# Is it cheaper to install a Rooftop deck about a garage then a traditional roof?



## jlhaslip (Dec 31, 2009)

That 40 lb per sq ft would not be enough to carry the live load AND snow load in many Northern areas.
So, it might depends on where you are located.


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## kimballfount (Aug 30, 2017)

We get like 2" a year in SC, do you guys require a 50 or 60lb per foot live load for decking up north? 

A side from the load characteristics, is that pretty much how you go about building a rooftop deck?


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## NotyeruncleBob (Mar 9, 2017)

I think the real question here is do you _want_ a rooftop deck?


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## Nealtw (Jun 22, 2017)

We do lot's of these out here but we don't have the huge snow loads either.
You always want to start high at the house and down from there but you just build the outer wall shorter and not tapper the joists. One car garage beside the house is not bad as the joists will be just one length 2x10 or 2x12 and the big door in the front will have a minimal header. 
2 car garages with a flat top would require beams.
Elevation is another consideration. You want the top surface to be 6" lower that the floor inside. 
If you want go all out and get a concrete deck you lower it another 3 1/2 inches.


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## kimballfount (Aug 30, 2017)

I do, especially if its cheaper or the same price as a roof


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## kimballfount (Aug 30, 2017)

Both the house and garage will be on a slab. If the garage has an 8' foot ceiling and the houses main level has a 9 foot ceiling, I should still have plenty of room for the decks top surface to be 6" below the 2nd floors floor, right? The garage door would be facing out, similar to that middle picture. So I think what your saying is I would have to make either the front or rear wall of the garage shorter to allow for drainage. Wouldn't the joists not rest flatly on the outer support wall if they were slightly inclined? How do you go about making the deck boards and sleepers so they're not on an incline, or is 1/8th" a foot not really noticeable?


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## Nealtw (Jun 22, 2017)

kimballfount said:


> Both the house and garage will be on a slab. If the garage has an 8' foot ceiling and the houses main level has a 9 foot ceiling, I should still have plenty of room for the decks top surface to be 6" below the 2nd floors floor, right? The garage door would be facing out, similar to that middle picture. So I think what your saying is I would have to make either the front or rear wall of the garage shorter to allow for drainage. Wouldn't the joists not rest flatly on the outer support wall if they were slightly inclined? How do you go about making the deck boards and sleepers so they're not on an incline, or is 1/8th" a foot not really noticeable?


So the middle picture the low wall would be where the big door is.
Usually the joist would hang from the house wall and a garage is to long for joists so you would need a beam about halfway to the door end.

We do a solid surface deck here either vinyl, fiberglass or concrete over membrane.

What ever you use it is supposed to run 8 inches up the wall and under the door into the house

You have something different in mind with sleepers and things, we just live with slope, you never notice it.


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## kimballfount (Aug 30, 2017)

ohh ok, I didn't think about using a support beam for the joists. Now I see what you're saying. As far as costs go, do you see any savings with an elevated deck, compared to a traditional roof? about the same?


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## Nealtw (Jun 22, 2017)

I think you have to get quotes on roofing and trusses and 7/17 osb 
And the cost od a deck or a pad that will go somewhere else.
and compare that to
2 beams, 2x10 joists and t&g plywood and what ever you will cover that with
Hand railing and maybe stairs and trim around the top.
Think the actual labour for building it would be pretty close either way.


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## Tizzer (Jul 24, 2010)

What about access? Will family and guests have to trudge through your home,upstairs and go thru a door like the brick house picture?:vs_worry:
Or a set of stairs outside like the middle pic. That's more expense.


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## kimballfount (Aug 30, 2017)

I was thinking something like this. Instead of having a back door and porch, just have access to this access through a side door. Also have access to the porch from the master bedroom.


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## Nealtw (Jun 22, 2017)

Are you sure you would use it.. We build decks on most if not all new houses and they either hardly get used or have some sort off roof over it later.
Just sain.


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## kimballfount (Aug 30, 2017)

I wanted a garage and the wife wanted a balcony, but we're on a tight budget. This seems like the perfect compromise, especially if there is an actual cost savings.I also need a place to put my telescope, its been collecting dust at my apartment. Plus, the lot has a mountain view, but its not really great unless youre like 10ft off the ground.. I think it looks kinda cool, the elevated handrail seems to add to the colonial vibe.


