Need help with on-grade deck dilemma


Old 08-05-20, 10:46 AM
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Need help with on-grade deck dilemma

I am building a deck in my back yard, it will be attached to the house with a ledge board, the opposite edge obviously needs to be supported, but a typical deck block/girder support as shown in the 1st picture will not work because it would be below grade and if I were to dig a trench it would fill with water. The only solution I could think of would be to dig out and pour a 12"x12" footing and attach some of the joists using wedge anchors, as shown in the 2nd picture.

The 3rd picture shows the layout of the deck boards.

Is this an adequate solution? Should the joists rest directly on the concrete? There is very little room to work with, the 2x8 joists will barley fit as it is. The joists in the photograph (4th picture) are 2x6 and you can see they are practically resting on the ground.

I have never built anything like this and any tips or advice would be greatly appreciated.



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Old 08-05-20, 10:57 AM
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That is not a good place for a deck! You need to have air circulation under the deck so it doesn't stay moist. You'd be better off with a concrete patio ..... or even pavers.
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Old 08-05-20, 11:35 AM
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I agree. Not a good application for a wood deck. I would want 6" minimum, 12" preferred clear space below the joists for ventilation. I would pour a concrete patio or use pavers.
Old 08-05-20, 09:21 PM
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I would create a patio. If dead set on a deck, I wouldn't attach it to the house.
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