Roof sheathing is a covering installed over roofs to provide support for hanging shakes and shingles and protect the underlying roof structure.Various types of roof sheathing include oriented strand board(OSB),plywood,concrete,skip sheathing and wooden boards.Each type has its own benefits,making it suitable for various requirements and budgets.
This article discusses the importance of roof sheathing and discuss different roof sheathing materials.
Types of Roof Sheathing: 5 Options
Roof sheathing differs depending on the type of material used for making it and the spacing provided between the sheathing panels.
They are made of plywood, OSB, wood panels, and concrete.
| Type of Roof Sheathing | Pros | Cons |
|---|---|---|
| Oriented Strand Board (OSB) | Economical, less prone to warping or swelling over time, thick panels | Vulnerable to water damage, presence of formaldehyde |
| Plywood | Lightweight, available in a range of sizes and finishes, does not swell when exposed to water | Expensive, high maintenance, smaller panels |
| Concrete | High strength, fire resistant, long-lasting, can be painted, protection from rots and insects | Costly, high maintenance, more manpower for installation and delivery |
| Skip Sheathing | Resistant to moisture, durable, less material cost | Ineffective in areas with significant rainfall and windy rains, expensive |
| Wooden Boards | Robust, excellent insulation | Difficult to install, susceptible to warping with time |
Here are the different types of roof sheathing:
Oriented Strand Board (OSB) Roof Sheathing
OSB is a popular choice of roof sheathing that is a synthetically manufactured material made out of different fragments of wood.
The fragments are held together by special adhesives, which make strong bonds between the layers of an OSB board.
They are less prone to warping or swelling over time, come in thick panels and have a uniform finish.
Compared to its alternatives, it is also less expensive.
Plywood Roof Sheathing
Plywood is another common and popular sheathing material.
Similar to OSB, plywood is made out of numerous wooden layers that are bonded using special adhesives.
The layering in plywood is quite dense and forms a thick board that is beneficial for nailing purposes.
These layers also help prevent the shrinking and warping of the plywood boards.
The high density of plywood also prevents moisture from reaching the core layers.
Due to this, plywood retains its strength and durability for a long time.
Plywood and OSB are also common wall sheathing options.
Concrete Roof Sheathing
The concrete sheathing is used where there is a high strength requirement, and sufficient support is available for carrying the sheathing itself.
Concrete is also increasingly becoming an essential part of green projects.
It replaces wood and thus saves a lot of trees, but it also has its own carbon footprint.
Additionally,they withstand wind loads,making them a low maintenance and long lasting option for homes.
Skip Roof Sheathing
Skip sheathing is a type of roof sheathing in which the wooden planks are placed with a certain spacing in between them.
They allow air to pass through the sheathing and aid the drying of roof structures.
1x4 boards of plywood or OSB are used in skipped sheathing with a spacing that ranges from 5” to 10”.
Although effective, skip sheathing degrades over time and has to be re-sheeted.
Therefore ,new materials with built-in small pores that allow air passage are largely replacing skip sheathing.
Wooden Boards Roof Sheathing
This is a traditional method used for roof sheathing.
They are made of solid wood such as pine or fir and come in various thicknesses;the thickness usually range from 5/8" to 1/2".
These wooden boards provide good insulation properties and can be easily cut and shaped to fit any roof design.
However,they are susceptible to rotting,warping and insect infestation.
When to Replace Roof Sheathing?
Like all other structures, roof sheathing degrades over time, and require replacement.
Here are the signs that indicate your sheathing needs replacement.
Cracks in Roof Sheathing
Cracks can develop in roof sheathing due to improper load distribution,such as when a tree falls directly onto the roof.
Other reasons include continuous freezing and thawing of moisture within the sheathing.
The cracks thus developed cause water to seep into the house and affect other structures.
Water Damage
Long-term exposure to moisture degrades the quality of the sheathing, making it lose its strength.
This can ultimately lead to warping or twisting of sheathing boards.
Consequently, the shakes and shingles start to fall off.
It is thus important to check the roof sheathing does not retain moisture for long periods of time.
Rotting in Roof Sheathing
If you start to notice blackened spots on your roof, it means the wood panels have started to rot.
Press against these spots and check if the material gives in easily. If so, then the integrity of your roof has been compromised.
Sagging in Roof Sheathing
Sagging is one of the major signs that indicate your roof sheathing is in need of replacement.
Roof sagging is both dangerous and aesthetically unpleasant.
Check the alignment of your roof from the outside to see if it has formed any waves.
Roof sagging can also be checked from the inside by going up to the attic and seeing if any part of the roof seems closer to you than the other parts.
Roof Sheathing Dimensions
Roof thickness is determined based on the steepness of a roof, the amount of snow load it has to bear, and the spacing of rafters.
Roof sheathing panels come in 4’x8’ rectangular blocks,with a thickness of 7/16" thickness.
In general, roof sheathing thickness lies between 1/2” and 5/8”.
3/8” is the minimum thickness recommended for plywood sheathing.
8d nails are used to install the sheathing over the rafters.
Cost of Roof Sheathing
The cost of sheathing depends on the thickness and type of sheathing boards.
As the thickness increases,so does the cost.
A single standard plywood sheet having 4’x8’ dimensions costs between $70 to $100, with a thickness of 1/4" to 5/8 ".
In contrast,OSB boards are more budget-friendly,costing around $32 and $77 for a 4' x8' board.
Frequently Asked Questions (FAQ)
How Long Does Roof Sheathing Last?
Generally,roof sheathing lasts for 20 to 30 years.
It varies depending on the climate and material used.
Do You Need to Glue Down the Roof Sheathing?
Roof sheathing shouldn't be glued like flooring. Nail the panel.
When using a power tool, be careful not to overdrive the nails through the panel surface.
Can I Use Screws for Roof Sheathing?
Screws provide greater holding strength than nails and can be used for securing roof sheathing.
It is recommended to use galvanized screws to help protect against weather action from the exterior side of the roof.
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