A sturdy, waterproof roof is just as vital on your garage as it is on your home, keeping your vehicles and other sensitive equipment in an insulated environment sheltered from the elements. However, if your garage has a flat roof, choosing the correct roofing materials to cover it can be challenging, as flat roofs have some particular requirements that should be addressed with specialised materials. Take a look at the following common choices for roofing flat-roofed garages before deciding which is most suited to your needs:

Built-up roofing (BUR)

This traditional type of flat roofing has been used for decades but can still be a viable option for covering modern garages. Consisting of several layers of tough, waterproof bitumen held in place with adhesive tar and a layer of gravel ballast, a built-up roof is an enormous, sturdy addition to your garage, and can be expected to last for decades with little to no maintenance. The layer of gravel ballast combined with the weight of the bitumen makes this type of roofing enormously resistant to wind damage.

Unfortunately, built-up roofing cannot be used on every flat roofed garage, and the enormous weight of a finished BUR only really makes them suitable for sturdy brick or concrete garages. They also take some serious equipment and technical know-how to assemble, so the cost of hiring professional roofing experts can make this one of the more expensive flat roofing options out there.

Modified bitumen

This form of bitumen bears little resemblance to the bitumen used in built-up roofing and consists of a relatively thin and highly flexible membrane, made from bitumen mixed with tough rubber polymers. This membrane is tough, completely waterproof and provides excellent heat insulation, and is simply stretched and fitted over your garage's roof. It is fixed in place just as simply, either using built-in adhesive strips or by melting the edges into place using a blowtorch. This simplicity makes installing modified bitumen without professional help a viable prospect, keeping costs down.

However, while this thin membrane is surprisingly tough, it can be vulnerable to tearing and puncturing caused by falling objects, such as falling branches or masonry. It is also quite pale in colour, and while this increases its heat reflective qualities to leave your garage pleasantly cool in summer, it can also become badly stained and discoloured over time. This can look particularly unsightly from house windows which overlook your garage.

EPDM

A merciful abbreviation of ethylene propylene diene monomer, this material is a tough and highly weather-resistant form of rubber sheeting and can be affixed to your garage's roof in the same ways as modified bitumen sheeting. It can also be fastened with roofing nails or staples, and is much lighter than other flat roofing materials, so EPDM is a very user friendly option if you intend to fit a new garage roof yourself.

Unfortunately, EPDM is almost always only available in black, which increases its heat absorption properties and can make an EPDM-roofed garage intolerably hot in summer. EPDM is also more expensive compared to both modified bitumen sheeting and built-up roofing, and may be a prohibitively costly option for roofing very large garages. 

Contact a roofing contractor for more information.