Roofing Considerations for New Construction in the Pacific Northwest
The housing boom in the Pacific Northwest has reached Portland, Oregon. If you’re one of the many residents considering building a new home, take into consideration what home and roof design fares best in the region. By choosing the right design, you can save money in the long run by constructing a home that is more impervious to heavy winds and rains, and provides greater energy efficiency.
How Hurricane Research Helps You
Although hurricanes don’t threaten Portland, research on hurricane- and tornado-resistent housing design can help Oregon residents choose a structural design that better withstands the state’s windy, wet weather. Some home shapes and roof types withstand high winds better, says Dr. Rima Taher, civil engineer and researcher at the New Jersey Institute of Technology. Taher conducted a two-year study to identify the best home designs, and construction methods and materials for withstanding extreme wind events and hurricanes. According to Taher’s findings, the best design for a low-rise structure includes:
- An elevated structure
- A square, hexagonal, or octagonal plan form
- An open foundation
- A hip roof
- A central shaft with aerodynamic features that reduce wind forces.
What Is A Hip Roof?
No, hip doesn’t refer to how cool your roof is. You’re probably most familiar with gable roofs. They feature two slopes and look like the uppermost part of a capital “A.” Gable roofs cost the least to construct, making them the most common. Hip roofs feature four slopes. Multiple slopes fare better under wind force. A roof slope of 30 degrees performs best.
Hip roofs also provide protection from heavy rains, explains Dr. Claudette Reichel, a housing specialist for Louisiana State University AgCenter’s LaHouse, a demonstration house in Baton Rouge, La. that features the latest developments in disaster-resistant and energy-efficient construction. The overhang of a hip roof sheds water away from walls and helps protect the home’s windows. Limit overhangs to 20 inches to reduce the possibility of uplift.
Generally, wind forces on a roof cause uplift, often causing the roof to blow off in extreme wind conditions. This make the roof to walls connection most important. Stapled roofs, once common, were banned after 1993’s Hurricane Andrew severely damaged Florida. Reichel highlighted some important building choices in roof to wall connections:
- Roof trusses should use OVE structural members or engineered wood girders.
- Tie the roof to load-bearing walls or bracing with hurricane straps, aka hurricane ties.
- Use baffled ridge and soffit vents in the attic instead of more common through-the-roof attic vents. Through-the-roof vents blow off more easily in high winds providing a wind and water entry point.
Approach home design with an open mind. Although you may have your heart set on the same design you grew up with, it may not fare well in the Pacific Northwest climate. A roof consists of two water barriers, the sheathing that attaches to the rafters and the cosmetic covering the neighbors see made of shingles, tiles, metal, clay, sod, etc. Use at least 5/8-inch exterior plywood or exterior composite material for your roof’s sheathing attached using 8d ring shank nails at least every six inches. Asphalt shingles perform well in most weather conditions including heavy rain and moderate winds. In hot, dry climates they tend to curl or soften allowing them to blow off more easily. In Oregon’s damp weather though, they perform admirably.
Metal roofs withstand heavy winds and rains. They provide a durable, long-lasting material that lasts between 50 to 100 years.
Slate roofs provide such an extremely durable material. Some used on Colonial New England homes are still in use. Slate does well in any climate and keeps out heavy rains.
Avoid wood shingles and shakes. They perform poorly in damp climates, as they tend to rot. Clay tiles do best in the South and Southwest since they easily take damage from snow, ice, and/or hail.
A roof that performs best against high winds costs a little more. A high-wind resistance roof also adds to the re-sale value of your home though. Ultimately, your home is an investment you live inside. According to NW Home Exteriors, the roofing costs depend of the quality of materials and wind-resistance requirements. In areas prone to high winds, add $5,000 to the roofing budget.
Becoming a homeowner and building a home present major milestones in a person’s life. Build a home that provides comfort, safety, and longevity. Choosing the right roof helps protect your whole home and that protects your investment and your family.