The subfloor is the layer that is placed on top of joists and beneath the floor finishing. There are several materials that can be used to make the subfloor, such as plywood, oriented strand board, wooden planks, concrete and composite materials. Plywood performs the best as a subfloor material.
This article aims to explain the advantages and disadvantages of the different subfloor material choices you have.
What is a Subfloor? Understand
Floors systems are typically made of four layers to ensure their structural integrity.
The first component is the joist which is a load-bearing member and transfers all the loads from the floor surface onto beams.
Concrete floors do not require any joists for supporting loads.
The second component is the subfloor. This is the layer that is provided over the joists and under the finishing.
Sound support and insulation are the main goals of this layer.
The third layer is the underlayment which is an extra layer provided in some floor systems where extra smoothness of the floor is required.
Typically, plywood is used to construct it.
The floor finishing is the exterior most layer that is provided for decorative purposes.
It is usually made from tiles, laminate, or hardwood.
Underneath the finished floor lies the subfloor layer.
It differs from the underlayment as it is a structural layer placed over the joists, whereas the underlayment is nonstructural.
Concrete slabs can be considered subfloors in concrete floor systems.
Subfloor Material Choices: Best Options
|Oriented Strand Board
|Structurally consistent, cost-effective
|Prone to water damage
|Durable and stiff, lightweight
|Strong and durable
|High maintenance, susceptible to moisture
|High -Performance Panels
|Engineering expertise is required
|Tough and sturdy
|Liable to warping
Oriented Strand Board Subfloor
Oriented Strand Board (OSB) is another material that has gained significant popularity over the years.
It has also largely replaced traditional wooden plank subflooring.
OSB is manufactured synthetically using various wooden fragments.
These fragments are mixed and held together using special adhesives which makes the bond between the layers of OSB very strong.
OSB is a relatively new material, that offers sufficient strength and has a uniform finish.
The uniformity of OSB means that OSB in comparison to plywood has little to no defects in its final form.
It offers the same advantages as plywood and has a similar installation process.
Additionally, compared to plywood, it is more affordable, making it a better choice for projects with a limited budget.
The reason for the lower cost of OSB is that it is made from residual fragments of wood.
Plywood is regarded as the best-performing subfloor material and has been in use since the 1950s.
It has gained significant popularity over time and has largely replaced wooden plank subflooring.
Like OSB, plywood is made from several layers of wood held together using special adhesives.
The layers are quite dense, which gives plywood enough thickness to be nailed properly.
Moisture is unable to reach the core of plywood, due to its dense layering, making it moisture-resistant.
The layering also helps prevent shrinkage and warping of plywood planks.
As a result, plywood can retain its strength for a long time.
Plywood subflooring has different variations, with the standard plywood being ½” thick.
The other variations come in a thickness of ¾” with tongue and grove interlocking.
By interlocking, the floor becomes stiffer along the edges.
The sheet size is typically either 4x8 or 4x12 feet.
Plywood panels are first glued onto joists using special adhesives and then nailed.
For floors with tile or hardwood finishing, it is recommended to use a higher thickness for subflooring.
In regions where wood is not the most common material for construction, concrete is used to make floors and other structural components of houses.
Concrete is being integrated more and more as part of green projects.
It replaces wood and thus saves a lot of trees, but it also has its own carbon footprint.
In concrete flooring, the concrete slabs are generally regarded as the subfloors, which are highly rigid and durable and have a smooth finish.
The subfloor is then covered with a layer of tiles or stones. In some cases, underlayment is also provided over the subfloor.
Moisture can penetrate through concrete pours which can gravely affect its performance.
For this reason, a moisture barrier is applied over the concrete in moisture-prone areas of a house.
Concrete flooring has its own challenges, as it conducts heat from the building into the ground and cannot be nailed into.
Subfloors with High-Performance Panels
High-performance panels are being incorporated more and more in buildings.
These are specially engineered components that have similar advantages as that of OSB but with certain additional benefits.
To be moisture resistant, they are specifically engineered using special resins.
The engineering behind these panels significantly reduces their rate of water absorption.
In contrast, plywood and OSB are prone to swelling due to moisture absorption.
High-performance panels are not only resistant to swelling due to moisture but also cupping and warping.
This gravely reduces replacement and maintenance costs.
Additionally, high-performance panels are more durable in terms of strength as compared to Plywood or OSB panels.
They can also hold nails better as well due to a higher panel density.
High-performance panels are available in many variations, including but not limited to 19/32”, 7/8”, 1” etc.
In the United States of America, Weyerhaeuser is a pioneer manufacturer of high-performance subfloor panels.
Wooden Plank Subfloor
The traditional practice was to use planks from local woods to make the subfloor.
