Utilized in both residential and commercial roofing, flat roofs offer both aesthetics (a unique architectural looks and styles) and convenience (a place to install HVAC units, for example). They also come with a bit of a reputation for causing problems, however.
Flat roofs are often more prone to leaks and damage than their sloped counterparts, and as such, both homeowners and commercial building owners tend to look after them with a little more care and caution. That extra care and caution carries over to the choices you’ll need to make when replacing your home’s flat roof.
When installing a flat roof, your main goal is to create a barrier that will be impenetrable to water. Flat roofing, also called low-slope roofing, is not entirely flat – they are slightly angled to allow water and melting snow flow into a downspout. Still, they must be able to handle pooling water, snow and ice.
Flat Roofing Installation: Top 5 Materials, Their Cost, Benefits And Drawbacks
Popular options include felt and bitumen, built-up roofing, single-ply PVC roofing, and EPDM roofing, but which of these is best? What are their advantages and disadvantages? How much do they cost? Below is an overview of most popular flat roofing materials.
Single-ply PVC membrane roofing is one of the most popular flat roofing material. This option is made up of a PVC membrane base, which are sealed together to form a watertight barrier that is practically maintenance-free once it’s installed. PVC membrane roofing are especially strong and durable, and energy efficient (especially white-colored ones), as they reflect heat away during the summer and help keep it inside during the winter. PVC roofing often comes with lifetime warranty.
The down side? PVC membrane roofing is one of the costlier options, though it does provide excellent long-term value.
Cost of Installation: $7.00 to $10.00 per square foot.
Lifespan: 20 to 30 years.
Ethylene propylene diene terpolymer (EPDM) roofing is another option. These rubber roofs are highly durable, lightweight, and energy efficient. Since it forms an insulation barrier, EPDM rubber helps prevent heat transfer, keeping your home cooler during the summer and warmer during the winter. They are low-maintenance and resistant to wind, hail, fire and ozone damage.
EPDM roofing is easy to install, which can be done in one of three ways: it can be attached mechanically, installed fully adhered, or ballasted together. The EPDM roofing membranes are sealed off with specially formulated tape adhesives or liquid bonding agents.
EPDM roofing is also less expensive on average than single-ply PVC membrane roofs, but at the same time, their welded seals are not quite as impenetrable. They also don’t trap heat inside your home very well, which can contribute to rising home heating costs during the winter months. EPDM is also more vulnerable to punctures than other choices.
Cost of Installation: $4.00 to $7.00 per square foot.
Lifespan: 15 to 30 years.
Thermoplastic Polyolefin (TPO) Roofing
TPO is a single ply membrane consisting of a polymer base, mesh fabric reinforcing layer, and tough thermoplastic polyolefin top layer. TPO membranes can be adhered, fastened or ballasted. When adhesive is used, the membrane is chemically bonded to either the roof decking or to an insulation layer. Likewise, the membrane can be mechanically attached to either the decking or to an already fastened layer of insulation. In a ballasted installation, the membrane is laid down and then covered with a layer of river rock or pavers to hold it down.
Like other roofing membrane systems, TPO is an ideal choice for application on commercial buildings which have expansive roofs with little or no slope, combining the strength of EDPM rubbers with hot-air weldable seams. It’s durable, highly reflective and energy efficient, UV and heat resistant, also resistant to chemicals, dirt, and biological degrading. It’s also recyclable. A properly installed and maintained TPO roof has a lifetime of 10 to 20 years, and most manufacturers offer a full warranty.
On the downside, not all TPO membranes are created equal, and some perform a lot better than others. Longevity varies, so purchasing from a high end supplier is critical. They also don’t stand up to heat well.
Cost of Installation: $6.00 to $8.50 per square foot
Lifespan: 10 to 20 years.
Modified Bitumen Roofing
Modified bitumen roofing is a multi-ply roofing material. The traditional material used to cover a flat roof consists of a felt underlayer, which includes a fiber or paper base that is coated with bitumen. This underlayer is then covered over with a top coat of gravel to protect against weather elements. The main advantage of this option is its low cost; felt-bitumen flat roofing materials are cheap and easy to install.
Torch-down application used in their installation is a fire hazard, however, and not recommended for occupied buildings. These roofs are also prone to damage over the medium term, and most felt-bitumen flat roofs have maximum lifespans of 10 to 15 years. They can also be easily damaged, and often require intermediary repairs.
Cost of Installation: $3.00 to $6.00 per square foot.
Lifespan: 10 to 25 years.
If you’re looking for a comparable option that’s got a lot more durability, built-up roofing (BUR)–also known as tar & gravel roof–is comprised of similar elements. However, BUR is much thicker and more durable than standard felt-bitumen roofing, enabling it to withstand more damage and last longer. Consequently, BUR roofs can withstand heavy foot traffic. Its drawbacks: relative to standard felt-bitumen flat roofing products, BUR is more expensive. It is also a lot heavier, making for a more difficult installation and introducing more weight pressure on your roof, the added weight often requiring reinforcement to the supporting structure.
Cost of Installation: $4.00 to $7.00 per square foot.
Lifespan: 15 to 20 years.
Installation Quality Matters
The advantages of each option should be carefully weighed against their drawbacks, taking factors like local weather and climate patterns into account while considering your budget. Remember that the up-front cost of a flat roof replacement only tells part of the story; the longer your roof lasts, and the more energy it helps you save, the greater the long-term value it will deliver.
This article was provided by Lukasz Sobczuk, the owner of LGC Roofing, a NJ & PA contractor with over 30 years of experience in residential & commercial roofing. Call (609) 712-8157 or (215) 932-7850 for your FREE ESTIMATE!