Flat roofs mean the pitch of the roof is either low slope or 100% flat level. We can see flat rooftop buildings everywhere such as high rise condominium, warehouses, factory, shopping plaza and school, for residential you only find them in older communities since new home builders do not often design flat rooftop homes because of the problems associated with it. The problem with flat roof is their low to none slope characteristic, slow rainwater and snow run off make it more chances to leak and once it starts leaking it can hardly stop because most flat roof will have pond of water/snow remaining for a long period of time. That is why you need to have a real good waterproofing system when it comes to flat roofing.

There are wide range of materials choices for flat roofing system, the most popular systems in the market are as follow:

Built up roof (BUR)/Tar & Gravel

This flat roof system has a history of over 100 years and is still the most durable and reliable system. On a hot Built-Up Roof, the multiple plies are fused together using hot-mopped asphalt to create a monolithic barrier. Every inch is firmly and completely adhered over the entire roof area. Each ply of a Built-Up Roofing system contains a mat of felt paper, glass fiber, modified bitumen or polyester reinforcement. When multiple plies are combined and sandwiched between layers of water-resistant asphalt, the result is a longer. However this is an expensive system because it takes a complete crew of roofers and many heavy hot tar equipments to tackle the job. The average life of a flat roof is 25- 35 years with hot asphalt.

 

Single ply membrane roofing

 

• Modified bitumen flat roofing

Modified Bitumen (MB) roofing is an asphalt-based, close cousin of the Built-up-Roof (BUR) designed for buildings with low-slope or “flat” roof structures. A two ply roofing system composed of 2 layers of rubber, a base membrane and a granulated cap ideally suited for smaller projects, high traffic areas and roofs used as outdoor living spaces. MB may be installed by the torch-application method, or “hot-mopped” like BUR, or applied with “cold-process” adhesives. The best method to install this material will be heat welded application since it is meant to be installed this way and it is the heat from the fame that will melt the membranes to make a 100% watertight bonding. Also this is more economical than BUR system because it requires less manpower and no heavy equipments other than a torch-propane set, it is a favor of many flat roofing contractors. However, it is the open fame torch application that bothers a lot of home owner and builders, there has been many cases of burning down building and homes due to failure of this application.

 

• EPDM flat roofing

This is a low cost single ply roofing system composed of a rubber membrane ideally suited for small or large commercial and industrial projects. It does not require heat (no open fame), can be applied using either a fully-adhered glue system, loose-laid with gravel (ballasted) or mechanically fastened. Furthermore, it is an environmentally friendly roof, as it involves reduced emissions from equipment, fewer petroleum based products, and less waste in landfills. The drawback with this system is it is relatively vulnerable to puncture and requires a factory trained installer for a warranty job.

 

• PVC roofing

PVC roof single-ply membrane, featuring fusion-welded seams for permanent water tightness. This roofing membrane works extremely well in any environmental conditions providing reliable roof protection even when your roof is covered with snow and ice, blazed by strong hail, or covered with ponding water. The seams are hot air welded creating the permanent bond that cannot be penetrated even by the standing and freezing water. In addition it reflects over ninety percent of solar radiant heat resulting in some very significant energy savings and keeping your house much cooler than it would be with conventional roofing membrane. Two common categories of thermoplastic membrane are Thermoplastic Olefin (TPO) and Polyvinyl Chloride (PVC). The membrane is usually produced as a reinforced, white sheet ranging in thickness from 45 to 80 mils. (thousandths of an inch).