Question

What kind of roof should I use? I live in Oregon and it rains all the time.

Asked by Izabella Weedman
Happy Valley, OR

If a planted roof, what kind should I use? Our weather has changed a lot. Longer winter months.

Answer

David Willson

Answered by David Willson

Sebastopol, CA

Advanced Home Performance

May 23, 2011

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.

Tagged In: green roof, metal roofing, composite roofing

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