Adding Concrete Footing to Porch Posts


Old 07-28-14, 07:29 AM
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Adding Concrete Footing to Porch Posts

I have an odd small second floor porch that is supported by 3 posts that are 10' tall. The porch is about 10.5' wide X 5.5' deep with the width spanning along my house and connected to & accessible from my 2nd floor. The rightmost post, while overall in good shape, has rot damage at it's base and is hardly adding support, if any at all. Fortunately the posts are not evenly spaced and the next post is closer to it than the 3rd one.

The damage to the post only seems to really affect the bottom 6-8". I'm looking for advice on adding a cylindrical cement footing. Even though the post isn't doing much at the moment, I presume for security's sake I can temporarily screw some supports to the post, cut off maybe the bottom 12 to 14", and put a cylindrical forming tube below, adding cement up to the level where I cut the post, and later removing the temporary supports.

Any critiques or suggestions of that process? What width form tube should I use? How far should I dig down? Should I add a post anchor? (The post's actual size is just over 3.5"x3.5")

Thanks in Advance,

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Old 07-28-14, 01:54 PM
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What you're planning isn't as effective or permanent as completely replacing the rotten columns, but it's the next best thing. You can minimize the likelihood of any further column rot taking place by installing Simpson galvanized steel post bases (with anchors and stand-off bases attached) at the column cut-off points. Then just pour concrete up to the bottom surface of the base. Make sure to treat the wood cut ends with copper naphthanate or a similar preservative, before installing the post base.

For average soil conditions and 4 x 4 columns, I think a 12" diameter Sonotube would work. If your soil is mushy, larger would be better.
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