Do People Need A Vapor Barrier Between Concrete And Wood Flooring – You can find the requirements for vapor barriers, also called vapor barriers, in residential construction in 2019. In section R506.2.3 of the International Residential Code (IRC). But before we look at the regulatory requirements for vapor barriers, let’s clarify what a vapor barrier is.
What is a vapor barrier? A vapor barrier is essentially a thin layer of waterproof material used to keep moisture out.
Do People Need A Vapor Barrier Between Concrete And Wood Flooring
As mentioned previously, the code uses the term vapor barrier. Although most people use the term vapor barrier, the two terms are essentially the same and are used interchangeably.
What You Need To Know About Concrete Vapor Barrier
For consistency, this article will refer to vapor barriers as this term is commonly used.
Now the “barrier” may appear as if it is completely blocking moisture. This is probably why we use the term “timer” in the code, as it is a more technical term.
Without going into too much detail, the code divides vapor barriers into three classes: Each class has a rating that measures the material’s ability to limit the amount of moisture that can penetrate it.
Do you need a vapor barrier under a concrete slab? Yes, IRC Section R506.2.3 states that 6 millimeters of polyethylene or other approved vapor barrier with a beam overlap of at least 6 inches must be placed between the concrete cover slab and the base layer or the prepared soil.
Concrete Foundations: Under Slab Vapor Barriers Done Right
Concrete itself is porous, so it allows moisture to pass through. In most cases, concrete slabs are open and unsealed, allowing water vapor to pass through the slab.
When a floor such as tile, linoleum or wood is laid over a concrete slab, moisture can penetrate between the slab and the subfloor as water vapor passes through.
In the long term, this can lead to problems such as loosening, warping or blistering of the flooring. Not to mention other issues related to the quality of the indoor environment.
This is why installing an under-slab vapor barrier can help reduce many moisture-related problems. If vapor barriers are not drilled during construction and properly overlapped during installation, they can provide significant protection.
The Best Moisture Barrier For Protecting Concrete Slabs And Floors
It is important to note that with the exception of material thickness, the code in this section does not specify a minimum vapor barrier classification for this application.
When do you need a vapor barrier? There are four exceptions where a vapor barrier is not required under a concrete slab: These exceptions include:
How thick should the vapor barrier be? This part of the code does not specify the classification of the vapor barrier, but it does specify its thickness. There must be 6 million of them under the concrete slab. polyethylene or other approved vapor barrier.
A 6 mil barrier basically means the material is 0.006 inch thick. It may not look that thick, but it is the minimum amount of protection needed to reduce the risk of water vapor penetration.
No Vapor Barrier Behind Stone Veneer?
Moisture protection for existing concrete slabs How to install a vapor barrier on an existing concrete slab?
Sometimes you can convert a garage into living space or have an existing structure that does not have a vapor barrier installed under the slab. How can I meet this vapor barrier requirement if the panel is already there?
The code does not specify how to address these scenarios, but alternative methods may be suggested to meet the intent of the code under these existing conditions.
One option is to apply a product on top of the concrete slab to protect it from moisture. A widely used product is known as RedGard and can be used for a variety of applications.
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This is just one of many products available, but it is popular. The key is to make sure it is listed and tested for this program.
For more information on vapor barrier requirements, see 2018. In Section R506.2.3 of the International Residential Code (IRC). Protecting the concrete slab and building interior from moisture underneath starts from the very beginning. Steam cleaning panels is a complicated and expensive solution. Although choosing a minimally protected moisture barrier can be beneficial to save initial costs, the consequences often turn into long-term problems.
These potential problems and costs can be avoided with proper planning and design. Choosing the right sub-slab vapor barrier is essential for your finished floor as well as your overall health and safety. Properly selected and installed, a quality under-slab moisture barrier will ensure a successful finished floor system and provide long-term safety and comfort.
Moisture control is essential to the longevity of floor coverings such as gym floors. Photo credit: ISI Building Products
For Concrete Subfloors
What should you pay attention to when choosing a vapor barrier under the slab? First, let’s summarize some of the sources of moisture under the concrete slab and how they can affect your finished floor and indoor air quality.
The building envelope is typically surrounded by an active HVAC system, so the relative humidity below the slab is close to 100%. To find a balance, water vapor can diffuse through porous concrete, increasing the pH and alkalinity of the slab. The high pH and alkalinity of flooring adhesives at the panel interface can compromise the adhesion of expensive prefinished flooring systems.
The high pH and alkalinity of flooring adhesives at the panel interface can compromise the adhesion of expensive prefinished flooring systems.
Additionally, water vapor passing through an unprotected concrete slab can cause high relative humidity, mold, and failure of the concrete slab and its components.
Does Thickness Matter When It Comes To Vapor Barriers?
Historically, the slab was placed directly on top of the sand layer to protect the polyethylene sheet from damage during concreting and to allow water to drain from the newly placed concrete. The problem with this method is that although the sand layer absorbs excess water, once the water reaches the polyethylene sheet layer, it remains trapped.
Similar to the diffusion of water vapor from the soil, when the building is closed and the relative humidity below the slab is in equilibrium, the trapped runoff has no choice but to rise. It is often permissible to lay foundation systems in advance because there is no water in the sand layer.
Therefore, it is generally recommended to place the concrete slab directly on top of the under-slab vapor barrier.
ISI Building Products Viper II 15 Mil Concrete Ready Vapor Barrier. Photo credit: ISI Building Products
Capillary Break Beneath Slab
A key step in choosing a vapor barrier is the difference between a vapor barrier and a vapor barrier. The industry accepts a steam-retarded water vapor permeability of 0.1 to 0.01 perm. Vapor barrier materials are considered to have a water vapor permeability of less than 0.01 perm.
For product comparison purposes, long-term exposure results are often expressed as particles/(ft2*h*Hg). These conditions and performance results apply to product evaluation and are available from the manufacturer upon request for a data sheet.
The highest quality vapor barriers start with pure resin that contains no recycled content. Photo credit: ISI Building Products
With the development of plastic film production, high-quality materials are becoming more and more popular. It is important to find a moisture-resistant product made from 100% pure resin. They are also typically produced using multi-layer or coextrusion techniques. Coextruded films are in high demand because they combine the best properties of different resins and bond them all into a single film structure.
Vapor Barrier Under Slab
When considering these innovative plastic film techniques, professionals should note that thickness is not always directly related to performance. Less robust materials such as clear or black polyethylene sheets (also known as Visquin) have been used as a minimalist means of protection against the aforementioned moisture-related issues. These types of products are usually made with a lot of recycled materials. Concerns about these products include long-term performance and defects in areas such as strength and water vapor resistance.
High performance vapor barriers and barriers are typically 8 mil, 10 mil, 15 mil. and 20 million thickness. As mentioned earlier, increasing thickness does not always improve performance. Avoid unique extruded products made from recycled content. For example, a 10 mil single-layer extruded film made from recycled materials does not match the performance of a thinner 8 mil co-extruded film made from virgin resin. When evaluating vapor barrier and barrier products, it is important to determine whether the product is made from pure resin or coextruded film.
The vapor barrier must overlap the seams by at least 6 inches and be sealed with manufacturer-approved tape. Photo credit: ISI Building Products
Industry organizations such as the American Concrete Institute and the American Society for Testing and Materials have established specific testing guidelines and standards for vapor retarders and under-slab barriers.
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For example, ASTM E 1745 (Standard Specification for Plastic Vapor Retardants Used in Contact with Soil or Granular Aggregates Under Concrete Slabs) is the testing standard used to determine product performance. ASTM E 1745 classifies the material as A.
