[{"_1":2,"_79":-5,"_80":-5},"loaderData",{"_3":4},"routes/resources.roofing-components.category.$category",{"_5":6,"_14":15},"category",{"_7":8,"_9":10,"_11":8,"_12":13},"slug","decking","name","Decking","prefix","description","The structural base layer that supports all other roofing materials.","components",[16],{"_7":17,"_9":18,"_5":8,"_12":19,"_20":21,"_27":28,"_43":44,"_49":50,"_51":52,"_56":57,"_62":63,"_75":76,"_77":78},"roof-decking","Roof Decking: Plywood vs OSB","A comparison of plywood and oriented strand board (OSB) as roof decking materials, covering structural performance, moisture behavior, cost, and how decking condition affects insurance claim outcomes.","keywords",[22,23,24,25,26],"roof decking","plywood vs osb roof","roof sheathing","roof deck plywood","osb roof decking","specs",[29,34,37,40],{"_30":31,"_32":33},"label","CDX Plywood","value","Cross-laminated wood veneer, standard residential thickness 15/32 inch or 1/2 inch",{"_30":35,"_32":36},"OSB","Oriented strand board, compressed wood strands and resin, standard 7/16 inch or 15/32 inch",{"_30":38,"_32":39},"Span Rating","Common residential: 24/16 (24-inch rafter spacing for roofs)",{"_30":41,"_32":42},"Fastening","8d ring-shank nails at 6 inches on center at edges, 12 inches in the field","commonIssues",[45,46,47,48],"OSB swelling at edges when exposed to prolonged moisture, which does not return to its original dimension when dried","Plywood delamination from sustained water exposure where the veneer layers separate","Soft spots from prior undetected leaks that compromise the structural support for the shingle system above","Gaps between panels installed without the recommended 1/8-inch spacing for expansion, causing buckling in hot weather","insuranceRelevance","Roof decking replacement is one of the most common supplement items on storm damage claims. During tearoff, damaged decking is often discovered that was not visible during the initial roof inspection. Adjusters and contractors should document decking damage with photos showing the location, extent (measured in square feet or number of sheets), and the nature of the damage (rot, delamination, soft spots, hail bruising). Xactimate line items separate decking replacement from shingle and underlayment costs. The type of decking (plywood vs OSB) and thickness must be specified for accurate pricing.","relatedComponents",[53,54,55],"roofing-underlayment-types","roof-shingles","roofing-nails-for-shingles","relatedGlossaryTerms",[8,58,59,60,61],"sheathing","osb","plywood","span-rating","faqs",[64,69,72],{"_65":66,"_67":68},"question","Is plywood or OSB better for roof decking?","answer","Both are acceptable and widely used. Plywood has better moisture tolerance because it swells and dries more evenly and does not suffer the permanent edge swell that affects OSB. OSB is less expensive and provides consistent structural performance across the entire sheet. OSB is used on the majority of new residential construction due to its lower cost. In areas with high humidity or frequent roof leaks, plywood's superior moisture behavior gives it an advantage. Both perform equally well when the roof above them is intact and the attic is properly ventilated.",{"_65":70,"_67":71},"How thick should roof decking be?","Standard residential roof decking is 15/32 inch or 1/2 inch for rafter spacing up to 24 inches on center. The span rating stamped on the panel (such as 24/16 or 32/16) indicates the maximum rafter spacing for roof and floor applications. For rafters spaced at 16 inches, 7/16-inch OSB or 3/8-inch plywood meets the structural requirement, but most builders use 1/2-inch panels for additional rigidity. Local building codes and the engineer of record specify the minimum thickness for each project.",{"_65":73,"_67":74},"When does roof decking need to be replaced?","Decking needs replacement when it is structurally compromised. Signs include visible rot, delamination (plywood layers separating), edge swell (OSB edges thickened from moisture), soft or spongy spots when walked on, and visible daylight from the attic. During a roof replacement, any section of decking that does not provide solid, flat support for the new roofing materials should be cut out and replaced. It is standard practice to budget for some decking replacement on any re-roofing project, particularly on homes over 15 years old.","body","

Plywood Roof Decking

CDX plywood is the traditional roof decking material. It is made from thin wood veneers layered in alternating grain directions and bonded with waterproof adhesive. The \"C\" and \"D\" refer to the face veneer grades (C is the better face, D is the back), and \"X\" indicates exterior-grade glue. Standard residential roof plywood is 15/32 inch or 1/2 inch thick in 4-by-8-foot sheets. Plywood's cross-laminated construction gives it good dimensional stability. When exposed to moisture, plywood swells relatively evenly across its surface and returns close to its original dimensions when it dries. Delamination (separation of the veneer layers) occurs with prolonged water exposure but takes longer to develop than the edge swell problems that affect OSB. Plywood is slightly more expensive than OSB and accounts for a smaller share of new residential construction but remains preferred by some builders and in regions with high moisture exposure.

OSB Roof Decking

Oriented strand board (OSB) is engineered from compressed wood strands (typically aspen, poplar, or southern pine) bonded with resin under heat and pressure. The strands are oriented in layers, with surface strands aligned in one direction and core strands perpendicular, providing structural strength similar to plywood. OSB is the dominant decking material in new residential construction because it costs less than plywood and offers consistent performance across the full sheet with no knots, voids, or weak spots. The standard thickness for residential roof decking is 7/16 inch or 15/32 inch. The primary weakness of OSB is its moisture behavior. When OSB edges are exposed to water, they swell permanently. Unlike plywood, OSB does not return to its original dimensions after drying. This edge swell creates ridges visible through the shingle surface, commonly called \"ghosting\" or \"telegraphing.\"

Moisture Performance and Ventilation

The moisture behavior difference between plywood and OSB is the most important factor in the choice between them. Both materials perform well in a properly built and ventilated roof assembly where the decking stays dry. Problems arise when leaks, ice dams, or condensation expose the decking to moisture. Plywood tolerates occasional wetting better because its cross-grain construction limits directional swelling and it recovers more fully when dried. OSB absorbs moisture through the edges and at any cut or damaged areas, and the resulting swell is permanent. Proper attic ventilation is critical for both materials. A poorly ventilated attic traps moisture that condenses on the underside of the decking, particularly in cold climates. This sustained condensation degrades both plywood and OSB over time, but OSB shows damage sooner because of its edge swell characteristics.

Decking and Insurance Claims

Roof decking condition is discovered during the tearoff phase of a roof replacement. It is one of the most frequently supplemented items on insurance claims because the damage is hidden under the shingles and underlayment and cannot be fully assessed from the initial exterior inspection. When decking damage is found, the contractor should stop work, photograph the affected areas with a tape measure showing the extent, and submit a supplement to the adjuster before proceeding. Xactimate prices decking replacement by the square foot, with separate line items for plywood and OSB at their respective thicknesses. The number of damaged sheets, their locations, and the cause of the damage (storm-related leak, long-term moisture, prior unrepaired leak) should all be documented. Storm-related deck damage, such as rot from a leak caused by wind-displaced shingles, is covered. Pre-existing rot from a decade-old plumbing vent leak is generally excluded as maintenance neglect.

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Decking

Roof Decking: Plywood vs OSB

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