The roofing system is a complex structure where several elements work together to ensure safe and durable protection against the elements.
Roof sheathing, also known as roof decking, lays the groundwork for the functionality of this system.
Understanding the ins and outs of roof sheathing can help you make all the right choices and set up the rest of the roof for success.
What Is Roof Sheathing?
Roof sheathing is a protective layer of material (typically wood-based) installed directly over the roof rafters or trusses.
This layer covers the roof’s entire surface, offering a sturdy support system for the roof covering (asphalt shingles, wood shakes, metal roofing, etc.)
Average Cost Of Roof Sheathing
On average, installing roof sheathing costs between $2 and $8 per square foot.
Let’s say you want to install the sheathing on a 2,000-square-foot roof. Based on the average cost range, you’ll need between $4,000 and $16,000 for this endeavor.
Roof Sheathing Cost Breakdown
| Roof Sheathing Type | Cost per Square Foot | Average Total Cost per 2,000-Square-Foot Roof |
| Plank | $3.50-$12.50 | $7,000-$25,000 |
| OSB | $0.50-$2 | $1000-$4,000 |
| Plywood | $2-$6 | $4,000-$12,000 |
| Concrete | $7-$25 | $14,000-$50,000 |
| Skip | $3.50-$6.50 | $7,000-$13,000 |
| Wooden Boards | $14-$25 | $28,000-$50,000 |
Most home improvement projects require homeowners to consider two costs – materials and labor.
Installing or replacing roof sheathing is no different.
Most roofing contractors charge between $1.50 and $3.50 per square foot to re-sheathe a roof.
Of course, this price can significantly fluctuate depending on the material choice, the roof’s pitch and complexity, and your location.
Pro Tip: Some contractors will automatically include a specific amount of replacement roof sheathing in their estimates when replacing your roof. To avoid being charged for it even if the contractor doesn’t use it, go through their estimate point by point before agreeing to its terms.
As for the materials, the prices can vary dramatically based on the type you choose.
Most wood-based materials, like plywood, range from $0.50 to $3.50 per square foot.
However, some robust materials, such as concrete and wooden boards, can cost as much as $17 per square foot.
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Plank Sheathing
Before there was sheet sheathing, plank sheathing reigned supreme.
This sheathing type consists of long rectangular wooden boards that usually come in two sizes (1 inch by 6 inches and 1 inch by 8 inches).
Although plank sheathing is no longer the go-to material for re-sheathing a roof, it’s still a relatively popular option.
If you opt for it, expect to pay between $3.50 and $12.50 per square foot.
Sheet Sheathing
Sheet sheathing is the most popular material option for roof decking.
Sheets are what most contractors will install by default for roof sheathing.
There are two types of sheet sheathing, one significantly less expensive.
Oriented Strand Board (OSB) Roof Sheathing
Oriented Strand Board (OSB) sheathing is the most affordable material option on the market.
You can re-sheathe your entire roof using this material for as low as $0.50.
Given its low price, it isn’t surprising this material is also the most popular option across the U.S.
OSB comes in thick, strong panels that consist of wood fragments bound by special adhesives.
This construction makes it less prone to swelling or warping over type.
Throw the low price into the mix, and you’ll probably feel you’ve hit the jackpot.
But be careful. OSB isn’t always allowed by local building codes.
Even when it is, it isn’t exactly the most durable sheathing option.
So, what you save on the upfront cost, you might end up spending on repairs and replacements in the long run.
Plywood Roof Sheathing
At $2 to $6 per square foot, plywood sheathing is considerably more expensive than its OSB counterpart.
However, it also resists moisture and retains its strength significantly longer.
This lightweight sheathing is available in boards of various sizes (three-eighths to three-quarters of an inch), each characterized by a high density that prevents moisture from penetrating the core.
Like OSB, it consists of several wooden layers held together by adhesives.
Concrete Roof Sheathing
Sometimes a roof covering requires more support than wood-based sheathing can offer it.
Enter concrete sheathing.
Besides being greener than its wooden counterparts, concrete is more robust and uniform and doesn’t let water enter the house.
This long-lasting sheathing type typically costs $7 to $25 to install.
Skip Roof Sheathing
Skip roof sheathing has a pretty self-explanatory name.
It consists of wooden planks placed with spacing between them (skipping small portions of the roof).
This placement allows air to pass through the sheathing, helping dry the roof in case of moisture exposure.
Re-sheathing your roof in this way will cost you between $3.50 and $6.50 per square foot.
Did you know? Skip sheathing was the go-to method in the 1800s when most homes had wood shake roofs. This sheathing type allowed wood shakes to dry after heavy downpours. With the advent of asphalt roofing, it declined in use.
Wooden Boards Roof Sheathing
Unlike plywood and OSB, this sheathing type isn’t wood-based.
It’s solid wood. As such, it also comes with a higher price tag.
