Concrete over vinyl deck membrane, Topping compound over torch on roof
I have a new vinly deck and new small flat roof section (torch on). Both are 6 months old. I have a metal roof. I am hoping to treat the deck and torch on such that they last as long as the metal roof ( 50 years? ). Currently the vinyl is likely rated at 10 years, the torch on 20 years? and the metal roof somewhere close to 50. The vinyl deck is overtop a living space. The torch on is also over a living space.
My idea is to apply 1.5″ of concrete on top of the vinyl deck surface and a concrete topping product over top of the small torch on roof. The deck is 100 sq ft and the torch on membrane with integrated gutter holes is 50 sq ft.
Has anyone done this before or have any reason I should not do this? The deck currently squeaks groans after the sun has been hitting it and you step on it, possibly the sleepers are expanding in the sun and then cause the groan. I am hoping applying the concrete layer will distribute the weight more evenly and prevent the materials from heating up as much and ultimately eliminate the squeak.
All thoughts welcome.
MG
Replies
Concrete weights about 150 pounds per cubic foot. You'd be adding about 1875 pounds (nearly a ton) of dead load to your deck. Are your footings designed for that weight?
Weight
Footings are the poured concrete foundation of the house, so I'd have to say yes.
How much is the deck going to sag when you pour the concrete on it? Remember, 1.5" is not enough to provide any real strength. You need to get the dimensions of the joists and calculate sag.
That is not a good sounding idea to me. Concrete cracks, and is not waterproof. Could you provide shade for the deck? That would be my best idea. I simply would not worry about the roof, but if it is reasonably flat you could put down a layer of light gravel to shield it from UV.
Thanks for the response.
Yes Gravel might work. The problem with gravel is that tree litter will collect and weeds will grow in it. The flat roof is very visible from the main room of the house so this needs to look good.
While concrete is not water proof that isn't really the point, the point is for it be protect the membrane against uv. Concrete is a water sink, water will wick into it.
Concrete can crack, on a 100 sq ft pad I wouldn't expect more than slight surface cracks which could be patched if they are unslightly.
There is also elastomeric roof coating (sno roof?) that is a nice white color. It may not be compatible with your roofing material though. I'd hate to try to prolong the life and actually shorten it. May be an option though.