decking over a concrete patio


Old 09-17-06, 06:43 PM
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decking over a concrete patio

I want to do a low lying deck over concrete patio. the deck will also extend past my concrete slab.

Do i need to put some kind of spacer between the joist and the concrete?
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Old 09-17-06, 11:01 PM
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In my opinion, if you are going beyond the concrete patio, I would just act as if it wasn't even there and pour the proper footings for the deck support. Counting on the existing concrete patio for deck support isn't the best long term idea, you have to consider the load factor of the weight of the new deck on basically a 4 or 6 inch slab as opposed to 42" footings.
Old 09-18-06, 03:27 AM
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Welcome to and the deck forum.

I'm guessing that there is a door into the house at one edge of the slab. How much height is there between the slab and the threshold of that door? That's going to limit what you can do if you are thinking about decking right to that door.

The answer to your question is yes, you need some space between the joists and the concrete. Once you get past the slab, you'll need footings. How deep they have to be depends on whether frost is an issue or not. (See the sticky at the top of this forum.) Troy141 is in Chicago. Frost is an issue there, therefore his footings need to be 42" deep. I'm in No. CA where frost isn't an issue. Therefore, my footings are only 12" deep.

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