Question
What kind of roof should I use? I live in Oregon and it rains all the time.
If a planted roof, what kind should I use? Our weather has changed a lot. Longer winter months.
Answer
Izabella,
You appear to be asking about different types of roofing materials, and possibly about a "green" or "living" roof. So let me run through your options.
Composition shingles
The old standby. The heavier, architectural-grade shingles make for an excellent roof that can last as long as 40 years for the high-quality shingles.
The up-side of a shingle roof: it's inexpensive compared to other types of roofing and it's easy to install and repair.
The downsides: it's heavy and, having a rough surface, catches needles and leaves. I've even seen it build up enough of a load of organic debris and moss to back water up under the shingles and leak into the house.
Standing-rib metal
If your house is under trees -- and in Oregon they could well be fir trees that shed a lot of needles -- a standing-rib metal roof has one large benefit over composition shingles: it's easy to sweep the needles off once or twice a year, and if your roof's steep enough, they may slide off by themselves.
- Metal is available in a lot of colors, including a few certified "cool roof" colors, though this may not be of much interest to you in Oregon.
- Though the initial cost of a metal roof is as much as double a high-quality composition roof, its ability to shed organic debris easily could be a big plus where you live, and some homeowners like the clean, smooth look.
- Plus, metal roofs work just as well on steep roofs as on low pitched roofs.
Other types of roofing
There are other types of roofing materials:
- rolled composition,
- vinyl, slate, and
- wood, for instance.
But none of these are suitable for most homes in the West, either because they're short-lived, expensive, or fire prone.
Living roof
Lastly, I'd like to mention "living roofs." A living roof uses a vinyl or rubber/vinyl membrane and a moisture-retention pad covered by a planting medium that can hold a variety of low-growing plants like sedum, for instance.
- There are a variety of herbaceous plants that can be used in your climate, and Greenroofs.com is a good place to start if you want to look at one.
- In a high rainfall area such as yours, a living roof could stay green all year.
The upsides: the vinyl membrane can last a very long time since it's completely protected by the organic green mat above it. It's a better insulator than composition or metal, and it looks "organic."
The downsides: A drought can kill your roof. Also, it's heavy, and gets heavier when it rains, so many existing roofs can't handle the load. A 4" layer can weigh 25 pounds per square foot, which may be over the limit for older roofs.
A living roof works best on a low slope or nearly flat roof. If your roof is over 4/12 or 20 degrees, it may suffer from slumping in heavy rains.
Recommendations
Your choice partly depends on what you like to look at, as your type of roof often creates a major theme.
But if you can afford it and like the look, the ease of care and longevity of a metal roof may be your best choice for a high rainfall climate.
For more information:
Read "I'm reroofing a typical sloped roof -- what materials should I be considering?" a Q&A answered by David Edwards.
