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Concrete over wood @ exposed deck

Concrete over wood @ exposed deck

Concrete over wood @ exposed deck

Hi all!

What is everybody's detailing preference at a wood framed deck topped with concrete? The deck will be exposed to rain. I'm inclined to put a pressure treated plywood deck, waterpoofing membrane over that and then pour concrete. If the concrete is capped with a closure angle, due to concrete being porous, is there a chance of water pooling at the waterproofing membrane since it would have nowhere to drain?

The detail I'm thinking of going with is a 1 1/8" PT deck, a layer of felt paper, then topped with a concrete with integral waterproofing. Is this overkill for my situation? Please see attached detail.

RE: Concrete over wood @ exposed deck

Specify marine plywood, a PT ledger (maybe 3X considering the length of nails for the hangers, and vent the soffits with strip vents fore and aft.

Mike McCann, PE, SE (WA)

RE: Concrete over wood @ exposed deck

Looks very similar to the balcony which collapsed at Berkeley. Whatever your detail, it will never be done correctly, and it will leak, and the wood will deteriorate with time.

RE: Concrete over wood @ exposed deck


The detail is very poor - water will be trapped between the ply and concrete, and between the HSS and the ledger.

Take a look at the article at the link - Joe shows how to do it:


Also, I'd be inclined to use precast pavers instead of concrete so repairs can be done with minimum fuss.



RE: Concrete over wood @ exposed deck

Def. do not use a closure angle. Form that up an inch or so past the HSS and put a cspillary break notch in the bottom.

RE: Concrete over wood @ exposed deck

Second to XR250.

You'll could get water between the steel angle and the concrete. Ditch the angle and push the concrete out a few inches beyond the HSS.
I've seen architects detail an upside-down "V" notch in the bottom of the concrete to force water to drip there.

Do you have occupied and enclosed space below?

RE: Concrete over wood @ exposed deck

suggest 1/4" per foot

RE: Concrete over wood @ exposed deck

Thank you all for your input!

I've followed DBronson's link for detailing this situation. Concrete over wood framing stinks in general. How do you think the clients would react to specify concrete with integral waterproofing in addition to this detail (Hycrete). I have no idea how much this stuff costs. Revised detail is attached. Thanks msquared for ledger nailing depth advice.

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