Using Roof For Deck

sorry about the cross-posting. I just bought a duplex and have access part of my tenant's flat roof via a window. I was considering replacing the window with a door and using the roofs as a deck... maybe even building stairs down to the yard as an alternate exit to my apartment. I'm concerned about the underlying strength of the roof though. I need to make sure it is up to code, especially when I ultimately rent out my apartment to other tenants. I may be able to access the substructure of the roof via my tenants apartment, but I need to know what I should be looking for in terms size and spacing of the crossmembers, etc. Any help or resources would be appreciated!
Thanks, Jon
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<< I need to make sure it is up to code, >> << I need to know what I should be looking for in terms size and spacing of the crossmembers, etc. >>
These questions need professional answers. Over the long term you will save money by getting an architect to do your planning. Anything less puts you at risk if there are future problems. You can make more money as a responsible landlord than you can by being a sloppy owner or slumlord. HTH
Joe
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you probably need an engineer. normal roofs aren't usually designed for load bearing uses. if you're doing this to provide emergency exit, then i don't see a problem since you wouldn't be holding star gazing parties up there, but the next person who buys your house might.
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What I would to is open the ceiling up at 32" intervals at the edge of the roof, directly over the supporting wall underneath, and put blocking there from the top sill to the roof deck. Run posts above that, and a ledger along the wall with the window in it. That way, all the loads are carried by load bearing walls, and you have the added bonus that walking noises aren't transmitted directly through the roof into the apartment below.
Unless the room below is a converted porch, it's likely to be built exactly like any other load bearing wall in the house, and the rest of them support two floors and a roofload of snow. *IF* you have any idea what you're doing, opening the ceiling to put in the blocking will let you see enough of the wall plate and studs to know whether there's going to be a problem. How big a flat-roof section are we talking about here?
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Thanks for all the responses-- they are helping give me some ideas. The roof is only 6x12, and I'm not too worried about the noise transmitted from walking around on it (the rest of the house is already noisy, and the roof is over my tenants laundry room...). I'm commonly out on it (crawl through the window a couple of times a week) and know that the last tenants did this also. I've thought about suspending the deck, so support is along the edge, or even via posts to the ground, but the simplicity of just using the existing surface (or putting sleepers down with decking on top) is tempting enough for me to do my homework to see if it will support it. One thing to note is that I'm in western Pennsylvania, and houses should be built for pretty substantial snowfall. A person from Boston posted (in another thread) that he/she has built many roof-decks using the existing surface because houses are built to withstand the heavy snow-loads during the winter...
In any case, if there are more comments, please post. Otherwise, thanks for all the advice!
Jon
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On 6 Apr 2004 08:02:50 -0700, snipped-for-privacy@yahoo.com (John Q homeowner) wrote:

Many flat roofs are problematic in their own right, and most likely not designed to serve as a deck. Contract a licensed structural engineer to assess your situation
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