But they have since been extensively replaced by newer improved materials.
The planks are usually made from wood such as pine and are given 1x6 dimensions. They are directly nailed onto joists.
When using this material, there is a chance that the boards can become loose and squeak when stepped on.
To avoid this, specific and sufficient nail sizes should be used to nail the subflooring onto joists.
Older homes that used wooden planks as subflooring materials have since undergone remodeling.
They have incorporated a hardboard underlayment for smoothness.
In many cases, the subflooring is a mix of different materials, such as a concrete slab being paired with either plywood or OSB.
These options are often efficient and cost-effective. They are also durable, easy to install, eco-friendly and attractive to look at.
Composite flooring can be achieved in a variety of ways.
One is to lay 2” sleepers over concrete and cover them with plywood.
Another method is to use tongue and groove OSB panels over the concrete using some special adhesives.
How to Pair Subflooring Material and Floor Finishing
The subflooring material depends on the floor finishing that is to be installed in a floor frame.
For tile finishing, concrete subflooring is generally the best option as tiles require a uniform and hard surface underneath them to avoid flexing and ultimately cracking.
On the other hand, for hardwood finishing, plywood is the most suitable option for subflooring.
It is easy to install hardwood over plywood, due to its dense nature.
Laminate floor finishing is like hardwood but is a bit thinner in comparison.
Generally, OSB or plywood subflooring is best suited for laminate finishing, however, an underlayment is also required to protect the laminate against dents.
Plywood vs OSB Subflooring
Plywood and OSB are among the popular choices for subflooring material.
They have many similarities, and both offer sufficient advantages to be used in the construction of floor frames.
However, there are some key differences that may affect the choice of a designer when choosing between these materials.
In terms of structural strength, plywood comes out on top, being more rigid and strong as compared to OSB which is slightly weaker.
Plywood also has greater moisture resistance, as it does not swell when exposed to water, however, the edges of OSB are prone to swelling if they get wet.
All floor finishes are compatible with plywood. In contrast, OSB is not compatible with ceramic or stone tiles.
Plywood panels also have a greater thickness, making them more suitable for nailing purposes than OSB panels.
But when it comes to cost, OSB 4x8 sheets sell for about $16 per sheet.
Whereas Plywood 4x8 sheets go for about $21 per sheet.
So, when it comes to being cost-effective, OSB is a clear choice.
What is the Best Subfloor Material?
Plywood is generally regarded as the best material to be used for making subfloors.
This is largely based on the various characteristics of plywood that make it out to be the superior material.
High-performance panels are not as commonly used in construction as plywood due to their lack of availability and high prices.
Plywood has the greatest strength out of all the subfloor materials making it an excellent choice for all types of finishing.
It dries out faster than OSB, which makes it resistant to permanent swelling.
The quick drying of plywood helps retain the evenness of floors.
A properly installed plywood subfloor is bound to last as long as the life of the house itself due to its strength and stiffness.
Plywood is also the best choice under ceramic or stone tile finishing.
Construction crews also prefer working with plywood because of its greater nail-holding capacity and superior strength, making the floors more secure.
Plywood subflooring may also fetch a greater resale value for a house.
Based on all these benefits, plywood comes out on top as the best subfloor material.
The subfloor is an important part of floor frames which ensures the stability and smoothness of a floor.
There are multiple types of subfloor materials being used in the industry like wooden planks, OSB boards, plywood, high-performance planks, etc.
Out of all the options available, plywood is the best due to its greater strength, and high moisture resistance.
But if cost is an issue, then OSB is a decent alternative that provides sufficient strength for a cheaper price, hence being more cost-effective.
Concrete subfloor is usually opted for in regions where timber is not the main material for construction.
Frequently Asked Questions (FAQ)
How much time does it take to Replace a Subfloor?
Subfloors can be replaced within hours if done by experts. Usually, it takes up to 8 hours for a professional to fix and replace a small-sized subfloor.
It depends on the size of the room that needs replacement.
If you decide to replace the subfloors yourself, it can take about a week.
How to know if my Subfloor is Rotting?
A subfloor that has been damaged by moisture feels spongy when stepped on.
It may bounce and let out squeaky noises when you walk on it.
Damaged subfloors are also characterized by spots, sagging, and unpleasant smells.
If any of the above signs occur, it is best to replace the subfloor before the damage increases.
What is the Best Thickness for a Subfloor?
The thickness of plywood panels is determined by the underlying joist spacing.
For 16” joist spacing, it is recommended to use a minimum thickness of 15/32” for the plywood subfloor.
A 3/4" layer of plywood is needed to meet the subfloor requirements for spacings greater than 16".
The thickness varies from region to region so it is important to consult local codes for up-to-date information.