Flat roofs can be used as a simple roofing method but they are not recommended for homeowners. Due to the construct, they are prone to sagging, leakage, damage when any remodeling, repairs, or add-on occurs. They are also not recommended for use in cold climates as the accumulation of ice and snow can lead to blocking the flow of any water on them which can cause leaking. Flat roofs were often used in architecture back in the fifties and sixties-a lot of residential homes from this time especially those in warmer climate states such as Florida have flat roofs on part of their structure. Mostly this is found on enclosed patios or Florida rooms (sun rooms). Unfortunately this is a high moisture state and one prone to tropical storms and hurricanes leading to a lot of roof damage.
Flat roofs are made from a variety of materials, some of the higher end ones being metal roofs using copper or tin. Using metal sheets for the such a roof allows the pieces to be soldered together which does provide a more sealed finish. However, in most cases when a contractor is laying a flat roof, they will do it as one single sheet as overlapping and stacking is difficult and inadviable. Gravel and asphalt are another material used in the construction of roofs and are actually used more often than metal, because of their cost. Asphalt is not recommended in high moisture climates as it tends to break down slowly in water and the higher the exposure, the faster the degradation. The benefit of asphalt is that it can be easily added to and repaired, if you do not mind frequent repairs.
The rubber like material EPDM is often used in single-ply roofing and is not only easy on the budget but has a lifespan of fifty years and with new innovations in the market for EPDM, not only has it cut down on labor costs but the lifespan continues to rise. This type of roof can be attached by balancing with large stones, mechanically in high wind areas, or fully adhered. The latter method is the most expensive but it also lends best quality and durability.
Vinyl roofing is another popular material for such roofs. It is extremely strong and recommended for calamitous areas. This type of material is heat welded and forms a permanent watertight bond. However, because of its construct, PVC resin modified with plasticizers and UV stabilizers then reinforced with fiberglass mats, it is a flexible roofing material.
While such roofs are not recommended for residential homes and buildings they can still be used, and are in some instances where the benefit outweighs the consistency. If you are interested in using a flat roof construction for one of your projects talk to a contractor about what options and materials would be best for you. They may offer an alternative that will be most beneficial to you in the long run.