Roof decking is the foundation of your entire roofing system, the flat layer fastened over your rafters or trusses that everything else is built on. Choosing the best roof decking material affects your roof’s strength, moisture resistance, lifespan, and cost, so it is worth getting right. The main options are plywood, oriented strand board (OSB), and metal, with tongue-and-groove and concrete sheathing in specific cases.
This guide compares those materials head to head and helps you pick the right one for your climate and budget. If you want the basics of what decking is and how it works first, see our explainer on roof decking, and note that decking and roof sheathing are simply two names for the same layer.
Best Roof Decking Materials Compared
| Material | Cost | Moisture Resistance | Strength | Best For |
|---|---|---|---|---|
| Plywood | Higher | Excellent (dries and recovers) | High | Wet climates, steep/large roofs |
| OSB | Budget-friendly | Fair (slow to dry) | Good | Cost-conscious projects, dry climates |
| Metal | Highest upfront | Excellent | Very high | Longevity, energy efficiency, fire resistance |
| Tongue-and-groove | Higher | Good | High | Exposed/vaulted ceilings, older homes |
| Concrete sheathing | High | Excellent | Very high | Green builds, fire-prone areas |
For damp regions like the Pacific Northwest, moisture resistance is the deciding factor, which is why plywood is the most common quality choice here despite costing a bit more than OSB.
Plywood vs OSB: The Core Decision
Most roof decking comes down to plywood versus OSB, and the difference is in how they are built. Plywood is made of thin wood veneers stacked with the grain alternating direction, which gives it cross-grain strength and better moisture behavior. OSB is made of compressed wood strands bonded with resin.
Plywood resists bending and sagging under load, making it the better pick for larger or steep-slope roofs and for severe-weather regions. Its biggest advantage is moisture: plywood swells when wet but returns to its normal size as it dries, without damaging the roofing above it. That matters enormously in a rainy climate.
OSB is more budget-friendly and consistent in quality, which makes it popular on smaller residential projects and in drier climates. The trade-off is that OSB dries out much more slowly once wet and can degrade faster with repeated water exposure.
For Portland-area homes facing months of rain each year, plywood’s moisture recovery usually justifies the higher price. In a hail-prone region, plywood’s better impact resistance is another reason to favor it over OSB.
Metal Roof Decking vs Wood
Metal decking is a different category, prized for durability and energy performance. It reflects heat to keep homes cooler, carries a higher R-value for better insulation, and resists extreme weather, standing up to winds around 140 mph. Metal is also one of the more eco-friendly choices, made from 35 to 95% recycled content, 100% recyclable at end of life, and often installable over an existing roof to cut waste. The catch is a higher upfront cost, though long-term energy and replacement savings can offset it. If a metal system appeals to you, weigh the full picture in our guide on the pros and cons of metal roofing.
Other Decking Types Worth Knowing
Beyond the big three, a few specialized options serve particular needs. Tongue-and-groove boards interlock for a tight, attractive surface often left exposed in vaulted ceilings and common in older homes. Solid sheathing provides a continuous surface ideal under composition roofing and built-up systems, while open (skip) sheathing leaves gaps for ventilation under wood shingles and shakes. Concrete sheathing is a durable, low-maintenance, non-wood option increasingly used in green and fire-conscious building. Whichever you use, the decking has to be matched to your framing; our explainer on rafters vs. trusses shows what it attaches to.
How to Choose the Right Roof Decking
Three factors drive the decision.
Climate. Wet and rainy regions need moisture-resistant decking, which favors plywood or metal over OSB. Hot, dry climates can take advantage of metal’s heat reflection, and areas with big temperature swings benefit from materials that handle expansion and contraction well.
Budget. OSB is the most affordable and works well where moisture is not a constant threat. Plywood costs more but buys durability and moisture recovery. Metal carries the highest upfront price but the lowest long-term cost. For how decking fits into a full project budget, see our breakdown of the cost of an asphalt roof.
Durability. Look for materials that last with minimal maintenance. Plywood offers strength and moisture recovery, concrete sheathing excels in harsh weather, and metal leads on lifespan. Spending a little more upfront on durable decking usually prevents far more expensive repairs later, which is why decking problems often surface during a roof replacement.
The Bottom Line for Portland Homeowners
There is no single best roof decking material for every home, but there is a best one for yours. OSB makes sense on a budget in a dry climate, metal wins on longevity and efficiency, and plywood is the dependable all-rounder, especially where moisture is a constant. For the Pacific Northwest, plywood’s ability to shed water and recover makes it the default quality choice for most roofs, with metal worth considering if energy savings and lifespan are priorities.
Decking is hidden once the roof is finished, but it determines how long that roof lasts, so it is not the place to cut corners. River City Roofing inspects and replaces decking as part of full residential roofing across Portland and the surrounding 30-mile metro. If you are planning a new roof or suspect soft, water-damaged decking underneath, book a free roof inspection, and we will assess it and recommend the right material.
FAQs
Does roof decking need to be replaced during a new roof?
Not always. Sound decking can be reused, but soft, rotted, or water-damaged sections should be replaced during a re-roof to ensure the new roof has a solid base.
What is the most recommended roof decking material?
Plywood and OSB are the two most-used materials. OSB is favored for cost and consistency, while plywood is preferred for moisture resistance and strength in demanding climates.
What is the difference between roof decking and sheathing?
There is none. Roof decking and roof sheathing are two names for the same structural layer installed over rafters or trusses to support the roofing materials.
Is plywood or OSB better for roof decking?
Plywood is better in wet or hail-prone regions because it resists moisture and impact and dries without permanent damage. OSB is cheaper and fine in dry climates but degrades faster when repeatedly wet.
What is the best roof decking material?
Plywood is the best all-around choice for most homes thanks to its strength and moisture recovery, especially in wet climates. OSB is the budget option, and metal leads on longevity and energy efficiency.
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