The floor that you walk on seems like one solid layer under your feet, but it’s actually made in layers, which is a method that was developed hundreds of years ago. Layering starts with a heavy subfloor that is attached to the floor joists. Then, the underlayment is put down. There are different kinds of underlayment that can be used depending on what kind of flooring you are going to finish with. The top layer, which is the cosmetic floor covering, doesn’t support anything. Its main purpose is to look good.
Many people are unsure which they need when they are looking for structural flooring material. There is a lot of confusion between what subfloor is and what underlayment is. Let’s take a look at the two and talk about when you use them in the building process. We’ll see if we can get your feet headed in the right direction.
WHAT IS THE SUBFLOOR?
The subfloor is the layer of flooring that sits right on top of the joists. Generally, it is the thickest layer of flooring and is made of plywood. Quality subfloor should have two or three layers of plywood for the most solid foundation for your floor. We recommend using moisture resistant plywood for your subfloor in every room of your home.
At times OSB, often called flake board, is also often used for subfloor. Both plywood and OSB subfloor should range in thickness from 19/32″ to 1 1/8″. Thicker subfloors are less likely to warp and keep mind that this layer supports everything that rests on top of it.
There are five main types of subfloor.
Plywood is made by layering several sheets of wood gluing them together to make a thick sheet of material. It is the most common building material that is used for building floors because it is flat and strong.
They generally use pine flooring materials in apartments, home and other residential buildings.
ORIENTED STRAND BOARD (OSB)
OSB, also called flakeboard, is madeout of flakes of wood that have been pressed and glued together with a resin. OSB should only be used in dry applications because it is easily damaged by water.
Particleboard is similar to OSB except it is madeout of sawdust and small chips of wood. Since it is not as dense as flakeboard it is more susceptible to water damage.
Concrete is normally found in basements. If it is porous and clean you can install tile directly over it. Other flooring materials, such as hardwood will need to have an underlayment installed on top of the concrete first.
WHAT IS THE UNDERLAYMENT?
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Underlayment is the layer of flooring that rests on top of the subfloor. It provides a smooth surface for the floor covering unlike the rough surface of the plywood or OSB. There are different types of underlayment depending upon what type of floor covering you are going to use.
Foam underlayment can help to keep your floor warmer and also acts to reduce noise. There is standard foam underlayment which is a simple, thin layer of foam that is paired with a moisture barrier. The next step up is upgraded foam underlayment which is just a more advanced form of the standard foam. It does last longer than the standard foam underlayment. Then, there is the combo underlayment which combines the foam and moisture barrier film into one piece.
CEMENT BACKER BOARD
Cement Backer Board is the underlayment that is used when you are laying stone or tile flooring. The heavy sheet can hold up to the application of the mortar and the weight of the stone and tile.
FOAM LAMINATE UNDERLAYMENT
Foam laminate underlayment is used under laminate flooring. It has a moisture barrier making it an excellent choice for use in kitchens and bathrooms. There is an upgraded version that is more durable with better sound absorption as well.
Acoustic underlayment reduces the amount of sound that echoes back of the floor. It is usually madeout of cork or felt. It is a good choice for office, apartment buildings and hotels.
Carpet underlayment comes in a wide variety of thicknesses. However, they are generally all made out of foam and rubber. The best way to decide which carpet underlayment is best is to talk to your local flooring expert.
HARDWOOD FLOORING UNDERLAYMENT
Hardwood flooring underlayment has the widest variety of options to choose from. You can use everything from foam, felt, under hardwood flooring. Which one you choose will depend on your needs. Foam is the least expensive, and the least durable. Rubber is the most expensive, and it is moisture resistant and sound absorbing. Felt and cork fall in between those two.
SUBFLOOR VS UNDERLAYMENT: WHAT’S THE DIFFERENCE?
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BENEFITS OF SUBFLOORS
Subfloors are permanent and generally cannot be repaired without tearing out and replacing the entire floor. They provide many benefits that underlayment cannot offer. Below are some of the major benefits of subfloors:
Subfloors are the foundation of the floor. Without it, the floor would not have strength and structural integrity to support the rest of the floor, the furniture, or the people that travel across it.
BASE FOR UNDERLAYMENT AND FLOOR COVERING
This layer provides the base upon which the underlayment and eventually the floor covering is applied. It is a flat, level surface upon which the rest of the floor is built.
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FLOORS LAST LONGER
With the heavy wood of the subfloor underneath, the floor on top of it lasts longer.
They help to prevent moisture from seeping into the floor above keeping moisture damage to a minimum.It also helps to protect your furniture from moisture damage by preventing moisture from entering the room.
This layer supports all the furniture that is in the various rooms in your house. Underlayments alone aren’t strong enough to do this over a long period of time.
BENEFITS OF UNDERLAYMENT
Underlayments can be removed and replaced when they wear out. They provide their own unique set of benefits to the floor. Below are some of the major benefits of underlayment:
EVENS THE SURFACE
Subfloors usually have a rough and uneven surface. Underlayment helps even them out, which adds extra stability as well.
Underlayment helps to reduce noise because it absorbs excess vibrations caused by people walking back and forth across the floor.
KEEPS FLOORS WARM
Underlayment acts like insulation, preventing heat from escaping and keeping your floors warm. This is especially nice on those cold winter mornings when you first put your feet on the floor.
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Most underlayments are waterproof. This makes them a great barrier to moisture seeping through the flooring and into the rooms of your home. This helps to protect not only your floor, but your furniture as well, from moisture damage.
Underlayments are made of soft materials so they absorb strong impact and help protect against injuries. It also just makes the floor more comfortable to walk on.
Underlayment adds an additional layer of support to already existing flooring. This will make your floor more durable and add years to its lifespan.
HOW FLOORING IS LAYERED
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Joists are the first layer of flooring. They are typically made of lumber and support the entire floor above it. All floors, except concrete floors, have joists.
This is the next layer above the joists and is the structural support for the underlayment. Its thick plywood or OSB provides a stable, level surface for new flooring to be installed on.
Underlayment is the third layer just above the subfloor. The underlayment acts as a sound barrier and protects your floor from moisture and excess heat.
This is the top layer that everyone sees. It has no structural purpose. The type of finish flooring should be chosen based on which room it will be used in, if it is a high traffic area or if you have children and/or pets.
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So, now you know that subflooring is the permanent, rough floor that is the foundation of the floor. It provides the stability and level surface that is needed for your floor to be strong and last for many years. Underlayment is the layer that is between the subfloor and the finished floor. It gives your floor the nice, smooth surface needed to lay the flooring material on. Both layers are necessary for most floors to be strong and durable.
Now that you know the difference between the two, you are ready for your next trip to your local builder’s supply store. If you are building a new home, or adding on an addition, you will probably need both. However if you are remodeling and just need to fix up an old floor, you are probably only going to need to buy underlayment. And, when a store associate asks you if you need any help, you’ll be able to floor them with you knowledge of flooring.
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