Deck as a roof...idea

[billyvray]

I'm in the beginning stages of planning a backyard shop/pool house type structure. The shop will be a basic garage, about 20 something X 20 something.
My idea is to build a deck on top, rather than just a gabled rod. I'll lose storage, but no big deal. Iim think the deck would overhang one side towards a future pool to serve duty as a shaded area too.

I'm looking for ideas on roofing of the shop under the deck. Maybe just build a single slope roof with the while deck as a secondary structure above?
I would really like to incorporate the roof and deck as a unit, but I've never seen a goo way to do this and have adequate drainage. No worry about snow loads but we get some pretty good rains.

Any thoughts on this ? Places to look for inspiration?

Thanks in advance

Bill in GA

 

[Big Bad Dad]

The house next door to where I grew up had a 1 car garage, and the roof was a solid concrete slab that doubled as a patio. This was on a hilly, sloped lot.

 

[MushCreek]

Usually, when you want a deck over an area that has to stay dry, they build a gently sloped roof deck which is then waterproofed with a thick rubber (EDPM) sheet. The deck is then built over it, with special care taken not to compromise the roof membrane when fastening the deck. I always feel that the more pitch to the roof, the better. Roofs with a very shallow pitch always seem to develop low spots where water pools instead of running off.

 

[Stuart in MN]

Usually, when you want a deck over an area that has to stay dry, they build a gently sloped roof deck which is then waterproofed with a thick rubber (EDPM) sheet. The deck is then built over it, with special care taken not to compromise the roof membrane when fastening the deck.

This is how the roof of my back porch is built. Slightly sloped, with EPDM rubber glued down, and the deck on top of the roof rests on sleepers that simply lay on top of the EPDM. It works fine.

 

[Voi]

I've never used it myself but have seen a concrete covered porch with garage space underneath. It was poured over an insulated concrete form called Lite Deck.

http://liteform.com/icf-deck-forms/

If I'm understanding your project correctly this would allow you to pour the ceiling at what you're currently considering for deck level and get a bit of height back.

The one time I saw this used it was strong enough to park on top of so maybe it could be cantilevered on the side where you want the overhang.

I'm guessing this is expensive but maybe not as much as building a sloped membrane roof with yet another structure (the deck) over the top. Plus the extra ceiling/storage height might be worth it.

 

[theoldwizard1]

I have friends that has a second story deck that is over a walk out basement. For several years they have want to screen in the area under the deck, but they have not found a system that they are comfortable with would result in a dry area !

 

[bczygan]

I have friends that has a second story deck that is over a walk out basement. For several years they have want to screen in the area under the deck, but they have not found a system that they are comfortable with would result in a dry area !

Think of the deck framing as structure.

Most decks are built for fairly light loads, but you can check what the members are made of, their strength and size and spacing, and reverse engineer what loads they are capable of supporting.

Then, check what kinds of loads a roof with snow loads would be required to support.

Likely the deck will be adequate. If not, you can reinforce it as required.

Then, for a proper job, install the foundation and exterior walls needed for an enclosed space below the existing deck, using the deck as the roof framing.

Pay particular attention to where the deck attaches to the existing structure.

Then remove all the deck boards and railings.

Install treated plywood floor sheathing.Install rubber roofing on sheathing.

Reinstall deck boards as a floating finished walking surface.

Reconfigure railings and install without piercing roofing membrane. Probably by fastening to face of walls.

Sound doable?

Basically you are just using the deck structure for the roof structure of the new room and reusing the rest of the deck materials for a walking surface on top.

 

[volleyball]

There have been several posts started on this same subject.
I had thought of doing it the ways listed above but realized it was a short sighted plan as it will require expensive redoing down the road. Decades down the road but will still be there. Like building a deck without PT lumber.
I have had for years an 18' d X 28' w deck with a full dry basement under it. It is bone dry at this very moment after heavy rains all day. The pitch is a little over 1" for the entire span so it works like a flat roof but drains like a pitched roof. And it sits in winter with maybe over 2' of snow on it.
I used waterproof aluminum decking. You can see the underside of the decking below where I have just as much dry storage as the deck size.
Here is a different, newer product that mimics a composite deck.
It is not cheap to buy but when all you need is the framing to support it and it adds to the structure rigidity, then it is a cheaper solution.

 

[6768rogues]

I did a similar project. The roof was built with a very small amount of slope and covered with a heavy rubber membrane. Then 2x4 sleepers were laid on the roof with scraps of roofing membrane under them to add another layer of protection for the roof. Then a deck was built on the sleepers using screws short enough to not penetrate all the way through the sleepers. Gravity holds it in place. I used a leaf blower to clean the membrane before laying down the sleepers so that there would be nothing to penetrate the membrane.

 

[Autorotica]

I built a deck with a 2" slope across the 16' depth and screwed up corrugated plastic panels on the underside that I obtained from Lowes.

Chris

 

[fastjohnny]

I used an extruded aluminum decking called lockdry. Lockdry.com I think. Lifetime guarantee. I installed a 16x22 deck between house and garage with living space and a breezeway below. It has been great. I framed the walls/ceiling with uniform height, using I joists for ceiling, then built up each succeeding joist 1/4 inch with various combination of plywood strips and eventually 2x material, then sheeted as normal, applied ice and water shield, then decking. It has a 200lb/sq foot load rating IIRC. My hot tub has been up there for 10 years without problems. minimum pitch is 1/8" per foot.

 

[volleyball]

When you use an aluminum extruded product, The most important thing is to frame it like a porch and not a deck. That means the side walls are the load bearing walls. Because the boards need to run out from the building, not in parallel like a deck.
And it makes it easy to set your pitch, just lower the support at the outside.
The suppliers will send you a sample pack for free so you can see the product.

 

[KELLHAMMER]

One way is to use a PVC membrane like Dura Deck