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The front of my house has an overhang extension of the roof, held up by three posts. The posts are loose on bottom and I'm wondering how best to affix them to the concrete.

view of posts overall

While they are stable most of the time, if I pull up on a post, it can move side to side a bit. If someone leaned with all their weight on one of these posts, I wouldn't be surprised if it would slip out and get loose of the soffits/roof overhang.

As you can see in this next picture, there are indents in the concrete, presumably for these posts. The bottom of the posts don't fit snugly in those holes, though, or not enough to stay put when the posts or horizontal plank between them gets pushed on. To show these indents, I lifted up the post a little by the horizontal planks attached to it, then it can sway side to side a few inches. The roof extension and its vinyl soffits seem unaffected by any of this.

indents for posts

What's the simplest way to affix these to the slab? I'm not opposed to holding them in place with bricks, I'm just not sure that's enough if someone were to put their weight on it (I'm trying to make it safe in case someone were to lean against it, or stumble and push on it).

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  • Looks like the (ceramic?) bottom pads are doing a good job of keeping the post away from water on the ground. The concrete looks like it's not very thick at all and so probably isn't suitable for embedding an anchor.
    – Armand
    May 23, 2023 at 2:03
  • @Armand related post about painting: diy.stackexchange.com/questions/272897/…
    – cr0
    May 23, 2023 at 2:10
  • @Armand does seem like ceramic. Shoving a ruler underground, the slab is at least 4" thick and maybe 6". On one side of that front "porch", the far end in the first picture, the slab is 10"+ thick as grade goes downhill. That said, anchoring into concrete is far less simple for me than your suggestion with rebar in soil - thanks!
    – cr0
    May 23, 2023 at 2:11
  • Are those little holes (in the last pic) the original location for the standoff at the bottom of the post?
    – Huesmann
    May 23, 2023 at 12:58
  • @Huesmann to the best of my knowledge yes, they've been this loose/unsecured since I got here
    – cr0
    May 23, 2023 at 20:41

3 Answers 3

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There are many kinds of post bases available which are designed for exactly this purpose. You want something attached to the concrete. You'd do that with concrete screws and a hammer drill.

"Holding them in place with bricks" isn't viable. A brick (or even a small pile of bricks) provides very little lateral support. The solution doesn't come close to being effective or safe, structurally speaking. It would also increase moisture retention, accelerating rot.

Something stuck in the ground won't work well either unless it's deep and rigid, such as a pipe or treated 4x4 down at least 36" or embedded in concrete. A bit of rebar will flop around and be practically useless. It'll also look like poop.

I would want to know whether these posts are intended to bear load, or if they're just decorative. If the former, you may need to jack the roof back into position before you install bases or new posts. You could have some sag that shows on the roof plane and strains framing.

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    Have a look at the bottom photo. They're apparently out of position now and need to be brought back in a fair bit.
    – isherwood
    May 23, 2023 at 15:07
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    From the top photo it is not clear that they should be several inches back from the edge - perhaps the OP can clarify. That giant crack also isn't giving me a warm fuzzy that trying to solidly attach a post base isn't just going to shatter more concrete. Just something for them to contemplate if they want to try that. As indicated, I know that post bases can work just fine, there are some issues for them to consider here though.
    – Jon Custer
    May 23, 2023 at 15:10
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    4x4 posts can carry massive weight, and we have no idea what sort of beams could be in the roof.
    – isherwood
    May 23, 2023 at 16:03
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    @isherwood Let's not exagerate, they can stand their load, but not massive ones over the years, the OP moved one easily to show the indents, which is a good clue
    – Kaddath
    May 23, 2023 at 16:16
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    Those would work, but I like these better. They're less conspicuous and the concrete fasteners are hidden. They also keep the wood off the concrete.
    – isherwood
    May 23, 2023 at 20:54
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Why not drive a 3 or 4 foot length of 1/2" rebar into the ground right at the dirt edge behind each post? Leave 1 foot above the surface and use U-shaped pipe/conduit "two hole straps" to secure each bar to the back of a post. The rebar will rust, so first paint the above ground end with "galvanizing" or similar paint.

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  • This is the kind of simple and easy fix I was hoping for! I wonder if it would be strong enough to hold the posts in place? It helps that the most likely direction people would push on the posts would be directly against the rebar.
    – cr0
    May 23, 2023 at 2:14
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    @cr0 1/2" rebar is pretty strong, and with 2 or especially 3 feet underground will be well-anchored. Just use 3 or 4 straps on each above-ground section with strong 3" long screws to secure them into the wood.
    – Armand
    May 23, 2023 at 2:19
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    That would look hideous and provide only modest support. The rebar would move around a lot in soft soil. It's very flexible, and most of the load will be right near the surface.
    – isherwood
    May 23, 2023 at 13:34
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    Also, after noticing the original post position, you'd need a standoff to reach the edge of the slab.
    – isherwood
    May 23, 2023 at 14:31
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    I agree with isherwood on this, a rebar straight in soil will offer very little resistance to lateral forces, particularly when the soil is wet, the rebar will just move in the soil, and the more loose it will get, the less it will resist, as the space around the rebar will fill with water when it rains. Drilling a hole in concrete is simpler and quicker than stick a rebar 4 feet in the soil
    – Kaddath
    May 23, 2023 at 15:49
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What isherwood said is correct. You need to know how structural these posts are. Based solely on your photos, they seem to be holding up on the overhang part of your roof.

What I would do is remove the soffits and see what you have underneath. How are these 4x4s doing their jobs? Are they bolted? Lag bolted? Screwed? Nailed? Can they be easily removed?

The good news for you is it may be simple to not only fix this better than it is now, but you would gain a little porch space in the process. It looks like the roof overhangs a bed in front of your house. With the soffits removed, I would dig out three new footings in line with the existing posts. Pour concrete in and add a column base to each one. Be sure these are in-line with your roof trusses and square with both the ground and roof.

Once cured, add new 4x4s in. Bolt them to the trusses and the column base. You can now remove the existing posts (they appear to merely sit on the concrete, which is why they can move). Done properly, your roof shouldn't move at all. This gives you the full use of your porch pad and should be more structurally sound. The only catch here will be the soffits, which might need replacing.

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  • I will try to confirm how these 4x4s are doing their jobs. I might be able to see from the attic, I had looked before but not in this much detail. It sounds like removing the soffits is likely a destructive process, they'd need to be cut and replaced? I'll poke around, thanks!
    – cr0
    May 25, 2023 at 1:12

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