What Decking Does (and Why It Fails)
Your roof decking serves two primary functions:
- It’s the Nailing Surface: This is its most important job. It must be solid enough to grip thousands of nails, holding your shingles firmly in place against wind, rain, and gravity.
- It’s a Structural Component: Decking provides shear strength, helping to tie the entire roof frame together and keep it rigid.
So, why would this solid wood fail?
- Old Leaks: A missing shingle or failed flashing can let water drip in the same spot for years, causing the wood to rot and become soft and spongy.
- Poor Ventilation: This is a silent killer. An attic that can’t “breathe” traps hot, moist air. This moisture condenses on the underside of the cold decking all winter, leading to mold, mildew, and “dry rot” that rots the wood from the inside out.
- Age & Delamination: The glues in older plywood can simply break down over 30+ years, causing the layers to peel apart, or “delaminate.”
The AR Roofing Promise: We Will Not Cover Up a Problem
Imagine paying a mechanic to put brand-new tires on your car, but he just bolts them onto a cracked, rusty rim. That’s exactly what nailing a new roof onto bad decking is.
Here’s what happens when a roofer takes that shortcut:
- The Nails Won’t Grip: Nailing into soft, rotted wood is like nailing into a sponge. The nail has zero “pull-out strength.”
- Shingles Will Blow Off: The first 60-mph gust of wind that hits your house will lift those unsecured shingles right off the roof.
- Your Warranty is Void: The shingle manufacturer’s warranty is 100% contingent on a proper installation, which requires a solid, “nailable” deck. A roofer who covers up bad wood instantly voids your warranty.
- The Problem Spreads: The rot won’t just stop; it will continue to spread, compromising the structural integrity of your roof frame.
Our Process: An AR Roofing estimate will always include a clear, up-front, per-sheet price for replacing any compromised decking we find. When our crew leader finds a bad spot, we stop, take photos to show you exactly what we’re looking at, and get your approval before replacing it. No surprises, just honest, professional work.
Is OSB or Plywood better for roof decking?
This is one of the most common and best questions a homeowner can ask. You will almost certainly have one of these two materials on your roof, and if we replace a sheet, we’ll be using one of them. Let’s break them down.
Plywood: The Classic Choice
Plywood is made by gluing together several thin layers (or “plies”) of wood veneer. The grain of each layer is alternated, which gives it its strength.
- Pros: It has exceptionally high nail-holding power. It is also more resistant to swelling at the edges when it gets wet and can often dry out without losing its structural integrity.
- Cons: It is generally more expensive than OSB. Because it’s made of real wood veneer, it can have “soft spots” or knots that are natural flaws in the wood.
OSB (Oriented Strand Board): The Modern Standard
OSB is an engineered wood product. It’s made by compressing and gluing thousands of cross-hatched wood strands (not layers) together under immense pressure.
- Pros: It is very strong, rigid, and structurally uniform—you don’t get the soft spots or knots you can find in plywood. It’s also more cost-effective, which is why it’s the standard for new home construction.
- Cons: It’s heavier than plywood. Its main weakness is that if it gets completely saturated (especially at the edges), it can swell and may not return to its original shape, potentially losing some strength.
The Verdict: Which is Really Better?
Both plywood and OSB are excellent, code-compliant, and reliable materials for a roof deck. While plywood has a slight technical advantage in how it handles water, AR Roofing believes the “better” material is the one that is part of a better system.
The real goal is to ensure the decking never gets wet in the first time.
The debate isn’t really about plywood vs. OSB; it’s about a high-quality, watertight installation vs. a cheap one. A roof system built by AR Roofing—with its properly installed ice & water shield, high-quality underlayment, new flashing, and balanced attic ventilation—will keep both OSB and plywood bone-dry for decades. And that is the foundation you can count on.
