Paint after applying primer to rooftop?

Question

I recently pressure-washed my entire rooftop, and now it's plain porous concrete. I want to add something that will be soaked by the concrete and reduce (or eliminate) any leaking.

After doing some research, I decided to double-coat the rooftop with color primer because, supposedly, it's very liquid and will soak into the concrete. I'm the only one that uses the rooftop, so it doesn't have to look beautiful, but the concrete needs to soak whatever I apply to it. Also, it can't be white because it'll burn my eyes.

So my question is: do I need to apply exterior paint after applying the primer? I've read that primer turns whitish, but a few people have told me that they've used primer and that's it.

The reason I ask is that a decent 5-gallon tub of primer is over $100 + tax, and I need two tubs. That's $200 + labor (about $150). Easily, it'll be over $350. Decent exterior paint is easily $100+ per 5-gallon tub, so that's $200 more + labor. I can't do it because I work all 7 days.

Regarding the conditions, I live in the Caribbean and my rooftop gets very strong sun. If there's no extreme sun, then it will rain.

Any help is appreciated.

Answer 1

I don't know what kind of paint or primer will work best. But a key in a hot sunny area, like the Caribbean, is to use white paint. That is because in addition to protecting the concrete, you want to reflect as much sunlight away from the roof (and from heating the building underneath) as possible. And it just so happens that primer is, by default, white, which may be why plenty of people recommend primer.

In general (e.g., indoor walls) usage, primer effectively hides the different colors, patches, etc. of a wall so that you can put on color paint and get consistent quality results. That doesn't matter much on your roof. However, your roof doesn't benefit at all from the cosmetic qualities of paint, only protection from sunlight and water, so primer may indeed be the best choice. But whatever you get, make sure it is specifically designed (or compatible with) concrete. The stuff you throw on drywall will look OK at first, but I doubt it will last very long.