I'm confused.

Old 06-12-03, 11:25 AM
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I'm confused.

I keep seeing things about building a roof-top deck... and I'm totally confused by a few things.

Let's say you have a semi-flat roof (slight pitch, away from finished wall... the roofing is the membrane type... not sure which one... but that's not the question...

I see in books etc that people build a deck right over the roof. Heck I've seen it first hand.

So here's my question.

A) decks by nature are very heavy... if the rafters (joist in this case) of the exsisting roof are 2x8 with a 12' span... how the heck are people building a deck up there? Sounds like an accident waiting to happen!?

B) let's say the roof could hold the load. People build the deck right on top (maybe with some neoprene bushing... but for all practical reason... it is on top... Now let's say you get a leak... what the heck to do? Rip the deck off to search for the leak? Water travels ya' know!...

With this being said, what the heck do people do -- when they want it done right?

Just think a'loud...

Old 06-12-03, 05:06 PM
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Hi Mike,

All very good points!!

"when they want it done right?" - they probably shouldn't have done it to begin with.
You are correct- lookin' for a Membrane leak will be a "PAIN"

Old 06-12-03, 09:26 PM
bungalow jeff
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This Old House added a roof deck to the Boston row house a few years ago. Major reframing to support the loads and allow fo the new walkout. The deck sits on sheets of membrane on the roof. It was never clarified if adhesive was placed between the roof and these sheets, I would worry about a Nor'easter blowing the deck away.
Old 06-13-03, 04:19 AM
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We have done this in our office a couple times. You're right, the structure has to be designed to support the deck loads; 2x8 spanning 12' is pretty skimpy.

What we do to protect the roof membrane is use screw the decking to 2x6 sleepers laid flat, placed over a 3/4" thick piece of polystyrene, placed over an extra scrap of (EPDM) roofing. We build the deck in 6'x6' (or so) sections so it can easily be lifted out if a roof leak develops. We have not had any problems with wind uplift; the sections are still fairly heavy and we don't have some of the high wind speeds like other parts of the country.


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