Cork and bamboo are still niche products compared to “traditional” hardwood flooring, but increasingly being noticed for their sustainable origins. Cork comes from the bark of the cork oak tree, which can be harvested without damage to the tree. Bamboo is a woody grass that grows quickly and can also be harvested, every three to seven years, without causing damage to the plant. These products are finding their way into more and more residential and commercial settings, and with that comes the need to know how to install them.

Cork Flooring and Underlayment. Tim Tompkins, Amorim Flooring North America national marketing director, said floating cork flooring is easy to install, using similar steps as engineered hardwood. “These floating systems sit well over plywood, concrete or even existing flooring.”

He added that cork underlayment can also be installed similar to other underlayment. “The underlayment can be floated with an 8mm poly vapor retardant or direct glued over properly tested slabs with moisture-cured urethane adhesives.”

Avi Hadad, owner of Avi’s Hardwood Floors in the San Francisco Bay Area, said when choosing a cork underlayment, installers and contractors should be careful not to just choose the thickest one unless the project calls for it. “You need to remember that the really thick underlayments can put stress on the joints, and over time the floor might get out of sync.”

Don Jewell, Capri Cork technical service manager, offered these three tips for installing cork flooring: “1. Read the instructions provided by the manufacturer. 2. Follow the instructions. 3. If you have any questions, contact the manufacturer and have a conversation with the person who can really answer your real-world, job-site questions.”

While these are simple tips, he said he is amazed how many installers do not follow them, adding that assuming to know what you’re doing without reading the instructions can lead to disastrous consequences. “There are manufacturers that have pre-applied contact adhesive on the back of the cork tiles and you would apply the other half of the contact adhesive on the jobsite. There are site-applied contact adhesives that require rolling after placement, and site-applied contact adhesive that requires you to set the tile by impacting it with a soft mallet. There are now spray adhesives being recommended for cork flooring and also the old-school single side trowel-applied adhesives that are still lingering.”

Jewell noted that he often hears installers complain that cork is difficult to work with or that it always curls. To those complaints he says, “While installing a cork floor with contact adhesive is different, it is not ‘difficult.’ A cork tile curling up on the floor is almost always a result of improper installation. A phone conversation before the installation reduces or eliminates the dreaded phone call after installation. Get the phone number to the technical support person who can, and will, help you succeed. I often say the most valuable tool in your bag can be a cell number.”

In regards to cork underlayment he stated, “There is not much difference between [installing] cork and recycled rubber underlayment. If you will be gluing a finished floor on top of the cork underlayment you will likely be required to adhere the underlayment to the substrate. A good rule of thumb is to use the same adhesive for both. This will eliminate the chance of weird chemical reactions between two different adhesive types. Both urethane and acrylic/latex adhesives can be used for cork underlayment as well as MS polymer-type adhesives.”

Bruce Graye, Corksribas product manager for EcoTimber, shared the following on installing cork tiles: “Cork tiles are still being used commercially and a little residentially, and since it is a ‘wood’ product it has a tendency to move – a contact system is the only method that will work. Installers must follow the directions, making sure the adhesive covers the entire back of the tile, the entire floor, and it dries. Otherwise, it will start cupping.”

He added, “A common misconception is that because it’s a tile floor, any VCT dealer can install it, and that it installs like a VCT floor. It actually takes more time and needs to be done carefully. Also, when using the contact cement on the back of the tile, you need an area for the tiles to dry. So depending on the size of the job, the space needed to dry should be taken into account?.”

Renee Tester, Harris Wood product marketing and technical services manager, said her company’s Harris Cork Collection featured an integrated insulating underlayment, so it does not need additional underlayment “unless the installation is over concrete or below grade, which would require a minimum 6 mil poly film for moisture protection.”

She noted that the company’s line is prefinished, and does not need an on-site finish applied. “Our technical services department often receives calls about our Harris Cork line, asking if an additional finish should be applied after installation. This is not necessary and often will void any finish warranties with the manufacturer if this process is completed.”

Brad Miller, Q.E.P.’s vice president, product management and development, said installers should keep a few things in mind when working with cork underlayment. “It is important to read the manufacturer’s recommendations and use the proper adhesive when gluing cork down. When floating the flooring over cork, tape the seams together with a strong tape to keep the sections from pulling apart.”

According to Joe Tedder, USFloors claims manager, installers and contractors working with cork flooring need to understood both its advantages and its limitations. “Cork is photosensitive and will change appearance with direct exposure to sunlight. Also, depending on the construction of the material (floating plank vs. glue down tile), it will have limitations for continuous runs of connected flooring space. Specifying the correct material to achieve the optimal results is critical.”

When working with a cork underlayment, he added, “It can be loose laid under floating floors or glued down in a ‘double-stick’ fashion for use with installing hardwoods. The underlayment can be torn fairly easily during installation, so keep traffic to a minimum.”

