Rear patio overhang column support

My client sent me this image of the bottom of the rear patio overhang support column. From a phase inspection.

I didnt notice it when I was there because as far as I know, those metal wings were bent upward and it looked normal to me.

Client is worried about this plywood deteriorating & rotting and allowing settlement of the patio overhang.

Is this typical to essentially shim a support column with plywood?

Should be treated lumber in my opinion.

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That makes sense to me.

Again, This image was taken by the client…What if this was actually exterior grade plywood? would that be just as good or no?

If the plywood is rated for long-term outdoor exposure than I suppose that would be just as good as treated lumber.

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Why not the right product for the installation to begin with?


What’s holding the metal post base in place? Also, it doesn’t look like it’s attached to post.

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It’s relatively cheap to support the deck, and swap in the proper secured bracket down there.
Treating the end of the post, even it’s its redwood or PT, can help also. You know where it’s going to rot.

I don’t think even marine grade plywood will survive long in that position, and they need to fix the nailing anyway.

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No shimming in my opinion.

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^^^^^ This from Marcel ^^^^^ :+1: :+1:

When you encounter these things on a phase inspection (which appears this is), even final or one year warranty, you need to look at all angles and typically one will lead you to the answer. In this case plywood is not manufactured to be placed in compression which is what will happen here. No need to comment on anything else like not knowing (since you don’t) if it is treated or not since the first makes all other points moot!


I agree with all of the upper posts above me. The only thing I would be comfortable with would be a proper length post and alleviate the shim. The builder can chalk it up to holding his employees accountable for not measuring 2x before a cut.
From your picture, that looks like 3/4" OSB subfloor, and it will not last. No way to tell as is, but that will fail over time.

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I was thinking sub-floor as well.

I don’t have a problem with shims if they are installed correctly and use the correct material. I haven’t seen anything stating they are not allowed.

I think this might cover that.

R317.1.4 Wood Columns

Wood columns shall be approved wood of natural decay resistance or approved pressure-preservative-treated wood.

That looks like a piece of Advantech OSB under the post. OSB should never be used in that way. It will rot eventually and will cause compression. Should use pressure treated or steel, or have them recut the post to the proper length. Can also swap out the bracket with the one Marcel referenced.

I don’t read that as not allowing shims. I would say it speaks more to the type of material.

I am not saying it is not allowing, I read as it has to be pressure treated, so it is wrong as the OP’s picture.

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Gotcha. I agree with that for sure.

Which would be what in this situation?

I’d be fine with pressure treated 1X board, treated plywood, treated decking, etc. But I would also prefer the shim be at the top of the post if possible.


The other thing we don’t know in this case is how long the post is. I’m not throwing away a $50 post because it is 3/4" short. But if it’s a 3’ post just cut a new one and move on.

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At a minimum… common sense! The “shim” (cough-cough) should have been installed at the TOP of the post!!