Second story deck ... dry underneath?

vancleaveterryJanuary 9, 2008

I will start building a garage this spring with an apartment above. A door on the second floor north gable end that faces the back yard will open onto a deck that will, of course, be nine or so feet in the air.

The deck will hopefully be 24' X 24', probably finished in composite with a concrete slab deck down below on ground level.

We live on the gulfcoast (frequent hurricanes). Should this deck be attached to the house? Or built free-standing but adjacent to the gable end?

I'd like to park a new tractor under the deck. What's the best way to keep the rain from getting through the deck? It doesn't have to be perfectly dry under neath, but it'd be nice to shield the tractor from 95% of the rain.

Any ideas will be appreciated.

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I would attach a 2nd story deck to the building, for lateral stability.

There are a number of systems designed to keep decks dry underneath. All of them are fairly costly. Have you considered a tarp for the tractor.


    Bookmark   January 10, 2008 at 1:02AM
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We have attached Lexan panels to the bottom of our second-story deck. They are overlapped and sloped to allow drainage, and there is a gutter with downspout at the far (drainage) end. So it is pretty dry under the deck (not perfectly dry, though), and this was not expensive. It has been there for over 10 years, no end in sight.

One caveat...we are in a windy area, so when we have rain and gusty wind, rain blows into the area to some degree.


    Bookmark   January 10, 2008 at 7:16PM
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Add a second set of joist to form a slope below the deck joist. Run 1x4's or 2x4's perpendicular to those on 16" centers. Then screw on metal roofing on from below. Use a high grade metal roofing, something with 1 1/2" profile humbs. That's where you screw, using neoprene washer screws. Flash the siding for water tight storage underneath. Way cheaper & more effective than those under deck drainage systems. I've done it on a lot of decks for storage rooms & workshops.


    Bookmark   January 10, 2008 at 8:38PM
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Thank you for the responses.

Mark, I figured it was best to attach to the building. But I wondered that if a really bad hurricane started lifting my deck, if that might damage the building as it ripped off....

Roger and Al.... That's the kinda idea I was leaning towards. But I hadn't thought of using metal roofing...I like the idea. I was thinking of corregated tin or lexon, but the metal roofing might look better from below.

Will it be possible to get the slope needed for a 24 foot deck?

Do you find wasps and hornets to be a problem nesting between the two layers?

    Bookmark   January 10, 2008 at 9:20PM
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i would bet that in order to pass inspection it MUST be PROPERLY anchored to teh house. this means a good ledger board bolted into the frame of the house. most places have tightened down on above ground decks after all teh fatalities a couple years ago when sub-par decks collapsed. if the hurricane is bad enough to lift the deck, the house is going to have dmage anyway. jsut make sure you HOI, FLOOD AND WIND insurance are paid up and have proper coverages!

you may get a few wasps that nest up there, nothing much you can do short of keeping a spray can handy.

as to the slope, you want 1/4" per linear foot for optimum drainage, though you could get away with less. at 24 ft, that would be a 6 inch drop to the outside. the less slope you put on it, the more water will tend to stand there.

    Bookmark   January 11, 2008 at 5:43PM
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1/4" drop per ft. is not enough for proper drainage. I would go with a 1/12 pitch minimum. For a deck 24' away from the house you need enough clearance to bring it down 2'. Do not use corragated metal if you mean that wavy stuff, it does not seal well at all. I use rainguard roofing that is painted all ready, not the galvalum, as it holds up better. The rainguard has a double hump at the overlap which makes for a good seal. If you have to cheat a little on the pitch then seal the overlaps with a good silicon sealer or NP1 sealer.

You can always frame in the area from above the metal roofing to the rim joist on the deck & cover it with siding. This can be a problem tho cause leaves that get thru the cracks in the decking can clog up at the end of the roofing where it's closed off.


    Bookmark   January 11, 2008 at 10:24PM
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On an application like yours I'd suggest treated plywood decking over the joists, using stainless or copper panels (very pricey) over it, then runners with the new porch decking screwed into the runners. A 1" on 4' drop with 1" standing seam panels should do fine
Fasten and flash well to the side of your building.

See ya,

    Bookmark   January 12, 2008 at 8:17PM
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The reason that we used white lexan rather than anything that didn't pass light (like metal roofing) was that we wanted the light to come through to the lower patio (under the second story deck). On the other hand, we didn't want to see dirt accumulating, so we didn't use clear lexan.

If you don't care about having a nice light area under the deck, then go ahead and use whatever you like. Personally, I like the white lexan, it gives you a nice light area, kind of like having a full ceiling skylight. If it were sheet metal roofing, I'd like it a lot less.


    Bookmark   January 15, 2008 at 7:57PM
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I see your point Roger. That sounds nice.

I hope Kelly, David, and others are correct and I don't need two feet of drop for a 24 foot deck.

Otherwise, I think I will follow Al's plan.

Thank you.

    Bookmark   January 15, 2008 at 9:46PM
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Ya know Guys,a person could always install a hmmm 2'' drop or fall in the framing in 24',put down a torchdown roof,stringrs laying on the roof in the direction of the flow,screw the decking to the stringers. Bang Bang Done.

    Bookmark   January 15, 2008 at 9:52PM
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I don't know exactly how much drop there is in the added lexan panels that we have for our 10' deck, but nowhere near a foot, maybe a couple of inches...and it has been fine.

John's plan sounds good (like how you would normally put a deck on a roof over living space) if you're starting with no second story deck like the original poster is. Our solution was a low budget retro-fit.


    Bookmark   January 17, 2008 at 4:02PM
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A standing seam metal roof like I described or a torchdown bitumen like John described, with runners (stringers) is the best way over a run (24') like that with minimum pitch. I really wouldn't recommend using exposed self sealing screws on such a minimal pitch. John's advice would probably come in around the same price as Al's.
Any of the ideas from the these men would achieve your goal, some are just a little more long term and less likely to have leaks.

See ya,

    Bookmark   January 18, 2008 at 10:54PM
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What about aluminum decking? I understand it is watertight without needing any additional construction beneath. Does anyone have information regarding the aesthetics of aluminum decking?

    Bookmark   February 2, 2009 at 7:33AM
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The alum decking is defentley not watertight and down the road it moves around a lot. J.

    Bookmark   February 2, 2009 at 6:07PM
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I am currently researching products to keep it dry under my deck so that I can screen it in. Rain Escape, Deckdrain, Dryspace, etc., as mentioned above they can be expensive! We are not DIY'ers so we are at the mercy of a contractor. Our deck is approx 50x16 and so far estimates are approx. $8000 to a high of $10,000 that does not include the screened in porch!!! I will be watching this post to see any feedback on options to keep the space dry!

    Bookmark   February 5, 2009 at 7:18AM
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