I am putting a utility room in my pole barn.
In it will be the breaker panel, water heater, urinal, frost proof hydrant that serves as shut off valve for the building and a big 80 gallon air compressor.
1/2" OSB on the exterior and interior walls.
Exterior walls will have rusted barn metal wainscot, barn wood on it with a sliding barn door.
Put one coat of Sherwin-Williams Extreme Block oil based primer on the interior a couple days ago, caulked the seams yesterday with DAP Alex Plus caulk. I'm going to let that cure a couple days then I am going to give it another coat of primer and then paint the walls and ceiling with haze gray latex.
I used a 1/2" nap roller for the first coat of primer which I now realize was a mistake. I have 1 1/4" rollers for the next coat of primer.

