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under-deck "carport" needs a proper roof...

10270 Views 5 Replies 3 Participants Last post by  Jeremy Hillary Boob, PhD
I live in the Santa Cruz mountains, about 12 miles from the ocean. We get a lot of rain and fog in the winter. We've only been in this house for about 1.5 years. It's a fixer, and I've done several things, some fairly major. Anyways, there is a deck on the front of the house, and to keep the rain out, the previous owner put plywood under the redwood decking. The plywood is now moldy, and I'm going to remove it. I'd like to build a proper roof over this "carport", but I'm not sure how to do it.

At this point, I'm open to any suggestions as to how best to keep the rain out. I'd like to eventually enclose it (at least on 3 sides), and I plan to pour a concrete pad, but none of this will be of much good without a solid roof. I've seen decks built on top of garages, and that looks good. However, I'm not sure how to do this without trapping moisture, which would cause the whole thing to rot in a few years---I want something that's going to last. Also, we have big redwoods and douglas firs (which means lots of pine needles), so the drainage needs to be good. Thanks.
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Do a search for, "under deck systems", and you'll get a bunch of choices.
Yes, I've looked at a few of those, but I have not found anything reasonable (if you have a specific brand to suggest, please let me know). For example, one of them costs more than $8 per ft^2 and it looks to be nothing but cheap vinyl that hangs under the deck. And that's one of the cheaper ones that I've seen. It seems like I ought to be able to accomplish the same thing for considerably less than that.
How much room do you have underneath?

Many people build the roof on the ground
Then raise it up under the deck & then build the walls
But you need enough slope to allow water to shed

You could even build the back part on hinges
Then you only have to raise the front & support
I like these ideas... One down side is that the roof would need to be cleaned regularly (accumulated pine needles clog up everything in winter, and they are a fire hazard in the summer), which might not be easy.

Btw, the height varies, but it's about 12'. There are large supports that hang down, reducing the effective space. It's also a fairly large area, at more than 10' deep and nearly 20' wide. We want to get as much space as we can, since we're very short of (dry) storage area. So, something that would somehow combine the roof and deck surface into one might be preferable.
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.
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