Flat Roofing vs Sloped Roofing

Flat roofing falls flat when it comes to giving your home or commercial building the protection, insulation, and stability it needs. Why do some homes and buildings have flat roofs? The answer mostly comes down to location. Many buildings in the Philadelphia area have flat roofs that are in desperate need of replacement. Most are found on city homes and buildings built between 1900 and 1950. By contrast, almost everyone who lives in a suburban neighborhood has a sloped or pitched roof with shingles and sheathing that are guaranteed to keep homes protected from snow, rain, and the elements for 20 to 30 years. As a result, new roofing is one of the most important Philadelphia home improvements you can make.

The flat roofs that pepper the skyline within city limits have very little pitch or slope. This becomes a big problem when it comes to drainage. In fact, owners of these homes and commercial buildings can usually attest to the fact that their roofs are constant sources of stress because they create moisture nightmares that allow for leaks, mold, rot, and structural damage. The history of these flat roofs is interesting. Traditionally, rolls of fiberglass were installed over older layers of roof coverings using hot asphalt to create new membranes. As stated above, flat roofs create nightmares for drainage. One only has to picture a flat roof versus sloped roofs to understand that water doesn’t have any momentum after rain showers. That water is left to sit instead of simply rolling down into the gutters the way that water does on a traditional sloped roof.

The drainage issue with flat roofs is the reason why the warranties on these roofs max out at eight to 10 years. In addition, these roofs actually need to be coated with fresh layers of asphalt every three years in order to keep warranties valid. The shingles simply cannot withstand the constant exposure to standing, stagnant water without careful vigilance and maintenance on the part of the owner.

Not all homeowners replace their flat roofs after a warranty expires. Many structures throughout the Philadelphia area have flat roofs that are 30, 40, or 50 years old. Many of these roofs are in need of major repairs and replacements. You can imagine the state of a roof that has been covered with new layers of asphalt over and over again throughout the years. As each layer is added, the durability of the roof is substantially reduced. The method of applying layer over layer is very different from the replacement method for pitched roofs.

Generally, a contractor will recommend full removal of an existing roof when replacing a traditional sloped roof. Applying a new roof over an existing roof is typically discouraged by contractors. A fresh start offers several benefits. First, the new roof is simply more stable because it’s being applied as a first layer. It is like truly starting from scratch with a new roof. In addition, homeowners are able to upgrade to the latest roofing technology when they replace their roofs. This offers incredible benefits for both aesthetic value and energy efficiency. Many new roofs also offer warranties beyond 40 years. Getting a fresh start without leaving behind any rotting, deteriorating materials from the original roof is a preferred way to handle a new roof installation in Philadelphia.

The technique of simply adding on new layers to a flat roof stands in direct contrast to all of the benefits gained when doing a fresh replacement of a sloped roof. There’s a simple visual that makes it easy to understand why flat roofs give property owners so many problems. Picture a classic Styrofoam cup filled with hot coffee. Let’s say that you notice a hole on the side of the cup that’s allowing coffee to trickle out. You add a little duct tape over the hole. It does a good job of preventing the leak long enough for you to finish your cup of coffee. However, you decide that you’re going to keep the cup instead of throwing it out. You refill it with hot coffee several times. The hole eventually begins to widen as the duct tape loses its stickiness and grip. You continue to add new layers of duct tape over the first layer of duct tape every time the cup becomes more unstable. How many pieces of duct tape over the Styrofoam cup would it take for you to start to wonder if you’d be better off simply getting a new cup? The experience is very similar with a flat roof.

Common Problems for Flat Roofs in Philadelphia

What if your home in the Philadelphia area currently has flat roofing? It’s impossible to say that your roof needs replacement without conducting an in-person inspection. However, it is important to know about the common problems with flat roofs.


Leaking is the most common problem with flat roofs. In fact, there’s a good chance that your flat roof has some sort of leaking issue unless you have a completely level roof with a modern drainage system in place. Any rainwater or runoff that’s permitted to pool inside any of the divots or crevices in the roof is sure to cause degradation of the roof. If left unchecked, leaks will eventually cause damage to the framing and foundation of a home or building.


While Philadelphia isn’t alligator country, the city is peppered with scaly roofs that are reminiscent of these reptiles. Alligatoring refers to the appearance of cracking and bubbling on the surface of roofs. Also known as blistering, this problem is caused by moisture that’s trapped beneath the surface of a flat roof. This trapped moisture eventually causes the membrane of a roof to detach from the layer under it to form deep cracks and crinkles. This is very common in flat roofs because the asphalt layers used to build up flat roofs lose their elasticity over time. When left untreated, alligatoring causes extreme splits in the membrane that can ultimately cause serious leaking.


Not all cracking in a flat roof is caused by the alligatoring effect. In many cases, the pressure caused by the design of a flat roof simply leads to cracks in the roof. Sloped roofs don’t have this problem because the sloping design does a better job of distributing pressure compared to the design of a flat roof. If a flat roof cracks, it’s important to have the situation looked at by a professional immediately because the integrity of your roof is in jeopardy.

Compromised Flashing

Flashing refers to the metal strips that are applied at all points where a flat roof meets another surface. Flashing is essential because it prevents water from entering your property to cause rot. Flashing problems are relatively common with flat roofs due to a mix of pressure and contraction. Asphalt is prone to expanding and contracting when temperatures change from hot to cold. This problem is especially common in the Philadelphia climate because buildings experience wild shifts in temperature throughout the seasons. Over time, it’s common for this constant cycle of expanding and contracting to cause flashing to pull away from the edge of a flat roof. When this happens, leaks and moisture threaten the integrity of a building.

Punctures or Tears

Flat roofs don’t always perform strongly in storms. They tend to be susceptible to punctures and tears caused by everything from high winds to sharp debris. Serious damage can often be avoided by simply having a flat roof inspected after any major storm.


The pooling of water that’s common with flat roofs doesn’t just increase chances for mold and rot. It can also invite vegetation and bacteria. This growth can eat away at roofing. It can also cause health hazards for the people inside the building. Biological growth on a flat roof is something that should be monitored using routine roof inspections.

Repairs and Maintenance for Flat Roofs in Philadelphia

The good news about flat roofs is that they can be repaired or replaced using cutting-edge roofing materials and techniques offered by a local Philadelphia home remodeling service. The first step to getting on track with your flat roof is simply booking an inspection. If small issues are found, roofing experts can use routine maintenance and repairs to get your roof functioning at peak performance once again. Getting on a schedule for routine roof maintenance for your flat roof in Philadelphia may even help you to safely extend the life of your existing roof by several years.

American Home Concepts of Bala Cynwyd, PA is the trusted name for Philadelphia home remodeling. We offer help for failing flat roofs all throughout Philadelphia County. Offering more than 60 years of combined experience, Jonathan Calloway and Richard Schindler founded American Home Concepts out of a passion for helping Philadelphia-area residents preserve, restore, and beautify their homes using the highest standards for quality. We have built a pristine reputation for quality workmanship and proven results for our customers! Work with the best roofers in Philadelphia. Contact American Home Concepts for a quote today!

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