FLAT ROOFS: CONSTRUCTION, MATERIALS AND BENEFITS, AND COOL ROOFS
Water collecting on a roof is usually related to slope. A roof that has a slope of less than 3 inches per foot is considered flat. A totally flat roof would never drain and water would exert extreme weight pressure. Any roof must have some slope, or pitch, to allow water to run off. The minimum slope for water to run off is 1% or 1/8″ per 1′. Slope is determined by the vertical rise in inches for every horizontal twelve inch length called the “run”.
A 7/12 roof means that for every 12 inches horizontally (the run), the roof rises 7 inches. Some common roof slopes (rise and run) and the terms which classify them, include:
Flat Roof: 2/12
Low Slope: 2/12-4/12
Conventional Slope Roof: 4/12-9/12
Steep Slope: 9/12 and higher
FOUR BASIC TYPES OF FLAT ROOF SYSTEMS AND THEIR RELATED MATERIALS & BENEFITS
Flat roofing is an economical choice from a building perspective, although they can be trouble when it comes to water leakage and accumulation. In order to preserve flat roofs and the buildings beneath them, they must be covered with a good waterproof material and have a good drainage system. Below are some of the most popular flat roofing systems and a few benefits and drawbacks of each.
BUILT UP ROOFING – BUR ASPHALT
Asphalt degradation occurs when UV-rays oxidize the surface of the asphalt producing a chalk-like residue. Also, plasticizers leach out of the asphalt and the roof becomes brittle, causing cracking and alligatoring. This allows water to penetrate-causing blisters, cracks, and leaks.
Regular maintenance is required to ensure that a BUR roofing system attains its life expectancy. Improving the reflectivity of the existing base of a BUR system is important. Even though they are the most durable roof systems available, it is possible to extend their life cycles even further with coatings.
TORCH APPLIED MODIFIED BITUMEN
In most parts of the United States, APP-modified-bitumen systems are heat-applied, as opposed to hot asphalt or adhesive applications. Built-up roofing is more commonly found on commercial buildings than on residential homes, but it’s still well suited for houses with flat roofs.
Modified bitumen is most commonly available as a smooth-surface material, although granule surfaces are available. While built-up roofing is the most economical choice for flat roofing, sunlight will eventually break down the asphalt base and the roof will need to be replaced sooner than other options.
Elastomeric coatings can smooth cap sheets to turn their black surfaces white thereby extending roof-system’s life. The coating also lowers energy costs. Both elastomeric Acrylic and Silicone coatings provide a cool, bright white, protective seal. They maintain their bright white surfaces for long-term performance.
Single-ply roofing works well for any type of flat roof and single ply is much more secure than tar or spray-on materials.
Single ply is generally categorized as either:
Thermoplastic (TPO) and PVC), or Thermoset (EDPM). The benefit of thermoplastic is that it can be heated repeatedly without damage. This allows the seams to be welded together forming a solid line of roofing which prevents leaking between the pieces.
TPO membranes combine the properties of EPDM and PVC. In other words, TPO is supposed to be as UV-and heat-resistant as EPDM, and is as heat-weldable as PVC.
TPO is specifically formulated for long term weather resistance, without the use of plasticizers which have a poor performance record.
TPO roofing membranes are more expensive than EPDM. Installation of a TPO roofing membrane is a more complex process requiring specialized knowledge.
An EPDM rubber roof is easier and faster to install than a TPO.
EPDM requires no special installation equipment, but TPO needs to be hot air welded. While a beginner roofing contractor will most likely be able to properly install an EPDM membrane, you should only hire an experienced contractor to install a TPO roof. Improper installation will invariably cause leaks and will require costly repairs or replacement. It is better to spend more money and invest in a thicker membrane. Both EPDM and TPO roofs perform better and last longer if they are thicker.
Even so, EDPM seams come apart over time. Longevity of a single-ply roofing membrane depends on the method by which the overlapping seams are attached together. Permanently attached seams are the safest solution; improper attachment can be the cause of 99% of leaks.
As seen below, two of the hardest flat roof systems to tell apart are the PVC roof (left) and the TPO roof (right).
Both are white, heat welded systems that look virtually identical, but TPO is one of the most popular commercial roofing materials and costs less than PVC.