If you want a solid support base that offers excellent insulation for your home, you’ll have to pay between $14 and $25 per square foot.
Additional Sheathing Cost Factors
So, add up the above-mentioned material and labor costs, and you get the estimated total cost of your project, and that’s it?
Unfortunately, not quite.
A few unforeseen expenses can sneak in and raise the total cost of your project significantly.
To avoid this unpleasant surprise, check out some of the factors that can influence the cost of re-sheathing your roof:
Lumber prices
Lumber prices vary dramatically based on availability and other external factors.
What does this mean for your project?
It means that the material prices can exceed the ranges mentioned above at any time.
Building codes
Even if you want a more budget-friendly option, your local building code might stand in the way.
Some codes require you to use thicker sheathing materials, which are, in turn, more expensive.
Roof pitch
Is your roof pitch greater than 4:12?
If so, expect a higher labor cost.
Old roof removal
Removing the old roof before installing the sheathing can add between $1 and $3 per square foot to your total cost.
Rafter replacement
Roof sheathing is installed directly over the roof rafter.
However, if the rafters are damaged or structurally compromised, replacing them is necessary before moving forward.
In terms of money, this means adding a charge of $5 to $15 per square foot to your final bill.
Cost per sq. ft.
Roof Size:
Roofing Material:
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Benefits Of Roof Sheathing
Roof sheathing is a must for a properly functioning and durable roofing system.
Discover some of the essential benefits of this protective layer.
Stopping Leaks
Adding roof sheathing means adding another layer of defense in the never-ending battle of preventing water from entering your home.
Sure, the roof coverings used today are much better at preventing water damage than their predecessors.
Still, it would be best if you did everything you could to prevent potential leaks and prolong the lifespan of your roof.
Adding Strength and Support
Roof sheathing ensures your roof is sturdy enough to withstand everything that might come its way.
This can refer to heftier roof coverings like asphalt shingles or heavy rainfall and snow loads.
No matter the load, the sheathing will distribute it evenly, thus preventing your roof from sagging or bowing.
Offering Fire Protection
Combustible roof coverings like wood shakes and shingles desperately need roof sheathing.
Most sheathing materials are treated with a fire retardant, allowing them to play a crucial role in preventing fires on the roof or the attic.
When Is The Best Time To Install Roof Sheathing?
The best time to install roof sheathing is during re-roofing.
This way, you’ll pay for the roof removal only once instead of removing it for re-sheathing and re-roofing separately.
Homeowners installing roof sheathing for the first time should wait for the fall.
During fall, roofing contractors often offer discounts that can help you save money on your roofing project.
What Is The Best Material For Roof Sheathing?
Plywood is the best material for roof sheathing.
It’s relatively affordable, incredibly durable, and can withstand heavier roof coverings like concrete tiles or slate.
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What Type Of Plywood Is Used for Roof Sheathing?
OSB and CDX are the types of plywood most commonly used for roof sheathing.
OSB consists of compressed wood fragments held together with a special adhesive.
Swap the wood fragments with thin wood veneer sheets, and you get CDX.
Should Roof Sheathing Be CDX or OSB?
CDX (veneer plywood) and OSB are two popular types of sheet sheathing.
But which one is better?
Did you know? The “C” and the “D” in CDX represent the quality grade of each side of this plywood material. One side is C grade, while the other is D. As for “X,” it stands for exposure. This letter signifies that the plywood material can withstand some moisture thanks to the adhesive used to bond its veneers.
If you’re looking for a short answer, it’s CDX. If you want to know more, keep reading.
CDX outperforms OSB in almost all regards.
When exposed to moisture, it might swell, but it will also quickly dry out and return to its standard size.
The same can’t be said for OSB, which takes ages to dry. And when it finally dries, not all swelling will disappear.
As moisture gradually takes a toll on this material, it will degrade significantly faster than CDX.
CDX is also more lightweight, easier to install, and resembles authentic wood more closely.
The only upper hand OSB has is its lower price.
Roof Sheathing Thickness
There isn’t a single standard thickness for roof sheathing.
This aspect depends on the roof’s steepness, the rafters’ spacing, and the expected load.
Generally, roof sheathing is between one-half and five-eighths of an inch thick.
Pro Tip: When it comes to sheathing thickness, you shouldn’t go below three-eighths of an inch. If your roof sheathing is too thin, it might bend and sink over time, compromising the integrity of your entire roof structure.
Cost per sq. ft.
Roof Size:
Roofing Material:
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Does Roof Sheathing Need To Be Pressure-Treated?
No, roof sheathing doesn’t need to be pressure-treated, especially if the roof is constructed correctly.
However, pressure-treating the roof sheathing can’t hurt. In fact, it might even help prevent rotting and protect the sheathing from termites.
Does Roof Sheathing Need To Be Spaced?
No, roof sheathing doesn’t need to be spaced.
