Ok, I have a great flat roof that would make an Awesome deck, it's got a great view and once we put a dormer and french door in, we will be golden. I heard tat this Old House "Floated" a deck over a roof. Does anyone know how this works? We have to get the roof re-done at some point, so if i'm going ot have to tie things in i'd rather do it then. I als might make it so it is easy to access under the deck, just incase.
Can anyone be any help?
Thanks,
Adam
I think they did a conventional rubber membrane roof and placed special pads down on the roof that the deck sections rested on.
I don't think any roofer would give you any warranty at all if you wanted to put any kind of tie in that would penetrate the membrane to attach the deck to the roof. I don't think any amount of flashing and sealant would keep your roof leak free.
I've done this using a removable 'Pallet' system. The deck was set on the roof in 4x4 foot pallets using simple thick roofing felt/ treated lumber pads underneath. Each pallet was 2x4 treated, decked with treated 5/4 1x6 with 2 boards left out leaving gaps in the deck at 1/3 and 2/3 of each pallet. After setting the pallets in place LONG 16 foot boards were dropped into the 2 spaces tying 4 pallets to each other. The deck was 12 x 16 . along the 12 foot sides a 12 foot fascia board tied the 3 sections together. Steel railings were bolted on top. The intention was to remove this deck if the tar/gravel ever leaked. That was 15 years ago and the deck is still there and the roof is still leak free.
They did remove a few boards to be able to add a bit more felt in areas that started to bounce a bit, but that was 10 years ago.
My only question is what happens in a VERY strong wind / Hurricane. Is there any chance it would blow-off, etc/ it's in a fairly sheltered area, back side of a LARGE roof, and i think any big hurricane would come from teh south / east which would be protected.. I coudl some how "bolt" it to the house.
Thanks
There are some other issues associated with putting a deck on a roof. Even a "flat" roof is sloped slightly so it will drain. You'll have to allow the new deck to follow the roof slope or shim the support points to level the deck. Don't place members on the deck that could dam or otherwise obstruct water flow as water could build up and flood the roof. Water weighs a lot and it is common to collaspe roofs if the water builds up. The added weight of the deck will also make the roof sag a little more and potentially increase the ponding effect (and load).
Additionally, depending on where you live, a roof is not sized to take the additional load of a deck and the added people/furniture associated with the deck. Typically, a roof is designed for 12 to 20 pounds per square foot additional live load (not including the existing material load). A deck could weigh 10 psf plus the live load of 40 psf, well you can quickly overload the roof. If the roof was designed for a heavy snow load, then the 40 psf live load won't be there when the big snow hits.
Lastly, high winds actually try to lift up items off a roof, especially around the edges and corners. Not tieing down the deck could damage the roof during high winds and cause a public hazard if it actually clears the roof parapet.
You may want to contact a local structural engineer is address the load capacities of your roof before preceeding.
Paul.
This is very common in NYC. I don't know how that helps you but maybe it will.
A friend's 3-story 20 aparment building had a deck on the roof with wooden lawn furniture, electricity, etc., and the roof door was unlocked so that anyone could go up there. But aiui someone was actually paying rent for the roof and others didn't use it, at least not when the tenants wanted to. My friend never used it, but she burned in the sun, so maybe that was why. A lot of buildings from private homes to large apartment buildings have roof decks.
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