brilliant idea?
I think I've come up with an ideal solution to the problem. I've carefully measured the space, and I want a "carport" roof over a space that's 16' by 20'. There is a large (4" x 12") beam running down the center---it goes the long way, down the full 20' length. So, here's what I plan to do.
I'm going to install plywood a few inches under the supports for the deck, with one "row" of the plywood on one side of the big beam and one row on the other side. Each of these need to span almost 8', so there will be very little waste. That'll take 10 sheets of plywood. The plywood will form the roof of the carport below, with the big beam extending below into the middle of the ceiling.
Then I plan to buy EPDM pond liner and lay it on top of the plywood (it'll be about 8", or so, under the deck surface). This will be done in 2 parts, so that I don't need to puncture the liner in the center (in fact, I won't need to puncture it at all). The pond liner will also run up the sides, but not on the end where the water will drain out. In addition, I'll put wire mesh on the ends, to keep the rodents out, and I'll also add a "door" on each end, so that I can easily clean out the pine needles (or any other junk) that falls thru from the top.
I hope that's reasonably clear...
In any case, I think this is an ideal solution for the following reasons:
1) It should yield a waterproof roof for my carport, with good drainage since I can easily slope it 1/4" or more per foot (the commercial systems recommend 1/8" per foot)
2) It allows ventilation under the deck surface, so the surface won't rot
3) It keeps the rodents out of a space they would undoubtedly like (rodents are a constant problem here---too much natural food available)
4) It's reasonably priced. I'm figuring at most $2 per ft^2, whereas the best price I could find on any decent commercial systems was $7.50 per ft^2, and that's for an aluminum deck surface, which I do not find appealing
5) It will be essentially invisible, since it's mostly hidden under/near the supports of the deck
6) It will be fairly easy to install, since I have to remove the deck surface anyway. The previous owner made a "carport" by taking up the deck surface, placing cheap plywood on top, then replaced the deck surface. As a result, the plywood has rotted and the lack of ventilation has even damaged some of the redwood decking.
If anybody sees any problems with this plan let me know. I'd really like this to be a permanent solutions. Thanks.