I was commissioned by a client to inspect the Hardwood flooring failure in an upscale Resort.
The issue is cupping. The structure was built within the last 2 years and supposedly every
effort was made to avoid this type of failure.
The contractor/builder chose to install a quality moisture suppressant system in place of a
vapor barrier under the concrete when the concrete was poured. The flooring was installed
approximately 8 months after the concrete pour. Accurate information regarding the ambient
temperature, ambient relative humidity, concrete moisture test results, and moisture content
of the wood prior, to installation, could not be obtained.
The concrete received a two part epoxy moisture suppressant system followed by gluing with
the recommended adhesive for installing 4’ by 4’ CDX panels. Each panel was nailed with
1.5 inch shot pins in each corner and one pin slightly off center in the middle of each plywood
panel. Lastly, the hardwood was both glued and nailed to the CDX panels.
The flooring is a 3/4 inch solid oak, 6” wide x random lengths to 74” with beveled edges
& ends, factory finished, installed over 3/4 inch CDX plywood cut into 4’ by 4’ squares and
grooved every 12 inches on the back (per manufacturers’ recommendations). All vertical
seams were staggered. Seven thousand square feet of Harwood was installed.
Several months later the flooring exhibited a cupping condition and has continued to worsen
with time. The question being asked is why is the moisture suppressant system failing?
Moisture Suppressant System Breached
The manufacturer’s instructions did not suggest or recommend to shot nail the CDX panels.
The above application would void the warranty for the moisture control system for several
reasons. First, shooting two thousand one hundred eighty-five 1-1/2” nails in to the barrier
would create that many points of entry for moisture to wick up through. Second, the flooring
is wider, thicker and in some cases longer than the recommended size of 1/2” thick, 5” wide
and 4 ft. in length. Third, the wrong glue was used because the manufacturer’s adhesive
#4234-or adhesive # 4235 are the required adhesives for installations of solid wood. And
finally, the coverage rate required for solid wood flooring is 250 sq. ft. per gallon, which was