Fiberboard Sheathing Explained: Pros and Cons

Fiberboard sheathing used in walls, interior ceilings, and roofs is made of wooden fibers held together with asphalt binder or resin. Generally, they come in 4 x 8 feet boards and provide structural stability in construction projects. They are more affordable than other sheathing options like OSB and plywood.

What is Fiberboard Sheathing?

Fiberboard is an engineered wood made from the fibers of many different wood types and is primarily used for wall and roof sheathing.

Depending on their density, fiberboard can be classified as low-density, medium-density, or high-density fiberboard.

While high-density fiberboard is used for doors, windows, and cabinets, low-density fiberboard is used for acoustic applications and picture frames.

On the other hand,medium-density fiberboard is used for flooring, decorative projects, baseboards, and crown molding.

Furthermore, fiberboard production utilizes wood pulp as a raw material for creating rigid sheets.

Additionally, various other materials, including bagasse (sugar cane waste), grass, flax, jute, newspapers, oat hulls, peanut shells, sawdust, and straw, are used.

The raw mix is pressed under rollers and bonded using adhesives like asphalt, clay, dextrin, wax, plaster, resin, or other suitable binders.

Pros and Cons of Fiberboard Sheathing

Pros of Fiberboard Sheathing	Cons of Fiberboard Sheathing
High thermal resistance	Weaker than OSB
Affordable	Screws do not adhere well
Stable	Heavy
Allow water vapor to dissipate	Emits an unpleasant asphalt odor
Reduce noise transmission	Difficult to recycle
Allows smooth cutting of edges	Need paint or other coating to prevent swelling
Sustainable	Susceptible to rot and mold

Pros of Fiberboard Structural Sheathing

Fiberboard offers high thermal resistance, making it an excellent sheathing material.

Since it is made out of wood and plant waste, it is also an affordable choice.

In addition, they are resistant to expansion and contraction due to temperature changes, making them a stable material.

Fiberwood sheathing also has gaps that allow water vapors to dissipate and avoid being trapped within the sheathing.

It can also reduce noise transmission to a certain extent.

Moreover, the uniform texture of fiberboard ensures smooth cutting of edges without splinters or holes.

Additionally, it is highly sustainable, as they are made of recycled materials.

Cons of Fiberboard Structural Sheathing

Since fiberboard is made of recycled material, it is not as strong as its alternatives.

Screws also do not hold easily onto the fiberboard.

Besides, fiberboard sheathing is heavy due to its density and thickness.

When exposed to sunlight, fiberboard emits an unpleasant asphalt odor and releases small amounts of formaldehyde, affecting indoor air quality.

Recycling fiberboard is also difficult as it is treated with heavy amounts of fireproofing chemicals and asphalt.

Furthermore, if left uncoated with paint or other protective substances, fiberboard sheathing may swell.

Moisture-induced rotting can decrease its strength by up to 30% and lead to mold development.

Fiberboard vs Oriented Strand Board (OSB) vs Plywood Structural Sheathing

As sheathing materials, fiberboard, OSB, and plywood are often compared.

Characteristic	Fiberboard Sheathing	OSB Sheathing	Plywood Sheathing
Strength	Weaker than OSB and plywood	Stronger than fiberboard	Stronger than fiberboard
Nailing	Cannot hold screws	Can hold screws tightly	Can hold screws, but not large ones
Insulation	R- value:2.64	R- value:0.5-0.62	R- value:0.63-1.25
Moisture Resistance	Susceptible to moisture damage	Greater moisture resistance than fiberboard and plywood	Moisture resistant than fiberboard
Dimensional Stability	Does not expand and contract to an extreme level	Prone to expansion and contraction	Prone to expansion and contraction
Texture	Uniform appearance	Rough texture and flaxy appearance	Patchy finish
Cost	Cheap	Affordable than plywood	Expensive

Strength Comparison

Both OSB and plywood are strong materials compared to fiberboard.

The layers of wood in OSB and plywood are arranged in a cross-grain pattern, which enhances their strength.

Additionally, the manufacturing process of OSB and plywood involves layering and compressing wood veneers together with adhesive, making them stronger than fiberboard.

