Best Materials for Flat Roof Construction

Generally seen in commercial construction, the flat roof is also used on homes. There are many homes that do have this type roof, especially in drier climates. A flat roof is just that, flat with little or no slope. Without the need for rafters, this type of construction saves both time and material costs. Every flat roof has a few elements in common: a curb around the roof; waterproof membrane; gutters and downspouts; and slight slope to direct water to a drainage point. Bearing all this in mind, there are four types of flat roof. Choosing which material is best for you is an individual preference. If you are determined to lay the roof yourself, the roll asphalt will likely be your choice. While the built-up roof can be done by an experienced do-it-yourself buff, the underlayment or waterproofing course should be done by a professional.

The long life (10-30 years) of a built-up roof likely makes it the most economical. With this application, there are several layers of roofing felt impregnate with tar. Each layer is coated with hot tar, using mops. After several layers of felt and tar are applied, the roof is held in place with crushed gravel. The crushed gravel also serves as protection from the sun. The biggest problem with this application, is if it leaks – good luck locating the leak! The gravel essentially hides the problem area making it virtually impossible to patch.

Lasting no more than 10 years, the most common roof on garages and sheds is a roll asphalt roof. This is a single layer of asphalt impregnated felt. The felt is fastened down with galvanized nails and roofing cement. Much like the built-up roof, crushed gravel is the final layer on the roll asphalt type construction. Although this is likely the easiest do-it-yourself flat roof, it will have the same problems as the built-up system as far a finding and fixing leaks.

The remaining flat roofs are the single membrane and the sprayed polyurethane foam (SPF) roofs. Both of these require professional installation and special tools. The single membrane roof will last 10-15 years and is made in one piece from thermoplastic or thermoset membrane. The SPF is a two layer system consisting of the foam and a protective membrane. The single membrane roof is probably the easiest to locate problems and repair, as the roof is one piece. The material is UV resistant and the contractor ‘welds’ any seams together. Repairs are simple with patches and glue. The down side to either the SPF or single membrane is expense, because each must be installed by a professional.

All flat roofs require routine maintenance. It is important to remove any debris or leaves from the roof surface as well as the gutters and downspouts. Areas where flashing was used require inspection on a regular basis to prevent water infiltration. One major concern around flat roofs is fireworks. Especially with SPF materials which are highly flammable. In other words, if there is even a remote possibility that fireworks will land on your flat roof – don’t light them!