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Thread: Painting OSB - how many coats?

  1. #1
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    Painting OSB - how many coats?

    Hi All, OK, I know this is a rather open-ended question, with lots of variables. We just downsized post-retirement, and the new-to-us place has a real, proper shop -WooHoo! The interior is lined with OSB, and that stuff, in its native state, soaks up lots of light. Previous owners kindly left a good bit of white paint, so I had resources with which to work.

    i knew that the OSB would soak up, in addition to light, lots of paint as well. Iíve used an airless sprayer to do a small section, just for starters. Paint Iím using is pretty much ďgenericĒ indoor latex. After first coat, Iím not sure if on additional coat is going to be enough, or if Iíll be needing two or more additional. This obviously doesnít need to be a perfect job, but I do want the coverage to be reasonably complete.

    So - for budgeting and job planning purposes, words of wisdom/experience, please? Thanks in advance!

    Marty
    "Never attribute to malice that which can be adequately explained by stupidity" - anon

  2. #2
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    Too much depends on the quality of the paint, the brushes and roller covers and technique for a definitive answer. I used two coats of Behr Premium semi gloss in the laundry room on OSB, it covered pretty well, but then I slop it on almost to the point of running..
    NOW you tell me...

  3. #3
    Join Date
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    Marty -- It depends on what you're trying to accomplish. If all you're trying to is to brighten up your shop, one coat might be all it takes. But, if you're trying to make the walls 'look good', you'll probably never accomplish that objective. OSB wasn't designed to be a paint-ready surface. It's supposed to be covered with something more than paint. That doesn't mean painted OSB can't make a shop-worthy wall. That's what many of us have and are perfectly happy with. But, I wouldn't consider it for a bedroom or den! So, give it a coat and, if the light still isn't good enough, give it another coat. If the room is still too dark, focus on upgrading your lights.
    David Walser
    Mesa, Arizona

  4. #4
    Join Date
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    two coats of primer then two coats of color is a minimum for me. I buy a 5 gallon pail at the box store of a mismatched color for primer. Sometimes the primer color is good and we use that other times wife insists on a change for the finish coats.
    Bil lD

  5. #5
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    My answer...."too many". It wasn't designed to be painted and it soaks the stuff up in many cases which requires extra coats if you want things to look even. Having the "smoother" side exposed for painting helps, but it's still a chore. I avoid the stuff, honestly.

    So if you are using quality paint, I'd budget for three coats and hope it does the job. And that's after primer.
    --

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

  6. #6
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    If you want it to look like painted drywall, you're probably going to have to apply a skim coat of drywall mud, with taped seams/edges, sanded smooth. And even that may not survive the thermal/moisture expansion & contraction.

    Otherwise, embrace the OSB texture, printing through your paint a little or a lot, depending on number of coats.

    -- Andy - Arlington TX

  7. #7
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    I did my OSB walls with 1 coat of primer and 1 coat of semigloss white, sprayed on, both latex. That gave a very good finish (with the pattern still showing, of course) that would not be improved by any additional coats. That would take a skim coat & sanding. I don't care about the pattern, just a bright, easy to clean surface. Rolling would probably take 2 top coats, if one wanted to be real fussy.

  8. #8
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    I did one coat primer, one coat semi-gloss white paint rolled on.

    Aug-2011-cleats.jpg

    Zinsser BIN covered in one coat and the paint went on in one coat. The quality of your primer and paint will actually save you money if you don't cheap out.
    "The Danish government believes that if we train 5,000 designers, and produce
    one Hans Wegner, the money is very well spent." - Ole Gjerlov-Knudsen

  9. #9
    I skimmed the OSB walls with drywall compound before I painted it. I did not try to make them smooth, I just wanted to fill the voids on the surface of the OSB. They hold dust. Then I put on two coats of cheap white ceiling paint, if I remember right. I might have primed but I don't think I did. The drywall compound added very little cost and I think it reduced the dust buildup on the walls significantly. I rolled the paint on the walls (and ceiling). Still cannot remember for sure what paint I used. It could have been the ceiling paint I normally use which is the stuff that goes on pink then changes to white. I think that is pretty good ceiling paint.

  10. #10
    It's a product that varies, since it's not sold as a wall face . I once saw a batch that was absolutely smoothe on one
    side ,even had a little gloss. Almost bought some ,though I had no immediate need.

  11. #11
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    I've painted a lot of 4x8 sheets of OSB with a big airless sprayer using high quality exterior latex. One heavy coat was enough. One thing to keep in mind is a Mel mentioned, some OSB is far different than other OSB. I bought a large quantity from a reputable building supply and both sides were much better than some other I've seen.

    JKJ

  12. #12
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    I have osb on all my shop walls. The only place I painted was behind the wood lathe. That spot wasn’t well lit and the white background makes it easier to see the shape of the work as I’m turning. I just grabbed a can of white and a brush and painted. No primer. The guys are right. Osb is very thirsty. As I remember, it took 4 coats to get a nice white.

    so, don’t do what I did. Prime!

  13. #13
    Join Date
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    Thabks for thee insights, tips, and even war stories! Y'all pretty much confirmed what I suspected - that OSB stuff is porous and soaks up lotsa paint! I THINK I have plenty, courtesy of previous owners, so I'm going to plan on two coats and calling things good. Someone suggested upgrading lighting, that may be necessary but I'll wait and see until I've had some experience using the shop with the "incumbent" lighting.
    "Never attribute to malice that which can be adequately explained by stupidity" - anon

  14. #14
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    Apr 2013
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    Quote Originally Posted by Marty Gulseth View Post
    that OSB stuff is porous and soaks up lotsa paint!
    That is a blanket statement that just isn't accurate for the most part. OSB typically has a rough side that will soak up a ton of paint, but the other side is much smoother & has a water resistant coating. It's what keeps OSB from degrading from being exposed to rain during construction before the building is dried in. That smooth layer doesn't take a lot of paint to get good coverage.

  15. #15
    One good primer coat , hitting the black ink stripe twice w/ the primer . Two color coats on top . I love it . Put it on as heavy as possible without drips etc .

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