Moisture Barriers for Concrete Floors

Moisture barriers play a crucial role in maintaining the integrity and longevity of concrete floors. As a flooring enthusiast, it’s essential to understand the significance of moisture barriers and how to choose the best one. In this comprehensive guide, we will explore different types of moisture barriers and provide expert advice to help you make informed decisions for your concrete flooring projects.

Moisture can cause various problems on concrete floors, including mold growth, deterioration, and flooring failures. To prevent these issues, moisture barriers act as a protective layer, preventing moisture from seeping through the concrete and reaching the flooring material. By installing a proper moisture barrier, you can ensure a stable and long-lasting floor.

Before installing flooring over concrete, it’s crucial to ensure that the concrete has reached an appropriate level of humidity. The generally recommended humidity level for concrete prior to flooring installation is below 75% relative humidity (RH) according to industry standards. However, specific flooring manufacturers may have their own guidelines, so it’s essential to consult the instructions provided by the flooring manufacturer for the optimal humidity level.

Types of Moisture Barriers for Concrete Floors

Vapor Retarders

Vapor retarders are materials that slow down the passage of moisture vapor through the concrete. There are different types of vapor retarders available, including sheet, liquid-applied, and peel-and-stick options. Sheet vapor retarders provide excellent moisture resistance, while liquid-applied ones offer seamless coverage. Peel-and-stick options are easy to install but may be costlier. 6 Mil Polyethylene Sheeting This is one of the most basic and commonly used vapor retarders. It’s a thin, flexible plastic sheet typically about 6 mils (0.006 inches) thick. The polyethylene sheeting is laid directly over the compacted soil or gravel layer before pouring the concrete slab.

Vapor Barriers

Vapor barriers are impermeable materials that prevent the passage of moisture vapor. Commonly used vapor barrier materials include polyethylene, epoxy, and polyurethane. Polyethylene is cost-effective and easy to install, while epoxy and polyurethane provide superior durability. Perma-Flex® 6 Mil Polyethylene Vapor Barrier Perma-Flex® is a high-quality vapor barrier designed specifically for use under concrete slabs. It is made of durable polyethylene material, providing excellent moisture resistance. Thickness: 6 mils (0.006 inches), which is a standard thickness for polyethylene vapor barriers used in concrete construction.

Waterproofing Membranes

Waterproofing membranes are designed to provide a watertight seal on concrete surfaces. They can be either sheet or liquid membranes. Sheet membranes offer excellent protection against water intrusion and are suitable for areas with high moisture levels. Liquid membranes provide flexibility and can be easily applied to irregular surfaces.

RedGard® Waterproofing and Crack Prevention Membrane RedGard® is a popular waterproofing and crack prevention membrane manufactured by Custom Building Products. It is specifically designed to protect concrete substrates from water damage and to prevent cracks from forming in tile and stone installations.  RedGard® is a liquid-applied membrane that comes ready to use. It is made of a blend of elastomeric polymers, Portland cement, and other proprietary additives that provide flexibility, durability, and excellent waterproofing properties.

Under Slab Moisture Barrier

A moisture barrier under a concrete slab is really important because it stops water from getting into the building. It’s usually made of a strong plastic called polyethylene. This barrier is put down on the ground before the concrete is poured. It covers the whole area where the concrete will be.

This stops moisture from moving up from the ground into the concrete. If moisture gets into the concrete, it can cause a lot of problems like mold and damage to the building. The barrier also helps keep out gases from the soil that can be harmful.

Building rules often say you have to use a moisture barrier in concrete slabs, especially where there’s a lot of water in the ground. It’s important to check the barrier sometimes to make sure it’s still working well. Overall, having a moisture barrier under the concrete helps keep buildings strong and safe for a long time.

Moisture Barrier Paints and Coatings

Moisture barrier paints and coatings create a protective layer on the concrete surface, preventing moisture penetration. These products are available in various formulations and can be applied like traditional paint. Ensure you select moisture barrier paints and coatings that are specifically designed for concrete floors.

Drylok Latex Concrete Floor Paint is a popular choice for moisture barrier paints and coatings designed specifically for concrete floors. It is manufactured by UGL (United Gilsonite Laboratories) and is formulated to protect and beautify interior and exterior concrete surfaces. Drylok Latex Concrete Floor Paint is a latex-based coating that contains advanced water-based technology. It forms a durable, waterproof barrier when applied to concrete surfaces.


In conclusion, choosing the best moisture barrier for your concrete floor is crucial for preserving its integrity and preventing moisture-related issues. Evaluate the different types of moisture barriers available, considering factors such as environmental conditions, flooring type, application method, and durability. Follow proper installation techniques, conduct quality control checks, and implement additional moisture management practices for optimal results. By understanding the importance of moisture barriers and following best practices, you can ensure a long-lasting and beautiful concrete floor.

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