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  1. #1
    Join Date
    Jul 2009

    Default Install Pier and Beam Over Existing Slab?

    My wife and I recently purchased a 1920's bungalow. It sits on a fairly typical (at least for this area) pier and beam foundation. In the mid-1950's, a previous owner added a carport on the rear of the house that opens to a side street. Sometime after that, the existing roof gable was extended out over the carport.

    We would like to close in the carport for a master bath/closet and dedicated laundry room. The carport floor is a concrete slab that appears to be 4 to 6 inches thick at the entrace and about 18 inches thick at the back. The lot is sloped which accounts for the varying thickness. The slab appears to be in good shape with no apparent cracking or shifting.

    Is there any reason I can not install a pier and beam foundation for our planned addition directly over this slab? I envision having the concrete block piers placed directly on the slab with the sills, floor beams, and floor joists installed as would normally be done.

    I plan to consult with an engineer, but I was wondering if anyone had any thoughts before I did so.

    Any advice is greatly appreciated.

  2. #2
    Join Date
    Aug 2007

    Default Re: Install Pier and Beam Over Existing Slab?

    Posts should usually be supported by some kind of foundation or footing & not bear on a 4" to 6" slab. It is unlikely the slab is actually 16" thick. Even if it is, their is likely no reinforcing other than some welded wire fabric.
    What an engineer is likely to do is ask for a portion of the slab to be cut out and a proper footing poured. Not a big deal and your nice uncracked slab should stay that way.

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