Solid sheathing is installed without any gaps in the material.
However, spacing the material will be necessary if you opt for an open-sheathing method.
The exact spacing will depend on the roof covering you choose. For instance, wood shingles usually require 5 inches, while their shingle counterparts need 10.
Concrete tiles call for even bigger spacing ranging from 12 to 14 inches, depending on the tile type.
Metal roofing wins this highest sheathing spacing race with 24 inches.
Do Roof Sheathing Nails Need To Be Galvanized?
Yes, roof sheathing nails need to be galvanized.
Making the nails resistant to rust will help prevent the sheathing from the adverse effects of the elements.
Pro Tip: Instead of roof sheathing nails, use screws. They offer better strength and will secure the sheathing more tightly. Just make sure to get them adequately sized by a professional contractor.
Does Roof Sheathing Go Over Fascia?
No, roof sheathing doesn’t (or shouldn’t) go over the fascia.
Ideally, the roof sheathing should reach the fascia without extending beyond it.
Is Roof Sheathing Waterproof?
No, roof sheathing isn’t inherently waterproof.
Most sheathing materials are water-resistant at best.
However, this layer plays a crucial role in waterproofing the entire roofing system and extending its lifespan.
When To Replace Roof Sheathing
Ideally, you’ll replace the roof sheathing at the same time as the roof, thus saving time, money, and effort.
But only do so if the sheathing isn’t in optimal condition.
Check out the tell-tale signs that it’s time for new roof sheathing.
The Roof Sheathing Is Compromised
A damaged sheathing is easy to spot.
There will usually be broken boards, surface cracks, and even sawdust.
If you’re lucky, your contractor will be able to replace only the damaged portions. But if the damage is too extensive, say goodbye to the entire thing.
The roof sheathing can get damaged in numerous ways. Most commonly, a tree branch or a similar object will hit the roof, shattering its underlayment.
Moisture can also be detrimental to the sheathing.
If it continuously freezes and defrosts within the sheathing, it can lead to cracking.
And, of course, the roof sheathing’s age plays a massive role in its current state.
There’s Water Damage on the Sheathing
Water and roofing elements are mortal enemies.
If you see any water stains, leaks, or puddles on your ceiling, there’s been a battle, and your roof has taken the brunt of the damage.
Further inspecting the sheathing typically reveals water-damaged boards that are warped or twisted.
If the water damage is extensive, you might even notice some parts of the roof covering missing (like shingles or shakes).
Two things are crucial regarding water damage – dealing with it promptly and doing your best to prevent it in the future.
The Roof Sheathing Is Rotting
Blackened spots on the roof can only mean one thing – your sheathing has started to rot.
You can double-check if this is the case by pressing against these spots and seeing whether the material gives in quickly.
If yes, it’s replacement time.
The best-case scenario is that the rot has only reached a few sheathing boards.
But given how quickly the decay can spread a total replacement is more likely.
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There Are Holes in the Roof
Unless they’re intentional, holes are never a good sign in construction.
Your roof can develop holes for numerous reasons, including pest infestations, moisture damage, and substantial impacts.
With holes, the most important thing is to act quickly.
Don’t wait for a gaping hole that will cost you a fortune to fix.
Grab a flashlight, go to the attic, and see if you can spot any light passing through the roof. If yes, call a roofing contractor immediately.
The Ceiling Is Sagging
Sagging in the ceiling or the roofline is one of the most evident signs that your sheathing is in trouble.
Besides being unsightly, this phenomenon is quite dangerous.
If not fixed promptly, your entire roof can cave in.
The Roof Sheathing Can’t Support the New Roof
Sometimes, your roof sheathing might be in excellent condition, but it still has to go.
This will happen if your roof contractor determines the current sheathing isn’t strong enough to support the weight of the new roof covering.
Did you know? The need to replace roof sheathing isn’t solely based on the contractor’s estimate. There’s actually a building code that specifies when the sheathing must be replaced. The main goal is to ensure that the installed sheathing matches the specifications from the installation instructions issued by the manufacturer of the chosen roof material.
Is Roof Sheathing Necessary?
Yes, roof sheathing is necessary.
This useful addition helps distribute weight evenly across the roof and adds rigidity to the trusses or the rafters.
It also plays a considerable role in waterproofing the roof and protecting it from water damage.
Invest In A Guardian For Your Roof
The roof sheathing is one of the most essential components of your roofing system.
It will keep the roof and, in turn, your home safe from the elements and other dangers lurking on the outside.
Choose the appropriate sheathing for your roof covering, and be confident about your roof’s durability and longevity.
For over 20 years Leo has run a successful roofing business in New England, specializing in metal roofing, as well as cool flat roofing technologies. Having replaced and installed hundreds of roofs in New England, Leo has first hand experience with pretty much every residential roofing material and roofing manufacturer available in the US.
