Weather proof roof under a deck

[WisJim]

We have a back porch about 10 by 12 feet that has a second floor deck above it and we would like to enclose the porch to make more of a sun room out of it, and need to have a good roof for it that doesn't take up any space. I found a product Rain Tight Decks that looks interesting. Rain Tight Decks Has anyone used this or anything similar that would provide a reliable leakproof roof without taking up space below the upper joists?

 

[K'ledgeBldr]

If you want a “sunroom” with a roof deck, and you want it done right, you’d most likely have to tear-off the deck and build the sunroom with a waterproof roof with pitch. Then build the deck on top of that.

But if you just want a dry “patio”, any of many different “under deck” systems will work. But they do have some drawbacks because of debris buildup.

 

[rburke65]

Something with a PDM (?) rubber membrane I’m sure

 

[rayra]

steel roof panels, mounted under the upper deck.

Building An UNDER DECK ROOFING SYSTEM​

 

[jmiller_2308]

I second @rayra suggestion of steel roof panels. It is much cheaper and can go up pretty quickly, especially if you can order them cut to size like you can at Menards.

I put steel roofing on the underside of my deck last year by first ripping 2x material into a long wedge and then attaching it to the underside of the deck joists. I ran them perpendicular to the joists and spaced them to be the distance between the ridges on the steel roofing. This 2x material gave me the mounting and slope I needed for my steel roofing panels to be attached and drain.

I then attached the roofing to the ripped 2x material using steel roof screws. The roofing was attached such that the ridges faced the deck and screwed directly into the ripped 2x material. This left the larger area of the roof panel to act as a channel to drain water and minimized steel contact with the wood. I left openings at both ends to help ensure there would be additional air movement to dry things out.

I don't recall specifics but I believe I have 3" of slope over 10' and it drains really well. Winter hasn't been bad. I do clear my deck of snow and that likely helps but the roof of the house drains onto the deck so I did have quite a bit of water freezing and melting on the underside of the deck but because of the drainage and the number of screws I put in it seems to be holding up well without any signs of ice weight pulling it down.

 

[WisJim]

Thanks for the feedback. My son did the steel -roofing-under-the-deck method at his house, but I have less headroom than he has so I need the minimal slope. 3" over 10 feet could work for me, and Shakopee MN is straight west of me so similar climate and rain/snow fall.

 

[CraigStu]

I did corrigated plastic roofing under my deck. It extends 10 ft out from the house and total slope is about 2.5 inches.

 

[rayra]

sewer pipe slope is typically 1/4" of drop per foot of travel. And that's for moving solids. If you just want to move rainwater and your material is continuous from high to low end, you can go even more shallow than that.

 

[KJ in VT]

Ice would be my concern with any panelized product. Wouldn't take much of a dam to back water way up the roof with such low slopes. And not much thermal drive to keep the venting working and the roof cool; at least it would be in the shade of the deck, I guess. Maybe not a big deal...until it is.

 

[Bretny]

For typical metal roofing you need a 3/12 pitch. But this is not a typical installation and with a deck over top of it you wont really see snow on the roof.

 

[firebirdparts]

I just did one; I found that some folks complained about rot between the deck and a suspended roof. That was the only real concern for adding one on. I was building a new deck, so I eventually chose to put an EPDM membrane under the decking and I fanned it out so that it droops on one end and the rain all runs to one end. It's a good solution, and it can't rot, but I have seen some accumulation of maple seeds and tree junk under there. My trex fasteners puncture it, but I doubt it'll leak any because of that. Could be a concern.

 

[Innovate1]

We just got a quote for a 8 x 16 ft deck and labor and materials was 10k! Seriously considering doing steel roofing. Would like to leave some room for ventilation as the house is on three sides of the deck. Thinking I should also screen it against squirels and such. Thinking I could rip some 2 x material to different widths and run them perpendicular to the existing framing and that would also be perpendicular to the ridges in the roofing so no issue with making sure they line up with the ridges. Then use the same screws used for roofing (I have a bunch left from when the garage ceiling was done) and put them in the peak of the ridges from the underside. The main issues as I see it are how to leave a gap for ventilation (and make it look good) and how to do the edges so there isn't leakage to the underside of the roofing and drips underneath.

 

[Innovate1]

Seems to me the wavy panels don't have much room for leaves and debris to flow under the lumber it is attached to and the metal roofing with ridges has much more space. Just an observation and reason I am leaning to the roofing.

The video shows black top side and white underside. Think some of the roofing only paints one side so may have to look around for painted on both sides if the underside finish is important. Can someone confirm that some is painted on only one side?

 

[Innovate1]

Checked with the place that supplied my ceiling metal. They first said it is painted on one side but then said the other side is white so it is also painted, just not the chosen color. Perfect for under deck as the white side will be down. Cost of the needed panels is $200, box of screws $20. I will need to get some flashing, gutters and other stuff but think I can stay within the $6000 for the material for a real under deck system. Probably will be 1/10 of that total. And the $4000 cost to install seemed pretty steep too. Just thought I would post here the costs. I knew they would be a lot less but expected a bit more than $200. Still interested in finding some flashing details from others. Seems like that is key to keeping the bottom dry.