Construction Help - Diesel Forum

Silverlode · 12-06-2007, 11:39 PM

I want to build an enclosed shed under my deck. I am pouring a concrete slab and then constructing on top of that. I haven't quite decided the best way to address the roof however.

I have seen a product called Underdeck that looks like it might work pretty well, but it is really expensive. I don't have a lot of extra room to play around with, meaning that I would like the roof not to exceed about 6" distance from the bottom of the deck.

Anyone have any experience with this sort of thing? There has got to be a good and watertight way to approach this that isn't going to cost me $6K just for the roof. I have spoken to a few contractors and they all have gotten a look on their face like I get when I try to do calculus.

The enclosed space will be about 14'x 20' if that makes a difference.

Thanks for any suggestions.

88beast · 12-06-2007, 11:56 PM

doa slope of 2in per foot over the 14 foot part sloping down like a normal roof then pull rubberroofing (buy scraps way cheaper)
pull it over and leave a foot on the side
roll each side around a 2x2 and deck screw to building
then just leafblow off from topside each year

Silverlode · 12-07-2007, 12:11 AM

2" per foot for 14' would give me a drop of more than two feet on one side of the shed. I could probably afford a foot if I had too, but would prefer to keep it more around 6" for headroom inside. Do you think that approach would work with about 2" every 4'?

DragRag · 12-07-2007, 12:35 AM

Even a 2" slope per foot is not enough for regular asphalt roofing shingles. A 3 and 12 is recommended as a minimum for using that, any lower you are going to be using a material that water can not come back up under, like a commercial hot mopped roof, foam roof, or metal roof. I would go for the metal roof for sure. Just my .02

Band_Member · 12-07-2007, 08:07 AM

I don't know if this might help you some.

I built a roof (so to say) under my deck where there is a concrete patio. I wanted for us to be able to sit out there while its raining without the rain coming through the deck and dripping down on us.

I ripped strips the lenghth of the deck joists (in my case 10') out of 2x treated material figuring a 1/4" per foot pitch. Over 10' the strip went from 2 1/2" to nothing. I ripped as many as I needed for every joist above the patio. Then I predrilled the screw holes on the strips. I glued and screwed (s/s screws) the pitch strips on the underside of the joists with the 2 1/2" end away from the house.

This provided the pitch for the water to run away from the house on the top of the 1/2" treated plywood that I predrilled and screwed on next using a lot of caulking especially around the screw holes.

I'm thinking you can do the same then frame your shed walls up to it. You can also put a gutter where the water spills out and lead it away.

If anything accumulates up there (twigs, leafs, etc.) just break out a backpack leafblower and blow it off.

Just a thought. Maybe it'll work for you.

hayhauler · 12-07-2007, 08:30 AM

I agree with dragrag, with the slope you're trying to get, metal is the only way to go. Since it's under a deck, you won't have to worry about leaves and such. I would probably buy an aluminum pan roof system with built in gutters.

rtmartens · 12-07-2007, 10:47 AM

With the deck above, I'd imagine the water that does make it through will be well-distributed and coming through rather "gently". I would surmise your slope could be quite minimal, especially if using metal or plastic/fiberglass roofing material. I'd make sure my house-side flashing was well-placed and sealed.

You could also "build" your roof at a workable level and then hoist it into position. Maybe even build it in sections (to make it lighter for raising), making sure the section seams overlap correctly and are well-caulked.

Silverlode · 12-07-2007, 12:23 PM

OK, thanks for all the good replies and advice.

Would metal work better than a single sheet of a rubber type roof product stretched across plywood? I see single sheets of rubber for sale on ebay that would cover the whole area for under $500 delivered. Any idea what a metal roof would cost?

DragRag · 12-07-2007, 01:05 PM

About the same price depending on where you get it. Met al is good or the rubber you are speaking of. Do not use asphalt shingle with less then 3 and 12 pitch. It might keep out the water when new, but it will not last with less then that slop. I have built many houses, plus I know a good roofer, and I know that is his opinion on the matter.

whitjo · 12-07-2007, 04:01 PM

What about the translucent fiberglass panels, no need for lots of pitch and they will let light in below your deck too.
could be pricey though??

bosspsd · 12-07-2007, 08:37 PM

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: whitjo</div><div class="ubbcode-body">What about the translucent fiberglass panels, no need for lots of pitch and they will let light in below your deck too.
could be pricey though?? </div></div>

I used that method under the deck on my last house, I attached it from underneath using rubber washer nails like you use on pole barns.

MOUNTAINMAN444 · 12-07-2007, 09:52 PM

The fiberglass will come out cheaper than the metal roof. Run it at a minimal slope and it will do just fine. I've done this on more than one deck for folks and never had a problem.
Joe

hayhauler · 12-09-2007, 02:47 AM

I think the fiberglass would work very well and last quite a while under the deck like that. I'm accustomed to using the alumninum pans, but for that application either fiberglass or "tin" should work fine.

F350_6 · 12-09-2007, 10:40 PM

How much wind will your roof be subject to? The rubber type roof will work but if it will be subject to high winds you will need to "glue" it down using a bonding adhesive. The rubber roof will work on slopes down to 1/4" per foot so that won't be an issue.

The inexpensive rubber material (EPDM roofing) will not be a reinforced product so if it develops a tear it will rip open. If you decide to go this route make sure you use screws to put the plywood deck on your shed. A nail backing out will puncture the roof membrane, but may only cause a leak small enough to rot the wood where you won't notice until it's too late.

The material will be available from a local roofing distributor. It sounds like a 20' x 50' roll will give you more than you need for a single piece install. If you decide to go with a contractor tell them your interested in a single ply roof (EPDM, TPO, PVC) and see what they would charge.