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  1. #1
    Ron Bishop's Avatar
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    Default unlevel floor surfaces

    I observed slightly unlevel floor surfaces inside the kitchen of this structure during my inspection. During the crawlspace inspection, I found that a plywood subfloor was present, with 4x6 girders 8"OC, and no joists. It appears that the subfloor cannot adequately support the weight of the kitchen appliances, and some minor sagging of plywood is occuring as a result. Any thoughts? Any code gurus out there that can impart some wisdom? This structure was built in 1964.

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  2. #2
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    Default Re: unlevel floor surfaces

    Quote Originally Posted by Ron Bishop View Post
    with 4x6 girders 8"OC, and no joists.

    I suspect you missed typing in a number in front of the 8 at 8"OC ... ???

    Mostly likely, the span rating has been exceeded, and, depending on the number you add in, possibly even exceeded by way too much.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  3. #3
    Ron Bishop's Avatar
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    Default Re: unlevel floor surfaces

    woops...8'OC


  4. #4
    Ted Menelly's Avatar
    Ted Menelly Guest

    Default Re: unlevel floor surfaces

    8' on center with just plywood above and no joists between is not just way to much of a span but an absurd span. The floor needs to be engineered or joists at 16 to a max of 24" on center. With just plywood above I would say 16 on center. A case of sliding a bunch of joists and appropriate hangers onder the home and putting them in place. Should be fun concidering the plywood and flooring materials are sagged down so one end of each joist slid into its hanger and the other end jacked up. Probably a fairly involved job and new floor covering once it is jacked up level.


  5. #5
    Ron Bishop's Avatar
    Ron Bishop Guest

    Default Re: unlevel floor surfaces

    aye...caramba...


  6. #6
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    Default Re: unlevel floor surfaces

    Quote Originally Posted by Ron Bishop View Post
    I observed slightly unlevel floor surfaces inside the kitchen of this structure during my inspection. During the crawlspace inspection, I found that a plywood subfloor was present, with 4x6 girders 8"OC, and no joists. It appears that the subfloor cannot adequately support the weight of the kitchen appliances, and some minor sagging of plywood is occuring as a result. Any thoughts? Any code gurus out there that can impart some wisdom? This structure was built in 1964.
    Ron,

    In my area, we have a lot of single story home floors that are supported with 4x6 girders spaced on 4 foot centers supported by wood posts spaced anywhere between 4-6 feet apart. The plywood is a 1 1/16 inch thick tongue-and-groove plywood. Very common throughout much of the 1960s and 1970s. Your pic looks like that kind of construction. However, you refer to 8 foot centers. That is way too far for the plywood to span, so I assume that the posts are 8 feet apart along the girders. 8 foot spans seem a bit excessive. Like I said, I typically see spans that do not exceed 6 feet.

    The two primary problems that I find with this type of construction are:

    Expansive soils. We have a fair amount of clay and adobe soils around here. As a result, the concrete piers will heave/settle seasonally as the ground shrinks and swells with the rains. Consequently, the floors are often uneven. This will also contribute to interior cracks and out-of-square doorways. Generally, this can be controlled with proper drainage and installation of a moisture/vapor barrier. The goal is to keep a constant moisture content in the soil to prevent swelling/contraction of the clay soils. Not sure what kind of soils you have over in Bishop, but if there is adobe or clay, this could be part of your problem. Where we do not have expansive soils, the floors are level. Correction often means adjusting the height of the posts (cutting if too long and replacing if too short), however this will also introduce new cracks into walls and ceilings.

    Deflection/springiness. Since the plywood spans 4 feet between girders, the floors deflect/bounce somewhat more than a floor constructed with 2x joists on 16" centers. Large furniture, particularly china cabinets and the like, will move noticeably when a person walks by. I have seen, in rare cases, where a support wall missed a girder and was being supported totally by the plywood. This can cause the plywood to deflect drastically along the base of the wall, creating a trough parallel to the wall. To correct some of the deflection, I typically recommend installation of blocking perpendicular to the girders in those areas that it is the most noticeable. The blocking can be installed 24 inches apart and will help to stiffen the floor system. I realize that the blocking is now parallel to the plywood grain, but the thick plywood can handle the span.

    I have seen a lot of this and feel comfortable giving my clients a fair amount of information about what they are likely to run into and methods to correct/remediate some of the standard problems/conditions. However, if this is unusual in your area or you are uncomfortable making recommendations, defer to a structural engineer.

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  7. #7
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    Default Re: unlevel floor surfaces

    Quote Originally Posted by Jerry Peck View Post
    exceeded by way too much.
    Quote Originally Posted by Ted Menelly View Post
    but an absurd span.
    First, structural panels are rated for spans based on two or more spans, i.e., three supports, there are only two supports, one at each end, NO WAY is that plywood being used anywhere near properly.

    Must feel like a trampoline up there on the floor.

    Report states to the effect of: Install floor joists, spaced as required for span rating of plywood subfloor, supported as required for the joists, with blocking between the joists as the joists will be perpendicular to the girders but parallel with the face grain of the plywood - have structural engineer design appropriate repairs, then issue engineer's letter stating that repairs were made in accordance with the engineering design. Cost = (you don't even want to think about the cost - just Git R Done)

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  8. #8
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    Default Re: unlevel floor surfaces

    8' OC?!
    What is that, 5/4 oak plywood?


  9. #9
    Ted Menelly's Avatar
    Ted Menelly Guest

    Default Re: unlevel floor surfaces

    Based on what Gunner is saying. I would not give any advise for any new support until the soil under the home is stabilized. To do anything with additional support posts (piers) and or shimming or cutting any post without stabilizing the moisture content would not be wise at all. At the least a foundation company but I would lean more to the engineer. The foundation company can help get the soil stabilized and any additional piers added/adjusted. An engineer will give you the proper build specs. No matter what the age and what was acceptable at that time it really does not matter at this point. It is when problems and concerns are encountered to take care of it with todays specs. The past is dead and gone now. Repairs are needed. Do it right now.


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