How to Coat Your Flat Roof (and Why You Should)

How to Coat Your Flat Roof (and Why You Should)
Photo: jorgeflorez, Shutterstock

The need for roofs is universal. No matter where or how you live, having a roof over your head is vital to protect you from the elements and give you a secure home. If you own your roof–or, rather, the home it’s attached to — you know it can be a source of anxiety in spite of its necessity. If you’ve ever woken up in the middle of the night to the drip-drip sound of a leak, you know the sheer terror an ageing roof can strike into the hearts of men.

Many homeowners make the mistake of treating their roofs as something they only need to worry about when they leak. Your typical flat roof will last anywhere from 15 to 30 years depending on the materials used, the climate conditions it has to endure, and how much maintenance you perform. With proper maintenance, a flat roof can even last as long as 50 years. If you want your roof to last as long as possible — reducing your expenses and anxiety — there’s one pretty simple thing you should consider: Coating it.

Why coat your roof?

Your roof takes a lot of punishment. It bakes in the sun, soaks in the rain, and freezes in the snow. No matter what material your flat roof is made from, it will eventually begin to suffer from these extremes. You’ll start to see ponding (or areas where water doesn’t drain off properly), cracks, discolorations, and other signs that your roof is ageing. In other words, your roof is sort of like the “skin” of your house: It protects you, but it can be damaged from exposure to the elements.

A roof coating is like sunscreen and moisturizer for your roof. Coating your roof provides a few fundamental benefits:

  • It seals the roof, preventing any invisible water penetration that is eroding your roofing material
  • It bounces solar radiation away, reducing the temperature of your house (and thus reducing your cooling bills)
  • It protects the roofing material from sun damage
  • It extends the lifespan of your roof so you have to replace it less frequently
  • It prevents leaks, so repair costs are lowered

The good news about coating a flat roof is that it’s fairly inexpensive to do. It’s typically a project any reasonably handy person can do on their own depending on the material used in your roofing system. If you can paint, you can probably seal your flat roof DIY-style, but even if you have to hire someone, it’s not a terribly expensive job. When you consider that coating your roof will absolutely extend its lifespan, this investment is very much worth it.

Roof-coating 101

If you’re now fired up to coat your roof and you’re thinking you can do it yourself, your first step is to determine exactly what material your roof is made of. Not all flat roofs are the same, and you’ll want to make sure that you select a coating that is designed for your roof. Old-school built-up roofs (which have a gravel-like top layer) can be more challenging to coat because their top surface isn’t smooth.

Once you know the material you’re coating, identify a coating product that is compatible. This should be pretty easy to figure out from the label or the web listing. If you’re doing this yourself, look for a coating that can be applied using standard painting equipment like brushes and a roller. Check to see if a primer is recommended.

Before you do anything else, you’ll want to clean and inspect your roof. Note: Safety first. Make sure your ladder is sturdy and reaches the roof easily, and consider using a harness to save your butt if you slip and fall. Sweep away all the dirt, and scrape away any accumulated cruft from the corners and seams using a trowel. Check the flashing and look for any cracks, gaps, or other problems and re-flash as needed. Then it’s just a matter of applying the primer and sealant according to the manufacturer’s instructions, and voila — you have just added years to your roof (and it probably looks a lot less janky now, too).

Pro tip: Don’t forget to avoid literally painting yourself into a corner on your roof. No one will ever let you live it down.

If you want to sleep easy during the next torrential rainstorm, coating your roof will go a long way toward dispelling leak-related anxiety.

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