When it comes to roof sheathing, making the right choice is critical to get the performance, durability and return on investment you expect from a roof.
This comprehensive guide provides home owners, contractors and architects with key factors to consider when selecting roof sheathing materials along with complete installation process.
Key Takeaways
Key Considerations When Choosing Roof Sheathing
Choosing the optimal roof sheathing depends first on clearly defining performance requirements and constraints like:
- Roof style – Gable, hip, flat and other roof designs involve different spans, loads and exposures that impact ideal sheathing materials.
- Insulation R-value – Meeting energy codes for your region involves tradeoffs with thickness limits in framing bays.
- Climate factors – Temperature swings, wind, snow loads and moisture exposure often dictate sheathing grades, durability ratings and gaps.
- Budget – Plywood, composite boards and panel quality vary greatly in cost and value over their lifespan.
- Weight – Minimum 15/32″ panels work for most roofs but specific weights per sheet require structural checks.
- Outgassing – Formaldehyde treatments in some panels require proper installation gaps and curing times before enclosing.
Carefully evaluating this criteria prevents misapplication of roof sheathing that fails prematurely. Materials not designed for prolonged heat/moisture exposure or heavy snow loads will undermine roof integrity down the road.
Plywood vs. Oriented Strand Board (OSB) Roof Sheathing
The two major structural panel plywood and OSB options each offer unique advantages:
Plywood
For high-moisture areas, use plywood; for cost-effectiveness and ease of installation, use OSB.
OSB
OSB roof sheathing costs less upfront but requires careful sealing and an understanding of designated exposure time limits that can expire in as little as 30 days if unprotected.
Both offer sufficient strength when specifications match the roof design constraints. Moisture management often dictates the best value over the full life expectancy.
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Roof Pitch and Required Sheathing Thickness
Steeper sloped roofs involve greater sheathing span capacity between trusses or rafters. As a general standard:
However, roof framing spacing, snow loads and municipal codes might dictate thicker sheathing regardless of pitch. Always consult local building codes for roof assembly requirements. An example common panel thickness by rafter spacing guidelines:
| Panel Span | Minimum Thickness |
| 16″ rafters | 3/8″ |
| 24″ rafters | 7/16″ |
| 32″ rafters | 1/2″ |
In this table, higher thickness compensates for wider framing spacing that would otherwise undermine strength. Use these recommendations only for panels with an exposure durability rating for the regional climate.
Evaluating Sheathing Grades and Exposure Durability
Understand a few key details from company stamps on roof sheathing panels:
Plywood Grades
OSB Exposure Rating
When using OSB, carefully review expected duration of unfinished roof exposure in your region before enclosure to determine grade requirements. Higher grades prevent degradation that undermines structural integrity.
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Using House Wraps and Rainscreens for Moisture Protection
Before final roof covering installation, multiple layers provide essential water resistance:
- Underlayments – Self-adhering ice barrier membrane along eaves first then 30lb asphalt saturated roofing felt across entire roof deck.
- House wraps – Breathable synthetic wraps like Dupont Tyvek or lighter Grade D asphalt impregnated paper.
- Rainscreen – Create 1/4″ to 3/4″ ventilation gap between panels and finishes for drainage and evaporation. Recommended for metal, stucco and wood cladding but also best practice for asphalt shingles.
Vapor barriers on the interior protect from condensation within warmer attic spaces. Following these guidelines prevents mold risks and sheathing failure early in roof service life.
Installing and Replacing Roof Sheathing
Use the sequence below whether building new or replacing storm damaged or worn out roof decking:
When replacing storm damaged sections or entire roof, first properly dispose of debris. Remove all old roof components down to expose roof framing for rebuilding the new layered roof system.
Disposing of Old Sheathing Responsibly
Salvage or dispose old roof sheathing with environmental impact in mind:
Responsible sheathing removal protects workers and communities from exposure and environmental contamination for the long run.
Conclusion
Installing inferior roof sheathing ultimately leads to premature failure, moisture infiltration and expensive tear-off projects down the road. Follow the recommendations in this article to select optimal materials matched to your precise roof type, climate, budget and longevity expectations.
Getting sheathing specs right the first time saves money and headaches for decades to come. Contact our team of experts if you need any guidance assessing options for an upcoming roofing project!
FAQ’s
What is the recommended sheathing for a roof?
For most roofs, 5/8″ CDX plywood or 7/16” OSB rated for exposure times provide optimal durability and strength at a moderate budget.
Is it better to use plywood or OSB on a roof?
Plywood resists moisture damage better long-term but costs more. OSB matches strength at lower cost but requires protected exposures and proper gapping during installation per type rating.
Can 7/16 OSB be used for roof sheathing?
Yes, 7/16” tongue-and-groove OSB panels work as roof sheathing when an exposure rating matches climate conditions and retail stamped as complying with regional building code standards.
What is better for roof sheathing OSB or CDX?
OSB roof sheathing costs less but requires protection from moisture exposure as soon as possible before degradation affects structural integrity. CDX plywood costs more but reliably handles temporary construction exposure making it the easiest to apply properly.
What is the cheapest way to sheet a roof?
The cheapest roof sheathing uses 7/16” OSB2 rated panels paired with ice barrier underlayment and 30lb felt paper to allow up to 6 months of exposure protection during construction before permanent roofing installation.