All About Flooring Installation: Underlayment and Subfloor Explained

While it is not evident just by simply looking at the floor covering, every flooring structure is a system of multiple layers designed to provide support, stability, and strength. Underneath your favorite surface floors such as hardwood, laminate, or vinyl is every layer of underlayment, subfloor, and joist. These layers make up a good flooring installation. In this blog, we will focus on two of these floor layers: underlayment and subfloor. Here we will explain the functions, benefits, and types of underlayment and subfloor.


First Layer Underneath Your Floor Covering: Underlayment

In flooring installation, an underlayment is any piece of material that rests between the subfloor below and the floor covering above. Aside from flooring, underlayment is also used in roofing. It serves typically to provide a smooth, consistent base for your surface flooring. Though underlayment is an optional layer, it is recommended by flooring contractors in Maryland because it can hide the bare floor from any harsh elements of the external environment.

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Benefits of Underlayment

While underlayment is not compulsory in all flooring installation, it serves myriad benefits that homeowners need to consider. Here’s how underlayment will improve the performance of your flooring.

1. Reduces Noise

Some flooring materials such as laminate flooring can be a bit annoying because it creates unnecessary noise. This is where installing an underlayment makes more sense. The flooring underlayment blocks noise from one room to another. This flooring layer can absorb excess sounds and vibrations and keep it from traveling to other areas or rooms of the house. Hence, it makes your floor much quieter when you walk on. The installation of underlayment is reasonably perfect for a nursery or baby room. You may also talk to your flooring contractor in Maryland to install it if you really want to lessen unnecessary sounds inside your home.


2. Smooths Minor Subfloor Imperfections

Not all subfloors are consistent in levelness. Generally, floors are uneven, so it may need an underlayment that can form to a certain degree around the roughness of the subfloor. A flooring underlayment can level them by smoothing out the surface. This creates reliability and adds stability to the entire flooring structure. Not to mention that it can help cut down extra prepping time.


3. Absorbs Impact

If you’re looking for flooring where you can walk comfortably, you may need to install an underlayment. A flooring underlayment serves as a cushioning agent that absorbs stress or impacts on the surface floor. Typically, it is made from soft materials, which makes your flooring comfortable to walk on.


4. Helps in Moisture Protection

Most underlayment substances are impervious to water. They have a built-in barrier that blocks water or moisture from penetrating the floor. This is beneficial if you have floor coverings that are very susceptible to moisture or water damage such as hardwood and carpet. If you also have a concrete subfloor, which typically emits moisture, an underlayment is necessary to prevent any contact with water.

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5. Keeps the Floor Warm

Underlayment is a good insulator of heat, keeping your floor warm while providing additional comfort during seasonal temperature changes. It has an in-floor heating system that allows heat to spread evenly around the house. So, even if you’re barefooted, you can walk atop the floors if you have an underlayment beneath your surface flooring.


6. Improves Adhesion

In flooring installation, there are surface materials such as ceramic tile that does not adhere well when directly installed to a subfloor. As a result, it may expand and contract, especially when exposed to water for a long time. With this, a flooring underlayment can help by providing a good surface for a tile flooring to adhere or bond to.


7. Provides Additional Support and Stability

A hard, durable underlayment can provide better stability and strength to your entire floor. If installed properly, this layer can prevent your floor surface from compressing and warping. As a result, you can expect that your entire floor can have a longer lifespan.


Types of Underlayment

A flooring underlayment can be categorized into three main types: standard foam, upgraded foam, and combo underlayment.

1. Standard Foam Underlayment

As the name implies, this is a thin layer of simple foam over the subfloor. Most standard foam underlayment has a moisture or vapor barrier to prevent any moisture from passing through the floor and the entire room. 


2. Upgraded Foam

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This type of underlayment is an upgraded version of the standard foam. It has a noise-absorbing material that reduces sounds and prevents it from traveling. It does not only hide the subfloor, but it typically lasts longer than the standard foam version. 


3. Combo Underlayment

This flooring underlayment is a combination of film and foam. It is very comfortable underfoot and acts as an absorbent material to suppress moisture or water from passing through the floor. Normally, a combo underlayment is laid over a concrete or plywood subfloor.


Special Considerations

When choosing an underlayment, opt for a thinner type. Thicker underlayment can pose certain problems in the future as they can cause offset issues among rooms with different floor coverings. It is challenging to transition rooms in your house if the floor level in one room is higher than the others. Also, thicker underlayment may shorten the height of your room, especially if the room has a low ceiling. Make sure to discuss this with your local contractor before any flooring installation. 


Second Layer Underneath Your Floor Covering: Subfloor

The subfloor is the second layer beneath the floor covering and the hardest amongst floor layers. It is a layer that lies directly on the joists. This flat surface below the underlayment and above the joist is a piece of material that holds up all the above floor layers, which includes everything in your home such as people, furniture, or heavy equipment. Unlike the underlayment, a subfloor is mandatory for any flooring installation. This is because the subfloor bears a whole lot of weight in your house. Thus, your flooring contractor must build a sturdy base floor or subfloor to support the entire house. With a strong subfloor, it can withstand the worst conditions that your flooring may suffer over time. The only time you need to replace, repair, or make any changes in your subfloor is during major construction or remodeling jobs. 

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A subfloor normally comprises 4×12-foot or 4×8-foot sheets of ¾-inch or ½-inch of A/C-grade plywood. This plywood is screwed or nailed to the joist. A/C grade means that one side of the plywood is rough, while the other side is smoothly finished. You can also use an oriented strand board, or OSB, as a subfloor material. This material has the appearance of giant cornflakes bound together to create structural panels. 


