When installing cork underlayment, the base materials and the type of flooring will guide how it is installed. You should also consult the manufacturer to see what they recommend.
Before we begin, it should be noted that cork underlayment can be used to level out different sub-floor heights. For example, say one room has hardwood flooring you don’t want to remove, and an adjoining room has carpet—making the two rooms different floor heights.
If the difference is a dimension of cork underlayment such as 1/4″, you can add another layer of 1/4″ cork to even out the two rooms—no need to mess with adding subflooring. This means no need for a transition strip between the two floors. Making the finished floor look better and have less chance of someone tripping.
If it is not a dimension that cork comes in, you may need to adjust the level of subflooring.
Also, remember the heights of door jams and the doors themselves when you do flooring. Sometimes you might need to trim jams and cut down doors (use a fine-tooth blade and tape to prevent wood splintering).
Let’s look at typical installations and learn how to install cork underlayment.
Installing Cork Underlayment for Floating Engineered Wood Floors
We recently completed this installation of cork with floating engineered wood flooring. And consider it one of the easiest ways of installing cork underlayment and flooring. No nailing or gluing is required.
You can buy cork underlayment in sheets or rolls. The cork sheets at the time of our installation were more expensive.
We purchased both to see how each one installed (manufacturer (QEP-PDF)).
The cork sheets were two feet wide by three feet long and the rolls were four feet wide by fifty feet long.
With the rolls being larger than the sheets we thought they would be better since it would create fewer seams.
Cork Underlayment Shrinking & Expanding
Cork is a natural material and will shrink and expand with changing temperature and humidity (below 35% and above 65% RH).
When it is cold, not as much water is in the air, and the cork could shrink slightly, leaving small gaps in the seams. As moisture levels rise, the cork will expand in all directions. If you install cork underlayment in the winter, leave some extra space around the walls for the expansion phase several months later.
Move your cork underlayment into the space you will be installing at least 48 hours before installation. This allows the cork to adjust to the proper indoor humidity level.
Installing the Sheets & Rolls
It was easier to move and place the cork sheets and trim the edges to fit the room.
Put the piece against the wall and mark where it meets the adjoining sheet. Then, cut with a straightedge (don’t forget to leave some space for expansion).
One of the goals of our project was to eliminate noise on the main level. Where we were installing the flooring and the basement below. We were trying to eliminate any gaps in the cork underlayment that would let sound travel through during the winter when the cork shrank.
The solution was that we needed to install two layers of cork underlayment with the seams going in opposite directions. This would allow movement in the cork without gaps and being thicker meant it would also have a higher STC rating.
STC is the abbreviation of Sound Transmission Class. A technique to detect the amount of sound that travels through different building elements like flooring, windows, doors, or even walls.
With two layers, it made the extra amount of seams on the sheets a non-issue.
Also, install the top layer of cork underlayment perpendicular to how the floor will be installed. You don’t want a seam in the cork lined up with a seam in the flooring.
One issue with the rolls is that the cork has “memory” and wants to keep the shape it was rolled into. You might have to tape it down. Although, the tape didn’t hold that well (even tried Gorilla tape).
In the end… after using cork rolls and sheets, we would choose the sheets for a floating floor. They were easier to install and laid flat. This may not be an issue if you are gluing the underlayment down. Although, not sure if this would be a similar issue with the cork trying to pull up from the glue/cement?
Gluing Down Cork Underlayment
Cork underlay is generally compatible with any water-based construction or wood underlayment glue. It is best to allow the troweled glue to be set up before installing the cork underlayment. This allows the liquid inside the adhesive to evaporate.
Installing Cork Underlayment With Tile Floors
It seems you can install cork underlayment with tile flooring as pictured above. Although, the deflection (PDF) of the cork may cause some issues.
You would probably be better off installing cement backer board rather than cork with tile.
Installing Cork in a Basement
Something to consider when installing cork underlayment is the presence of moisture.
Most newer homes are built with a vapor barrier installed under the basement slab. It prevents moisture from traveling up from the ground. So, after six months of the concrete curing, it should not have much moisture, and flooring could be installed. This should be checked with a moisture meter.
If your basement is very damp and has high moisture levels, you may want to fix that before adding flooring. This is often caused by poor drainage around the foundation.
Cork is a water-resistant material. However, it’s not a moisture-proof material. It should not be glued down to basement concrete and instead allowed to float. This will help the moisture travel through the cork and not cause any condensation that could lead to mold.
A proper installation for basement flooring would include rigid foam insulation, a subfloor, and flooring. Check out this article by Fine Homebuilding for details on this type of system. With this method, you really don’t need the cork and could install the flooring directly on the plywood. But, this is often more work than most homeowners want to do.
Consult a professional in your area that can determine if you need a vapor barrier for your installation. Building codes in your location may require one.
If you do indeed need a vapor barrier here is a video showing installation.
Hope this article helped you learn how to install cork underlayment. As it can be a bit of a complicated project when you get into basements and vapor barriers. But, if you are just floating the cork and flooring it’s really pretty simple to install.