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Is it a bad idea to put a fence post "through" patio stones? We're building a patio and then enclosing 2 sides of it with a privacy wall. I want to make the patio larger than the enclosed area so there is extra space for storage behind the wall.

After researching the right way to install a 4x4 post this is the design I came up with. enter image description here The idea is that I'll cut the patio stones to fit snug around each post. Then I'll caulk the edges. Below the patio stone is the sand and gravel. Halfway through the gravel the concrete of the post starts; it's dome shaped to divert water away from the post.

enter image description here

Things to note

  1. No dirt is touching the post; only sand and gravel
  2. 12' pressure treated posts
  3. A little less than 4 bags (80#) each post
  4. Posts are 6' apart
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Running the posts through the patio stones shouldn't cause any serious concerns. However, even though you won't have topsoil directly against the post (which could accelerate decay even with pressure-treated), ground water could still compromise the base of the post with your design. Ideally you want the base of the post above the surface with the surround sloping away. That may not be desirable from an aesthetic perspective but it will give the posts a longer life-span.
One other option might be to bring up the domed concrete footing to just below the brick and then coat the bottom few inches of each post with a water-proof sealant up to just the top of the bricks so it won't be visible. These sealants come in various colors and most work fine with wood.
enter image description here

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  • I don't think Flex Seal has any longevity. They do make it look great on TV though! – Steve Wellens Apr 30 '20 at 4:48
  • Just one product of many that will do the trick. The idea is to just keep moisture from penetrating the bottom two inches of the post. – HoneyDo Apr 30 '20 at 15:33
  • Thanks @HoneyDo for the tip. I wasn't going to add additional treatment, but I'll consider it now. The 4" of post sticking out the bottom of concrete is to be in a bed of crushed rock. I got the idea for that from this article: familyhandyman.com/garden-structures/fences/… But it doesn't exactly say why to do that... I mean, would it not be better if it was just enclosed in concrete? Or is the reason so moister can travel through the post and out the bottom? I dunno. – Thirdshift Apr 30 '20 at 19:42
  • That article has it right and you're smart to follow it. Note that the domed concrete in the article is above grade - yours is not. Given what you're trying to do I like the plan you have as the best way to drain water away from the post with gravel and sand. My only point is that wet sand and eventually wet soil will accumulate around the base of the post and I would try to protect the post base with some type of treatment. – HoneyDo Apr 30 '20 at 19:52
  • I always like to encase the post in concrete. But whichever way you do it, my experience is that most post rotting issues will occur above the concrete at the base of the post. Also, I noticed that your plan does not show gravel for drainage under the post which the article does. I don't like wood in direct contact with soil and moisture. IMO you should either add gravel or encase the post in concrete. – HoneyDo Apr 30 '20 at 19:55
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I think your plan looks excellent, the dome on the concrete will be a big advantage at extending the life of the post. As long as your pavers do not have a low spot that hold water and rot the post I would give your plan 2 thumbs up this looks well thought out and solid.

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  • I'll try my best to avoid create low spots, but the posts will be downgrade from the house. So worst case scenario, water will run across the bricks, hit caulking which is old and fails, so it makes it to the 4x4, travels through the sand and gravel, until it hits the concrete dome. I still think that is OK. My hope is it would last 10 years at least. Thanks for your feedback! – Thirdshift Apr 30 '20 at 19:38
  • I think that sounds good. – Ed Beal Apr 30 '20 at 22:13

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