The process of installing OSB and plywood subfloor is similar; both are screwed or nailed to the joist. Just make sure that the underlying joists are level and flat. Your flooring contractor should resolve any structural issues with the joists first before laying the subfloor. If the joist is slightly uneven, some contractors apply a bead of adhesive over the joists. This would make flooring installation more rigid and prevent squeaking and flexing of the entire floor. 


Benefits of Subfloor

Like your flooring underlayment, the subfloor offers a wide array of benefits to improve the performance of the entire floor. 

1. Avoids Moisture Absorption

This floor layer can absorb water and moisture, so it prevents passing through the floor and your room. If you are living in a humid area or environment, installing a subfloor is greatly beneficial. It is also ideal for floor coverings that are susceptible to moisture or water damage. 


2. Provides Stability

One of the main purposes of installing subfloors is to stabilize the foundation. As it bears the weight of the entire floor, it needs to be sturdy and durable, so it can possibly reinforce the structural composition of your flooring. 

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3. Improves Flooring Lifespan

Installation of subfloor can make your flooring last longer than those that are not. It adds value to your house as it can increase the lifespan of your entire flooring.


4. Acts as a Solid Base Floor

The subfloor acts as a strong foundation to handle household activities every day. It improves support to any overlying machine or furniture in your house. A firm base is important to withstand any worst condition that your floor might suffer over the years. 


Subfloor Types and Materials

In today’s flooring market, there are several materials used for subfloor installation. Here are the most common examples. 

1. Plywood

Produced by laying multiple sheets of wood, plywood is the most common material for subflooring. Because of its evenness, durability, and flatness, it is typically a top choice in most flooring installations. This material is available in thinner and thicker versions. The thinner form is ideal for vinyl flooring, while the thicker version is great for tile flooring. Plywood provides strong support, is easy to install, and has a reasonable cost. 


2. Oriented Strand Board (OSB)

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Another popular subfloor material, OSB is made from wood chips adhered together with resin. Unlike plywood, OSB has a smooth and dense surface. However, this material takes longer to dry when exposed to moisture or water. 


3. Particleboard

Particleboard or chipboard is made from fine wood particles, sawmill shavings, and wood chips. It is a compact subfloor material that can resist moisture to pass through the floor. However, builders don’t frequently use it in flooring installation as compared to plywood and OSB.


4. Flakeboard

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This subfloor type is manufactured from flakes of wood that are flattened, then glued together with a synthetic resin. Flakeboard is less compact than particleboard and more susceptible to moisture or water. This makes it a bad choice for moisture-prone areas. 


5. Pine

This subfloor is from pine wood—a soft and malleable type of wood. It is mainly used in apartments, homes, and residential buildings because it can be easily customized and shaped on the desired look. 


6. Concrete

A concrete subfloor is an ideal choice for the basement and ground floor. It is easy to fix, especially on tile flooring. However, there are special considerations when installing a concrete subfloor. It is entirely different because this subfloor has no joist. It can also become problematic as the concrete subfloor is very prone to moisture issues. Even if the concrete floor feels dry when you touch it, the residual moisture can accumulate and remain on the floor over time. This may cause structural damage in the long run. Unless it is a tile flooring which can be installed directly, you need an underlayment over the concrete subfloor. The flooring underlayment acts as a vapor barrier, so moisture won’t pass through the entire floor. 


Common Subfloor Mistakes and Ways to Avoid Them

In any flooring installation, the goal is to achieve a sturdy and stable foundation, so you’ll have a smooth, squeak-free surface flooring. With this, you need to avoid some common subfloor installation mistakes. 

1. Not Properly Nailed

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Improper nailing can cause squeaky sounds on your floor. To prevent this, you must choose the correct size of the nail before it even hits the joist. Spacing is also important. Typically, nails should be spaced 12” on the center on the interior support of the panels, and 6” on center along supported edges. You can also rely on the construction drawings for the proper spacing of nails. Also, make sure that the nails should fully penetrate the joists. 


2. Refrain From Using Glue

Before laying any subfloor, the joists must be level and flat. A glue-nail technique ensures that you will have a flat and stable floor. You may ask your local floor contractor which subfloor glue is better. 


3. Incorrect Glue Application

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In applying glue to the subfloor and joist, always follow the manufacturer’s specification. Always ensure that the joist is completely dry and free from any debris or dirt before applying the glue and laying the subfloor. Put only enough glue for every panel. Make sure to not let the glue dry before you completely fasten each subfloor panel. 


4. Subfloor Isn’t Dry 

A subfloor exposed during construction or flooring installation needs some time to dry. This is important especially if you plan to install finished flooring materials like hardwood flooring. Keep in mind that you need to store the subfloor panels under cover. It also helps discard any standing water on the subfloor. 


5. Improper Spacing 

The right spacing between the subfloor is necessary to avoid buckling. The improper spacing of subfloor panels won’t allow room for expansion. Subfloor panels must be spaced with a 1/8” gap at all ends and edges.


6. Not Checking Your Work

In any flooring installation, you should never forget to check your work. You can start by walking the subfloor to find out if there are any squeaks, nails popping out, improper nailing, or missing fasteners. This way, you can guarantee that the flooring structure is stable, squeak-free, and durable. 


What Makes a Good Flooring Installation?

Your floor plays a vital component in your house as it supports and handles any furniture, people, and hefty equipment on it. That is why professionally installed underlayment and subfloor are necessary to make sure that you have a stable foundation that will last for a lifetime. If you think that your flooring is in dire need of replacement or repair, don’t hesitate to connect with us. Schedule a free in-home consultation today!