Decking over concrete


Old 03-21-05, 09:37 AM
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Decking over concrete

I am building a deck, part of which is covering a concrete patio, what is the best way to secure the deck to concrete, there is a sloping gap to be considered, the patio slopes, the deck does not. What type of fasteners and how to secure the deck to the spacers
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Old 03-22-05, 03:33 AM
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Have you thought about floating deck

With a floating deck you do not attached to the house. Try using dek-blocks that sit on top of the concrete patio. The weight of the deck will keep the deck in pace. If you will need to cross brace the post. However anything over 60 inches is a no go.

Another part, if you bolt the deck post to the concrete and and dig holes for frost footers outside of the patio then you will have a problem. The concrete will rise with frost and the post not on the concrete will stay in place. See where I am going.

I used a floating deck for my pool using deck-blocks. I crossed braced them around the outside of the deck. Haven't had a problem yet. Just do a search for dek-blocks or you can see some photos of my deck at that might give you an idea.

Good Luck

Old 03-22-05, 03:29 PM
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Oh god.. do NOT use dek blocks on the slab and make it free floating. I would say that is borderline unsafe, surely if you are in a zone that frost heaving is an issue. Free floating decks are fine when done with proper footings. You do not mention what state you are from in order to say what the best methods are for this project.
Old 03-22-05, 07:17 PM
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How far above the concrete (at it's highest side) will the bottom of the deck boards be?

I'm assuming that this patio is outside of a door, and you don't have a lot of height from the slab to the threshold of the door. Probably don't have enough height for Dec Blocks, and that's not what you want to do anyway, as hellrazor pointed out.

I've got a bid out on one right now where I will be laying PT 2X4's on the slab (flat) because I only have 4" from the slab to the threshold of the slider. As the slab slopes away from the house, I will be cutting shims out of PT 4X4 every 18" to 24" to support the 2X4. The 2X4, and the shims will be secured to the slab with Tapcon screws, (The slab is small -- 8' -- so there will never be enough space to anchor a post base to the slab, except maybe at the outside edge. The 2X4 sleepers will run perpendicular to the house, so they don't trap water.
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