I am Looking for ideas to keep water from pooling under a new ground-level deck.

The frame in the photo was dug 8-10inches below the ground. I'm using composite decking so I need minimum 6 inches clearance from the dirt.

Do I go with French drain trenches diverting water out from under the deck ?

ground level deck frame

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    Jun 11, 2020 at 0:08

2 Answers 2


I like what you've done keeping the framing above grade. However, are those poured piers or are they concrete blocks sitting on grade? Hard to tell in the pic. Since you're asking about drainage, ground water is apparently a concern in your area. If that is so you first want to make sure that you sink piers to give your deck proper stability. No matter how good your drainage system is any foundation sitting on grade will eventually be compromised by ground water.
Assuming your piers are stable building french drains under and around the deck to channel away ground water is a good approach. You shouldn't get a lot of precipitation passing through the deck. The main concern is to grade around the deck to channel water into the french drains and away from the deck. Likewise proper grading under the deck should prevent pooling and move it into the drains.


First would be to eliminate the low spots that allow the water to pool, add fill to bring it almost up to your clearance minimum.

I would then Slope the grade under the deck slightly from the middle to all sides. Then dig a french drain around the perimeter just inside the rim joist and sloped so it all flows to the back side and then continue it out and away to the trees.

This is not my forte so other may have better ideas or point out the flaws in mine.

On a structural note: I am worried about the lack of beams. I would like to see your joists sitting on, or anchored to, beams and those beams on pier blocks. It is floating deck and it will move with ground fluctuations. As built i foresee that movement weakening or loosening your structural integrity.

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