Practical Considerations for Roofing Purchases

Roofing is a substantial budget item in any building's construction, making cost a dominant influence on purchases. But other practical matters should also help guide the selection process. Besides the obvious need to keep out the rain, snow and cold, the following issues should be given careful consideration in selecting materials and construction techniques.

Building Use

How a building is used can have a significant impact on rooting materials and construction choices. For example, due to sanitary requirements, some food processing plants do not allow the penetration of steel decks with insulation or membrane fasteners. In other installations, indoor pools or shower/locker rooms may produce humidity levels that dictate the use of a vapor retarder and special insulation.

Code and Insurance Requirements

Energy conservation as well as fire and wind resistance requirements may limit the types of materials or construction techniques available. In high wind areas, for example, gravel surfacing or ballast may be prohibited on high-rise buildings. Be sure to check Wisconsin’s revised energy code (ITHR 63-64) for its impact on approved roofing materials for new and existing structures.

Pitched Roof or Flat?

Pitched roofs offer the best drainage of rain and shedding of snow and ice, but some building owners opt for flat roofs to allow for the addition of floors at a later time. Flat roofs may also be preferred for installation of mechanical equipment, where foot traffic is required; or for aesthetic reasons such as a rooftop garden. Flat roof drainage can be improved with tapered insulation or other techniques, but they can add to the roof’s cost.

Attachment of Roof Components

A variety of screws, rivets, adhesives, nails and ballast materials are used to attach roofing components. These may include shingles, insulation and/or membranes and ballast, as well as mechanical components such as chillers, vents and piping. Attachment options depend on the type of deck construction used.

Resistance to Chemicals and Foot Traffic

Some manufacturing plants vent chemicals that can degrade or discolor roofing materials. Fortunately, most roofing manufacturers provide chemical resistance tables to facilitate material selections. Single-ply roofs are susceptible to punctures and compression of insulation under heavy foot traffic. Shopping mall roofs may therefore be best suited to modified bitumen or a built-up system if traffic can't be confined to walk pads.

Load Capacity

Roof load capacity becomes an issue when a second roof is built, when a ballasted single-ply system is used, or when heavy walk surfaces or platforms are used. A structural engineer can ensure that load capacity is not exceeded.

Other Considerations

Other issues affecting roofing choices include maintenance requirements, warranty coverage, and the skill of the roofing contractor. Be sure your contractor is experienced with the materials you'll be installing. Inferior workmanship can be very costly. On the other hand, a skilled contractor can often build a good system with materials that may be less than ideal.

Any roof will have to be replaced eventually. The way to maximize its service life and reduce its overhead is to weigh more than the initial cost alone.