Q: I have a question related to an earlier column you wrote about composition roofs. I am trying to decide whether to rehab my cedar shake roof or replace it with a composition roof.

In relation to the 40-year warranty on the composition roof that you mentioned, the representative argued that the warranty is for the composition shingles only and does not cover the plywood underlayment, the roofing felt or labor. He maintained that the plywood and felt would need replacement in 20 years or less. He said the composition manufacturers were in litigation on this issue in other states.

He suggested that I purchase his company’s rehab system for my 20-year-old shake roof. He argued that the cedar shakes from that period were from higher-quality timber and that mine are thick and in good condition. At about one-third the cost of a new composition roof, their system replaces individual shakes as needed, uses a preservative and fire-resistant treatment, replaces the ridge pieces on the peak of the roof, and provides a six-year warranty covering 100 percent of materials and labor plus an additional six years at 50 percent of materials and labor. The company has a long history of offering this in the San Francisco Bay Area and provides lots of customers for reference.

What’s your opinion?

A: We have an opinion all right. What a pile of baloney! Our dad used to say, "There’s a sucker born every minute, and two to take him." You’ve met one trying to take you. To criticize an alternative product with the misinformation he gave you is just so much flimflam.

Go with a high-quality "architectural grade" composition roof instead of doing a rehab. But don’t do it until the roof needs replacement.

We’re a bit puzzled why you’re considering these options on a 20-year-old shake roof. It should have five to 10 years of life left without doing anything major. If there is a missing shake or two, or the ridge cap needs re-nailing, hire a licensed roofing contractor to make those repairs. Forgo the chemical treatment, as it’s only a surface fix of questionable benefit and duration.

It strikes us as fishy that the rehab company is willing to warrant its job for only six years. As for the salesman’s comments about the warranties and longevity of composition roof components, some are true and some aren’t. It’s true that these warranties generally cover manufacturers’ defects in the roofing material. But, depending on the product, they also provide limited coverage on workmanship and labor.

It’s also true that roofing felt and plywood sheeting are not covered. But it’s a bald-faced lie that properly installed roofing felt and sheeting (either plywood or oriented strand board, OSB) needs replacement after 20 years.

Take a look at the warranties for GAF/Elkhorn and Certainteed, two major composition roofing manufacturers. You’ll see that the length of the warranty and the scope of coverage vary by product. Labor and other components such as flashing are included on some of the upper-end roofing material.

Roofing felt consists of asphalt-impregnated building paper. When installed, it is totally encapsulated by the roofing material above and the sheeting below. None of it is directly exposed to air or weather. If the roofing membrane is not penetrated, no decomposition will take place. The same is true for plywood sheeting, although it’s exposed to the attic or living space.

Proper attic ventilation is critical to ensure that moisture doesn’t condense on the underside of the sheeting. If properly installed and ventilated, sheeting will last as long as the house stands.

Your roof probably was installed over "skip sheeting" and roofing felt. "Skip sheeting" is boards nailed to the rafters spaced to allow air to penetrate to the shakes from underneath. If it were true that roofing felt fails after 20 years, the felt under your existing shake roof is shot and any "rehabbing" your salesman proposes is a waste of your money.

In the future, when the new composition roof goes on, the contractor will install new plywood or OSB sheeting. Thirty-pound roofing felt should be applied and composition shingles placed over them. That’s the way to go, rather than a bubble gum and bailing wire fix for an older roof that may not even be broken.

Now, to change the subject. In an earlier column we suggested that one of our readers install a drain pan under her water heater and run a drain line to the outside of the house so that if it sprang a leak her interior floor wouldn’t get soaked. We also suggested she route the pressure-relief valve into the pan.

One of our regular readers, Jerry McCarthy, a construction consultant in San Mateo, Calif., pointed out that we overlooked a line in the California Plumbing Code that doesn’t allow this. He writes:

"Hi Guys,

"It’s your code rat Jerry McCarthy again with the news that it’s against the California Plumbing Code to direct a water heater’s PTRV into its drain pain. Ref: CPC, Chapter 5 (508.5). Other than that, great article."

Thanks, Jerry. We’re glad you’re watching our backs. No discharging the pressure relief valve into the drain pan.


What’s your opinion? Leave your comments below or send a letter to the editor. To contact the writer, click the byline at the top of the story.

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