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Inspecting Structural Insulated Panels (SIP)

Structural Insulated Panels (SIP) are building panels used in residential and commercial buildings that consist of panels of insulated foam sandwiched between two structural facings. The facings typically are (Oriented Strand Board) OSB. However plywood could be used. These large panels are manufactured in a factory to exact specifications and shipped to the building site where they are assembled. SIPS construction is different than normal framing because of the way the panels are constructed; they actually are the structure. There are many differences. Foundation straps are used to secure the panels instead of sill bolts. Panel corners and roof to wall connections are screwed together. Special fasteners are used to attach porch roofs to SIPS buildings. Floor joists are attached with a top chord bearing hanger that is attached to the top of the SIPS panel. A ridge beam and possibly a mid span beam may be used to support the roof panels. Here is a video of a SIPS house being constructed:

What should a home inspector should be looking for?

  • Wood structural panels should be 7/16 of a inch thick or greater, unless plans call for another size
  • Corrosion resistant screws must be used
  • Bulges or spaces in the walls would be considered a major defect
  • Wall panels should be uniformly spaced on the foundation wall
  • Holes cut into SIPS panels should be no larger than 2 inches centered in the panel core. Vertical chases shall have a minimum spacing of 24 inches on center. No more than 2 horizontal chases shall be permitted in each wall panel.
  • The walls are fastened to the foundation using approved fasteners
  • Normally, SIPS walls should be no taller than 10 feet
  • SIPS walls should be capped with a top plate
  • Pressure treated sill plates should be used and anchored to the foundation with anchor bolts spaced a maximum of 6 feet on center. There shall be a minimum of 2 bolts per plate section with one bolt located not more than 12 inches from the end of each plate
  • Sill bolts should be at least ½ inch in diameter and extend at least 7 inches into the masonry. Nut and washers should be used.
  • Approved air barriers should be used on exterior walls and vapor retarders on interior walls


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