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  1. #1
    Join Date
    May 2010
    Posts
    1

    Default Wood posts in concrete

    I have a 15 year old ranch style house located in central Iowa. There is a concrete porch (6' X 30') across the front of the house with a corresponding roof overhang. There are 4 wood posts across the front, embedded into the concrete, that provide support for the roof overhang. The current posts are 6X6, and apparently are not treated, since they have started rotting where they meet the concrete. It appears the the posts were put into place, and then the concrete was poured around them.

    So it's time to make some repairs.

    It may not be practical to completely remove the posts so I thought I would do one of a couple things. Note-I'll make sure the existing roof is braced before I remove the posts

    1. Cut each post about a foot or so from the porch roof, cut a section out of the poured concrete porch so I can pour a footing for each post, and then use a metal beam (like an adjustable floor support in a basement) between the footing and the existing wood post. I would then box in the steel beam for aesthetics with composite lumber. I'd then form up the sections of porch that I cut out, and then pour new concrete into the voids.

    2. Cut the existing post about a foot from the bottom, cut the porch concrete enough to pour a footing, and then add in a piece of 6X6 treated lumber between the footing and the existing post. This would preserve most of the original post. I'd then form up the sections of porch that I cut out, and then pour new concrete into the voids.

    If #2 is a possible solution, are there any problems sitting a regular wood post on top of a treated post? I'd prefer not to do this again in a few years if there might be issues with the regular wood/treated wood connection.

    Any other possible ideas? I haven't started this project yet, so I'm open to suggestions.

    Thanks!
    Last edited by Mike/IA; 05-09-2010 at 08:27 PM. Reason: Spelling

  2. #2
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: Wood posts in concrete

    Ideally it would be stronger to have the columns run continuiously form footing to the roof.
    Having joints or splices will weaken the integrety of the columns.

    Option #1 --- steel is a good choice.
    One thing to consider the base plate where it comes into contact the concrete is too provide an isolation between the two. You can lay a piece of bituthene on the bottom side of the base plate --- otherwise use an industrial zinc based primer to protect against rust.
    Secure the top plate of the steel column to the roof support.

    Option #2 -- I wouldn't bother making a splice --- a Dutchman splice would be the only one I would consider -- but it still is a splice.
    If you're going through all the work you may consider a new 6x6 PT from the footing up to the roof.

    2 cents worth.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  3. #3
    Join Date
    Aug 2007
    Posts
    8,068

    Default Re: Wood posts in concrete

    If it were me, I'd support the structure, then pull the post, remove the rotten portion below grade, then fill the hole with concrete with either a wet set post base or pour the concrete flush with an adjustable post base, the reset the post. The post base you choose should elevate the post above the concrete so that it does not wick moisture and continue to rot.
    Come to Hidden Content for all your DIY needs

  4. #4
    Join Date
    Aug 2007
    Location
    Portland, Oregon, formerly of Chicago
    Posts
    1,950

    Default Re: Wood posts in concrete

    It is possible that the posts are not actually structural. Many ranch homes, built in later years using pre-stressed roof trusses, merely cantilevered out over the front porch. My former neighbor in Illinois had such a porch. If this is the case, it will be clearly evident from the attic. The fact that the posts are not actually resting on the slab, indicates that the porch slab is probably floating on grade and the architect anticipated possible frost heaving of the slab and did not want the posts pushing up against the roof.

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