Priming OSB

[Izzy Camire]

Hi Folks, I am getting ready to paint my shop. The first step will be to apply primer to the OSB. I have the rough side out so no waxy stuff to worry about. Just wondering if anyone has done this and what you used. Internet searches pretty much all say to oil based primer.
Izzy

[John Ziebron]

Izzy, I've done this on the walls in 2 shops so far. And I've use Kilz. I just wanted white to help with the lighting. And even though it's a primer I never intended, and didn't, put a finish coat on. First shop was sprayed and second one was rolled. I do have an occasional spot where there was a little bleed through but not enough to bother me. I'd probably go over those areas if I were to put a finish coat on.

[Jim Becker]

It almost doesn't matter what you use because the first coat is going to get soaked up a lot. OSB was never intended to be painted or even exposed. Once you get the first coat on and it dries, subsequent coats will adhere and cover much better. Spraying with an airless and back-rolling makes the job go easier if that's a possibility for you.

[Frank Pratt]

I sprayed latex primer followed by 1 coat of semigloss, sprayed as well. Did both coats in one evening. My OSB is smooth side out. There was a smooth coating of some kind on it, but definitely not waxy. I've never seen OSB with a waxy coating. Maybe it's a regional thing. Anyway, the paint stuck like snot to a blanket & there has been no discoloration from the OSB.

[Paul F Franklin]

Probably overkill, but I used SW premium wall and wood primer on mine and it worked very well. I did not bother to topcoat it as I only wanted to improve light reflectivity and a single coat of the primer got me a long way there.

[Rick Potter]

What I can tell you is that PVA primer for drywall does NOT work well on OSB.

My new garage is drywalled and has an uncovered 7X14 ridge beam. We shot it with PVA and two coats white paint, and it still didn't cover well, although the drywall is fine.

I never thought it would work well on the OSB, but went ahead, because it doesn't show up as bad as if we left it natural. Just wanted a nice bright surface to help with lighting.

[Bob Vavricka]

I put OSB in my shop and primed the sheets with oil based Kilz before putting it up and then top coated it with a latex paint after it was up and it looks good. I did need one small piece to finish out a small area and it wasn't primed with Kilz, I just coated it with the a couple of coats of the top coat paint. There was a definite difference in the smoothness of the surfaces. The piece without the Kilz primer is a lot rougher like the moisture raised the grain making it a rough surface. YMMV.

[Robert Engel]

I didn't prime it at all, just went straight to the top coat.

I had 5 gallons of paint a painter friend of mine gave me.

He told me don't worry about primer. No issues whatsoever. Apparently he was right.

I laid on first coat thick and followed up with a second coat.

No issues.

[Günter VögelBerg]

Kilz2. It will take two coats of primer.

[glenn bradley]

Rolled Zinsser BIN, no problem, nice and white. Topped with cheap white semi gloss.

[Frank Pratt]

Rolled Zinsser BIN, no problem, nice and white. Topped with cheap white semi gloss.

The one problem I did have with the paint was that where I'd used latex caulk to seal up gaps, the paint went kinda sticky, so those areas had dust & dirt stick to them. I went over them with Bin & then semigloss & problem gone. It's good stuff.

I attribute the problem with the caulk to the crappy Behr paint (it's never happened with other brands) I used. That was the last straw for Behr & I'll never use it again. Terrible paint.

[Perry Hilbert Jr]

Just curious, why OSB for a shop wall. We can't use it around here if exposed to high humidity. It swells lengthwise, buckles and looks "flakey" If a house with OSB is left empty for a year, the siding starts to look wavy.

[Frank Pratt]

Just curious, why OSB for a shop wall. We can't use it around here if exposed to high humidity. It swells lengthwise, buckles and looks "flakey" If a house with OSB is left empty for a year, the siding starts to look wavy.

It's inexpensive, strong and holds screws well. Summertime humidity isn't usually above 40%, except for short term weather events. Sometimes my shop gets quite humid in the winter from snow melt off the cars & there has been no effect on the OSB on the walls & ceiling.

[Jim Becker]

Just curious, why OSB for a shop wall. We can't use it around here if exposed to high humidity. It swells lengthwise, buckles and looks "flakey" If a house with OSB is left empty for a year, the siding starts to look wavy.

It's not exposed to "high moisture" on the inside of the shop...unless there is a leak. ;) Regular humidity isn't the issue, for the most part. Personally, I don't like the stuff, but the price is right for many folks.

[Izzy Camire]

https://www.sherwin-williams.com/painting-contractors/products/problock-interior-oilbased-primer
Thanks for all the replies. It seems like there is some leeway it what can be used. The above link was a primer someone local recommended. Sorry about it being above I did not have control on that. I do have a sprayer an have used it a lot so I can go with that. It seems like oil primer will not raise the wood chips so I will probably go with an oil based primer and the a latex paint.

[Izzy Camire]

Just curious, why OSB for a shop wall. We can't use it around here if exposed to high humidity. It swells lengthwise, buckles and looks "flakey" If a house with OSB is left empty for a year, the siding starts to look wavy.

What Jim mentioned about low humidity in the shop is correct. In addition I put this up by myself and I figured the weight of it was considerably less than sheet rock. At this point it has been up 4 years with no problems. I want to paint it so it looks better and I figure a painted wall will be better for reflecting light.

[Prashun Patel]

I've used both Zinsser BIN and KILZ on OSB. Both work flawlessly. The KILZ in my shop was used as the primer AND top coat. I think I used 2 coats. It has held up very well.

The only downside of KILZ is that it smells for a few weeks after. The BIN is great, but cleanup is a little bit of a pain because it's shellac-based.

[Perry Hilbert Jr]

Around here, the outside humidity in the 85 to 100 percent level is frequently normal even in the middle of the day. and when shops are only heated when used, the condensation gets into the walls. Vapor barrier insulation does little to keep out the ambient humidity in the unheated air. Even shop tools develop fine coatings of rust, unless treated with wax or oil regularly. I run a dehumidifier constantly and the humidity still runs about 70% inside the shop on warm humid days. The lowest humidity reading I have had in the shop, EVER, was 45% . Sometimes I envy the folks out west.

[Tom Bender]

I used a few sheets of OSB to build storage cabinets and wanted them to look better. Filled the OSB with a few coats of paint and they still look good after 30 years in the garage. Got the paint free by asking friends if they had any old paint to get rid of. Got plenty.

[Izzy Camire]

Well I bought Kilz original and started putting it on today. Wow this stuff is really disappearing into the OSB. I figure I will not get much more than 220 sq ft per gallon on coverage.
Very nice to see the change and white instead of the OSB.