About a month ago we built a small 8 foot handicap ramp out of pressure
treated plywood. Didn't treat it with anything. We had a lot of rain.
Noticing a long of cracking going on along the vertical plane.

Also made side barriers using plywood. The porous sides face horizontally.
I'm getting a bit of warping already. Need to seal off the top. I have
some door weather strips I'm going to seal off the openings.

Found a can of Minwax Indoor/Outdoor Helmsman Spar Urethane in the cellar.
I was thinking of spraying it over all the surfaces. Probably give it a few
coats. Would this be the way to go or should I apply something else and/or
use a brush?