Hello all! Last summer we as a family put in some collaborative sweat equity and came out with a great screen house in the back yard. The roofing was done by a local contractor who chose to use particle board as the base. So now, we look up and see bare particle wood and are starting to think about painting it. I'm thinking about the variables first:

The real question: What is the best / proper way to paint particle board?

• I am going to keep the beams / joists exposed and unpainted.
  
• It is an outdoor setting
  
• It’s a ceiling / roof (if any gloss should be considered for light reflection)
  
• Will I have to sand any glue / sealant on the board first?
  
• Do I have to prime or will your suggested paint be a one coat type?
  
• Can the imperfections of the particle surface be hidden /subdued in any way (hide the bumps)?
  

This message has been edited. Last edited by: kRySpiE,

#1 It's OSB not partical board.
You could paint it but it will look horrible.
For a far better look I would use beaded vinyl soffit instead.

Thanks Joe.

I should have mentioned in the post that I am going to keep the beams / joists uncovered and natural.

I dont know if this will work, but I'll suggest it anyway. You can get a heavy weight paper that is used to cover paneling then painted over. It is applied like wallpaper and should hide the osb. try it on a small inconspicous are first

I really doubt that would work, the boards to rough to get proper adhesion.

Someone suggested to use block primer?

Blocking primer, not block primer, Most use shellac to block stains from coming through.

"Someone suggested to use block primer?"

"Blocking primer, not block primer, Most use shellac to block stains from coming through."

No, Joe. He means a concrete block filler. You know, the kind you prime concrete block walls with to fill the roughness of the block before painting them.

Krispie:
I would just go ahead and prime that OSB with any good quality latex primer and top coat with any top quality exterior latex paint in a FLAT gloss. So far as I know, there's nothing about OSB that would require any surface prep prior to priming.

It may take a coat of primer and two coats of paint to hide the black printing on that OSB, but there are no ceiling mounted light fixtures to shine light at a sharp angle onto that OSB and exaggerate the roughness of the ceiling, and so you shouldn't notice any roughness looking up at the ceiling from below. Also, a flat paint will also help to hide the roughness of the OSB and flat paints hide an underlying colour better than glossier paints, everything else being equal.

You certainly don't need a block filler to prime over OSB.

PS:
If you're at all concerned about the adhesion of the primer to the OSB, simply paint some primer on, allow it to dry fully over the course of a few days, stick some ordinary masking tape to it and pull the masking tape off. If the primer comes off with the masking tape, then you're right; it's not adhering as well as it should. Otherwise you're good to top coat.

Another option would be to use Zinsser Bullseye 123 (available at Home Depot) as your primer. Bullseye 123 is a primer where they decided on which binder resin to use based on it's adhesive qualities, and so 123 will stick to lots of smooth and hard to stick to surfaces that other primers won't, but I really don't think you need 123 to stick to OSB. People paint over OSB all the time, and I've never heard of it being a problem to paint.

This message has been edited. Last edited by: Nestor,