How to Choose House Wrap

House wrap is designed to protect the home against rain, sleet, snow, and any other type of moisture that may seep through the exterior siding. This protective layer blocks the moisture from entering the wall cavity of the home, preventing wood rot, mold growth, and flooding. House wrap comes in a range of forms, including fabric, paper, and board material that covers the exterior sheathing of house walls to protect the wall framing.

However, it's important to note that house wrap is not completely impermeable or waterproof. The reason for this is that water can seep into the wall cavity from the inside of the home, not just the outside. If water becomes trapped in the wall and is not able to escape through the house wrap, then it can create rot, mold, and mildew issues. Use this guide to learn how to choose house wrap to protect your home.

Before Buying House Wrap

If you are building a new home or replacing the exterior siding on an existing property, then it's a good idea to consider investing in house wrap. This water-resistive barrier (WRB) wraps around the sheathing of the home, preventing the entry of moisture into the wall cavity from outside, while remaining permeable enough to allow moisture to escape from the inside of the home. Most house wrap options have a permeability rating between five and 60. Typically, a minimum of five is required by most building codes.

However, it's necessary to mention that most types of house wrap do not serve as an effective air barrier to prevent cold air from entering the wall cavities. Only a few special products are designed to perform this function, and they must be installed meticulously to create a reliable air barrier.

Also, it's important to understand where house wrap is installed in the multi-layered construction of a home. House wrap is intended to be installed over the sheathing and behind the siding, regardless of the siding you are using. Additionally, siding manufacturers may recommend specific types of house wrap to use with their products, so if you are unsure about the best option for your home, consider speaking with the siding manufacturer for suggestions.

Buying Considerations for House Wrap

Durability

The durability of the house wrap should be one of the main factors to consider when you are planning the project. House wrap remains in place for years, protecting the home from moisture, so if it isn't durable enough it could split, tear, or even crack, depending on the material. When you consider the durability of the house wrap product, think about the tensile strength of the material, resistance to high and low temperature extremes, and resistance to surfactants, which can be present in housing materials.

Water Resistance

The primary purpose of house wrap is to prevent water from reaching the wall cavity of the home, so it's necessary to find a product with a high level of water resistance. You can typically research various house wrap products to get a basic understanding of the water resistance capabilities, but if you still aren't sure about the best option, consider requesting samples or purchasing small samples from a pool of manufacturers.

Compare the water resistance of the samples using water pooling and hydrostatic water pressure testing. Additionally, you can use this test to find out how effectively each house wrap sheds water. This is important because you don't want to purchase a house wrap that will trap water in puddles, leading to mold growth and insect infestations.

UV Stability

The UV stability or UV resistance of a house wrap product may not initially seem very important because the house wrap will be covered by exterior siding. However, if you are installing house wrap on a new building, the wrap typically remains exposed to direct sunlight during construction, which can last for several weeks. If the house wrap is not resistant to UV radiation, it can begin to break down during this period, so it's recommended to invest in a house wrap with built-in UV protection.

Vapor Permeability

House wrap is designed to be permeable so that moisture can exit the home, instead of getting trapped inside the wall cavity. The permeability of the material depends on the type of house wrap, but can also vary between individual products, so it's important to check the listed permeability of the product before purchase. Permeability is measured in US perms, with one perm equal to one gram of water vapor per hour per square foot per inch of mercury.

Impermeable materials will typically have a perm rating of 0.1 perms or less, while most house wrap products have a perm rating that falls between five to 60 perms. High permeability may not seem like a good idea for moisture protection, but it actually helps keep the home dry by allowing more moisture to exit the home. However, the ideal perm rating for house wrap tends to fall between 10 to 20 perms, balancing the inward and outward flow of moisture in the wall system.

House Wrap Types

Asphalt Felt

One of the most common types of house wrap is known as asphalt felt. It typically has a perm rating of about five and moderate water resistance, making it a good choice for use as a sheathing wrap. However, it's important to note that asphalt felt absorbs water when wet, which can increase the permeability of the product significantly. This high permeability promotes rapid drying by helping to ensure that water doesn't become trapped inside the home. Despite these attractive features, asphalt felt doesn't hold up well under direct sunlight, so it isn't recommended for locations that will be exposed to the sun for an extended period of time.

Grade D Building Paper

Another common type of house wrap is called grade D building paper. This product is essentially a kraft paper with asphalt integrated into the design to increase the water resistance of the material. It's often used under stucco exteriors and has a similar vapor permeability as asphalt felt house wrap. One drawback to using grade D building paper is that it can deteriorate if it remains wet for a prolonged period of time. To avoid this problem, many installers will use two layers of grade D building paper. When the paper wrinkles, this creates small air pockets between the layers to help improve air flow and increase drying time.

Polyolefin Fabric

If you are looking for a more reliable option than asphalt felt or grade D building paper, then polyolefin fabric may be the right choice. It is essentially a plastic house wrap that is available in woven, non-woven, perforated, and non-perforated options, so you can select the best type based on the needs of your home.

Polyolefin house wrap is light, easy to work with, and has a high level of vapor permeability, water resistance, and tear resistance. However, it is susceptible to the surfactants that can leach out of wet cedar siding, redwood siding, and stucco cement plaster.

Liquid Water-Resistive Barrier

Wrapping the home in a woven or non-woven wrap is an excellent way to protect the home, but if you are worried about the house wrap shifting, tearing, or degrading, then a liquid water-resistive barrier may be a better choice. This type of house wrap is essentially a water resistant liquid that is applied with a roller or sprayer to create a continuous, seam-free coating to protect the home.

The installation process typically takes longer, beginning with a base coat that starts at the bottom and goes up. After the base coat, the seams and corners of the building are reinforced with polyester joint fabric, then a second coat is applied. This process generally takes about two days to complete. It's also worth noting that liquid water-resistive barrier is one of the most expensive options to install.

Integrated WRB Sheathing

Recent developments have led to the creation of integrated WRB sheathing, which is essentially a structural panel that is designed with an integrated water-resistive barrier. This type of house wrap eliminates the risk of water getting trapped between the panel surface and the back of the house wrap material. It also increases the durability of this protective layer, instead of more traditional house wrap options that are vulnerable to ripping or tearing. However, the pool of integrated WRB sheathing products is significantly smaller that more common house wrap types and the cost of this material tends to be higher than most other options.

Cost

The average cost to install house wrap ranges from about $0.13 to $0.16 per square foot, while the total cost when you consider the price of labor and other materials ranges from about $1.02 to $1.22 per square foot.

This means that you will essentially be spending about $560 to complete a typical 500 square foot job. However, the actual cost of the project will vary depending on the location, job size, conditions, and finish options that you select.

How to Choose House Wrap

When it comes time to select a house wrap to protect your home, find a product that balances the needs of the home based on the typically temperature, humidity, and precipitation. If cost is a primary deciding factor asphalt felt and grade D building paper are affordable, effective ways to protect the home from moisture.

As long as you don't mind spending a little more on materials, polyolefin fabric, integrated WRB sheathing, and liquid water-resistive barrier are great options that balance water-resistance, permeability, and durability. If you aren't sure about which type of house wrap is best for your home, consider speaking to a siding manufacturer or getting suggestions from the house wrap installation company.