Whether a contractor’s clients are in the mountains with lots of snow or in a dry and warmer climate, their roofing material needs to protect them and their assets from harsh weather. Different climates call for different roofing materials and roofing solutions.

Although the design of a roof depends on the desired look of the property, its first—and most important—job is to keep them dry.

Flat Roofs
A variety of materials are available for flat roof applications. Some products seem to be suited better to certain climate zones. For example, if a contractor’s clients have buildings in drier and warmer climates, such as the Southwest, they have  a couple options that will hold up best.

Thermoplastic polyolefin (TPO) is an excellent choice for the Southwest because it is available in white and holds up well in dry heat.

The other option is spray polyurethane foam with elastomeric coatings. Because a polyurethane foam roofing system is seamless and is covered by a reflective elastomeric coating, it greatly reduces the risk of thermal shock for buildings located in areas such as Southern California and Arizona. Thermal shock occurs when rain falls on a roof that has been baking in the sun. The rain rapidly draws heat out of the roofing material, causing it to rapidly contract as it cools. This can cause the roofing material to crack because it is shrinking on the surface faster than the bottom can accommodate.

In climates that are cooler and wetter, polyvinyl chloride (PVC) is preferable to avoid shrinkage, and where it is more humid or colder (possibly with snow), silicone would be a better coating for application over spray polyurethane foam.

Other roofing materials, such as ethylene propylene diene terpolymer (EPDM), serve well in a variety of climates. In addition, atactic polypropylene (APP) modified bitumen or styrene-butadiene-styrene (SBS) modified bitumen are widely used torch-down products (now available in self-adhered), and are suitable for use in virtually any climate zone.

Pitched Roofs
Pitched roofs are the most common roofing system and do well in all climates; however, like flat roofs, it depends on the material a contractor chooses to use as well as the pitch of the roof (steeper for snowy climates, lower for temperate zones).

For example, if a contractor’s clients are in a cooler climate with moisture, wood shake would be a great option because the shakes won’t dry out and crack like they would in a dry and warmer climate.

Unlike flat roofs, many materials for pitched roofs work well in every climate zone (e.g., shingle and metal roofs). In the United States, tile roofs are generally installed in drier, warmer climates such as Arizona, Southern California and Nevada. However, in Europe, tile is installed in snowy climates as well. Slate historically has been used for roofing in cooler climate zones.

No matter what material a contractor uses, the pitch of the roof will have the most impact in different climates. In snow country, generally a steeper pitch works well to ensure that snow will slide off the roof. In more temperate zones, a lower pitch (4 6:12) works quite well because it reduces the cost of the truss system, provides visibility for the roof surface and sheds water.

 
Eric Skoog is president of Arizona-based SUNVEK. For more information, visit sunvekroofing.com.