Basements are notorious for being damp and musty.
A basement vapor barrier is a great way to keep your basement dry and free of mold and mildew.
But how should you go about installing one?
To install your basement vapor barrier, you’ll need to choose the right one, remove dirt and debris from the walls, cut the vapor barrier to size, and then secure it. You’ll also need to properly seal any cracks or holes in the walls.
Installing a basement vapor barrier can seem daunting, but I’ll walk you through it step by step so you can do it quickly and easily.
Let’s get started.
Table of Contents
- 1. Choosing the Right Vapor Barrier
- 2. Removing Debris and Obstructions
- 3. Measuring and Cutting the Vapor Barrier
- 4. Applying Adhesive to the Walls
- 5. Installing the Vapor Barrier
- 6. Attaching the Seams
- 7. Installing Insulation
- 8. Checking Damages and Making Repairs
- Final Thoughts
When it comes to basement vapor barriers, you want to choose a low vapor diffusion material. The lower the vapor diffusion, the more difficult it will be for water vapor to pass through.
The rate at which vapor diffusion happens is measured in perms. According to the International Residential Code, there are three different classes of vapor retarders:
- Class I – 0.1 perm or less. This class of vapor barrier is the most effective vapor barrier and is typically used in cold climates. No water vapor can pass through these materials. The low permeability keeps moisture from passing through and condensing on the cold surface of the foundation walls.
- Class II – 0.1 to 1 perm. They are typically used in cold or moderate climates. It is not as effective as a Class I vapor barrier. However, it will still significantly reduce the water vapor that passes through.
- Class III – 1 to 10 perms. This is typically used in hot climates. It may not prevent all water vapor from passing through, but it will help to reduce the amount of moisture in the air.
Vapor barriers come in various materials, including polyethylene sheeting, asphalt-coated paper, and kraft-faced fiberglass batts.
The type of vapor barrier you choose will depend on your area’s climate and the basement conditions.
Polythene sheeting is available in various thicknesses. 6 mils (0.006 inches) polythene is the most common for basement vapor barriers because it’s affordable, lightweight, and easy to install.
Polythene sheeting is made of low-density polyethylene (LDPE) and is available in rolls of various lengths and widths.
It is suitable for areas with moderate humidity and can be used in basements with concrete or block walls.
This heavy-duty vapor barrier is paper coated on one side with asphalt.
You can use this paper in commercial applications or residential settings.
If you are planning to install an asphalt-coated paper vapor barrier in your basement, there are a few things that you need to keep in mind.
First, this type of vapor barrier is not self-adhesive, so you must use a separate adhesive to attach it to your basement walls.
Second, asphalt-coated paper is not vapor-tight, meaning it will allow some moisture to pass through it.
However, it is still an effective vapor barrier that can significantly reduce the amount of moisture in your basement.
Kraft-faced fiberglass batts are a type of insulation often used by the construction industry as a vapor barrier. It’s composed of fiberglass fibers bonded together with a kraft paper backing.
The kraft paper facing is usually brown or black and is coated with a layer of asphalt to make it waterproof.
Kraft-faced fiberglass batts are often used in new construction and fit between the studs of walls.
However, they are also suitable as a vapor barrier in existing basements. When using kraft-faced fiberglass batts as a vapor barrier, install them with the kraft paper facing toward the living space.
Debris and dirt can accumulate on your basement floor over time. This can make it difficult to install a vapor barrier.
To prepare your basement floor for installation, you must remove all debris, including dirt, dust, cobwebs, and other build-ups on the walls’ surface.
You can use a vacuum cleaner with a hose attachment to remove any loose dirt and dust. Next, wipe down the surface of the walls with a damp cloth to remove any remaining dirt or debris.
If there are any obstructions on the surface of the walls, such as old pipes or electrical outlets, you will need to remove them before installing the vapor barrier. It will ensure that the vapor barrier will lie flat against the wall’s surface.
After you have prepared the surface of the walls, you will need to measure and cut the vapor barrier.
Here’s how to do it:
- Measure the length of the wall and add 6 inches (15 centimeters) to this measurement. This will allow some overlap between the seams.
- Measure the width of the wall. Add 6 inches (15 centimeters) to this measurement as well.
- Once you have the dimensions of the vapor barrier, cut it to size.
Make sure the vapor barrier is big enough to cover the entire surface of the wall.
You’ll need adhesive to attach the vapor barrier to the walls. Without adhesive, the vapor barrier won’t adhere properly to the wall’s surface and will not be effective.
Sealing the vapor barrier to the wall will also make it more durable and less likely to tear.
When choosing an adhesive, ensure it is compatible with the vapor barrier material.
An asphalt-coated paper should be attached with an asphalt-based adhesive. Kraft-faced fiberglass batts can be attached with an adhesive compatible with fiberglass.
Apply the adhesive to the surface of the wall using a notched trowel. The notches on the trowel will help spread the adhesive evenly over the wall’s surface.
Alternatively, you could also use double-sided construction tape or mastic-type sealant. If using this approach, place the tape as close to the edge of the vapor barrier as possible.
After the adhesive has been applied to the surface of the wall, you can now install the vapor barrier.
Start at one corner of the room, unroll the vapor barrier, and work your way around. This will ensure that the vapor barrier is installed evenly.
Be sure to smooth out any wrinkles or creases as you go. These can provide a path for moisture to pass through the vapor barrier.
Once the vapor barrier is in place, use a utility knife to trim any excess material.
A vapor barrier should have a 6-inch overlap at the seams.
The extra space allowance will ensure your vapor barrier fits snugly against the wall, even if there is a pipe or other obstruction.
To attach the seams, you will need to use tape.
There are various types of tape that can be used, but you will want to choose one that is compatible with the material of the vapor barrier.
To attach the seams:
- Clean the surface of the vapor barrier where the seams will meet. This will ensure that the tape will adhere properly.
- Apply a continuous bead of adhesive to one side of the seam. Be sure to apply it close to the edge.
- Press the two pieces of the vapor barrier together and smooth out any wrinkles or creases.
- Apply a continuous bead of adhesive to the other side of the seam.
After installing the vapor barrier, you can add insulation to the walls. This will help to prevent further moisture and cold air from entering your home.
Various types of insulation can be used in a basement, but fiberglass batts are the most common.
Fiberglass batts come in different thicknesses and sizes, so be sure to choose the right one for your needs.
To install the insulation:
- Cut the batts to fit snugly between the studs. You may need to trim them down to size using a utility knife.
- Leave a 1-inch space around all electrical outlets, pipes, and other penetrations. This will allow for expansion and contraction.
- Press the batts into place and then use adhesive to attach them to the studs. This will help to keep them in place and prevent them from sagging over time.
Once the vapor barrier and insulation have been installed, you will want to check for any damage or missed spots.
Be sure to check the seams and around all openings. If you find any damage, you will need to make repairs. This may involve applying additional adhesive or tape.
A basement vapor barrier is a necessary part of any basement waterproofing system.
By installing a vapor barrier, you can help to prevent moisture and cold air from entering your home.
While the installation process may seem daunting, it is actually quite simple. With a bit of time and effort, you can easily install a vapor barrier in your basement.