How to Install Engineered Hardwood Flooring Over Concrete Substrate
When is engineered hardwood a better solution?
What do you tell your customers who have a concrete subfloor and want to install hardwood? We recommend an engineered hardwood for several important reasons. One, it’s much less sensitive to changes in humidity compared to wood that can swell with moisture and temperature. Two, it can be installed at any grade level – including below grade. And three, it’s better than traditional plank for installing over in-floor heating systems.
However, while engineered hardwood flooring offers increased durability, that doesn’t mean it can be used anywhere. Installations in wet environments are one example where numerous other types of flooring options are much more suitable.
What are the first steps before installation?
Your very first step before installing engineered hardwood floors over concrete is to let the boards acclimate to the room where they’re going to be installed. Check the manufacturer’s recommendations, but in most cases it’s a minimum of three days with no maximum.
Next, check the boards for warpage or defects, and then remove any bad ones. If you skip this important step, you could face problems later if you need to replace even a single board.
Why is moisture so critical to surface preparation?
Engineered hardwood is sturdier than traditional plank – but surface preparation still matters. For any flooring installation over concrete, you should anticipate potential problems with moisture levels.
Like any wood product, engineered hardwood expands and contracts because of changes in moisture. For that reason, the adhesive you choose depends on the environment and the conditions during installation. You need to be aware of any concrete substrate that has known moisture problems, and remember that new slabs will be high in moisture.
What type of adhesive should you use?
You may not always know whether proper vapor barriers were installed or if there’s a suspected environment where moisture is going to be a problem. For those common situations, TEC® offers two urethane wood adhesive products that don’t require any moisture testing: Wood Assure and Wood Endure. If installed with the proper trowel, they both provide the necessary moisture barrier. If you encounter suspected concrete moisture, or you have tested it to confirm moisture, these two products are ideal solutions.
For excessive moisture vapor emission rates, you can choose to use a moisture mitigation system like LiquiDAM or LiquiDAM EZ prior to installation. Fill any voids or deflections in your substrate with a cementitious patch, like TEC® Fast-Set Deep Patch, or a self-leveling underlayment. It’s not your adhesive’s job to fill voids or deflections.
In those cases where moisture levels have been tested and they are not a concern, TEC® offers two additional products: Wood Go and Wood Ready. Wood Go offers an added benefit for improved acoustics and sound deadening. This can be preferable where hardwood flooring is installed over plywood, often in residential installations. Wood Ready is specially formulated for the challenges of engineered wood flooring.
How should you install the floor?
After inspecting your boards and removing any defective ones, plan on following a running bond pattern of the grain. This is the most popular way to install engineered hardwood flooring because it’s stronger and more aesthetically pleasing.
Remember to leave expansion gaps between the flooring and wall. Consult the manufacturer’s recommendations to see how wide the expansion gap needs to be. Installing engineered hardwood flooring over concrete too tight against a stationary object will not allow room for normal expansion, and may cause a failure.
Consult the product data sheet for instructions regarding specific trowel requirements. In general, use a notched trowel to spread the adhesive. Pass the trowel through the glue at a 45-degree angle and install hardwood flooring immediately after the adhesive is spread.
Lay the flooring into the adhesive with the tongue side of the board facing the center of the room. The hardwood may slip and move at first, so be sure to secure one row entirely before moving on to other rows. The initial row will limit the movement of subsequent rows. You may have to temporarily tape edges of adjacent planks together with painter’s tape until installation is complete. Bowed boards or boards over low spots should be weighted down while the adhesive cures.
Periodically lift a piece of hardwood to make sure you’re achieving a 90 percent adhesive transfer. If the board doesn’t appear to have this level of coverage, remove the dried adhesive and apply more.
Be sure to follow the manufacturer’s instructions after installing hardwood flooring over concrete. For example, we require that installers roll and cross the floor with a 100-150 lb. roller after installation to ensure proper adhesive transfer. Also, traffic in the area must be restricted for 8-10 hours. Heavy traffic should not resume until 24 hours after the engineered hardwood flooring installation is complete.
Note: When installing engineered hardwood floors over radiant heated subfloors, turn the heat off for 24 hours before, during and after installation.
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