Pro -- Cost
One of the most significant benefits of a flat roof is that it is less expensive to install than a pitched roof. Rafters and engineered trusses must be installed to support a pitched roof, while a flat roof usually requires only basic support beams. As a result, less labor and materials are necessary, so you can save considerable money.
Pro -- More Usable Space
While a pitched roof can provide attic space that a flat roof cannot, the area is not usually suitable for use as a room. With a flat roof, you may opt to have your interior ceiling extended to the point where the roof begins, creating additional usable space in your home. In addition, you may have extra support added to the flat roof so it can house a deck or patio, creating additional space for outdoor entertaining.
Con -- High Maintenance
The major drawback to a flat roof is that it typically requires more maintenance than a pitched roof. Because it is not sloped, the roof does not drain naturally so water can easily accumulate. If water puddles on the surface, it can soak into the roof through its seams and cause structural damage. You must check your roof on a regular basis to ensure that it is free of water and clean up any debris that has settled on the roof as well so the drainage system does not become clogged.
Con -- Shorter Lifespan
A flat roof typically does not last as long as a pitched roof. Its lifespan is affected by the maintenance measures that are taken, but -- depending on the material from which it is made -- a flat roof may have a lifespan as short as 10 years. Make sure that you address the issue of materials with your roofing professional to determine the most durable option for a flat roof.
Con -- Absorbs Heat
All parts of a flat roof are continually exposed to the sun, so the roof absorbs heat all day long. In warmer climates, the heat absorption may cause your home to become uncomfortably warm. You may also have a problem in milder climates during hot summer months. However, in a cooler climate, you may find the additional heat provided by a flat roof to be beneficial, particularly during the winter.