OSB is one of the strongest types of manufactured woods you can use for construction.
Based on its shear strength alone, it is comparatively stronger than MDF, Chipboard, and even Plywood. And that’s why it’s popularly used for roofing, wall sheathing, and attic floors.
However, OSB is a rather plain looking material. Which is why a few coats of paint can be a great way to spruce up the appearance of OSB walling.
But, not all type so paint work well with OSB. Use the wrong kind, and that paint coat may very well end up peeling right off.
So, in this post you will learn why masonry paint and emulsion paint don’t pair well with OSB. You will also find out why only a specific grade of OSB is suitable for your garage walls.
And keep reading to discover which all-in-one exterior primer is the single best type of wall paint for OSB…
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Can You Paint OSB (For Exterior Use)?
Absolutely you can. In fact, waterproof paint can be a great way to give OSB added water-resistance.
However, you should only use exterior graded paint in environments that experience high moisture or humidity. These specific types of paint have been formulated specially to resist mildew and UV fading.
What About Masonry Paint? Can You Paint OSB Board With Masonry Paint Too?
In theory, you could. However — in practice — you run across a recurring problem when coating this paint onto OSB.
Masonry paint is actually a type of acrylic paint. And like acrylic paint, it too is water-based.
Now, the primary advantage to using water-based paint is that it dries much faster than solvent-based paints. However, applying any water-based paint, finish or sealant onto OSB can cause OSB to swell.
That’s because OSB will quickly absorb the water inside masonry paint. And once that happens, the paint doesn’t have time to adhere and dry onto the surface, ultimately peeling off.
What About Emulsion Paint? Can You Paint OSB Board With Emulsion Paint Instead?
Emulsion paint will run into the same problems as masonry paint.
Why? Well, because emulsion paint is also water-based.
OK Got It. Will OSB Be Waterproof Once I’ve Painted It?
It won’t be waterproof, but it will certainly be much more water-resistant than without that coat of color.
Regular OSB isn’t very water-resistant. It’s only the very top OSB graded boards that can handle exterior conditions. So, in order to protect OSB from water-damage, you’ll need a more reliable sealant than a coat of paint alone.
Related Post: Is OSB Really Safe Enough For Indoor Use?
And Which OSB Grades Are Suitable For Exterior Settings?
Well, there are four standard OSB grades, ranging from OSB/1 up to OSB/4.
OSB/1 and OSB/2 are pretty much your all-purpose standard OSB. They’re meant only for interior furniture and fittings.
Also, they are not water-resistant and can become easily water-damaged in high-humidity spaces.
OSB/3 and OSB/4 are water-resistant in so far as their water-resistant adhesive can handle very humid conditions.
These particular OSB boards are the ones you want to use for exterior construction. They’re also stronger and more durable.
However, OSB/4 is the grade primarily used for siding, roofing, and other building construction work.
So What Kind Of Paint Should I Use On High Grade OSB?
Stick to solvent-based exterior-grade wall paints. And, if you can, try to use an all-in-one paint that combines both paint and primer.
If you don’t use an all in one product, then you’re going to have twice the amount of work on your hands. That’s because you will unquestionably need to apply a separate primer before coating a single-purpose exterior paint onto OSB.
So What’s The Best (Paint Plus) Primer For OSB Garage Walls?
Easily the best one on the market is KILZ Complete Interior or Exterior Multi-Purpose Oil-Based Wall and Ceiling Primer.
The name of the product is a bit of a mouthful, but that’s only because it packs in everything you need in a single pot.
You can apply this solvent-based exterior primer on almost any type of wall, whether it’s OSB panelling, brick or a metal sheet.
Also, this mildew-resistant primer dries to the touch in as little as 30 minutes. So, it’s ready for a top coat of color in under an hour.
How Long Will A Painted OSB Wall Panel Last? Top graded OSB/4 wall panels can last for up to half a century if properly maintained (repainted every 5-10 years).
To Wrap Up, Here Are The 3 Key Takeaways From This Post…
- 1). Only apply solvent-based paints and primers on OSB.
- 2). The most water-resistant and strongest grade of OSB is OSB/4.
- 3). You can apply solvent-based exterior primer on OSB walls.