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Thread: Painting OSB - how many coats?

  1. #16
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    Sep 2016
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    Modesto, CA, USA
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    If you can paint it laying flat outdoors before you install it. Then you can lay on the paint thicker with no runs. And no edging needed.
    Bill D.

  2. #17
    Join Date
    Feb 2008
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    E TN, near Knoxville
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    Quote Originally Posted by Bill Dufour View Post
    If you can paint it laying flat outdoors before you install it. Then you can lay on the paint thicker with no runs. And no edging needed.
    Bill D.
    That's what I did. I propped the sheets of OSB up in a row, about 10 at a time, and sprayed a heavy coat of external paint and let them dry in the sun. Then installed. This was for roofing, not interior paneling.

  3. #18
    Join Date
    Jul 2003
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    Winterville, NC (eastern NC)
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    2,100
    OSB lines my shop walls as well. Primer followed with the finish coat did the trick for me, applied with a 3/8" nap roller. Primer is the key to a decent application. Still a rough looking surface but it was friendly on the wallet.

  4. #19
    Join Date
    Jun 2014
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    Western PA
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    I just lined my shed with painted OSB. This was purely for economic reasons, otherwise I would have splurged for a better quality ply/T1-11. Like you, I also had leftover White paint from painting my garage. Iíd say 2.5-3 gallons on 9-10 sheets of OSB. I laid them flat on blocking across the driveway and rolled it on heavy. I went around with the 5 gallon pail and dumped paint on each to then roll out.

    Iíve often read how OSB always looks like dog poo and thereís nothing you can do to change that, but I feel differently now. My project really turned out just fine. Iíd go as far as to say, it looks good. I wouldnít hesitate to use it in a shop. Unfinished it looks atrocious, but once itís heavily painted the texture isnít offensive.

  5. #20
    I did my shop walls in OSB. Oil based primer for first coat, and then two coats of semi gloss white latex over that. The oil base does a good job of sealing the surface, although some of the black ink bled through. I gave those a spot second coat. I would not recommend going with a straight white paint though, it is a little hard on the eyes. If I did it again, I would use a light tan color.

  6. #21
    Join Date
    Mar 2003
    Location
    Vermont
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    256
    My shop walls are all OSB, smooth side in. I painted with one coat of the oil-based Kilz, as a water-based product tends to make the OSB swell and peel in areas. Then cover with two coats of your latex paint of choice, For me, I have a bunch of mixed brands and types of white paint, some flat, some satin, mixed all together in a 5-gallon bucket and rolled on. Whatever I can scrounge. Yes, OSB collects dust more than a smooth drywall surface, but five minutes with a leaf blower and the walls are clean.
    Jon Endres
    Killing Trees Since 1983

  7. #22
    Join Date
    Feb 2003
    Location
    Lafayette, IN
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    4,373
    Airless sprayers do lots of things well, but covering rough/porous surfaces isn’t one of them. Spray the first coat on heavy, but backroll it immediately, working it in well. Your first coat will be MUCH better that way.

    Addy protocol: former professional painter with 20 years experience
    Jason

    "Don't get stuck on stupid." --Lt. Gen. Russel Honore


  8. #23
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    Feb 2008
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    Quote Originally Posted by Jason Roehl View Post
    Airless sprayers do lots of things well, but covering rough/porous surfaces isnít one of them. Spray the first coat on heavy, but backroll it immediately, working it in well. Your first coat will be MUCH better that way.

    Addy protocol: former professional painter with 20 years experience
    Somehow I bought a quantity of OSB that wasn't porous and wasn't significantly rough on one side - perhaps it had more resin added to that side. The other side was a little rougher but not bad. I used an airless sprayer to apply one thick coat on the smoother side and it covered well. Maybe those looking for OSB to cover shop walls could find similar product. I don't remember but it may have been more expensive than more typical OSB.

    I painted these sheets before installation anywhere subject even temporarily to moisture or high humidity - under eves and on the exterior side of OSB applied to outside walls. I wanted to protect the sheets from moisture until I got time to cover with the final siding. Some painted offcuts left in the weather about 5 years have still not expanded, even on the cut edges - that stuff must have been really saturated with waterproof resin.

    BTW, my interior shop walls and ceilings are all 1/2" Radiatia pine plywood, very smooth both sides. 6" studs and 1.5" of sheet goods made for thick and hopefully sturdy walls.

    JKJ

  9. #24
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    Mar 2003
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    SE PA - Central Bucks County
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    John, there seems to be a lot of variability in OSB as a product when it comes to its outer surfaces. But even on the really smooth stuff, there's variation in height because of how the fibers/chips were compressed together. Spraying will likely get "most" of the contours for the really good surfaces, but I suspect that Jason's suggestion to back-roll will get an even better result as it will fill in those last little variations in coverage due to the nature of the product. Of course, the aesthetics of coverage is subjective...

    That said, enthusiastic use of OSB is also subjective. I personally hate the stuff.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  10. #25
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    Feb 2008
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    Quote Originally Posted by Jim Becker View Post
    John, there seems to be a lot of variability in OSB as a product when it comes to its outer surfaces. But even on the really smooth stuff, there's variation in height because of how the fibers/chips were compressed together. Spraying will likely get "most" of the contours for the really good surfaces, but I suspect that Jason's suggestion to back-roll will get an even better result as it will fill in those last little variations in coverage due to the nature of the product. Of course, the aesthetics of coverage is subjective...

    That said, enthusiastic use of OSB is also subjective. I personally hate the stuff.
    Somehow they must have messed up on my OSB and forgot to add variations to one side! The spray covered perfectly. If I remember correctly, there was considerable visible resin on the surface filling in between the chips. Printing on one side indicated the "good" side, is that normal for OSB? I'll have to check the next time I go to that building supply place and ask about that and if it was something special or made a different way.

    I hate it too, in general, and refuse to use it for anything except certain things on buildings that will be covered with something else. Or single use things like concrete forms.

    JKJ

  11. #26
    Join Date
    Jun 2009
    Location
    Spokane Valley, WA
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    186
    Looks as though I've stimulated some interesting conversation! As I originally noted, rough side out OSB is what I've got, and it's already in place so no laying it flat to paint.

    Since posting, considering all of your replies, I"ve resorted to the tactic of laying on one heavy coat (multiple passes) with the airless sprayer. Of course, I have to really put it on heavy over the black lines and seams. But - it's coming out GOOD ENOUGH for me. My primary intent was to lighten things up a bit inside. Sure, I have unsealed surfaces, etc. but I'm getting what I want/need.

    Thanks again for all of the comments and suggestions!
    "Never attribute to malice that which can be adequately explained by stupidity" - anon

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