Hello Everyone!
This is my first post at breaktime and I’m truly excited to see what others have to say in regards to my deck project.
OK, so my client wants a deck built over a section of roof that has about a 4:12 pitch.
My major concerns are whether or not her roof can carry the load and how to anchor the structure to the roof without compromising the integrity of the roofing membrane(composite shingle). I browsed some of the articles on this site for roof decks but they all seem to be detailing tips for near flat roofs with built-up type membranes. In one of these articles by Dan Rockhill, he cemented sleepers to his roof with cold roof cement on a pitch of 1/4″ every foot. I’m doubtful that that would be sufficient on a roof pitch of 4:12, therefor probably requiring some nailing along my sleepers to keep them from sliding down the roof on a hot day!
Given that my client’s roof can support the load, I’m curious as to what approaches to flashing and weatherizing these connections people have implemented.
And if the rafters wont support the added load, what possibilities are there for further distributing the load without rebuilding the roof.
thanks a bunch.
Replies
I'm assuming this is an asphalt shingle roof since you didn't specify, but the answer is basically the same for all steep slope roofing products. You'll need to find the appropriate bearing points and install posts through the roof to them (top plate for example). That post will need to be flashed with custom flashing.
After rereading your post, it seems you want to lay the supports on the roof. Good luck with that.
http://grantlogan.net/
Welcome to BreakTime! Hard to visualize the deck you're asking about - could you post a picture or sketch?
"I needed a drink, I needed a lot of life insurance, I needed a vacation, I needed a home in the country. What I had was a coat, a hat and a gun."
Raymond Chandler's Philip Marlowe
this drawing is an approximation of what I have in mind.
only the front most edge of the deck (in the drawing) is over an existing
wall and top plate. the room below has a vaulted ceiling so there is no attic space
to access, for reinforcing below. I'm no engineer, and I agree its a good idea to consult one
but it seems as though this load is broadly distributed. The drawing doesn't detail what
I imagine could be additional posts underneath to further distribute the load along the sleepers which aould be located directly above existing rafters.Any additional thoughts appreciated. this is new territory for me.thanks, greg
What Huck said, but your design could be made to work if you brought the deck out to the wall plate and supported it on two or three posts resting on the wall plate with the load properly spread downward. It's still reroofing problem, but just at the top and that could be accomplished by removing a few of the deckboards.http://grantlogan.net/
Huck,
In addition, the drawing you attached looks like the the section under the deck is framed in and sheathed, keeping elements out and i imagine the surface under the decking is a built-up roofing membrane with a minimal pitch. Is that what you're recommending I do as opposed to leaving the deck framing exposed? I guess that would take care of my worries of water penetration where the sleepers are nailed to the roof. But it does change the asthetic of the job, perhaps for the better, and adds to the finishing and material costs.greg
As you've drawn it, it doesn't look functional to me. How would you re-roof the house? Plus, is the structure of the deck tied to the structure of the house? - If so, how is this done without penetrating the roof surface - or, if the roof surface is penetrated, what is being done about potential leaks? If its not, then is it safe?
I would not approach this matter casually. There is a lot of liability involved in this project, and you would be taking a huge risk to build it as you've drawn it. Apart from structural and safety issues, water penetration alone is a huge risk. I once had a client claim their original Frederick Remington painting was ruined by a roof leak related to my project. Turned out they dropped the claim, but you see what I'm getting at.
I wouldn't touch that one, unless I had drawings and details provided by a licensed architect, stamped by a licensed engineer, and approved by the local building department."I needed a drink, I needed a lot of life insurance, I needed a vacation, I needed a home in the country. What I had was a coat, a hat and a gun."
Raymond Chandler's Philip Marlowe
Without more information it's hard to tell you much.
You have to tie in a bottom and a top plate to the roof rafters to rest your deck framing on, and then flash the plates accordingly. Do not set it directly on the shingle, (I know that some builders do but...), but strip the roofing away and have framing sitting on framing. That's assuming the roof rafters can support such a load. You should consult a licensed engineer to tell you what you can and can't do.
If you need further support for the deck, chances are you won't need to rebuild the roof framing, you'll just have to fortify it by maybe doubling up on the joists or having the outer edge plate of the deck bear onto the top plate of the outer wall so there's a direct load all the way to the foundation. Then on the other side you should maybe have Simpson hangers attached to the rafters where they meet the ledger. Or would that side be onto a ridge?
These are only general suggestions since I don't know the specifics of what you're working with.
Jer,thanks for the input. I just posted a drawing of my roof deck, to give you and others a better idea of what I'm trying to achieve. If you have time, please take a look and let me know what you think. Also, peek at the drawing Huck attached in his reply. Do you think that built-up approach is better or more conventional, or is it "6 here and a half dozen there?"greg
By your drawing, your deck's outer edge is right in the middle of the span of the roof. I doubt the existing roof was built to take such a load. You need to consider what I originally posted, going to the roof's edge with the deck load, or if you want to keep the deck as drawn, you need to fortify the existing roof framing.
The other problem is what the others are telling you...leaks and re-roofing. Why not build as you want and just roof the deck itself with proper flashing and drip edge all the way around? Do a thick quality membrane roof, and then simply lay down pallets of decking on the roof, or lay sleepers and screw deck boards onto them being careful not to penetrate the roofing.. I've done a few like that and it works fine.
Any way you look at it, this is the type of job that to the average Joe may look easy enough, but isn't at all. You're doing the right thing by asking about it and your next step should be to hire professionals who will sign off on the project. Do not try and slip this one by the local building board. Have it stamped, approved and inspected. On this type of job the liability is too great, and besides, that's what they're there for.
Thanks Boys,All of your input confirm my original concerns. I agree it sounds like best practice would be to extend the deck end over the top plate to transfer loads straight down to the foundation. Also to enclose the whole structure and roof my platform with a built up membrane covered by pallets of deck or sleepers. I understand that my load points will be at the top plate and ledger/ridge beam under the door. And i understand that this connection to the ridge will be my biggest water penetration threat.Anyone know of a good engineer in Portland, OR?Thanks Again,
greg
Don't touch the roof . Hinge at the wall . Big sealed steel beam at outer edge of deck.
From beam, cables to reinforced top of wall. Lift deck when it's time to re-roof.