After 11 years, cedar-shake roof may need tending

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Q: Multipart question: What are some things to look for as far as wear patterns are concerned on an 11-year-old cedar-shake roof, and what is the best way to take care of it? We have no trees over the roof. I see companies installing metal roofs set directly over cedar shakes. Is this a good idea?

A: At 11 to 12 years of age, your house's hip and ridge shakes, also called ridge caps, begin to deteriorate, loosen and separate. Replacement of select ridge caps is not uncommon at this stage. Tar paper beneath the roofing should lap over the top of the peak, but in about a third of cases it does not, leading to a small amount of leakage eventually.

Roofers or roof-care specialists may slide prebent flashing pieces, called tin shingles, beneath the peak to prevent leakage should the ridge separate. Longitudinal splitting of the shakes begins to become very noticeable at this stage. Replacement of individual pieces is needed when they have multiple cracks. Curled, cupped and broken or missing shakes should also be replaced. At this stage, there will be some shakes of lesser quality that will show signs of deterioration along their lower edges. These should be replaced. Lacking trees, you won't have a lot of debris to keep clear of the valleys, but lichen and mosses will still build.

There are two schools of thought on shake-roof cleaning: The old-school belief is that the best care is no care, and that any feet on the roof for other than broom-clean purposes will lessen its life. While the latter may be true, I believe that this hands-off approach had more validity when shake roofs were of a higher quality, lasting longer than 17 years.

It is inevitable that people will walk on the roof for satellite-dish installation, painting, cleaning the skylights, gutters, etc. This traffic breaks down shake roofs. Broom cleaning alone isn't sufficient in treed areas. Left alone with heavy tree cover, I've seen total deterioration in 10 years.

Pressure washing is very popular, but on softer and older roofs is not advised because of the damage inflicted on the wood fibers. Pressurized air or chemical cleaning should be used in these cases. Wood preservatives, linseed oil and commercial shake-roof treatments are used to replenish oils native to cedar and protect from UV rays. These treatments may also have colorants, allowing the older and newer shakes to blend, avoiding the kaleidoscope look.

I advise against covering deteriorated LP siding and similarly advise against covering a wood roof with metal. The simple reason is pests. Cover that deteriorated wood and it may become a haven for carpenter ants or whatever creepy critter likes the taste of decayed cedar in your neighborhood.

Too good to pass up: Both the Journal of Light Construction and The New York Times have recently featured Eleanor Adair, an Air Force scientist and her crusade for new residential-heating methods.

Adair, is a proponent of residential microwave heating. Yes, a simple $11, 700-watt magnetron could heat the occupants of a home at a load of between 60 and 100 watts per occupant.

"If you hold your house at 45 degrees, with radio frequency introduced on demand to individual rooms, the energy savings would be really exceptional," Adair proclaims in the Journal.

Indeed they would. And indoor-air-quality problems would be moot. Of the hurdles still to be overcome are metallic furniture and kitchen appliances, which tend to arc during heating cycles. Adair has found no ill effects on rats, monkeys or humans during testing, only "warming of the tissues."

Adair faces a long uphill battle getting the public to accept microwave heating. "People are told there is some energy out there - they can't see it or smell it, and they don't know what it is. Someone tells them it's radiation, and then you've lost the ballgame," Adair told the Journal.

Point taken: We get loads of "radiation" from the sun, but as Adair points out, we see it, understand it, and it doesn't make the cat explode if she lays in it too long. It does sound promising. I just want someone else to test it out first.

Darrell Hay answers readers' questions. Call 206-464-8514 to record your question. Or e-mail dhay@seattletimes.com. Sorry, no personal replies.