How long do flat roofs last?

flat white roof

Choosing a flat roof

With all the things involved in owning and managing a commercial building, one of the most important is the flat roofing. It is the building that houses the employees, products, and services. It is the place that clients and vendors come to do business. It is essentially, the crux of the business. 

With this in mind, routine inspection and flat roof maintenance are important. Especially flat roof drain maintenance to make sure that ponding and puddling do not occur. When flat roofing has ponding and puddling, the water can seep into the underlayment and begin diminishing the flat roofing stability. 

What pitch is considered a flat roof?

A pitched roof can have an incline between 12.5 degrees and 85 degrees. A flat roof is defined between 1 degree and 10 degrees on the average and cam be pitched at 12.5 degrees. 

Flat roofing products consisting of two layer bitumen felt roofing system  can be used on an inclined/pitched roof application with proper application and installation is implemented. With a pitched roof, only roofing products specified for pitched roofing with a minimum pitch as designed. 

How many layers should a flat roof have?

Every flat roofing can be unique, depending on the existing material. A layer of EPDM or TPO installed over existing flat roofing coating are common with both be a durable material. How many coats of either the EDPM or TPO will depend on how many of layers of the existing flat roofing coating. 

Depending on local building codes and the stability of the structure, a professional commercial roofing contractor may recommend that the old layer should be torn off prior to installing the new flat roofing coat. Additionally, any noticeable damage of the current flat roofing should be repaired before installing any new flat roof coating. 

If the current flat roofing is in good with solid stability from the base and through the layers, the EPDM or TPO flat roofing can be installed directly on the existing roof.  In the end, the number of flat roofing layers is dependent upon the original layer. It is recommended not to add any more of layers than necessary, as extreme layers can create issues for the foundation of the flat roofing. These issues can include water damage, which can do more damage to the structure itself. 

Do flat roofs always leak?

First, let’s clarify that flat roofing is not 100% flat. There is a slight slope to all “flat roofing” architecture. Second, they do not “always” leak.  However, flat roofing that doesn’t have enough low sloping will have the tendency to leak as it ponds and pools water in low places or the drainage is clogged. 

Another cause for flat roofing to develop a leak is after a hailstorm or windstorm, but if you perform the monthly inspection following a flat roof maintenance checklist as recommended, these leak possibilities won’t happen. Here, we list the most common problems for flat roofing leaks: 


Many commercial flat roofing designs are bad, and this allows areas for standing water to form. Ponding or puddling water causes extra weight in that specific area that will weaken the flat roofing membrane, and the leak begins forming. Ponding water of one foot in size weighs approximately five pounds per square inch. That is a lot of weight in a small area.   


This is due to a bad design and part of why ponding and puddling will form on a flat roofing surface. When the slight slope is too low or not in the right direction of the drainage, or the drainage becomes blocked or clogged, the rain will pond and puddle, and that five pound of water is formed as described above. 


The flat roofing membrane and the flashing are essential on a commercial structure with flat roofing.  If either of these are damaged, loose, or missing, flat roofing will for a leak.  


Every roof has various outlets, pitched or flat roofing. Those outlets can be a source for leaks if they are not sealed properly. The areas your monthly inspection should check that the flashing is in place and secure are: 

  • Drains
  • Gas lines
  • Hot stacks
  • HVAC unit
  • Pipes
  • Vents

Each of these are installed through a hole in the flat roofing membrane. If they are not sealed, flat roofing will leak around them. 


Flat roofing on a building is like many other aspects of that building, at some time, it will become too old to repair and replacement is necessary. Most flat roofing that has been installed properly will last up to 20 years.  With a re-coating, flat roofing lifespan can be extended another 10 years if proper, routine inspections and maintenance are performed.

How often should you seal a flat roof?

If flat roofing shows any indications of leaking, resealing needs to be done immediately, unless the commercial roofing contractor advises it is beyond resealing.  Otherwise, flat roofing should be resealed every 5 years to prevent future water damage and leaking.

How can I make my flat roof more attractive?

Commercial structures can often be work of architectural beauty from the street level However, the actual roof top, behind the façade of architecture style, is typically flat. Not that is a view from the street that you need worry with it being attractive, but from other buildings around that are taller can see the plain flat roofing.

What many commercial and residential building owners with flat roofing styles are doing is creating a rooftop garden. This requires engineering inspection first, simply to make sure the structure can withstand the extra weight a rooftop garden will add, but it can so much for your building and the environment, you may find the ROI is well worth the money and time. 

flat roof

A Few Flat Roof Maintenance Tips

As we have already stated, flat roofing has unique maintenance requirements due to their flat roof design. Monthly inspection and maintenance may have some expense, but with this routine, you’ll be saving a lot of money by minimizing the possibility of bigger issues happening. Our recommendation of maintenance tips are: 

  1. Regular inspections – monthly if possible, every 2 months minimum.
  2. Keep flat roofing decks cleared of debris.
  3. Keep trees trimmed back.
  4. Check the drainage during inspections.
  5. Check for weak areas and spots during inspections.
  6. Fix any damages or leaks immediately.

For all of your roofing needs, Trophy Roofing is here for you. Call 972-439-1145 today!