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## Nealtw (Jun 22, 2017)

The parapet walls will add a little for flashing and what have you for a guaranteed water tight project. But making it water tight with a handrail is trick too.


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## carpdad (Oct 11, 2010)

Regular lumber 2x10 or 12 will not give you the span you need even for one car garage. Very good chance of mid sag and ponding roof. Doesn't matter snow or no snow. If you plan for mid beam, then you can. Measure a pick up and plan the garage. 3' on each side of the door and min 1' nose and the end. The chart you looked at gives you the minimum to average ratings but esp for roof you want to over estimate the load. Try using the deflection number in the 400. Also a good slope (1/2" per 12" or so), rail that is better than deck rail attachment and flashing (time and chance of failure), more expensive flat roof material, a deck on top and how to protect the roofing material from the deck material. Also good to have a small overhang over the transition door. Counting for these, it costs more to have a roof/deck. Regular roof can be done with regular lumber and cheap shingle. Flat roof also will need leaf cleaning and better than regular gutter. Gutter guards will clog more and need more cleaning. On the gutter end, foot overhang, sheet metal facia, spacer for the gutter and flashing between the drip edge and into the gutter helps.


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## Oso954 (Jun 23, 2012)

> I also need a place to put my telescope,...


A roof deck is a lousy place to use a telescope. It is possible to use one if you are alone on the deck, but with other people present, the vibrations are extremely annoying. You will be repeatedly asking people to freeze in place.


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## joed (Mar 13, 2005)

A roof deck still requires a roof to protect the garage and then you have to build a deck on top of it. The roof needs to be built in such a way that it can also withstand a deck on top of it. If anything it will more expensive than normal type roof.
And then when it is time for a new roof you have to tear the deck off first.


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## kimballfount (Aug 30, 2017)

Well you're using less sheathing, you're not using shingles, you're not using trusses, and youre killing two birds with one stone, because you're negating the necessity of a back porch. To meet the structural needs to withstand the additional weight, you only need to add a support beam in the garage, or go with bigger joists...The deck doesn't get "torn off", you set retractable screws to maintenance the membrane and access the subfloor.


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## Nealtw (Jun 22, 2017)

joed said:


> A roof deck still requires a roof to protect the garage and then you have to build a deck on top of it. The roof needs to be built in such a way that it can also withstand a deck on top of it. If anything it will more expensive than normal type roof.
> And then when it is time for a new roof you have to tear the deck off first.


A solid surface deck has to be covered and treated as a roof and most products sold today are approved for that here. So that would be a question for inspectors where the house will be.
Vinyl sheet decking is considered roofing.


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## kimballfount (Aug 30, 2017)

"If you plan for mid beam, then you can. Measure a pick up and plan the garage. 3' on each side of the door and min 1' "

Do you mean run a support beam along the ceiling, and then have 3 feet on each side of the garage supporting the beam?


If the garage is 14' x 18', why couldn't I just run joists spanning the 14'? I could have one of the walls without the garage door be a little bit shorter to allow my 1/2-1/8" taper and drainage. Surely a 2x12 joist can span 14 feet with 60lbs of load and minimal deflection...


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## Nealtw (Jun 22, 2017)

kimballfount said:


> "If you plan for mid beam, then you can. Measure a pick up and plan the garage. 3' on each side of the door and min 1' "
> 
> Do you mean run a support beam along the ceiling, and then have 3 feet on each side of the garage supporting the beam?
> 
> ...


Draw that on the plan and see if they approve it. You just build the slope in the two side walls


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## Tizzer (Jul 24, 2010)

From what I've read the house isn't even built yet. This garage/deck will be a DIY project afterwards I guess? Because you're here, on a DIY site.
Let the engineer that draws up the house plans do a sketch-up on both a traditional garage roof and the deck roof to compare costs.


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## kimballfount (Aug 30, 2017)

eh, to save on costs Im not going to use an architect to draw up my plans, Im just going to modify a plan I found online. If the building department has questions or concerns about the plans I try to submit I will then go to an engineer for approval. Engineers from what Ive read can be pricey, especially if you just show up with a bunch of questions and lack any clarity. After approval I'm to get some quotes from some different framers in the coming months, it'll help me determine if I'm going to be doing this project myself or contracting it out. Either way, I need to know as much as possible about this project before I try to get it permitted.


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