What is the best material for a flat roof?

flat roof with black material

Choosing your flat roof material

Most commercial structures are a flat roof building, but why? Why would an owner choose a flat roof vs pitched roof for a commercial structure? The first reason is the cost of construction. A flat roof is less expensive in the construction phase and afterward, they are easier to maintain, which makes them less expensive. 

A flat roof gives the builder more space both inside and out too, so they can give the owner more efficient space. There are more flat roof benefits to be had by the owner or occupants too. 

How long does a flat roof last?

There are several factors that can determine the lifespan of a commercial structure’s flat roof, but on the average, we give them a lifespan from 10 years up to 50 years. The climate and environment, the type of membrane applied, and the maintenance and upkeep can affect their life expectancy. 

  • TPO flat roof system life expectancy – 22 to 30 years
  • EPDM flat roof system life expectancy – 22 to 35 years
  • Metal flat roof system life expectancy – 30 to 45 years
  • Asphalt flat roof system life expectancy – 20 to 40 years

What causes flat roof leaks?   

As we mentioned earlier, builders and owners find a few advantages with a flat roof on a commercial structure. They are less expensive to install; they are less expensive to maintain, and they are easier for contract workers to access and service, like electricians, plumbers, and make it easier for commercial HVAC service technicians to install and repair HVAC units.  

Like any roof though, a flat roof can have problems too, like leaks and it can be just as difficult to determine where and why a flat roof is leaking, a primary concern. Four of the most common causes of a flat roof leak.

  • Improper Drainage: Improper drainage is a common cause, perhaps the most common of all reasons. Because it is a flat roof, when snow melts or rain collects on a flat roof, the drainage system is the only way for that water to shed.   
  • Flashing and Membrane: The best method to keep a flat roof from flashing is proper and timely roof maintenance. Regular inspections allow the opportunity to detect early signs of problems with the flashing and membrane.   
  • Age: Regardless of how strict you are with inspection and maintenance, a flat roof will age, making it more susceptible to spring leaks. There are factors that play into how long a flat roof will last, such as climate and environment conditions and the quality and type of membrane installed on the roof.      

Do flat roofs leak more?

This is a misconception that has been handed down from generation to generation. A flat roof that was properly installed, has had regular inspections, maintenance kept up as needed, and the flashing kept in good condition, a flat roof won’t leak any more than a sloped roof.

How do you waterproof a flat roof?

Common sense tells us that a flat roof won’t shed water like a sloped roof, but this is a problem that has a solution. A roofing contractor with experience in flat roofing can provide an analogy of the roof and offer the best method to waterproof it. For the convenience of the building owner or maintenance crew reading this, here we offer the steps it takes to waterproof a flat roof. 

Step One

Take the measurement of every surface of the flat roof. To get the total square footage, measure the length by width in feet then multiply the total length by total width. Your local big box or hardware store can assist you in determining how much coating you’ll need. 

Step Two

Clean the roof with a broom or pressure washer, making sure all the dirt, debris, and dust is removed. For a heavily dirty roof, mix 1 quart of trisodium phosphate with five gallons of water, and use a push broom to clean the surface. The roof must be dry before the coating can be applied. 

Step Three

Pour one gallon of the elastomeric coating onto the roof and spread with a paint roller, starting in one corner and working around the roof as you walk backward. Avoid stepping on the coating you’ve applied. Repeat the process until you have covered the entire roof, allowing 24 hours between coats. 

seamed black flat roof overlooking town

How often should a flat roof be coated?

Every type of roof should have regular inspection and maintenance, and a flat roof isn’t any different. Flat roof maintenance is typically applying a coating on it, which should be done every 5 years. This process will save money going forward because it will need fewer repairs and keep the roof sealed from leaking. A flat roof offers the owner, occupants and maintenance team several benefits:

  1. Construction is cost less expensive
  2. Easier and faster to install
  3. Access and maintenance are easier

Want to learn more about flat roof systems in Chesterfield and St. Louis, MO? Dial (314) 786-3732 to speak with the professionals here at ProCraft Exteriors!