Under Deck Panels Collapsed

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Old 09-14-08, 01:25 AM
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Under Deck Panels Collapsed

I built two decks, one over the other. The lower is 8’X32’ and the upper is 16’X10’. I wanted to be able to sit on the bottom deck and stay dry in the rain. And I didn’t want to spend a fortune to do it, like the product called “underdeck”. I used 12’X24” corrugated polycarbonate panels, running perpendicular from the house under an eave 11' to the edge of the 16’ side of the upper deck. I pitched them more than was necessary, 3” over 10’ to insure the run off from water falling through the spaces between the deck boards above would run off. I ripped down 3 pieces of PT pine, ˝” , 1 ˝ ” and 3” high and screwed them perpendicular onto the joists of the upper deck. Then 3 rows of rubber washer screws after pre-drilling the holes slightly larger than the screw so it could expand and contract without cracking, into the 3 different sized ‘hangers’. Then I installed pvc gutters at the low end for the run off. The panels overlapped each other by a couple of troughs and then I ran a bead of silicone II from one end to the other sealing them together. It wasn’t fun doing this without help, but it was working just fine and looked good to boot. Halfway through the first winter KABOOM! The whole thing collapsed from the weight of the 6-8 inches of ice that had accumulated on it. Ouch. I had done the same thing under the front deck a year earlier and it wintered without problems. Why did the back accumulate so much snow/ice and collapse when the front had no problems?? It finally dawned on me that the front of the house faces north and the back south. The snow on the back wasn’t removed, because its winter and the deck is not used, when the front deck is the entryway to the house and of course shoveled. The freeze/thaw/freeze cycle happened on the south side because that side had a chance to do that when the north side pretty much stayed frozen. The accumulation in the back was caused by the freeze/thaw cycle, melting during the day and freezing at night. Freeze/thaw, layer by layer the ice just kept growing, finally collapsing under the weight. I had thought the 3” over 10’ pitch was steep enough that nothing would stay put. Wrong answer.
I must do it all over again before this winter comes, but obviously need to do something different. Any suggestions would be greatly appreciated. Thanks!
 
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Old 09-15-08, 01:00 PM
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I.M.O., just like a roof to a house, the only way to keep it from collapsing, is to keep it clear of snow and ice. Could you reach up with a broom and clear it away after a snow fall? Heat tape?
 
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Old 09-15-08, 01:37 PM
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There is only a couple of inches (˝” , 1 ˝ ” and 3”) between the panels and the 2x8 joists above. The panels are flush with the framing at the sides. Underdeck relies on gravity to clear water from the installation. How would I use heat tape?
 
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Old 09-16-08, 05:10 AM
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I just had to redo one for a lady that was improperly done, so I sympathize with you. Not implying yours was improperly done, of course. The only thing I question is the fall. 3" in 10' isn't much. Water won't free flow at that low a pitch. I had to repitch the one I did to 6" in 12'. Of course, the pitch wouldn't have mattered in your situation with snow/ice, since neither "flows". I am looking forward to our first good rain to check hers out, but, now, you have me wondering about any snow/ice. We'll have to wait and see.
 
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Old 09-16-08, 05:57 AM
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Panels

Three rows of screws on a 12 ft. long panel is not enough screws. The rows of screws should be no more than 2 feet apart.
 
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Old 09-17-08, 09:47 PM
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Wirepuller38-funny you should say that. Tuftex makes the panels, this is their installation page. Its all about using the panels on top of the framing as a roof. This is the page I read when I put them up over a year ago. So I had to estimate how to do it under the framing as a deck drain. (I also stand corrected, I used the PVC panels, not the polycarb.) Either way, in the lower left of the first diagram, one can see that the instructions for spacing the screws is not clear. Thats why I used 3 rows over 10". Anyway, I guess I was ahead of the curve because they now make a product called "Deck Drain". Imagine that. Its the same product, but it comes with mounting brackets to create the slope. Still confused, I called them. Typically, the panels are installed perpendicular to the joists. I was talking about installing them parallel to the joists. Being almost as confused as I was , they put me on with the guy who started the company. He told me that my 3" on 10' slope was fine, but that I just needed more rows of screws! He said "every 24 inches or even better, 18 inches" Also, I predilled the screw holes, which is not necessary under the deck.

Nothing is ever easy.
 
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