Vapor Barrier: A Must-Have for Your Basement

A vapor barrier is a thin plastic-like layer on your basement or crawlspace walls to prevent moisture from condensing through. In high-humidity areas, vapor barriers protect your basement from excessive moisture and mold and mildew infestation, all while reducing home energy costs.

What is a Vapor Barrier?

A vapor barrier is a thin waterproof material that adheres to basement or crawlspace walls before applying a finishing layer such as drywall or plaster. In warmer climates, the barrier may lie outside the insulation.

Vapor barriers are made of plastic, polyethylene, or specific waterproof materials. These barriers prevent moisture from invading your basement over time. 

What is a Vapor Barrier

Benefits of Installing a Vapor Barrier

Protects Against Moisture and Mold

Vapor barriers control moisture by preventing it from seeping into the house. They reduce the risk of condensation on your basement or crawlspace’s walls, preventing long-term damage to the structure. This prevents mold and mildew from growing. 

Helps Insulate The Room and Improves Energy Efficiency

When moisture infiltrates a building, cooling or heating systems work harder to stabilize the temperature. Vapor barriers help insulate your home’s lower regions from weather factors, preserving temperatures and increasing energy efficiency. 

Improves Air Quality

Vapor barriers help create a healthier indoor environment by reducing the risk of mold and mildew. Mold releases spores that can be toxic when inhaled, not to mention causing an unpleasant musty smell. 

It Makes Your Basement More Comfortable

The combination of lower humidity, less unpleasant smells, and a lack of mold or mildew results in a space with better air and living quality. Vapor barriers may help you transform a dusty, moist basement into a livable space to enjoy time with your family.

How to Install a Vapor Barrier

Installing an effective vapor barrier is only for experienced DIY experts. Otherwise, hiring a professional is best. 

1. Gather Your Materials

  • A low vapor diffusion material for the vapor barrier itself. There are three classes of materials based on their vapor diffusion, Class I, II, and III. Class I is the lowest.
  • A vacuum cleaner or a broomstick and shovel to remove debris. 
  • Tools to remove old, unused pipes and electrical outlets from the walls.
  • Utility knife or heavy-duty scissors to cut the vapor barrier.
  • An adhesive that’s compatible with your selected type of vapor barrier. 
  • A notched trowel to apply the adhesive to the wall.
  • Rubber seam tape to join the seams of the leftover vapor barrier pieces.
  • Fiberglass batts insulation.

2. Clean the Basement

Clean all surfaces and pay special attention to the walls where you’ll apply the barrier. Remove all dust, dirt, cobwebs, and anything else that’s built up on the walls’ surface. Debris interferes with the application, so remove it with a vacuum cleaner or broomstick and shovel, then wipe the surface with a damp cloth to remove any smaller pieces of debris.

3. Install the Vapor Barrier

  • Cut the vapor barrier: Measure the wall length and add 6 inches in all directions. Cut the barrier using a utility knife or heavy-duty scissors. The extra material will give you enough room to maneuver for the entire wall to be covered.
  • Apply the adhesive to the wall and barrier: Follow the manufacturer’s application instructions. Once applied, install the vapor barrier. Install from a corner of your basement or crawlspace and work around it, ensuring there are no wrinkles and the barrier’s surface is as smooth as possible. 
  • Tape the barrier’s seams: After installing the barrier, you should have a 6-inch overlap at the seams, which allows you to fit the barrier even if you face obstructions. Use the tape to attach the seams.
  • Install the insulation: After installing the barrier, you’ll want to use fiberglass batts for insulation. Cut the batts to fit between the studs, leaving a 1-inch around all electrical outlets, pipes, and other penetrations. Finally, press the batts in place and adhere them to the studs.


Here are common problems that might come up when installing a vapor barrier and how to troubleshoot them:

  • Wrinkled barrier: Use a squeegee or similar tool to smooth out the barrier. If there are still bubbles, you may need to remove and reinstall it.
  • Barrier not sticking to the wall: This could be due to debris or dust on the wall. Clean the wall before starting, and use a high-quality adhesive compatible with your barrier material.
  • Seams not sealing properly: Ensure the seams of your vapor barrier overlap to prevent moisture from getting through. If you’re having trouble sealing the seams, try with a different seam tape and apply enough pressure to make a good seal. 

Fight Basement Humidity With Vapor Barriers

Vapor barriers are a must-have to protect basements from moisture, mold, and mildew. These simple yet effective protective layers can transform your basement into a comfortable, livable space. Stop basement humidity and prevent it from becoming a larger problem by installing a basement vapor barrier.