Trying to decide on a new roof? Are you overwhelmed by the options available? This brief overview of roof systems will help.
Flat Roofs
So called flat roofs are typically not actually flat. The technical term is Low Slope Roofing. Slope is how the steepness of a roof is measured. The rise in inches over the length of one foot is used for Low Slope Roofing. A typical “flat” roof will have ¼” slope, the roof surface will rise by ¼” for every foot you travel away from the drainage point.
There are many types of Low Slope Roofing and slope can be anywhere from 1/16” in 1 ft up to ½” in 1 ft. Dead flat roofs do exist, but modern building code requires minimum ¼” in 1 ft slope.
Low Slope Roofing can be put in two categories. Asphalt Roofing and Single Ply Roofing.
Single Ply roofing is the most common and consists of a single layer of waterproofing membrane, typically over insulation. There are three main membranes used, EPDM (rubber), TPO, and PVC.
Single Ply Roofing
EPDM Roofing
EPDM has been around for a long time and is commonly called rubber roofing. It has a long history and proven track record.
EPDM typically is black in color, although white is available. Black roofs offer superior energy performance where buildings cost more to heat than to cool. The black membrane holds heat in the winter and can reduce heating costs.
EPDM roofs use glues and tapes at the seams and where pieces of membrane overlay the main membrane at corners and edges, and this technology has advanced very far in the last 30 years. A rubber roof is very reliable, easy to repair, and easy to maintain.
However, EPDM gets less flexible as it ages and the membrane will shrink. This can cause issues that need to be repaired.
EPDM is moderately priced, and many different options are available within the category to meet most needs.
TPO Roofing
TPO is a type of heat welded membrane. Heat welded membranes use hot air to melt the surfaces together and form a weld. It became popular in the US over the late 90s to late 2000s and now has the largest share of the low slope roofing market.
Typically, white, grey, or tan in color and some special colors are sometimes available. White TPO membranes can reduce energy costs in areas where cooling cost exceeds heating cost. The white membrane reflects heat and light and stays cool.
TPO is primarily heat welded either by hand or using a robot. There are also tapes that can be used for certain details, although they have only been available for 10 years or less.
TPO can be prone to cold welds when installed, even with skilled installers. A cold weld is when the membrane appears to have welded, but it has not welded properly and can come apart later. TPO can also be prone to algae growth and needs to be cleaned periodically to maximize the benefits of the reflective roof.
As the roof ages the membrane can be prone to deterioration from chalking of the top layer of the membrane. Chalking is when the membrane deteriorates into fine chalk like dust which is from the wearing away of the surface.
TPO is the least expensive type of low slope roofing and is common on all sizes of buildings and types of businesses.
PVC Roofing
PVC is also a type of heat welded membrane. It is one of the oldest types of single ply roofing and quality PVC is known for having excellent performance.
PVC also typically comes in white, grey, or tan. White is the most common.
PVC excels at chemical resistance and is the most common choice of roofing for restaurants and many industrial applications. Grease will destroy almost all other kinds of roofing, but PVC is not damaged. Some types of PVC can also be installed on dead flat roofs.
Unfortunately, PVC will become more brittle as it ages and can crack or split. Cleaning can be needed to maintain the reflective properties. Algae growth is also common.
PVC is more expensive than EPDM or TPO. There are also many different options within this category and different types of PVC with varying performance are available.
Asphalt Roofing
Built Up Roofing
Built Up Roofing, or BUR, consists of multiple layers of felt mopped with hot asphalt and then flood coated with asphalt and either gravel or aluminum coating. Roofing felts are not waterproof by themselves and in this system the asphalt provides the waterproofing while the felt provides reinforcement and support. Typically, 3-4 layers of felt are used.
BUR roofing can last anywhere from 25-40 years or even more. Coal Tar Pitch can be used to install this system on dead flat roofs.
BUR roofs with aluminum coating are required to be re-coated every 5-7 years or the lifespan will be impacted.
BUR has many restoration options to extend the life of the roof, however, they can be expensive to repair, depending on your roof and the type of repair needed.
Though more expensive than most single-ply roof options, BUR roofs are very durable and difficult to damage.
SBS Modified Roofing
SBS is an asphalt membrane with rubberizer added for flexibility. Unlike felt membranes, which are not waterproof by themselves, SBS membranes are waterproof. They are typically applied with hot asphalt, torch applied, or cold adhesive applied. Typical SBS roofs consist of a base (bottom) ply and a cap (top) ply.
SBS roofing is very durable, lasting from 15-40 years depending on maintenance and manufacturer.
Consisting of multiple waterproof layers, to prevent moisture from penetrating the system, SBS roofs have laps every 3 feet. This means a quality installation is paramount for performance.
More expensive than many other single ply options, SBS roofing has many different restoration/coating options available to extend the system life and improve your ROI.
Steep Roofs
Steep Slope Roofing is when the slope is typically 1:12 or greater. The most common type is asphalt shingles. Metal roofing, slate, tile, and shake are also available options.
Steep Roofs measure Slope by the rise in inches over the length of 12 inches. A typical 4:12 slope roof means the roof rises by 4 inches for every 12 inches you travel from the drainage point.
Shingles
Shingles are the most common type of Steep Roof. Shingles are made of asphalt reinforced with fiberglass and coated with a variety of colors of granules. Shingles come in a variety of types and shapes. The most common are Dimensional Shingles, which get their name from the 3-dimensional appearance they offer which adds depth to the roof.
Shingles do not create a waterproof surface like flat roofs, they shed water onto a subsequent layer of shingles until the water leaves the roof. With a wide range in pricing, shingles average a lifespan of 15-40 years, depending on manufacturer, climate, and environment.
Shingles installed on less than 4:12 slope need full Ice & Water Shield underlayment instead of felt, and shingles should not be installed at all on roofs less than 2:12.
Slate, Tile, and Shake
These types of Steep Roofs also work the same way as Shingles. They shed water onto subsequent layers.
Slate Roofs can last 80-120 Years or more. This is a type of stone that is quarried and comes in a variety of colors and is usually installed in a pattern.
Tile Roofs can last 40-100 Years or more. There are a wide variety of tile roofs including ceramic, concrete, clay, and even composite tiles which contain metal.
Shake Roofs can last 25-35 Years. Shake is typically made from Cedar. Shake requires maintenance every 2-6 years to remove algae and other growth.
All these options are also available in synthetic options instead of using their natural materials. They are also generally more expensive than either shingles or metal roofs.
Slate and Tile roofs last a very long time when installed properly and all these types offer aesthetic options which are unavailable with shingles.
Metal Roofing
Metal is a popular option for Steep Slope Roofs. Metal is available in a wide variety of types and styles and can also vary widely in performance.
Standing Seam metal panels are one of the best types of metal roofing and use clips or batten strips to hold the panels in place without penetrating the roof panels. A Standing Seam metal roof can last anywhere from 20-40 years.
Exposed Fastener Lap Seam Panels are common on barns, sheds, canopies, and warehouses. This is an inexpensive panel which fastens with screws through the panels. These panels typically last from 15-25 years.
Metal Shingles are also available in a wide variety of styles.
If you prefer painted metal panels, you can anticipate the paint will last 20-30 years on a quality metal panel.
For more information about roofing system options, or to schedule your consultation with our roofing experts, please call A.H. Sturgill Roofing at 937-254-2955.