What is a Moisture Barrier and Do I Need One?

To get straight to the point, moisture damage costs U.S. homeowners nearly $20 billion a year.

The cost of moisture repair is staggering. Neglecting proper home protection can lead to repair costs ranging from a few hundred dollars for minor issues to tens of thousands for extensive restoration.  

To safeguard your home from costly moisture damage, consider the long-term benefits of a moisture barrier. 

While the initial expense of moisture remediation can be substantial, a high-performance moisture barrier is a relatively inexpensive investment that can prevent high costs in repairs and protect your home’s structural integrity.

What is a Moisture Barrier?

A moisture barrier, also known as a vapor barrier or moisture retarder, is a moisture-resistant layer installed beneath building materials.

This high-density material prevents water, whether in liquid, steam, or condensation form, from penetrating and damaging your home’s structure.

Moisture barriers are typically applied during new construction or renovations. 

They are placed over the exterior envelope to prevent moisture vapor from being trapped in the wall system and lower levels such as floors, basements, ceilings and crawl spaces, to protect the foundation from moisture.

They are most often used in the construction of walls and floors.

Moisture Barrier for Flooring

Moisture barriers are usually placed under the floor to ensure the durability and quality of the covering. They obstruct the passage and control the moisture content through the floor. They act as a protective layer between the substrate and the floor covering. 

There are various forms of barriers, sheets, rolls, coatings and other flexible materials. Each is adapted to a specific type of floor and environmental conditions.

The most important reason to decide to install a moisture or vapor barrier is the price ratio of the floor covering and the barrier. A much cheaper moisture barrier will protect your much more expensive floors from damage.

Whether you should put this barrier depends on factors such as climate, type of room, substrate and type of flooring.

A mild climate usually does not require a moisture barrier, but if you live in an area with severe winters and high humidity, a barrier is recommended. 

Also, rooms with low humidity such as bedrooms and living rooms may not be so demanding, but bathrooms, kitchens and basements definitely require a moisture barrier.

A damaged substrate, with cracks and unevenness, will lead to faster penetration of moisture into the floor covering. A concrete floor may look like stone to you, but concrete is actually a porous material and allows water to move upward from lower, high-pressure areas like your foundation and basement. 

Water-based adhesives used for floor installation are susceptible to moisture. Liquid water beneath the floorboard can evaporate, turning into steam, or condense and remain trapped under the flooring. Both scenarios can cause damage to the flooring.

When gradually exposed to moisture, most floor coverings will develop significant problems. 

If you do not protect your floor in the right way, swelling, rotting, peeling, discoloration and the appearance of unpleasant odors, mold and fungi can occur. A moisture barrier is a simple and affordable way to avoid this.

There are different types of floor barriers: 

1. The rolls are designed to be bonded together to construct a complete floating surface.
2. Some options are self-adhesive. 
3. Other moisture barriers can be glued to the substrate or painted like waterproofing coatings. 
4. There are substrates with an attached floor barrier as concrete screeds with additives to reduce moisture permeability.

When choosing a barrier, it is important to consider the type of floor on which it is installed.

Moisture Barrier for Different Floor Types

Natural materials such as wood, cork, stone are more porous and less waterproof. A vapor barrier in this case is highly recommended.

A vapor barrier is almost 100% necessary if you have a concrete base on which a wooden floor is installed. The combination of a concrete base and a wooden floor is one of the key cases when a barrier is used.

The porous nature of concrete will let moisture into the wood paneling which will warp and damage it. The moisture barrier is also recommended if wooden parquet is installed in the basement, regardless of the type of substrate.

There are several types of moisture barriers for wood floors: 

• You can apply it as a liquid coating that forms a protective layer.
• Also, there are waterproof flooring products such as adhesives that have a moisture control membrane. 
• To protect wooden floors from water on a concrete or earthen base, a complex waterproof two-layer film of high density is used.
• In order to protect the wooden elements from the penetration of water vapor from the room, a vapor barrier of increased strength with an improved anti-condensation surface is used. These types of vapor barriers are most commonly used in mansards, floor coverings and in floors in adapted attics.

