HighDesertHomeOwner

I am planning on adding about 300 sq feet to my house, a recreation type room. This is be just a shed roof (combined ceiling joists and rafters) extending 12 feet rafter span across about 24 feet wide.

The grade is about 0.5 inch per foot. This will make a ceiling height of about 7 feet six inches at the far end.

People say flat roof will leak, but I really wonder about this wisdom.

I have built 2-part epoxy coated plywood (not OSB though) wood structures (large fish tanks) entirely immersed in water and it has been nearly 20 years. There is still no leak.

If I coat the OSB roof shealthing with a couple of layers of epoxy, and particularly heavily at the seam attached to the rafters, the entire roof should not leak. It should be one whole sheet of waterproof material.

The greatest threat is UV from sunlight that will degrade the epoxy, but the felt and roofing cover will prevent sunlight from reaching the epoxy.

Has this epoxy approach been tried but has failed the test of time?

I will also color the epoxy to reduce sunlight effect during construction.

Thanks

inspectorD

Another thing to think about is the wind, anytime the structures move, they create a gap. Not to mention shrinkage and expantion at different times of the day.
It sounds like a neat idea, but everything moves.
The fish tank is small scale, and always humid , it probably has less movement just for that reason...and does not leak.

Good luck.

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oldognewtrick

If I had a vote on this, I'd suggest spending 500.00 and get a real roof system. Certainteed ( Flintlastic )and GAF ( Liberty ) make peel and stick systems that are made for low or no pitch roof decks. You don't have to reinvent the wheel to have a viable system that will last for years if you follow the instructions, and these are very user friendly applications that a homeowner can do without the need of specialized tools.