Why OSB and Metal Roofing Don’t Mix

OSB (Oriented Strand Board) is a popular and cost-effective building material. It works great for wall sheeting and general construction, and it’s often a little less expensive than plywood. But when it comes to roofs with metal roofing, OSB is not the best choice.

Here’s why:

• Screws Loosen Over Time: Metal roofing screws don’t grip OSB well. Over time, they loosen, causing leaks.

• Water Damage is Inevitable: Once water gets in, OSB starts to disintegrate, making the problem worse. The screws come out faster, and the roof deteriorates.

Plywood is a slightly better option, but not by much when used alone with metal roofing. Even thicker plywood, like 5/8", can give you a bit more durability, but it’s not a complete solution.

If you want to use OSB or plywood under metal roofing, here’s how to do it right:

1. Add Strapping: Install 1x4 or 2x4 strapping on top of the OSB or plywood. This gives the screws something solid to bite into, solving the looseness problem.

2. Upgrade Your Plywood: If you’re set on using plywood, choose a thicker grade (like 5/8") to improve performance, but still consider adding strapping for long-term durability.

   
   

   

   
   

We’ve seen roofs where OSB was used directly under metal (above), and after less than 10 years, the screws were loose, the OSB was deteriorating, and leaks were already a problem. Fixing it required removing the metal, installing strapping, and reapplying the roof—an avoidable and costly repair.

Taking the extra step to install strapping or choosing thicker materials upfront can save you time, money, and headaches down the road.