Where Does the Vapor Barrier Go in a Basement?

Vapor barriers should be located on the exterior of basement assemblies allowing inward drying to the basement space where moisture can be removed by ventilation or dehumidification.

Not to be confused with a vapor barrier—which is placed on the warm side of the wall just in front of the insulation and behind the drywall— a moisture barrier goes against the basement wall and behind the insulation and framing.

There are a few different types of moisture barriers that you can use, but the two most common are waterproof paints and sealants. Waterproof paints are applied to the surface of the brick and work by forming a barrier that water cannot penetrate. Sealants are liquids or gels that are applied to the mortar joints between bricks. They work by filling in the cracks and pores in the mortar, which then prevents water from seeping through.

Both options will help protect your brick from moisture, but it is important to note that they are not 100% waterproof. There is always the potential for water to find a way through, so it is important to take other preventative measures, such as installing a gutter system, to help ensure that your brick stays dry.

The purpose of a vapor barrier is to slow the movement of water vapor from the warm side of the wall to the cold side, where it could condense and cause damage. In contrast, the purpose of a moisture barrier is to keep groundwater from seeping through the basement wall and into the insulation and framing.

A vapor barrier is not as important in a basement as it is in an above-grade wall, because the temperature differential between the inside and outside of a basement is usually much less. However, if you have a moisture problem in your basement, you should install a vapor barrier on the warm side of the wall to help control the problem.

When installing a vapor barrier in a basement, you should install it on the warm side of the wall, behind the insulation and framing. A moisture barrier, on the other hand, should be installed on the cold side of the wall, behind the siding and trim.

If you’re not sure which type of barrier to install, consult with a professional contractor. In fact, hiring a basement professional is highly suggested. Especially, if you are thinking it is a DIY project, please think again.

Pros and cons of vapor barrier in basement

Some pros and cons of installing a vapor barrier in a basement:


  • Can help control moisture problems
  • It may help increase energy efficiency
  • Can prolong the life of framing and insulation
  • Inexpensive and relatively easy to install for a pro.
  • Because the material is translucent, it is easy to attach to framing


  • Material is fairly flimsy and can be easily damaged during installation
  • It can be challenging to install correctly without hiring a professional
  • May not be necessary for all geographical areas

Installation of a vapor barrier is a matter of personal preference and should be decided on a case-by-case basis. For example, if you are experiencing moisture problems in your basement, installing a vapor barrier to help control the problem is worth considering. However, if you do not have any moisture problems, leaving the vapor barrier off may be best.

Always consult with a professional contractor before making a decision.

Is a vapor barrier necessary in a basement?

If the framing is attached to masonry or concrete surfaces, or if the wood frame butts up against the outside basement walls, most building codes usually require a vapor barrier (4 mils plastic sheeting) on exterior basement walls.

The best vapor barriers for concrete floors and slabs are a new generation of Poly that has been developed to be less permeable, more strong, and resistant to punctures. The companies that manufacture these new vapor barriers make them in thicknesses of ten mils and fifteen mils with different widths and lengths.

Is a moisture barrier necessary?

When moisture penetrates your flooring, it can cause mold, mildew, and the potential for water damage. A moisture barrier helps control the water vapor’s movement to help protect your floors. Therefore, if you’re installing floors in an area that sees moisture, even a little, a vapor barrier is needed.

When the mortar is damaged, water seeps into a brick surface and can cause a significant amount of damage, such as mildew, rotting wood, and mold.

Exposure to moisture and repeated freezing and thawing experienced each year in places such as the Metro Detroit area of Michigan can cause mortar joints between bricks to crack, thus making a home susceptible to hazardous water damage.

Installing a moisture barrier can help protect your home from water damage and keep your brick looking great for years to come.

Why do you need tuckpointing?

Tuckpointing is the process of routing out the damaged mortar and replacing it with fresh mortar. Aside from halting mortar joint corrosion and restoring structural stability, tuckpointing also helps protect your home’s brick structures from damaging moisture.

Tuckpointing helps to prevent water from entering into the chimney system. If the mortar joints are not repaired, water will seep down the chimney and sometimes between the chimney and the flue lining. In addition, moisture can do a serious amount of unseen damage, such as mold, mildew, or rotting wood.

Although brick can last centuries, mortar may last only 25 years before needing replacing. Over time, weather causes damage to brick and mortar. If left untreated, the damaged areas become vulnerable to water entry brick movement and can cause the structure to collapse.

Where does the vapor barrier go in a basement?

Vapor barriers should be on the outside of the walls in the basement. This will allow the air to go in and take the water out.


Vapor barriers and moisture barriers are essential when it comes to protecting your home from water damage. However, it is important to consult with a professional contractor before deciding on whether or not to install a vapor barrier in your basement.

If you are experiencing moisture problems, installing a vapor barrier is the best way to control them. If you do not have any moisture problems, leaving the vapor barrier off may be best. Tuckpointing is also an important aspect of home maintenance and should be done regularly to protect your home from water damage.


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