Can I make a flat roof on a guesthouse?

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Old 12-13-04, 09:56 AM
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Can I make a flat roof on a guesthouse?

I see flat roofs on old townhouses all the time and my goal is to make my guest house with a flat roof so I can sit on the roof and sip on a beverage when the weather is nice. It would also be nice to have a "battle of the bands" at my next summer party where they could play on the roof.

The problem is I haven't found the answer on where the water/snow goes since there a flat roof has no pitch to direct the water downwards?

Anyone know how a flat roof is properly done?

I appreciate any suggestions on this,

Thanks,

-MC
 

Last edited by MichaelChang; 12-13-04 at 09:57 AM. Reason: rephrasing
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Old 12-14-04, 06:25 AM
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Most flat roofs have roof drains to remove water. They are installed into the roof and have piping running to the storm sewer. As far as what you want to do with this roof, you are going to have to get a Structural and engineering inspection. I also think you would have to build the roof and then put a deck over it. Most roofing is not made for the type traffic you want to subject it to. Good luck.
 
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Old 12-14-04, 08:01 AM
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I see so that's how it works

so basically I would build a deck over top of a regular roof, the deck is made of either pressure treated wood or composite so water wouldn't damage it.

My only curiosity is when you say "piping" brings the water to the drains installed in a flat roof, what does that mean? Are there small holes all over the roof that the water goes through which leads to a drainage system?

Thanks for the reply,

-MC
 
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Old 12-14-04, 08:11 AM
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I meant to say that the drain holes are NOT small. Most are 3" or larger drains with a cast iron basin that is even larger. They also have a domed cover to prevent leaves and such from plugging them. They are also making them in plastic now. The link below will give you an idea of what they look like. Good luck.

http://www.lspproducts.com/Catalog/PDrain.asp
 
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Old 12-14-04, 08:20 AM
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flat

Michael,
"Flat" roofs are not actually "Flat". There is a slight slope 1/4" per foot is the most widely used minimum building code standard. This is more than adequate to facilitate drainage. I would not suspect that the roof area would be large enough to require a roof drain. It will just need to slope to one side, or two opposing sides.

The framing for the deck to be built atop the roofing system can be sloped as well in the opposite direction as the roof, so the result is a level deck.

With that much activity on top of this deck DO NOT use a single-ply membrane. One cig. butt between the decking will burn a hole in the roof membrane. The only way to get at it to fix it would be to remove the deck.

Look into a multi-ply Modified bitumen roof membrane. Very durable.
And the deck sould not penetrate the roof membrane in any way. Simply sit on top. If securement is required it should be at the outer edges to the side of the building incorporated into the railing system.
Fabricate the deck in sections that are bolted together, so that in the event there needs to be roofing repairs or replacement performed, the deck can be dis-assembled and then put back without destroying it in the process.

Sounds like a lot of fun, however have an architect design it so that is Safe!If someone falls off because the railiing gave way.....They will see you in court!
 
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Old 12-14-04, 08:22 AM
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you sure do know your flat roofs

Ohh so the flat roof really isn't prefectly flat, it is eversoslightly sloped in order to guide the water to the drain holes.

With the way my projects have been turning out recently I just see this as a recipe for disaster. It's probably easiest to build the deck on top of the roof, I'm having a little trouble visualizing how that's going to work but I imagine it'll come to me soon,

Thanks,

-MC
 
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Old 12-14-04, 08:34 AM
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drains

Michael,
No drains....just a gutter on the perimeter.

If your planning on having parties up there....the potential for liability is HUGE.
Please consult with an Architect.
 
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Old 12-14-04, 08:48 AM
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hmm maybe I won't be doing a whole lot of partying on that roof

What I had initially envisioned is a single story 20 x 24 guesthouse with a roof that bands could play on while people on the ground below soaked in the entertainment and basically turn my backyard into a sesspool on occassional summer afternoons .

If people are going to start falling off and suing me I might have some thinking to do.

At minimum I will take your advice and consult an architect but even then if I'm not convinced that we can make the roof "fall off proof", I may scrap the whole idea and just stick a regular roof on there.

Thanks,

-MC
 
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Old 12-14-04, 09:31 AM
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Bands

Make the structure strong enough to park a truck on, and an over-designed railing and stair access, and be sure to send me an invitation

One other thing...Band require A LOT of Power...may need to have 200 amp service alone
 
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Old 12-14-04, 09:34 AM
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that's what I'll do

thanks for the tips,

-MC
 
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