OSB and plywood are also good choices for skip and roof sheathing, as well as subflooring.

Cost Comparison

Fiberboard sheathing is less expensive than OSB sheathing.

A 4’x8’ OSB sheathing panel has an average cost that costs between $32 and $77, depending on the type and thickness of the board.

In contrast, the average cost of a 4’x8’ fiberboard ranges from $8-$16.

A 4'x8' plywood sheet with a thickness of 11/32” costs between $15 to $120.

Ease of Nailing

Fiberboard cannot securely hold the screws, causing them to easily loosen.

In contrast, OSB sheathing holds screws tightly because of a stronger nailing surface available for the screws.

Also, screws hold well when driven into the face of plywood than its edges.

When large nails or screws are used, the plywood sheets can start to separate.

However, starting the process with a small amount of pre-drilling can eliminate this issue.

Insulation Strength Difference

Fiberboard has a greater thermal resistivity as compared to OSB.

The R-value for fiberboard is 2.64, whereas the R-value of OSB is between 0.5-0.62, and for plywood, it is between 0.63-1.25.

This means that fiberboard provides better insulation when used for sheathing purposes.

Moisture Resistance

All three materials are affected by moisture, but fiberboard has a greater risk of rotting and developing molds.

Fiberboard contains small joints made by joining wood particles, and if these particles do not bond properly, it can result in moisture infiltration.

OSB is more resistant to moisture than fiberboard and plywood.

Plywood also offers more moisture resistance than fiberboard because of its layers.

Each layer builds on the previous layer to produce a tighter bond, reducing the amount of moisture that can penetrate.

Dimensional Stability

OSB sheathing and plywood sheathing are more prone to expansion and contraction, making them less dimensionally stable than fiberboard.

Fiberboard sheathing retains its shape because it does not expand or contract to an extreme level.

Texture and Appearance

Fiberboard has a uniform appearance, which, when stained properly, can improve its appearance.

On the other hand, OSB has a rough texture and a flaky appearance, whereas plywood has a patchy finish.

How to Paint Fiberboard Sheathing

Fiberboard is a material used in both internal and external sheathing.

Applying a layer of paint can improve its functionality.

But care must be taken while painting over fiberboard as it is more porous than solid wood.

Follow the steps correctly to paint over the fiberboard.

Step 1: Preparing the Work Area

Place sheets below the sheathing surface to avoid getting paint on other structures.

Also, wear goggles to avoid getting dust in your eyes.

Step 2: Sanding

Sand over the surface and edges of the fiberboard sheathing to be painted.

Afterward, dust off the sand using a cloth.

Step 3: Apply Primer

It's crucial to wear a mask while applying, as primer releases fumes that cause cough.

Moreover, open windows to allow ventilation.

To apply the primer base, hold it one foot away from the fiberboard surface, spray it in an even manner, and let the surface dry.

Step 4: Apply the First Coat of Paint

Now use a paintbrush to slowly apply a thin coat of paint to the fiberboard surface.

When the first layer is dry, sand over it.

Sanding reduces brush marks and helps in bonding the second coat.

Step 5: Apply Additional Coats

Now dust off the sand and start applying the second layer of paint.

To make the surface smoother, apply more layers of paint.

Conclusion

Fiberboard sheathing is used to insulate walls and roofs while also providing structural stability.

It can also be used for decorative purposes.

Though fiberboard is a cheap and effective sheathing material, other materials, such as OSB and plywood, offer more durability and strength.

However, fiberboard is cheaper than its alternatives.

Frequently Asked Questions (FAQ)

How Thick are Different Types of Fiberboards?

High-density fiberboard is 1/8 to 5/16 inch in thickness, whereas medium-density fiberboards are 1/4 to 1 inch in thickness.

A low-density fiberboard has a thickness of 11/32 to 1 3/16 inches.

Does Fiberboard Sheathing Contain Asbestos?

In general plant-based and wood-based fiberboard sheathing do not contain asbestos content.

There are, however, some special types of fiberboards that include asbestos.

Asbestos is a hazardous substance that can lead to many health defects.

What is a Masonite?

Masonite is a hardboard type with a smooth surface and high strength.

It is ideal for building doors and wall panels and used as a backing material for painting canvases.