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AdvanTech Edge Swell and Surface Flaking

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  • AdvanTech Edge Swell and Surface Flaking

    Since this is my first post, let me introduce myself. My name is Cory and I am the owner/builder for a small residential construction company that focuses on remodels and home improvements.

    As an initial matter this is a question directed to the reason why I am experiencing edge swelling and surface flaking and not a question as to the validity of a warranty claim.

    I am building a shed located in the Midwest at the border between zones 4 and 5. I installed 3/4” AdvanTech subfloor over 2×8 pressure treated floor joists spaced 12” O.C. The subfloor was installed per the manufacturer’s installation instructions (subfloor adhesive applied to the joists, panels properly spaced on both the long and short edges, 6” nail spacing at the edges and 12” nail spacing in the field). The floor joists rest on 6×6 pressure treated timbers placed on a gravel pad formed of 3/4” crushed rock at least 4" in depth. A woven fabric is at the bottom of the gravel pad to separate the gravel from the clayey dirt while allowing water to drain out of the gravel pad. There is approximately 5-1/2” of clearance between the top of the gravel pad and the bottom of the floor joists.

    Because this is winter construction, the floor was exposed to rain and snow after installation and while the walls and roofed were framed. Within two weeks of the subfloor being installed (and still during the rough framing stage), I noticed that the subfloor was experiencing significant (to me) edge swell and surface flaking. The nails, which were left proud from the pneumatic nailer and hand driven snug (as opposed to flush), are now pulled through the upper surface of the flooring to the point that it appears I overdrove the nails during installation. This is also occurring in the field. While we have walked on and used the floor during wall and truss framing, nothing was applied to the flooring (e.g., salt) and only brooms were used to remove the snow.

    The regional manufacturer’s rep visited the site and took moisture content readings (pin style) of the floor, which was at 14% moisture content. The rep explained that since this was a shed floor, the underside of the subfloor was exposed to moisture and that was causing the swelling and flaking. He also said that the manufacturer expects 12% or less moisture content. In my research, this is only required immediately before a finished floor is placed over the subfloor and not the moisture content that is expected during the rough framing stage.

    The floor has been covered now for a couple of weeks and the frequency of surface flaking is increasing and the AdvanTech is still indicating that it has a high moisture content (gaps closed up). For my region and based on the data I have available to me, I can expect DF to have an EMC of approximately 14-15% moisture content for January/February. What I can see of the underside looks good. I also have a couple of pieces left over from the install and they appear brand new relative to what’s down.

    I can’t find anyone who has experienced edge swelling or surface flaking with this product (and posted about it online anyway) and my lumber yard has never heard of anyone having issues. To me, the Huber rep argued from the perspective of the floor's permanent installation performance (e.g., a year (for example) from now). I have no doubt that the moisture content of this floor will remain higher in the long run than that of a subfloor installed in a dried-in home. These issues, however, arose during the rough framing stage. I have a hard time believing that this subfloor was exposed to more moisture in those first two weeks than it would normally experience during regular home building.

    Please let me know if you have any questions and thanks for your help. Any insight would be greatly appreciated!


  • #2
    Did you gap 1/8" between the panels?




    • #3
      Originally posted by Cory Parks View Post
      The subfloor was installed per the manufacturer’s installation instructions (subfloor adhesive applied to the joists, panels properly spaced on both the long and short edges, 6” nail spacing at the edges and 12” nail spacing in the field).
      I believe he indicated that he did.


      • #4
        14% is not that far away from 12% and is still considered in the safe zone for wood. I find many wall cavities behind adhered stone veneer the exist in a higher humidity state than other areas on the house with siding.
        A moisture content reading on the interior face of the wall sheathing is 14% to 16% when we have tested. We have not found any issues with this elevated reading.
        I wonder if this is a little freeze damage. The construction you describe would lead to higher continued moisture exposure. If it's wet and freezes then there will be some expansion going on in the panel.
        Mark Parlee
        BESI(building envelope science institute) Envelope Inspector
        EDI Certified EIFS Inspector/Moisture Analyst/Quality Control/Building Envelope II
        EDI Seminar Instructor
        Level one thermographer (Snell)
        You build to code, code is the minimum to pass this test. Congratulations your grade is a D-