For the Northwest Environment
"The most important part of your house is not the kitchen, it's the roof."
When working out your design, remember that the Pacific Northwest is rain country. Despite this fact, many builders have fallen into building trends such as flat roofs with no overhang over stucco walls. These types of homes are highly susceptible to costly damage from the elements.
Designing and building a roof correctly the first time will guard against leakage, bring peace of mind, and allow you to concentrate on more enjoyable aspects of home ownership. The following advice is derived from Jim Merrill's 30 years of experience working on homes in the Northwest.
Avoid Large Flat Roofs
The majority of the roofs we design are sloped, however we occasionally design a project which includes a small flat roof. This a result of a budgeting compromise or simply the only sensible or appealing alternative. If a flat roof is to be approached sensibly in the Northwest, make sure it has positive drainage to either a continuous gutter or a plumbing style drain, (scuppers are prone to leaking), and that a torch down membrane is specified as the roofing material. The roof should also include some overhang beyond the wall because vertical parapets are troublesome.
Big Roof Overhangs
Deep roof overhangs are the best protection for exterior walls. Not only will big overhangs protect your siding and paint longer, they will also provide shade in the summer while letting in sunlight during the winter when the sun remains low in the sky.
A deep roof overhang in combination with the front porch will keep your guests dry as you welcome them into your home. Roof overhangs are also desirable in combination with decks and patios.
Deep roof overhangs are highly recommended if you choose to use stucco on the walls. Top quality stucco applied by an expert must still be protected by an overhanging roof to achieve longevity.
A Slight Roof Pitch
The overall style of your home may dictate the roof pitch, however steep pitch roofs can pose problems. Rain tends to run quickly down the roof and over, not into, the gutters while the steepness of the roof makes maintenance and repair difficult. More importantly, weather protection is compromised as the roof cannot extend as far over the walls of the house without blocking the view from the windows.
Keeping the roof pitch low is the best choice for a Northwest home. The lowest pitch acceptable to most types of roofing (other than membrane types) is a 3/12 pitch, although certain metal roofing systems can be successful on 1/12 pitch roofs. An 8/12 pitch, about 33 degrees, is the steepest pitch recommended for the Northwest. When it is dry you can still walk on this roof to maintain it (although proper safety precautions including utilizing a rope and harness system should always be taken on any roof).
Although good for letting in light, old fashioned green-house style roofs are usually disastrous. Pre-fabricated skylight units are a better alternative, but they can be a weak point in the roof and are the first likely point of entry for water. An aluminum frame and glass (not Plexiglas) unit is recommended.
An integral part of any green design should be the inclusion of more natural light, mitigating the need for artificial sources. Despite the possibility of leaks, skylights are wonderful for letting more light into your home, especially in the gray Northwest.
Durable Roofing Material
As desirable as a cedar shake roof might appear, it simply does not stand the test of time or weather. Unfortunately, many composite material alternatives have also been known to fail. If you want the look and feel of a shake or slate roof, asphalt composition roofs, (especially the 35 to 50 year warranty group), are a good option. Cement tile roofs are also a possibility, but they need additional structural support which makes them expensive. Additionally, they are difficult to maintain as they should not be walked on.
Combined with a continuous aluminum gutter, metal roofs are perfect for the Northwest. Contrary to popular belief, metal roofs are not noisier than any other roof. They withstand a lot of abuse, are fire resistant, and last forever. The appearance of a metal roof, however, is quite distinct and you need to enjoy this look to find it appealing.