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Design Considerations For Covered Deck Over Living Space - With Cantilever

 
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Old 08-24-2013, 08:41 PM   #1
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Design Considerations For Covered Deck Over Living Space - With Cantilever


Deck will be 14'x17' with 3' of the 17' cantilevered. The remaining 14' is above living space. Open on two sides. I am figuring on using 2x8 material.

This situation is different because most of the deck is covered - only the 3' cantilevered portion is open. Slightly less than that actually, due to the gable overhang of 12". Exposure is to the north and east

I am trying to keep the ends of the joists at tall(wide) as possible, as I will be attaching posts and railing to them.

Anyway, I would prefer to start the deck level out an inch or two below the finished floor, but I can only make a 1/8" slope work after starting with 1" decking and 3/4 sleepers - and the top of the deck board pretty much level with the interior sub floor. 1/4" per ft just won't work with the 10" I have to work with. This will give me the equivalent of a 2x6 setting on my stem wall.

I am hesitant to frame a portion of it level before starting my taper, but I may have no other choice. Could possibly move the exterior wall and shorten up the span to 12' with 3' overhang, but would prefer to maximize the outdoor space.


Anyway, looking for suggestions.

Last edited by acro; 08-24-2013 at 09:03 PM.
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Old 08-24-2013, 10:46 PM   #2
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Re: Design Considerations For Covered Deck Over Living Space - With Cantilever


I'd definitely want something like this engineered before I built it.

It sounds like you're planning on pitching the deck which is unnecessary as there's plenty of drainage between the boards. There obviously needs to be under deck drainage of some sort and that's where the slope will need to be. Using a deck mounted drainage system would allow you to use a thicker joist but you'll need to get other guys opinions on whether those systems are reliable enough for use over a fully enclosed living space. I'd use hot mop or EPDM on the roof/subfloor and then build the deck.

The amount of roof coverage this deck is going to have will be big help but you still need to account for blown rain and snow accumulation.

2x6 joists can give you plenty of room for a solid railing with the correct fasteners and blocking. There are some great threads on here just about that.

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Old 08-25-2013, 04:49 AM   #3
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Re: Design Considerations For Covered Deck Over Living Space - With Cantilever


I was planning on sloping the framing and bringing the decking back to level by tapering the sleepers.

I don't believe one of the deck mounted draining systems would be suitable. If you where referring to something like the RainEscape - which I have never used.

A system like that would simplify things, but it will be over conditioned interior space, not just a covered patio. I am not sure I am comfortable with that.
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Old 08-25-2013, 05:48 AM   #4
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Re: Design Considerations For Covered Deck Over Living Space - With Cantilever


Figuring on using 2x8 for what, floor joist or ceiling joist or rafter?

What type of wood will the 2x8 be?

The maximum span for a 2x8 treated SYP used as a floor joist on a deck is 11'10" which is why I am curious where you would use the 2x8.
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Old 08-25-2013, 06:41 AM   #5
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Re: Design Considerations For Covered Deck Over Living Space - With Cantilever


If the total span of the deck is 17' you only need one inch fall if a torch down modified or TPO roof is installed.

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Old 08-25-2013, 07:04 AM   #6
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Re: Design Considerations For Covered Deck Over Living Space - With Cantilever


Quote:
Originally Posted by jar546 View Post
Figuring on using 2x8 for what, floor joist or ceiling joist or rafter?

What type of wood will the 2x8 be?

The maximum span for a 2x8 treated SYP used as a floor joist on a deck is 11'10" which is why I am curious where you would use the 2x8.

You are correct. I was thinking of 2x8 LVL's for the floor joists - sorry for the confusion.



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Originally Posted by John Hyatt View Post
If the total span of the deck is 17' you only need one inch fall if a torch down modified or TPO roof is installed.

J.
That's less than 1/16 per ft. Have you installed such a low sloped roof before?

Last edited by acro; 08-25-2013 at 07:09 AM.
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Old 08-25-2013, 07:25 AM   #7
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Re: Design Considerations For Covered Deck Over Living Space - With Cantilever


The more I look into this, the more I think I may talk to the client about something like a alternative to the epdm/decking system.

Possible a lock dry system or Duradek

http://www.fsihp.com/products/deckin...-lockdry-works

http://www.duradek.com/

I have never used them, but other than some flashing details on the LockDry, it would definitely simplify the installation. And it will eliminate the possibility of future problems with the epdm caused by the sleepers bearing on it.

Last edited by acro; 08-25-2013 at 07:32 AM.
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Old 08-25-2013, 08:53 AM   #8
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Re: Design Considerations For Covered Deck Over Living Space - With Cantilever


I have installed a lot of them. Including my own wrap around upstairs deck.

Both those roofs are a commercial install very little pitch is needed. The underdeck retro systems always leak, always.

There is no future problems with the stringers laying on the roofing, think ac units siting on commercial building's roof.

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Old 08-25-2013, 09:47 AM   #9
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Re: Design Considerations For Covered Deck Over Living Space - With Cantilever


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Originally Posted by John Hyatt View Post
There is no future problems with the stringers laying on the roofing, think ac units siting on commercial building's roof.

JonMon
Good point about the commercial AC's and i did figure on wrapping the sleepers. What do you usually put under the EPDM? Ply or Advantech. Any buffer between them?
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Old 08-25-2013, 08:12 PM   #10
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Re: Design Considerations For Covered Deck Over Living Space - With Cantilever


Just for a little extra I have the roofer leave me some strips to place under the pt stringers that lay flat on the roof. The stringers are ground contact mcq 2x4s that I retreat with copper green. There is no need to wrap them with anything.

If this is your first one do not fasten the stringers thru and in to the roof. Do not let the decking fasteners do that either. Re Read. Again.

