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So my friend has a 20 x 20 roof deck that is laid on top of a concrete roof. The rood is pitched an there is drainage at the corner. The current deck is about 8 years old and is curling, splitting and coming up like crazy. The deck was there when he purchased the place. There are a couple things that come to my attention ...

  • The decking is laid on top of 2x4s that are laid on top of foam-core, but the are laid flat rather than like joists.

  • The decking seams thinker than usual 1 1/2", I'm used to 5/4

  • The drainage looks suspect ... it's possible that it all drains in
    one direction and at the end makes it's way across the roof to the
    drain but I cant tell

  • It's painted on top an not on the bottom

  • It looks like they used non epoxy coated screws ... I see allot of
    rust on the screws

I'm looking for some recommendations on how to re-build this I Thought perhaps of mimicking the same design but cutting gaps in the foam to allow better drainage, and using some better beefier epoxy coated deck strews. Also, currently the boards are spanning 2', so if I use 5/4 deck boards, I think I might have to span less. Something else to factor in is the sun ... it gets pretty hot up there, no shade at all.

Any advise or experience would be appreciated, I would hate to re-buiid this thing only to have the same exact problem. Please see photos enter image description here enter image description here enter image description here enter image description here enter image description here

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    The deck looks like it was built using the cheapest stud grade 2x4s available at the time. If so it looks about as expected after 8 years. – Michael Karas May 30 '15 at 9:17
  • @MichaelKaras Agreed, it looks like cheap crap ... but do you think that it's the wood or the use of sleeps on a concrete roof with questionable drainage that is causing the issue? – user379468 May 30 '15 at 20:46
  • It is somewhat hard to see but the sleepers underneath do indeed appear to have been getting rather decayed. If you do determine that it will be fully replaced do you have any option about raising the floor height some? If so it may be a good strategy to use 2x4's on edge the next time but support them up off the roof surface for say 1.5". If they were supported every 2 feet they should be plenty strong. The supports could be some type of small blocks made out of a decay resistant wood (cedar, redwood or maybe even cypress) that were made from pieces of a 2x6 cut off in (continued) – Michael Karas May 30 '15 at 21:13
  • (continued from above) 5 inch lengths. This would leave a good area of roof free to drain properly. A second consideration is that once the old deck was removed would be to renew any roofing treatment before laying down any new deck materials. – Michael Karas May 30 '15 at 21:15
  • @MichaelKaras - that is an excellent idea, we do have the option of lifting the deck up a bit. currently, the sleepers have what looks like riged foam adhered to the bottom, I'm assuming so they are not in direct contact with the concrete roof. One thought I had was to use the same technique, but rather than run the strips completely down the 2 x 4 , I would stagger it, but perhaps your idea is better – user379468 May 30 '15 at 23:36

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