If you live in a place that has hot or cold weather, you need a moisture barrier for your laminate flooring. That’s right! That includes just about everyone. Does it stay pretty dry and arid around your house? You still need one.
Most people think they don’t need these barriers in rooms other than the kitchen or living room, but that isn’t necessarily the case. You absolutely need a moisture barrier in those rooms, but you need it in others as well. So why do you need moisture barriers under laminate flooring, and are they really necessary?
We’ll take a deep dive into all the specifics of moisture barriers, so you can make the best decision for your home and flooring.
What Is a Moisture Barrier?
Water and moisture can cause a lot of damage to your floors. If your floor gets wet, it can cause mold, mildew, and other problems that can destroy your floor, lead to health issues and even cause safety concerns. Moisture barriers help to protect your floors from water damage, so they last longer. So, what is a moisture barrier, anyway?
A moisture barrier, also known as a vapor barrier, is a plastic sheet that is added to a multi-layer floor system between the underlayment and subfloor or concrete to protect against moisture penetration and damage.
A moisture barrier is easy to install, affordable, and very helpful to both prevent damage to the actual top floor as well as subfloors from any form of water or moisture damage. While a moisture barrier cannot stop all moisture from getting through, it does help stop moisture penetration to a large extent, which is good for your floors to protect them and maintain them long term.
Choosing a Moisture Barrier
Of course, there are different types of moisture barriers with different strengths. Also called “vapor barriers,” these sheets have different permeability.
There are three different classes of vapor/moisture barriers that you need to consider.
- Class 1 Moisture Barriers: are the strongest moisture barriers because they are impermeable and do not allow any liquid to pass through them. However, because these include rubber, plastic sheets, sheet metal, and glass, most of these options aren’t practical for flooring applications.
- Class 2 Moisture Barriers: (i.e., such as unfaced expanded or extruded polystyrene, 30-pound asphalt-coated paper, plywood, or bitumen-coated kraft paper) these are semi-permeable, meaning that some fluid can come through.
- Class 3 Moisture Barriers: these are permeable, meaning that water vapor can pass through very easily. Some of these moisture barriers include brick, block, board lumber, fiberglass, gypsum board, and more.
Choosing a Flooring Vapor Barrier
To choose your moisture barrier, you want to pick what works best for your home. Of course, this means the options listed above, but it also means the type of installation.
There are moisture barriers that tape together and create full-floating sheets. These are sold in rolls, and if you have more extensive work to do, you can use an underlayment with a vapor barrier attached to it.
You will also have to choose your installation: do you want to tape the moisture barrier, glue it, or even paint your barrier on?
Before picking a moisture barrier, you want to ensure that it works with your flooring type as well. Your flooring manufacturer should help you.
Do I Need a Moisture Barrier?
It will almost never hurt to install a moisture barrier before you put down flooring, especially laminate flooring. Laminate is impacted by moisture more than some other types of flooring, and if you want your floor to last a long time and look good, you want to use a moisture barrier.
If you still aren’t sure, you might want to consider these three things:
1. Subfloor
Moisture barriers are important with specific types of subfloor. You will need a moisture barrier if you are going to install flooring over concrete. You also want to use a moisture barrier over any floor that has been prone to moisture damage.
2. Climate
Climate matters when you pick your flooring. If you live in a climate where there is a lot of moisture, like blizzards in the winter or April rainstorms, you definitely need some kind of moisture barrier. If your summers are humid, you may also want a moisture barrier just to be safe.
3. Grade
Moisture barriers are important in homes that have areas below grade, such as a basement. These areas are prone to moisture seeping up from the ground. They are also common places to use laminate flooring, and you don’t want the laminate to start warping and bending. If your house doesn’t have a basement, the ground floor has a chance of moisture damage.
Basically, the closer to the ground something is, the more it needs a moisture barrier.
If you aren’t sure if you will benefit from a moisture barrier in your home, you want to tape a sheet of plastic (a tarp or even a dollar store table covering will work) to the ground. Leave it there for at least 24 hours (36-48 hours is even better).
This is a very easy test. If there is condensation on the plastic, then you need to use a moisture barrier.
How To Install a Moisture Barrier
If you are interested in installing a moisture barrier yourself, you may be glad to know that it is fairly easy to do. Select a high-quality moisture barrier that best suits your flooring’s needs and install it before you install your underlayment and flooring.
When using adhesive to install a moisture barrier, take the following steps:
- First, roll out the moisture barrier to cover the entire surface area from edge to edge.
- Then, tape the edges of the moisture barrier down to the subfloor.
- Optionally, install two sheets instead of one, and use vapor barrier tape to bond them together.
- To ensure the moisture barrier is fully secured, walk around the entire room and ensure every area is fully covered by the barrier and taped to the subfloor.
- In the case that you find any punctures, holes, or tears, cover them with a sheet and tape that is about six inches in diameter from the edges of the hole.
While these instructions are very general and may work well in most circumstances, be sure to read and follow the actual manufacturer’s instructions. That way, you will know for certain you have installed your moisture barrier correctly.
Can I Just Use Plastic Sheeting?
If any plastic sheets were used, the thickness and strength may not be sufficient to equal the strength of an actual moisture barrier made for flooring systems. Plastic can bunch up or be too thick to look good under your laminate flooring. Instead, get a moisture barrier that has been designed for floors or walls.
You don’t want a moisture barrier that is too thick. Six millimeters is the absolute minimum for how thin it can get, and around 20 millimeters is around the thickest it can get. The wetter your environment is, the thicker you want your moisture barrier to be.
Is There a Moisture Barrier Made Specifically for Laminate Flooring?
If you are installing laminate flooring, your choice of moisture barriers should include a plastic sheet that is at least 6 millimeters or thicker, or you can choose an underlayment with the moisture barrier already attached to it. It all depends on what you need for your flooring.
Do Moisture Barriers Ever Need to be Replaced?
In general, a moisture barrier should last a lifetime and help maintain and protect your floors for years to come. As long as the vapor barrier isn’t damaged in any way or exposed to the elements during installation, it will last for the life of your flooring system, which is good news!
Choose a Moisture Barrier That Lasts
Moisture barriers are an important part of your laminate floor installation process. Wherever you want to install laminate flooring, the better that process will be (and the longer it will last) if you use a moisture barrier. So, explore your options, and choose the moisture barrier that works best for your next laminate flooring project.
Sources:
Vapor Barriers or Vapor Diffusion Retarders | Energy.gov
The Difference Between Moisture Barrier & Vapor Barrier | Hunker
I appreciate when you explained that the instructions must be followed properly when installing moisture barriers for laminate flooring to ensure that they will work. We actually plan to choose a Mohawk Boardwalk Collective laminate flooring for the property that my husband acquired this year. And it seems that we should invest in the moisture barrier for the protection of the surface which can benefit us in the long run, so we will include that in the budget and the labor the workers we will hire will do.