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OSB, or oriented strand board, has a flaked appearance and bumpy texture.
OSB is made of many layers of chipped-up lower-grade wood; these are the strands.
These strands are arranged flat and then oriented perpendicular to each other.
The Spruce / Tessa Cooper
Cross-hatched strands impregnated with resins help create stability in OSB.
Oriented strand board is primarily intended to be a functional board, not a finished board.
But OSB has a few limitations and requires special preparation before you kick off rolling on the paint.
The Spruce / Tessa Cooper
Edges cut on-site are especially vulnerable to moisture penetration.
Factory edges hold up better against water because they are finished with a sealant during manufacturing.
Before You Begin
Before painting, you will need to do several things.
The Spruce / Tessa Cooper
Suppose you want to smooth out the texture so that the crosshatched wood chips are not visible.
Check with the manufacturer if the OSB has a thin wax coating to protect it.
Once your board is ready, be generous with the primer.
The Spruce / Tessa Cooper
Older OSB will be incredibly porous, requiring several coats of paint plus primer.
Lightly sand the surface butdo notsand the edges.
Clean the Surface
Thoroughly clean the surface of the OSB.
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Due to the OSB’s rough texture, tack cloth and cotton rags do not work well.
Instead, clean the surface with a shop vacuum and brush attachment.
Prime the OSB Multiple Times
Don gloves.
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Pour primer into a tray.
Dab the roller in the primer and thoroughly roll it out on the tray.
Prime the OSB by making W-shaped sweeps of the board.
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Do not apply too thickly.
After at least two hours of drying time, apply a second coat of primer.
Repeat this process until the OSB’s flake pattern no longer shows through.
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Prime with two coats of an oil-based primer, such as Kilz Complete or Sherwin-Williams ProBlock.
Apply it as thinly as possible.
Paint the OSB
After the last primer coat has dried, apply the paint.
As with the primer, do not apply it in thick coats.
Rolling vs. Spraying Paint
Roll on the primer and paint rather thanspraying the paint.
Then compare your satisfaction with the methods.
Sealing the Edges
Leave as many panels uncut as possible to preserve the factory edges.
While factory edges are not perfectly smooth, they are still smoother than edges cut with a circular saw.
OSB’s cut edges are susceptible to water infiltration.
For example, Weyerhaeuser Edge Gold OSB panels are warranted 200 days against edge swell resulting from water absorption.
OSB is made with an abundance of waterproof adhesives and resins that bond and protect the wood strands.
But any wood product can potentially absorb some moisture and some OSB products are more waterproof than others.
Check to see if your OSB was stamped as “waterproof.”
Painting OSB with high-qualityexterior paintcan add an extra layer of protection.
Painted OSB can last for years outdoors though it’s tough to put a time limit on the material.
There are many factors for how long painted OSB can last outdoors.
The smoother side should have some printing on it.
The rougher side may have “this side down” printed on it.
The smoother side is also more water-resistant.
The rougher side will soak up even more paint than the smoother side.
Ultimately, it’s suggested to prime and paint both sides of the board when possible.
Finishing Exposure 1 OSB Sheathing.APA The Engineered Wood Association.
Steps to Lead-Safe Renovation, Repair, and Painting.United States Environmental Protection Agency.
