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Currently, the porch uses tongue and groove boards that are painted. I think they might be original to the house. Whenever it rains hard, water will get on the porch. The water sits there in puddles. I'm assuming some makes it down underneath.

The porch wood needs replaced. I cut up a corner of the porch where the wood was sagging and the top 1.5in of the 2x10 joists is rotted away. I'm assuming that the water puddling is leading to the decay of the joists.

Underneath the porch is just dirt with some construction trash from when the house was built. There are two vents on either side of the porch built into the brick.

My question is: would it be ok to replace this wood with a decking type material with a gap between the boards?

My concern is the water that makes it down underneath. It makes it down there now because the wood is in no way stopping it but would having gaps somehow exacerbate the issue?

  • hould be fine,you've got a roof over the porch your gareden's going to flood before your underfloor.
    – Jasen
    Commented Mar 31, 2018 at 0:45
  • What state (or country) is this house located in?
    – Jasper
    Commented Mar 31, 2018 at 5:15
  • Located in Ohio USA
    – vini_i
    Commented Mar 31, 2018 at 10:33
  • All you need is a good slope with path for water to drain. The edges of the deck should be sealed tight after the deck has dried.
    – r13
    Commented Mar 18, 2021 at 21:25

3 Answers 3


You can and should have a gap for the water to drain away, and any water that does make it below, will have air in the "cavity" to dry it faster. If it is dirt, you shouldn't have so much water that it fills your "cavity" and floods, it should soak into the dirt and disappear. If it was any other material like concrete or wood, underneath, you could have other issues. But you said dirt, so no issues. When you have a deck on a house, attached or floating, you usually don't have a solid wall, but could have skirting, and the water drains to dirt below. Now if you had a concrete patio, and installed a deck over that, without proper drainage, you could have some potential issues. Again, you said dirt, so you are safe.

  • 1
    It helps if the under-porch dirt slopes away from the house.
    – Jasper
    Commented Mar 31, 2018 at 5:16

As long as there is a path for the water to escape if there's too much for the dirt below to handle, you should be fine with gapped boards. As stated by others, it helps more if this dirt also slopes away from the house.


It would be better to slope the floor slightly to the street. Then it wouldn't matter.

But just installing with a few relief gaps would solve the issue too. The other thing to think about is using a material that won't bow/curl were it depresses water into a pool. You use think wood and don't seal it, well it could cup water too.

That being said a little water under your porch should not effect things. However I would use this replacement time to remove trash/whatever from underneath the porch. It should just be joists, piers and dirt. Things left underneath give water a place to sit and drying will be slower.

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