Attach Deck to Concrete Patio Slab

by Norman
(Canton, Ohio)

Q: Hi

I am researching my next project. I would like to know how to attach a deck sub frame to my concrete patio, what fasteners to use, etc. My patio is 14' by 24'

Thanks,

Norman

A: For attaching a deck sub-frame to a concrete patio, Tapcon screws are a good choice. These are concrete screws that go into drilled holes. The hole for Tapcons is made slightly smaller than the diameter of the Tapcon itself, and the box tells you what size masonry drill bit you need. For example, the quarter-inch Tapcon uses a 3/16 bit, and the 3/16 Tapcon uses a 5/32 bit. To determine the length of Tapcon you need, go with the thickness of the framing and add 1" to 1.75" to it.

Rent a hammer drill to drill the holes in the concrete. If the Tapcons have a collar on the head (Some do and some don't.), you'll want to countersink around your drill hole so the screw head is flush with the surface.

What some people do is they use construction adhesive to get the framing where they want it, and then use the Tapcons to attach everything securely. You can drill through the framing and into the concrete with the hammer drill.

Make sure you drill the hole for the Tapcon screw long enough: too long is OK, but if you drill the hole too short, the Tapcon will go as far as it can and then stop. You can use the depth gauge on the hammer drill, or put tape on the drill bit to indicate the right depth. Vacuum out the holes before putting the Tapcon screws in. Concrete dust in the holes will keep the screws from attaching properly.

The Tapcons have really sharp threads, so when you're inserting them (which you can do with a regular drill), go slowly to prevent them stripping out the insides of the concrete. And, of course, always wear eye and ear protection.

Best regards,

Alan
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