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Should I Use A Vapor Barrier In My Garage Walls?

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You might be a DIY-er, or you might be genuinely curious about vapor barriers. Either way, you have come to the right place. In this article, we have taken the time to answer your questions about using vapor barriers in the garage.

Using a vapor barrier in your garage is truly up to you, but it is usually necessary if you live in a colder climate. It is also recommended to use a vapor barrier in your garage if you have repurposed it into a kitchen, laundry room, or anything else that creates a lot of moisture in your garage.

We will certainly get into the details later, sharing everything you need to know about vapor barriers and your garage. We will also cover the difference between vapor barriers, moisture barriers, and reasons you may or may not choose to install a vapor barrier in your garage. Now, let's get down to business!

Worker in using a stapler to mounts a vapor barrier in the wall, Should I Use A Vapor Barrier In My Garage Walls?

What is a Vapor Barrier?

Vapor barriers were designed back in the 1970s but became more popular throughout the '80s. Around that time the International Building Code began requiring vapor barriers. This requirement was implemented to improve the quality and safety of your home. 

Polyethylene protection vapour barrier

However, there are conflicting arguments on whether a vapor barrier is required by law. It mainly depends on your location. Most building codes do not require a vapor barrier, but they certainly might recommend it.

The "Why" to Vapor Barriers

One of a homeowner's biggest nightmares is water damage. We all know flooding is a disaster. However, moisture damage may seem small, but it can prove deadly!

Excess moisture in the home can cause mold and mildew. And it also can lead to the rotting of vapor-permeable material. These materials include the ones used in the structure of our home -- drywall, studs, and other non-waterproof materials. 

Too much moisture in the home can lead to stems from mold. The development of mold is not only gross but can trigger respiratory problems. Residing in living quarters where mold is built into the walls, can lead to many serious health problems which could turn deadly.

For these reasons, a vapor barrier was designed to protect your home's structural integrity, and yourself from the negative effects of moisture. 

Vapor Barrier Definition

A building contractor is installing vapor barrier

In short, a vapor barrier is a material that does not allow mist, steam, or fumes to diffuse through it. Imagine a giant piece of plastic weaving across the walls of your home, or in this case, your garage. Of course, this plastic curtain is on the inside of your drywall, or the finished wall of your garage.

Vapor barriers are placed to cover insulation, from the inside. If your garage is not insulated, the vapor barrier will cover the wall sheathing

If you are looking for more information on finishing garage walls, please visit this article:

How To Finish Garage Walls

What is the Difference Between a Vapor Barrier and a Moisture Barrier?

As mentioned earlier, vapor barriers are a measure of protection from moisture. It is designed for vapor not to seep through onto studs, drywall, insulation, and other interior materials.

Normally, a vapor barrier is made out of polyethylene plastic, the most common plastic used today. You will usually see rolls of this protective material in white. Sometimes it can be a different color, but that is not for fun or decorative purposes.

A moisture barrier is a layer of plastic film applied to the interior surface to prevent corrosion. Moisture barriers are used typically to cover pipes and jackets.

However, both types of barriers have the same goal - to protect against moisture and corrosion. 

How Do I Install a Vapor Barrier in My Garage?

Mounts a vapor barrier membrane to protect the mineral insulation

It is important to note exactly how vapor is transferred. There is a process called, vapor diffusion, which is when water transfers from a high-temperature region to a low-temperature region.

A home in a colder climate can help illustrate good when this happens. Because the living quarters of a home are well insulated, there is a significant difference between the temperature inside and the temperature outside. 

Vapor will try to escape to the outside potentially causing damage in the process; water forces itself through permeable materials.

In cold climates, there is a high rate of vapor diffusion. When hot air in a garage tries to escape through the walls, the moisture will condense and create moisture particles. These particles damage non-waterproof materials.

Insulation Process

You will need a few materials to start. Gather polyethylene plastic, staples, sheathing tape, and caulking. You might also want a vacuum to suck up dirt and small particles that can stick to your surfaces.

The last thing you might need is another set of hands, which will make it easier on you when applying the plastic barrier. 

Step 1

First of all, it is very important to install the vapor barrier on the warm side of the exterior wall. Start with about 8 feet of polyethylene plastic. This is a manageable size that allows control and efficiency.

Step 2

Line up the top of the vapor barrier with the top of the wall. Staple the barrier to the wall about a foot and a half apart. When you line up your next section, be sure to overlap a good amount. This will make it easier to completely seal. Tape your merging pieces at the seal.

Step 3

After you staple up your walls and your ceiling, cut out windows and doors. Next, use the sheathing tape to seal the edges of the cutouts. Don't forget about the electrical boxes! Those should be cut out and sealed as well.

Step 4

Down at floor level, pull up the plastic and apply a quarter-inch of caulking. This caulking is how you will seal the bottom. Press the vapor barrier into the caulking to complete the seal.

Don't forget the ceiling! The same processes are applied to the ceiling as the walls.

There you have it! The garage should be protected from vapor. Be sure to take your time and be diligent about your work, it will serve you better in the long run.

Does an Unheated Garage Ceiling Need a Vapor Barrier?

Sometimes garages are repurposed. Whether this is for fun or functionality, garages can be converted into bathrooms, laundry rooms, and other things. Garages are not just for stowing cars or storing Christmas trees.

Bathing and laundry are "wet activities". Because of the amount of moisture that is omitted through these activities, you might want to consider a vapor barrier. 

However, the garage is normally one of the driest places in the home. If the garage is unheated, there may be less of a difference between the outside temperature and the inside of the garage. Additionally, most vapor diffuses through garage walls, ceilings, and floors.

For these reasons, having a vapor barrier in an unheated, garage ceiling, is probably unnecessary.

Do You Need a Vapor Barrier Under a Garage Slab?

Cement slab inside garage

Attached Garage in Wine Country, Cement Slab, Cabinetry, Organized, Clean

The same rules apply to analyzing whether you need a vapor barrier under a garage slab.

Ask yourself questions like, "What kinds of activities are going on in the garage?" and "Is my inside temperature dramatically different from the outside temperature?"

Depending on the answers to your questions, you will have a better idea of whether you need a vapor barrier under your garage slab.

In most situations, you will NOT need a vapor barrier. The reason for this is that there will not be a difference in temperature between the inside and outside of the garage. Reminder, the primary need for a vapor barrier is to deal with moisture trying to escape to the colder outside, since this causes condensation. 

Final Thoughts

By now you should be an expert on all things - vapor barrier! Whether you are looking to finish some garage projects yourself, or simply into the function of vapor barriers, all the information is here for you.

In this article, we covered what a vapor barrier is and why it is needed. We learned this is an extremely important step to deciding if and when you need a vapor barrier in your garage. 

Each garage is unique to its own purpose. Reach out to local experts if you have any questions or are seeking further confirmation on your garage plans.

We are happy to be here to answer your home renovation questions. For more articles like this one please visit one of the following links:

How To Fill The Gap Between Garage Door And Floor

Should A Garage Have Windows?

Should Garage Walls Be Textured?