Well, I have been trying to avoid this subject for a while but here we go. Flat roofing systems are very controversial because of the malfunctions and debatable performance for long periods of time. There's many flat roofing systems, and of course many buildings and houses here in our Hampton Roads area and around the world that need some type of roofing system to protect it from the elements. Flat roofs exist because of the design from the Architects, demographics, cost efficiency (it saves money by avoiding more building materials such as rafters, decking) etc.
A flat roof system is usually installed in areas that are completely horizontal or have very little slope (pitch) for the water to run off to the gutters or drains. Flat roofs are very common on commercial buildings such as shopping centers, department stores, office buildings, etc. Not just here in the states but all over the world, flat roofing is predominant on commercial buildings and even homes to protect from the elements. The roofing materials used are very different also, because they don't have the extreme weather that we have here in the west. Some flat roofs in warmer climates where rainfall is less and freezing is unlikely to occur are just made of concrete and this method is good enough to protect from the heat of the sun and the ocassional rain.
Here in America, the most predominantly material on flat roofs will have some type of tar or asphalt ingredient, this "Tarpaper" usually paper or fibre soaked in tar is then applied over the roof deck (usually plywood or metal deck) . A tar coating can be applied in form of hot liquid to seal together the joints (this is not a fun job) and then is covered with gravel or river rocks to protect it from the elements such as UV rays, heat from the sun, hail storms, etc. These rocks protect the roofing system from cracking, blistering and degradation. Where there's any parapet wall (vertical) sometimes there's other materials derived from tar and impregnated with a layer of granules or small gravel.
Flat roofs have a reputation for failure, sometimes blamed on the installers who often are uneducated mechanics that can't get a "regular" job and end up in this dangerous and physically demanding job. This together with a lack of maintenance and many times human traffic on the roof causes the roof to leak, sometimes removing the rocks leaving the coating exposed to the sun, causing cracks and deterioration. This is unfortunate given the potencial use for flat areas. Another big reason for flat roofing failure is standing water for long periods of time and the roof chemical ability to not soak thru, anti-fungal properties and a combination of poor drainage and guttering system. Puddling water can freeze into ice which breaks up the roof surface as it expands while is freezes.
Sometimes leaks on flat roofs can be a nightmare to determine the point of entrance, sometimes the leak will go unnoticed for long periods of time and by the time the leak is noticeable there can be very expensive damage on the building, damaged wood, insulation, roof structure, etc. The water leak can travel a long way before causing visible damage, sometimes the only way to find these leaks is tearing off the old roof and installing a brand new one.
Old tar flat roofs quality were as good as their installation and workmanship for its success, climate is a big factor for its longevity as well, many manufactures are switching to more "green" roofs and other types of synthetic membrane to make it more economic and energy efficient for the consumer, the old tar roofs are a thing of the past, most people can't afford them anymore and they are not as energy efficient as this other new products claim to be.
These new modern single ply flat roofing systems come in all shapes and colors, some manufactures even offer a 30 year warranty on membranes that are 1/16" of an inch thick, the thickness of a penny! (I really want to see that happen). The most common single ply membrane roofing in the market is E.P.D.M. black rubber, this is the same rubber material you see car manufacturers use to seal windows and doors on vehicles, it is also use for hoses, tubing, etc.
Another type of Single Ply Roofing Material is PVC, the same type of material that they use for the PVC pipes but with the addition of plasticizers to make it softer and flexible. This type of roofing has been very common as well and since its introduction since the 60's and it's applied with a heat welding machine or heat gun, its has been some controversy about the toxic chemicals that come out of it while being made or installed and has been some problems also with the warranty on this specific roofing system, sometimes it will shrink to a degree that it will take down parapet walls on the roof, manufacturers were offering up to 25 years of warranty but these roofs were failing way before their time was up, often blaming it on the installer, PVC roofing can be very expensive, so manufacturers came up with another roofing system more affordable, TPO.
TPO Roofing ( Thermoplastic Polyolefin )is relatively new in the market, because of it's many changes in its formulation (about 6 times) the last one in 2011, many people doubt its effectiveness, only time will tell since manufacturers are offering 15 to 30 years warranty! Of course it hasn't been proven yet because it hasn't been in the market that long. If TPO results to be what the manufacturers claim to be, then its going to be a great product to keep around for a long time to perform in harsh environments , at a good cost for the consumer and very energy efficient. TPO seam are heat welded as well and come with all type of different accessories. Some of the biggest manufactures of TPO are Firestone, Versico, Johns Manville, Genflex, Carlisle, GAF etc.
If you are in the Hampton Roads area and need a Flat Roofing Contractor, don't hesitate to contact us.