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Do You Need Sheathing Under Siding? [Inc. Metal, Plywood, & Smart]

Choosing the right materials for your home is very important, and this includes everything from roofs to wall materials. During construction, the siding of the house is one of the things people are quite meticulous about, and you've probably wondered if you need sheathing under it. We researched this topic for you and here's what we discovered.

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Sheathing material is important for all types of exterior walls and siding. The sheathing acts as a nailing base and it adds extra insulation to the home. However, existing walls do not need sheathing unless you will be replacing the old siding or if the new material you will be putting up requires sheathing. 

Knowing about the importance of sheathing for home construction is important because it will affect the way you install your home siding. In this post, we will talk about different options of wall sheathing you may want to check out for your home. We will also discuss how thick the sheathing should be, so keep reading and enjoy this post!

Do You Need Sheathing Under Siding?

A residential house construction project showing plywood roof and dormer sheathing and oriented strand

If you are just about to build your home, your contractor may most likely discuss several things that you need to decide on while building. This will include decisions on choosing the right roofing material, insulation, and even the siding for your home. 

One of the things that you have to consider when you choose your siding is sheathing. This material is important because it protects the house from the elements. The sheathing is also important not just to exterior walls, but also to provide a foundation for roofs and floors.

Sheathing also serves as extra insulation for the house. A good sheathing layer will help keep your home more energy efficient and will hold more heat in the long run.

For new construction, you will need to put sheathing under the siding. The purpose of the sheathing is to provide a nailing base wherein you will attach the siding. Without sheathing, it will be hard for your contractor to install the siding of your home.

However, if you're planning to install brand-new siding over your existing ones, you don't need to add sheathing. This is only necessary if you will be stripping the old siding completely, leaving the exterior of your house bare. You also need to put sheathing if the siding material you will be working with needs to attach to a sheathing material during installation.

If you are thinking of using other types of siding material like metal, plywood, or Smartside siding, you'll be happy to know that they work well with most types of sheathing. These siding materials generally work well with plywood or OSB sheathing but seek your contractor's suggestions for optimum results. 

What Are The Options For Wall Sheathing?

Wall sheathed with insulation

Now that you know the importance of sheathing for your home, you're probably thinking of the different types you'll have to choose from. Generally speaking, there are a lot of sheathing options available that you can use for different kinds of siding. 

Before you go and purchase wall sheathing, you'll have to understand that there are two kinds available on the market. One is the structural sheathing, which builders use to provide support to the walls of the home. This kind of sheathing will add structural strength to the building's framework and this is where you will nail your siding.

Non-structural sheathing, on the other hand, is another layer that you add to the framework of the house for a different purpose. This kind of sheathing provides insulation to your home, and it will help keep the wind and water out. Along with the insulation you've chosen for your home, this sheathing will keep your house warm.

Types of Sheathing

Vinyl siding texture installed for weathering protection on new residential home, Do You Need Sheathing Under Siding? [Inc. Metal, Plywood, & Smart]

1. Oriented strand board (OSB) sheathing

The oriented strand board or OSB as it is one of the most popular choices of exterior wall sheathing available today. This material uses thin wood strands or wood chips that are pressed into a board using a mixture of resin and wax adhesives. 

This type of sheathing is popular because it is relatively inexpensive but holds up well during construction. It is very durable, and OSB does not absorb water as regular wood sheathing does. This particular sheathing works well with most siding types that are used for residential purposes.

2. Plywood

plywood sheets

Plywood is one of the most common types of sheathing you will find in the market and is one of the most popular choices for most builders. This type of sheathing uses cross-laminated wood sheets that are pressed together. These cross-laminated layers or plys give the board the stiffness and strength it needs. 

It's a popular choice for many builders because it is lightweight and moisture-resistant, which is great for wet climates. It is also fairly easy to install, which is why builders like to use them during construction. You can also use plywood for nearly all types of siding that you want to use for your home. 

3. Fiberboard

hands of a Carpenter who cuts fiberboard with a mounting knife using OSB

If you are looking to install sheathing that has a sound-proofing quality, this might be what you're looking for. Fiberboard sheathing is a structural sheathing that uses plant-derived cellulose fiber and adhesives. It is then covered in a water-resistant coating which is why this is also used as roof sheathing.

Aside from its sound-proofing qualities, fiberboard is also good at retaining heat, so it's a perfect choice for additional insulation. Typically, fiberboard is used with other types of sheathing because it is not sturdy enough to be the only sheathing layer of the wall. 

4. Foamboard

Foamboard is a non-structural type of sheathing that provides excellent insulation to your walls. Typically, this type of sheathing is installed underneath the structural sheathing for newly constructed houses. However, you will also see this being used over existing siding if the homeowners are planning to cover their old siding with a new one.

This type of sheathing is great at making your house energy-efficient. It can be used in place of a house wrap, so it can significantly lower the cost of materials during construction. However, it can be a little hard to install so make sure to get a professional to do this job for you. 

5. Gypsum

Another alternative for wood sheathing is gypsum. This sheathing is a type of sheetrock that's used for external applications. It is best paired with fiberglass and is quite affordable and durable. 

One of the reasons why some builders like to use gypsum is because of its fire- and sound-resistant qualities. If your home is prone to wildfires or natural disasters, gypsum is a great choice. It also provides extra insulation for your home and holds up better than fiberboard.

6. Glass mat

Similar to gypsum sheathing, this comes pre-pressed together with a fiberglass layer. Just like its predecessor, this type of sheathing is perfect to use in exterior applications. Typically, glass mat sheathing is used in commercial buildings. It is also resistant to mold and moisture, and it's a fairly affordable choice for exterior wall sheathing.

7. Cement board

This type of sheathing is best used for homes that have a brick or ceramic tile siding. Since these siding materials need a heavy base they can adhere to, cement board sheathing is a perfect choice. This type of sheathing uses cement and is reinforced with glass-fiber mesh for strength and stability. It is also moisture-resistant and non-combustible sheathing.

How Thick Should Sheathing Be?

For residential construction, you will find that most building codes require at least OSB or plywood sheathing that is 3/8-inch thick. This thickness is well within the standards of many building codes and you can safely install siding with this sheathing thickness.

However, many contractors and builders prefer using sheathing that is thicker. They often use sheathing that is 1.2 cm thick for plywood or 1.1 cm thick for OSB materials. This is what they normally call "code plus" and the thickness provides extra durability and strength to the exterior walls. 

Final Thoughts

Vinyl siding texture installed for weathering protection on new residential home

Building a structurally sound home will require quality materials and layers upon layers of these to create the walls of the home. Choosing the right sheathing for your house will make your siding last for a very long time. With this in mind, always take time to consider your contractor's sheathing suggestions to avoid further repairs in the future.

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