(Sorry, I accidentally submitted before I wrote my post!)

I'm rehabbing an old horse trailer (30-y.o. Arndt 2H BP)... I'm on a budget, not looking to restore this thing to showroom status, but I'd like to get a few years out of it and hopefully sell it for what I'll have in it.

I'm working on painting it right now; so far I've sanded and OSPHO'ed the rust inside and out, and I'm priming/painting the inside with Tractor & Implement Paint from TSC (light grey). My plan for the outside was to paint the outside using the same brand of paint-- white for the roof, and light grey for the rest of the outside.

However, I was doing a bit of shopping and stumbled upon elastomeric roof coating, which seems to be popular for RV's. It's supposed to be really good for keeping things cool... Would this be an advantage over regular white tractor paint for the roof? Seems like it would last longer, bsince it appears to be a bit more flexible than regular paint...

Elastomeric coatings are commonly used on metal roofs that have leaking problems. They are a rubberised product that coats easily and can provide protection for up to a decade depending upon the manufacturer. The white colours add reflectivity which lowers the roof temperatures. They seal well and can be recoated without removing the base coats. They do feature a flexible elongation property, which is an advantage if the roof's surface constantly expands and contracts, such as with an aluminum sheathing. It also does well caulking where vents and utilities commonly penetrate the roof's surface.

The oil based TSC paint you are using is a pretty decent product, especially for the price. When used over a good epoxy primer and mixed with the optional hardner, it provides a durable and colour fast surface. By using the white colour on the roof, you would experience the same or better temperature reductions as the Elastomeric products, at a lower cost. Like any applied product, it is only as good as the properly prepared surface upon which it's employed.

If your trailer's roof is welded steel, doesn't have any rust holes or open seams, I would go with the paint; at least two coats. The Elastomeric coating should also be a minimum of two coats, more if you are using it as a caulking. If there are small rust holes, poor seams or any places where you can see daylight, the Elastomeric products would serve you well.