Fiberboard sheathing is a structural sheathing applied on roofs, interior ceilings, walls, etc. It is engineered using timber waste and wooden chips held together with asphalt binder or resin. The sheathing comes in 4’x8’ or 4’x9’ rectangles with a thickness of either 1/2” or 25/320”.
Fiberboard sheathing is highly popular due to its low cost compared to its alternatives like plywood sheathing and OSB sheathing.
The texture of the fiberboard mimics that of real wood and is uniform throughout.
Fiberboard is installed on a building's exterior using diagonal bracing or plywood bracing panels.
The sheathing is nailed onto the wall studs, which makes the building more rigid.
This article discusses the pros and cons of fiberboard sheathing and its various applications.
I've also compared fiberboard sheathing with other sheathing materials.
What is Fiberboard Sheathing?
Fiberboard is an engineered wood made from the fibers of many different wood types.
Depending on their density, fiberboard can be classified as low-density, medium-density, or high-density fiberboard.
It is a material that was very common for making structural sheathing.
High-density fiberwood is used to make wall slabs, floor door boards, etc.
Heatproofing and acoustic coverings are made of low-density fiberwood.
Pros and Cons of Fiberboard Sheathing
Fiberboard is used both indoors and outdoors for sheathing surfaces.
It offers a wide range of advantages that make it a good sheathing material.
| Advantages of Fiberboard Sheathing | Disadvantages of Fiberboard Sheathing |
|---|---|
| High thermal resistance | Weaker than OSB |
| Affordable | Screws do not adhere well |
| Stable | Hard to install and handle |
| Moisture -resistant | Emits an unpleasant asphalt odor |
| Soundproof | Formaldehyde is released in small amounts |
| Uniform texture | Difficult to recycle |
| Sustainable | Develop swelling |
| Prone to rotting and molding |
Pros of Fiberboard Structural Sheathing
- Fiberboard offers high thermal resistance, making it an excellent sheathing material.
- Fiberboard is cast out of wood and plant waste making it very affordable.
- Fiberboard is resistant to expansion and contraction and is thus a very stable material.
- Fiberwood sheathing has gaps that allow water vapors to dissipate and avoid being trapped within the sheathing.
- Fiberboard sheathing also provides soundproofing.
- The texture of the fiberboard is very uniform. Thus, the edges can be cut smoothly without the formation of any splinters or holes.
- Fiberboard is a very sustainable material as it is largely 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 do not hold easily onto the fiberboard.
- Fiberboard sheathing is very thick, and due to this density, it is quite heavy.
- Fiberboard gives off an unpleasant asphalt odor when exposed to extreme heat by the sun.
- It also emits small amounts of formaldehyde which can affect the air quality of a house.
- Recycling fiberboard is difficult as it is treated with heavy amounts of fireproofing chemicals and asphalt.
- Sheathing done using fiberboard can develop swelling if not coated with paint or other coating chemicals.
- The rotting caused by moisture can decrease the strength of fiberboard sheathing by up to 30%.
- Long exposure to moisture also leads to the development of mold.
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 | Unpleasant 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.
OSB and plywood are also good choices for skip and roof sheathing, as well as subflooring.
OSB is made from the wood of trees, while fiberboard is usually made of wood and plant waste.
This makes OSB boards rigid and durable in contrast to fiberboard.
The strength of plywood is due to the fact that it is made up of different layers that are glued together.
Cost Comparison
Fiberboard sheathing is relatively less expensive than OSB sheathing.
A 4’x8’ OSB sheathing panel has an average cost that can range between $32 and $77, depending on the type and thickness of the board.
The average cost of a 4’x8’ fiberboard ranges from $8-$16.
A 4x8 plywood sheet with a thickness of 11/32” costs between $15 to $120.
Ease of Nailing
Fiberboard does not have a rigid structure to hold screws in place properly.
Screws applied to fiberboard sheathing can easily shake off.
In contrast, OSB sheathing holds screws tightly because of a stronger nailing surface available for the screws.
Screws driven into plywood do hold well when driven into the face than the edges.
When large nails or screws are used, the plywood sheets can start to separate.
However, if you start the process with a little amount of pre-drilling, this issue absolutely goes away.
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
The moisture resistance of a material is dependent on its internal uniformity.
All three materials are affected by moisture, but fiberboard has a greater risk of rotting and developing molds.
OSB is more resistant to moisture than fiberboard and plywood.
Fiberboard contains numerous small joints made by joining wooden chunks.
If the chunks do not bond properly, it allows moisture to enter.
Due to permeability, fiberboard sheathing is susceptible to swelling due to moisture intrusion.
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 straightness because it does not expand or contract to an extreme level.
Texture and Appearance
Fiberboard has an unpleasant uniform appearance.
It can be made to look stylish when stained properly.
Fiberwood comes in different colors, such as light brown, dark brown, charcoal, etc., depending on the raw materials used.
OSB has a rough texture and a flaky appearance in contrast to fiberboard, whereas plywood has a patchy finish.
Fiberboard is considered more attractive and superior to OSB and plywood in terms of appearance.
What is Fiberboard Sheathing Made of?
Fiberboard production is done largely using wood pulp as a raw material to make rigid sheets.
However, various other raw materials are used in making fiberboard sheets.
These include bagasse (sugar cane waste), grass, flax, jute, newspapers, oat hulls, peanut shells, sawdust, straw, etc.
Various techniques are used to provide the bond between the raw materials and give fiberboard desirable properties.
These properties include waterproofing, pest resistance, rigidity, structural integrity, soundproofing, and heat insulation.
The raw mix is pressed under rollers and bonded using adhesives like asphalt, clay, dextrin, wax, plaster, resin, or any other suitable binders.
How to Paint Fiberboard Sheathing
Fiberboard is a material used in both internal and external sheathing.
Its performance can be improved by applying a coating of paint over it.
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
Place sheets below the sheathing surface to avoid getting paint on other structures.
Wear goggles to avoid getting paint or dust in your eyes.
Step 2
Sand over the surface and edges of the fiberboard sheathing to be painted.
Dust off the sand lightly using a cloth.
Step 3
Ensure that the surface of the fiberboard sheathing is clean.
Wear a painter’s mask and apply primer base coating to the surface of the fiberboard.
The mask is vital because the primer base releases fumes that can cause coughing.
Open windows nearby to allow ventilation.
To apply the primer base, hold it one foot away from the fiberboard surface and spray it in an even manner.
Let the surface dry.
Step 4
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
Now dust off the sand and start applying the second layer of paint.
To make the surface smoother, apply a total of three 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.
Fiberboard sheathing can be used on the exterior and interior of a building for strengthening.
Though fiberboard is a cheap and effective sheathing material, other materials, such as OSB and plywood offer more durability and strength.
The biggest advantage of fiberboard sheathing is its low cost.
Frequently Asked Questions (FAQ)
Can Fiberboard Sheathing Get Wet?
There is no waterproofing on the fiberboard. It is quite porous.
Fiberboard can weaken and crack if exposed to moisture for long durations.
Therefore, paint is applied over the surface of fiberwood sheathing to form a strong coating.
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.
Is Fiberboard Stronger than Plywood?
Plywood is a much stronger sheathing material as compared to fiberboard.
This is largely due to the layering structure that makes up plywood.
Thus, for all structural purposes, plywood remains the superior option.
Plywood is also more moisture-resistant.
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