For glue-down cork floors, Ann Wicander, WE Cork president, said “the floor needs to be flat and clean, like it would be for VCT or LVT, but the moisture content in the slab must conform to requirements of the wood industry. After years of testing with various adhesives, we still believe that contact adhesive is the best and most effective way to install our glue-down.  Then, of course, do not forget the 80-100 lbs. roller to finish the job.”

For cork underlayment, Wicander added, “Be sure you use the right product for the desired results. You would not want to use our Warm&Quiet cork underlayment, which is primarily for laminate flooring, under LVT, which requires a much higher density and stable underlayment and is represented by our Silently-LVT. If it’s ceramic tile, use a multipurpose thin-set over our Soundless and Crackless products, which were developed specifically for the ceramic tile industry. If using a wood floor, our Warm&Quiet+ can be floated if under a floating wood floor or glued using wood adhesive if under a glue-down system.”

Installing Bamboo Flooring. Hadad warned fellow contractors about the acclimation time for certain bamboo flooring products. “Be careful when considering solid bamboo versus strand-woven. Solid bamboo acclimates similar to hardwood. Strand-woven [which is a highly compressed, hard and dense material] acclimates four times longer, so acclimate it as long as you can. More importantly, buy it from a reputable source.”

He added to check with the manufacturer on installation methods. “A lot of guys are gluing strand-woven down to concrete, and three years later the installation is failing. The moisture is coming up through the slab and the adhesive, but gets stuck under the strand-woven and the adhesive fails. Check your manufacturer recommendations to see if you can glue strand-woven to concrete or not.”

Joseph Rocco, owner of Artistic Floors by Design, said bamboo flooring is something he tries to shy away from installing in Colorado. “We are leery of bamboo out here because it’s such a dry climate in the winter and the spring. When you buy a cheaper bamboo product, some of those glues in the floor are not so strong and you have issues with that. My stance out here is I won’t do a bamboo installation unless it’s in a basement, because the humidity will be high enough to handle some of that drying out.”

Brett Miller, National Wood Flooring Association’s director of certification and education, stated, “Lots of manufacturers recommend our installation guidelines for installing bamboo products, but what many installers run into is the moisture meters they use may not have species correction values for the bamboo they’re installing. We recommend checking with the flooring manufacturers for proper testing methods and the meter manufacturer for proper settings on the specific type of bamboo.”

Looking at strand-woven specifically, he added, “Strand-woven products are a challenge to get a good moisture reading on. For these compressed, condensed products, acclimation time can be extreme. Even more important is to buy from a reputable, recognized manufacturer. Lots of the products that are coming here are not tested for specific environments. As long as the contractor makes sure to use a reputable product, and check with the manufacturer for proper installation methods, he or she should have success every time.”

Speaking about his company’s Plyboo product, Dan Smith, Smith & Fong founder, said, “Smith & Fong Plyboo bamboo flooring products are designed to be nailed or glued-down in installation. Most nail/cleat guns set to a 5/8” floor work great. Staple guns can also work, but thinner cleats or staples work best, as they displace less material and have a reduced chance of damaging the tongue area of the floor.”

He added, “For a glue-down application, most non-water-based adhesives work well. If and when there is a problem, we usually see this in one of two areas: acclimation and moisture abatement. A poorly acclimated bamboo floor will gap in dry environments and can swell or expand in wetter ones. It is best to work with a moisture meter and confirm compatibility of the product’s moisture content and ambient humidity prior to installation. We would like to see no more than a 2% variance between the flooring moisture content and what the environment is supporting.”

Smith said elevated moisture in a slab will require some form of abatement for a successful installation. “Too often I have seen moisture abatement systems fail due to loss of adhesion to a wet concrete slab or un-dried leveling compound. Shortcuts on moisture abatement rarely pay off for the installer.”

Tedder said using the proper fasteners and pressure setting for nail-down bamboo flooring is crucial. “Material not seated properly will have issues with gapping or noise due to movement along the fasteners. If the air pressure isn’t correct, the planks can be damaged.  Also, when installing solid strand bamboo in a nail-down application, it is important to use the correct fasteners as this material can be extremely difficult to nail. The most common issue is ‘dimpling’ at the insertion site and ‘fractured’ tongues. Installers should always be aware that you will need extra blades if performing a large installation, as this [strand-woven] material tends to dull saw blades faster than traditional hardwoods.”

For glue-down applications, “using an adhesive that is compatible with both the material and substrate is key. Adhesives that flash off moisture can cause the floor to cup. Always check with the adhesive supplier to ensure the proper trowel size is used. Always test for moisture (in the flooring itself and the substrate). USFloors requires that moisture levels of concrete must be below 3 lbs. per 1,000 square feet per 24 hours (1.36 kg per 92.9 m2 per 24 hours) using an anhydrous calcium chloride test kit according to ASTM F-1869 test method, or below 75% relative humidity tested in accordance with ASTM F-2170.”

When working with floating floors, Tedder added, “They will almost always require t-moldings when transitioning from room to room. If that is something you don’t want to do, you may want to consider another type of installation.”