Generally speaking, most residential structures are built with sloped roofs, while the majority of commercial buildings have flat roofs. Homeowners and building managers face some special concerns when dealing with flat or low-sloped roofs. Pooling water and drainage are a major concern, and choosing the right roofing material is critical to avoiding leaks. Fortunately there are a number of materials and installation techniques designed for flat roof surfaces, and most of these will work with residential and commercial structures.
Many factors should be considered when comparing material and installation options for flat roofs. Buyers should compare the cost of each material to the available budget for the project. Cost should include not only materials, but also installation, maintenance and the expected lifespan of each option. You must also consider the aesthetic appeal of each type of roofing compared with its visibility from inside and outside of the building. Also, evaluate installation, energy and environmental impacts, and durability to find the best material to cover a flat roof.
Rolled roofing is the cheapest option for covering a flat roof. This material is quick and easy to install, and often features a "peel-and-stick" installation method. It consists of rolls of mineral coated asphalt paper fastened to the roof deck with nails or roofing adhesive. On a flat or low-sloped roof, two layers of rolled asphalt should be used to minimise leaks. This material has a relatively short lifespan, and is not very durable. It should be considered a short-term option for most roofs, or an affordable way to cover an outbuilding or shed.
Built-Up Roofing (BUR) is considered a mid-range option for flat roofs in terms of cost and durability. It consists of multiple layers of fibreglass or felt combined with a bituminous resin like asphalt or tar. The asphalt or tar are heated to high temperatures during installation, making this a job best left to professionals. BUR systems are considered fairly unfriendly in terms of environmental impact because of the toxic fumes they produce.
Rubber membrane roofing is the most expensive option for finishing a flat roof, but also the most durable and long-lasting. It is made from sheets of vulcanised propylene or other polymers that are easy for more DIY homeowners to install. The sheets are sealed with heat-applied tape. This creates a truly watertight seal that prevents leaks and helps the roof hold up against wind, rain and other elements. Most rubber roofs have a black coating, though an optional white coating can reflect sunlight and keep the building cooler in the summer.