Quasi Diesel Related (Stretched)
 

Recently purchased an abutting property with an old 3-story P&B barn/shop. I have been renovating it steadily to accomodate storage/repairs/maintenance of my favorite fleet.

The question . . . what can I use to trim around a 3' x 3' area I cut in the fire code sheetrock that encompasses the brick/mortar thimble going through my exterior wall? I need to use something about 2" +/- wide that isn't combustible yet would serve the appearance of molding.

You have
 

the answer sheetrock.
Works great, easy to work, can be painted or use adhesive border paper.
The fire code has some flex, but if you try to trim in wood or plastic, the local inspector may condemn.
Seek out your local inspector, bring pictures, ask advice and follow it, you will pass inspection easy.