge & valley polycarbonate panels. The guy at the greenhouse supplier where I bought the panels advised me to use 1/2″ stainless screws in the valleys of the panels (to keep from warping or damaging the ridges). The old ones were screwed down on the ridges; all of my senses tell me to do the same. Does anybody have experience with screwing down polycarbonate panel in the valleys? Is the greenhouse guy wrong?
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Yes and no.
( I should be a politician!)
Normally the ribs are the right place for the fasteners so the holes where the screws seat are above the plane where water flows on certain kinds of metal roofing. I am not sure which kind you have.
But the plastic see-thru panels for lites are more brittle and deflect differently and they need the firm support, so they should be screwed in the flats.
As far as SS Screws goes - I haven't used them for roofing before - honestly didn't know they were available but it doesn't suprise me. What is important is thet you use the screws that have the built in washer and neoprene washer to self seal and that you do not over drive them. Too much pressure on the neoprene will fracture it and let water in. So tighten just enough that it starts to bulge from under the metal washer cap.
One other point on screws - What is normally sold is a #8 or #10 shank with a 1/4" drive head. I prefer the next larger sized screw which uses a 5/16" head. There is far more wood displaccement for a beter grip and the larger shank is twice as strong so there are fewer that break in stress such as wind storms.
Diffferent companies make varying roof panel patterns so make sure yours is a fit.
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I just happemed to think - is what you have the corrugated roofing style? That should be fastened always at the high spots. So far I'd been thinking of the ribbed panels with about a 1" rib every 9" or 12"
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Paul, I have installed this stuff a few yrs ago on green houses ( not GREEN houses, some were red and white, also..LOL) but the what I call wiggly strips ( that are made for the purlins,) have a neoprene gasket and are made from whitepine or spuce..
Thses pose a serious problem using them 5/16 headed screws..you MUST over bore the holes, IIRC the pilot needs to be 3/16 in the wiggly and the poly roofing needs a 1/4. These panels MOVE a LOT, I don't know why, but they will craze around the screw holes...spider web...if contained too tightly.
I would highly suggest that the holes be drilled and the use of ALUM nails be used, with just enough down force to seal the neoprene washer, and always on the hills not the valleys. The "cant" strips or fillers are extremely fragile as is the roofing it self.
Seems to me I recall those 12' panels GROWING a half inch per 20' from 12 dgreesF to 90 degrees F..so some lee way is advised in the fasterner dept.
SS fastners Are the way, and yup, they SAY to buy them ( from them+$$$$$$) but Alum, work just fine in the climate that I had installed in.
I'd not use anything but SS screws ona waranty covered job, but in reality a magnet will show that most screws supplied my the poly manu. are indeed alum.
I carry a rare earth quater sized mag in my left pocket ( actually 3 of them) and we had a discussion about the meturllagy of SS on the job site, it can coantain enough ferrous content to be called IRON, but labeled as SS.
Alum is what this guy wants..btdt.
Spheramid Enterprises Architectural Woodworks
I have irriatable Vowel syndrome.
I didn't think to mention it here, but I always over bore all my holews in te panels themselves, before carrying it up on the roof, for thermal expansion.
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I want to reemphasize what was said about predrilling. Polycarbonate has a huge coefficient of contraction /expansion. Commercial building I worked on 2 yrs. ago has a roof that needs to be entirely redone as a result of the roofers skipping the predrilling holes for the expansion /contraction.
Best if you can get your hands on a install sheet from the manufacturer. Probably available though your source of the material. Great material installed properly, lots of problems if not.
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