I always secure the rail post to the outside rim. Tpo roofing is the latest thing but torch down still works as well as it has for a 100 years or so and costs less. However with both of them hire a roofer that knows what he is doing.

J.
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Old 08-25-2013, 08:22 PM   #11
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Re: Design Considerations For Covered Deck Over Living Space - With Cantilever


Quote:
Originally Posted by John Hyatt View Post
Just for a little extra I have the roofer leave me some strips to place under the pt stringers that lay flat on the roof. The stringers are ground contact mcq 2x4s that I retreat with copper green. There is no need to wrap them with anything.

If this is your first one do not fasten the stringers thru and in to the roof. Do not let the decking fasteners do that either. Re Read. Again.

I always secure the rail post to the outside rim. Tpo roofing is the latest thing but torch down still works as well as it has for a 100 years or so and costs less. However with both of them hire a roofer that knows what he is doing.

J.
We have done a few of these as well. We applied tape to the underside of the 2x sleepers to keep them from scarring the epdm. The roofer also installed a substrate over our plywood prior to the epdm. We were fortunate in that our house joists were 14" tji so we had larger joists to start with. I think our deck joists were 2x12x14 that we tapered 2".
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Old 08-25-2013, 09:09 PM   #12
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Re: Design Considerations For Covered Deck Over Living Space - With Cantilever


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Originally Posted by John Hyatt View Post
If this is your first one do not fasten the stringers thru and in to the roof. Do not let the decking fasteners do that either. Re Read. Again.
J.

Yea, definitely would be floating
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Old 08-25-2013, 09:16 PM   #13
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Re: Design Considerations For Covered Deck Over Living Space - With Cantilever


I put the fall in the framing. No need to taper the joists.

A torch down modified roof is a lot tougher than you guys are giving it credit for. But what the hay do it the way you want.

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Old 08-25-2013, 09:22 PM   #14
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Re: Design Considerations For Covered Deck Over Living Space - With Cantilever


Well, i have two reasons for tapering the joists.

1. already pushing the span for the headroom I have to work with.Living space is framed with 2x10. I would have to use 2x6's to get the fall in the framing for this one.

2. Trimming the joists maintains a flat ceiling below.

Torch down contractors are getting hard to find in my area. Especially with such a small job. Though, i will admit I have not looked really hard.
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Old 08-26-2013, 05:14 AM   #15
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Re: Design Considerations For Covered Deck Over Living Space - With Cantilever


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Originally Posted by elviaduxc View Post
I was planning on sloping the framing and bringing the decking back to level by tapering the sleepers.
Got me

I edited the heck out of my initial post, must have missed that one. Mostly, I was thinking out loud while working it through in my head. I think I changed that post 6 times or so.

Initially, I briefly considered doing just that - sloping the flaming, but to do so, would have required at least 2x6 lvl's 12" oc. But I thought better of it and changed my mind.
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Old 08-26-2013, 05:35 AM   #16
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Re: Design Considerations For Covered Deck Over Living Space - With Cantilever


With as little fall as both those roofs need there would be no reason to bring it back to level on top.

None of my Wallets have even noticed it.

J.
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Old 08-26-2013, 06:17 AM   #17
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Re: Design Considerations For Covered Deck Over Living Space - With Cantilever


This is a great product for waterproofing decks over living space.
http://www.tileyourdeck.com/
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Old 08-26-2013, 09:34 PM   #18
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Re: Design Considerations For Covered Deck Over Living Space - With Cantilever


I am doing exactly the same thing on our current frame / build job. An open on three sides deck, second story, over living space. The three open (with rail) sides are cantilevered 4.5" outside lower wall finish. We used 2 x 12 treated and ripped a taper off the top of each to create put back sleepers. Deck is 11' long x 14.5' wide. Once the roof over framing is complete, we'll install 1/2" 5 ply and cover it with EPDM which will be one piece and drape down all sides. Tapered sleepers will be screwed back over joists through EPDM and decking applied. On sides we are putting 3/4" sleepers over draped EPDM to allow drainage. PVC boards / frieze to finish it off. I've done this quite a few times (10 or so) and EPDM is a very, very tough product. We do all high end customs, mostly on lakes, and this is one of our design selling points. A deck off the master suite, with a high view of the lake. Screwing sleepers through the EPDM (NOT nailed) and drawing them down tight will probably never leak in our lifetime. EPDM is covered with decking so no U.V. exposure. On this job we did a 1" to 2" taper over the 11' run which is close enough to 1" in 10'. As a test, the first time I tried this, I ran six screws through a scrap piece of EPDM, about 3' square with no draw down force. Just penetrated it with screws (left them in) and made a dish which I filled with water. It sat for three days and not a drop of water leaked around any of the screws! It just sealed around those screws as they went in. That's how tough / rubbery this stuff is. I also penetrated it with a nail and pulled it out. It barely leaked (as a bowl shape, with standing water 3" or so deep). Maybe a drop every couple of hours. I'll take pictures tomorrow but we're still in second story framing so finish work on the deck will be in another two weeks. I don't lay the EPDM until impact damage is very low, just in case....
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Old 08-27-2013, 04:45 AM   #19
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Re: Design Considerations For Covered Deck Over Living Space - With Cantilever


I am surprised that you screw through the epdm on the deck surface. Do you at least use stainless fasteners?
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Old 08-27-2013, 05:34 AM   #20
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Re: Design Considerations For Covered Deck Over Living Space - With Cantilever


The key word here is "Probably"

I have seen this many times. Fastening thru the roof causes a slow leak that is not noticed until a lot of damage has been caused. There is no "self seal "

Besides there is no reason to screw down the stringers.

J.

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