I was called out on an inspection in which pre-finished bamboo flooring had been installed over a concrete substrate below grade and had failed. There were a few things to investigate to get to the bottom of the cause. Was it the adhesive, the substrate, the installation method, or a combination of everything leading to the problem? Let’s look deeper.
The flooring materials were purchased at a big box retailer, and the installer used the recommended private label adhesive, trowel, and installation methods. On site, the installer noted that the existing substrate was concrete. Still, he did not want to do any kind of “prep” or “skim coating,” as he did not want to be blamed for any adhesive failure of a “reaction between adhesive and coating materials” that might occur with this type of installation. The installer took moisture readings upon delivery and noted between 7.9 percent – 18.3 percent readings. During installation, the installer used the recommended trowel provided by the manufacturer and followed installation instructions.
The contractor involved in the project noted that the concrete floor substrate was inspected prior to installation, and no issues had been noted. He also noted that there was styrofoam insulation and specialized drainage mats installed at the back wall of the home due to the significant amount of below-grade sections of the foundation walls being subject to water intrusion.
Upon my inspection on-site during destructive testing, I was able to lift the pre-finished bamboo flooring off the substrate with minimal effort. The adhesive had not adhered to the concrete, and there was visible moisture in some sections. It also was observed that the concrete flooring was “shiny and dark” in appearance.
After investigating the adhesive and installation requirements of the material’s manufacturer, it was noted that “concrete substrates must be free of sealers, curing compounds, stains, or other coatings, and should have no reflection of light.” In addition, a porosity test should be performed to ensure the concrete is porous and should be to a “broom finish.” When bamboo flooring is being installed, the concrete must include a calcium chloride or RH in-situ moisture test.
Sometimes trying to “avoid” a problem can cause other, bigger problems in the long-run. Installers should read manufacturer instructions and guidelines carefully for each product they will be using. Ensuring products are compatible with one another and performing each task specified by the manufacturer is required. When in doubt or when using a new product, try reaching out to the technical departments with questions or concerns and asking for assistance. Every manufacturer has a group of professionals that are able to walk you through each of their products. This is a great way to avoid falling into a potential trap by trying to escape blame or skipping steps. In the end, you will be confident in your reliable installation, and the steps you take to do so will be backed up by the proper use of the products.
Kelly Ragalie is an NWFA Certified Wood Flooring Inspector, Certified Sand and Finish Professional, and Certified Sales Advisor. Ragalie is the owner of Stafford Inspection Services, co-owner of Treadline Construction, and a technical sales representative for Loba-Wakol. She can be reached at treadline1@gmail.com.