RESTORATION/RE-COAT WITH ELASTOMERIC COATINGS
An elastomeric coating is, “a product designed to elongate or expand and contract to its original state.”
There are 2 types, Silicone or Acrylic. With either System the roof does not require complete tear-off and, for this reason, both are less expensive because the coatings are not as labor intensive as tearing off a roof. Both systems also provide a seamless, weather-tight seal over the existing Cap Sheet, Modified Bitumen System. Considered Roof Maintenance, the Restoration/Re-coat is considered a repair- Acrylic lasts for 10 years and Silicone lasts for 20 years- but they are both first year, one time tax write offs. In comparison, a Tear off, Re-roof is capitalized over 27.5 years for apartment buildings.
Three major differences between Silicone and Acrylic:
1. Silicone is a low volatile organic compound product (VOCS), Acrylic is not.
2. Silicone maintains its integrity despite standing water because, unlike Acrylic, it is not water based. As a result, Silicone is recommended and warrantied for roofs with ponding. An Acrylic system is not warrantied for ponding water.
3. Silicone lasts twice as long as Acrylic:
SILICONE WARRANTY: 20 YEARS MATERIALS 20 YEARS LABOR
ACRYLIC WARRANTY: 10 YEARS MATERIALS 10 YEARS LABOR
* Silicone is 100% waterproof. You can use it to line the bottom of a swimming pool.
* It withstands ponding water.
* It eliminates the need for a complete tear-off with the related cost of plywood replacement.
* Seals and repairs the existing roof and permanently protects against leaks, ponding water, and weather, and has excellent resistance to mold, mildew and staining.
* It will not require a re-coat for 20 years and has limited dirt pickup.
* It won’t break down over time; the product applied today won’t reduce or wear away tomorrow.
* Do it once and you’re done!
We highly recommend the Silicone Restoration Re-coat, as it is an excellent Roofing System for so many reasons!
If restoration is completed now, you will extend your roof’s life for 20 years. Plus, you can re-coat again in 20 years. As protection from the elements, the coating indefinitely prevents the roof from requiring the more expensive tear-off, re-roof. A tear off and re-roof is subject to greater costs due to the chance of requiring more rotted, roof deck wood replacement. With Silicone, only suspect areas require rotted wood replacement. Plus, a permit is not required because it is considered a repair, so there are no Permit Application fees.
Both the Silicone and Acrylic Roofing Systems are Title 24, Cool Roofs as are most of the Roof Systems that Edge Roofing Installs, including our Torch Applied Modified Bitumen, Single Ply TPO, and Shingles. A Cool Roof reflects the heat away from the building and lowers energy costs. The Title 24, California Building Energy Efficiency Standard for a cool roof is described as an Aged/ 3 Year Solar Reflective Index (SRI) equal to or greater than 75. The Voluntary CALGreen Tier 2 Aged SRI is 78. According to the Climate Resolve press release, cool roofs, can be more than 50°F cooler on the surface of the roof during a hot summer day and can cool the interiors of buildings by several degrees Fahrenheit, reducing chances of heat-related injuries or deaths. Keeping temperatures down on Extreme Heat Days saves on air conditioning costs and protects lives; energy efficiency will save millions of dollars; and cool roofs will help Los Angeles combat global climate change at the local level. Title 24 Roof, Cool Roof systems are requisite on LA City buildings.
COOL ROOF RATING COUNCIL AND LOS ANGELES DEPARTMENT OF WATER AND POWER REBATE:
Our complete line of Title 24, Cool Roof Systems are all approved by the Cool Roof Rating Council. Without their approved 3 year, Aged Solar Reflectivity Index (Aged SRI) product rating, the material is not a Cool Roof product.
Because Our Cool Roof Systems are approved by the Cool Roof Rating Council, Multifamily Apartment buildings that receive power service from the Los Angeles Department of Water and Power (LADWP) qualify for their Cool Roof Rebate. Edge Roofing extends its services to include completion of the LADWP Rebate.
LADWP returns between $0.20 to $0.30 per Square Foot.
Edge Roofing is a Manufacturer Approved Applicator of the Best Cool Roof Systems and We Save You Money!