Love it or not, OSB does have good qualities--low cost, high strength, easy availability. Is it possible to paint it and make it more attractive?
Yes, OSB can be painted. But there are strict limitations which are noted in detail below.
- Visible Texture: The texture will always remain visible. You cannot achieve a smooth surface on OSB.
- Priming Required: While priming may be optional with some surfaces, it is absolutely necessary with OSB.
- Wax Coating: Some OSB ships with a thin coating of wax which first needs to be stripped before painting.
- Extra Coats: The open strands readily suck up paint, requiring two coats at a minimum but more likely three coats. Older OSB especially will be more porous, necessitating several coats of paint plus primer.
- Extra-Porous Edges: OSB's edges are especially susceptible to water infiltration. Edges are initially treated with a sealant, but this is mainly for the purposes of shipping. This sealant is not intended to last over time.
OSB: While Not Beautiful, It Is Functional
Within the world of wood, OSB (oriented strand board), is a newcomer. Georgia Pacific, a major supplier of wood products, has only offered OSB since 1980.
OSB stands for oriented strand board, which means that layers of chipped-up wood are laid perpendicular to each other, increasing structural stability.
Under-Surface, Not Finish Surface
OSB is not meant to be a finish surface. It is intended to be an under surface for subflooring, wall sheathing, roofs, etc.
But it sometimes does become a finish surface: sheds, laundry rooms, mudrooms, basements, etc.
That is why this question of painting--a finishing process--is particularly interesting.
OSB vs. Moisture
OSB is designed to hold up during long-term periods of unintended exposure.
While OSB manufacturers do not recommend permanent exposure to the elements, OSB was initially designed as a way for remodelers and new home builders to deal with the occasional problem of building delays.
OSB stands up well against moisture, so the partially completed home will not immediately disintegrate during building slow-downs.
OSB rated as "Exposure 1" is very good at high moisture over long periods of time.
Interestingly, one reason OSB performs so well against moisture is because its rectangular-shaped chips of wood are so heavily impregnated with waterproof adhesives.
Industry Group's Opinion
While not all OSB is the same, The Engineered Wood Association (EWA) notes that Exposure 1 OSB can be painted.
The EWA's main reservation is that some OSB is shipped with a thin wax coating, which would inhibit painting.
The EWA also notes that, due to the prominent visible nature of OSB's strands, it will probably show through on one coat of paint.
A heavy primer may be required.
Avoid exposing OSB's edges to moisture; this may allow the OSB to swell and crack.