Installing a moisture barrier under a wooden floor has no disadvantages and the benefits are multiple. The floor becomes resistant to mold, rotting and warping.

Artificial materials such as laminate, vinyl and ceramic tiles are less porous, but a barrier is recommended for them too, especially in rooms with higher humidity. This is especially true for laminate.

Laminate flooring mainly consists of wood that swells and bends due to moisture. Due to the proportion of wood, the moisture or vapor barrier is highly recommended, especially if it is placed on mineral substrates such as concrete in rooms with moisture such as bathrooms and kitchens.

Even substrates that appear dry may require a moisture barrier, as conditions can change dramatically, especially in winter. A moisture barrier is also essential for heated rooms above unheated basements to prevent condensation buildup on the ceiling.

Vinyl boards have good water resistance. If they are placed on a concrete base, it is best to use a vapor barrier. If you are installing them on an existing base or plywood, the barrier is not so necessary.

Choosing a moisture barrier is an important decision when building or renovating, and price often plays a key role. 

However, it is not only the price that should be taken into account. The quality and performance of the vapor barrier directly affect the durability and efficiency of your building.

How to Choose the Right Moisture Barrier for your Floor

Moisture barriers are categorized into three different classes:

1. The first class includes thicker sheets that have superior vapor resistance. These are glass, sheet metal, polyethylene sheets and rubber membranes.
2. The second class contains materials with good vapor resistance. Bitumen-coated kraft paper, plywood, asphalt paper, untreated polystyrene.
3. The third class includes materials with moderate steam resistance. These are gypsum boards, cellulose insulation, plastic unfaced insulation.

The choice of barrier depends on the type of floor, the material of the substrate itself and the environmental conditions. There is no one-size-fits-all solution.

Polyethylene film is an economical choice. It is available in rolls and is placed on the base before the floor. It is usually used for concrete substrates. 

There are different thicknesses. A 6mm vapor barrier can cost about $0.15 per foot or about $160 to $200 for a 1200 square foot roll. A 20mm thick vapor barrier costs about $0.50 per foot or $350 to $500 for a roll of the same size. On average, you will pay between $0.25 and $0.50 per rate.

Bitumen-coated kraft paper is commonly used under hardwood floors. It comes in rolls and is designed to prevent the transfer of moisture from the substrate to the wooden floor. It also provides a flat surface for parquet installation. The price depends on the thickness of the paper, but it can be found from $0.12 to $0.60 per foot.

Rubberized asphalt membranes are versatile barriers suitable for all types of floors, wood, laminate and vinyl. They come in rolls and sheets. They have a rubberized asphalt layer that adheres to the substrate. They are excellent for uneven surfaces.

Epoxy moisture barriers are applied as coatings and create a durable moisture resistant layer. They are particularly effective in basements and provide protection against chemical and environmental damage.

The most expensive vapor barriers are aluminum foils, bitumen membranes and special synthetic membranes. They have vapor impermeability, high water resistance, resistance to mechanical damage and UV radiation and a long service life. 

Disadvantages are the high price and complicated installation, but the best possible protection and high energy efficiency are obtained.

The cheapest vapor barriers are thin PE films. They can be found for $0.20 per square foot. Low cost and simple installation mean a short lifespan, prone to damage and minimal protection from moisture.

Tips and Tricks – What Affects the Costs of Professional Moisture Barrier Installation

1. Size of the surface: a larger surface requires more working hours.

2. Availability of space: Hard-to-reach spaces such as attics and crawl spaces increase costs. 

3. Complexity of work: Irregularities in the construction itself or obstacles mean higher costs.

4. Type of moisture barrier: Installing higher quality and specialized barriers is more expensive.

5. Additional works: the price is affected if the old insulation has to be removed or if the damaged structure needs to be repaired.

6. Regional differences: The cost of materials and labor varies depending on the area.

7. Urgency of work: If urgent installation is important, contractors may charge additional costs.

Contact several contractors and ask for a detailed offer.

Conclusion

A moisture barrier is an important investment. In the long run, you will protect your home and take care of your family’s health. In order to do this in the right way, it is best to ask for the advice of a professional who will choose the type of protection.