Reader BRAD in SEATTLE writes:
“My 30×48 pole building is about 25 years old, and the roof looks in need of paint. Some small scratches and corroded patches near the gutter rail. I have pressure washed with pretreating bleach solution. That removed the green pollen/algae patches around the roof. I live in the Seattle area. I wonder about a recommended paint for the roof ( oil based rust-o-leum ?).“
Given the age of Brad’s building, it is very possible the original painted steel was a polyester finish: https://www.hansenpolebuildings.com/2014/05/polyester-paint/.
Think of your steel roof as if it is a car – use a high quality automotive paint. Here is an earlier article I penned in regards primarily to proper preparation of the steel for repainting: https://www.hansenpolebuildings.com/2013/01/repainting-steel/.
Here are a few words about the paint itself:
A great paint job can make an even average post frame building look special, and professional car paint is what you need to achieve the best results. Regardless of the budget for your building’s paint job, pro car paint products can make the work go faster and offer a much more durable finish to your pole barn’s exterior. Professional quality paints come in all prices ranges, and the best car paint to use will usually depend on the application and how much you are willing to spend.
Although economy auto paint is designed to be exactly what the name implies—cheap paint—professional car painters have learned some brands hold up better for inexpensive jobs than others. Just because a brand of paint is inexpensive does not mean you should not expect the paint to cover well, create a decent base for clear coats or glosses and last for at least a few years. The key word here being “few”. If you are going to go through the efforts of all of the prep work done right, I would not recommend going with economy.
When doing even a cheap paint job, try to avoid Chinese made car paints. They don’t hold up well at all, and are famous for chipping or peeling within a year or two. Instead, seek out economy paint brands like Sherwin Williams or Starfire.
If painting your building yourself, consider brands like Trinity 1945, known for good quality, yet low cost, automotive paints. For economy paints look to spend $40 to $80 per gallon.
It is no great surprise to find a high quality paint job requires better quality paint. There are several brands that stand out among the others.
Companies like Diamont, Duramix, Kuston Shop and PPG all produce high quality paints which are used in pro painting shops all over the country. Generally speaking, all of these brands are excellent and can be used successfully in a number of different applications and with various types of automotive paint spray guns. While cheap car paints are sold by the gallon, better ones are usually sold in pint or quart sizes. For high quality paints like these, expect to pay $30 to $100 per quart.
If you are looking for a truly outrageous or unique paint job for your post frame building, you want paints which are used for custom or very high end paint applications. While DuPont and PPG also offers some paints which fall into this category, you may want paints designed specifically for specialty jobs.
Brands like House of Kolor, SEM Color Horizons and Auto Air Colors allow painters to be creative with specialty finishes designed to provide showroom quality paint jobs. These brands can run as high $500 to $600 per quart.
In my humble opinion, given the labor, efforts and cost of great paint, I would replace the steel before I would repaint.