Letters

Verify shingle compliance

The article "Asphalt shingle selection," May issue, page 28, is excellent. As an overall comment, roofing contractors should require manufacturers to provide certification that their products meet designated ASTM International and Underwriters Laboratories Inc. standards.

Our firm has been involved in testing shingles on numerous projects throughout the U.S. On several occasions, we have observed shingles that do not meet ASTM International standards listed on the package and in marketing literature. Failure to meet these standards can obviously affect roof system performance. To be on the safe side, roofing contractors should require verification from manufacturers.

Jim D. Koontz, PE, RRC
Jim Koontz & Associates Inc.
Hobbs, N.M.

Readers disagree with NRCA recommendation

In "Why 1-inch overlap works," June issue, page 22, James R. Kirby, NRCA's associate executive director of technical communications, goes to great lengths to explain why NRCA recommends a minimum 1-inch overlap of roof edge metal onto the wall below. The Brick Institute of America recommends a minimum 4-inch overlap to prevent wind-blown rain from entering a wall. In addition, several masonry educational seminars presented at recent conventions held by The American Institute of Architects and Construction Specifications Institute also recommended a minimum 4-inch overlap. This is quite a discrepancy among national organizations.

It is frustrating for architects to encounter these kinds of discrepancies when researching design recommendations, especially in the current litigious society.

I would like to recommend that NRCA get together with other national trade organizations to coordinate recommended design details that address how materials come together. This would benefit not only architects, designers and contractors but also various trade groups by providing a unified approach that would eliminate confusion and better withstand legal challenges. I would hope each organization could overcome its biases and reach consensus in most cases.

James Simpson, AIA, CSI, CCS
YHR Partners Ltd.
Moorhead, Minn.

I read Kirby's article and agree with most of the technical data. However, I take exception to his comments regarding not placing sealant at an exterior wall face. Realizing NRCA tries to address issues across the U.S., there are times when a generic approach simply does not work.

Having been in the roofing industry all my life in Florida, I've seen many examples of tropical storm and hurricane conditions. Quite often, I've found entrapped water inside parapet membranes or evidence of membrane blow-off caused by wind pressurization from exterior wind force. Most construction techniques in Florida use materials that allow escape of entrapped moisture in walls, especially with air-conditioned space where vapor is extracted from air and discharged as condensate. Recently, I was involved in a project where the entire roof system failure was a result of this exact situation. When I pointed out the gaps in structure and failure of the general contractor and roofing contractor to seal the roof to walls, we reached a quick, mutual settlement.

I continue to use a sealant closure at a building face behind the wind cleat whenever and wherever possible. I would like to see NRCA take a broader view of any topic and consider its position in more of a geographic nature. After all, manufacturers design their systems based on region.

Les Knopf
Knopf & Associates Inc.
Riviera Beach, Fla.

When I read Kirby's article, I felt strongly that I must write a letter and make every effort to save roofing contractors from making the mistake of thinking a 1-inch overlap will work as Kirby states.

I have been in the roofing industry one way or another for more than 55 years. I run into this overlap problem many times each year. I strongly disagree with the figures stated in the article. My findings in the field show moisture will travel straight up an outside wall just about 6 inches in a 35- to 40-mph wind.

On projects that only had wall leaks, the only thing my company changed to stop the leaks was to install a new metal edge to extend at least 6 inches past the top of the siding. On 100 percent of these metal edge changes, all the leaks stopped with a 6-inch overlap.

Kirby's idea works in a lab or by the math; it does not work in the field under typical weather conditions.

To have a correct and leak-free edge, metal must extend at least 6 inches past the top of siding. I agree that no caulking is required on the edge detail if done correctly.

Lawrence T. Musil
Interbay Roof Inspection
Bothell, Wash.

I disagree with Kirby's assertion and do not think a 1-inch overlap affords adequate protection. The world of construction is not tidy. A mere inch gives little room for the variations found in the real world. I list a few:

• In windy, coastal or hilly areas where 1 inch is too little
• Rakes or inclines where rain crawls under the inch (If a wall is out of level 1/2 inch, you have a leak.)
• Air pressure differentials caused by cavities sucking in water on windy elevations
• If a roofing contractor applies the gravel stop well before the cladding shows, who ensures the lapping material is put below?
• If you have a nailer strip nearly 1 inch, you don't have a l-inch lap-you have none, but you have a leak.
• Roofing contractors commonly put gravel stops too close to walls, making them unlikely or impossible to be effectively flashed off. Commonly, plasterers leave a lump under the metal (to channel water the wrong way).
• Walls are not perfectly straight on top or on the face, so the gapping is not continuous.
• Caulking is a good idea below, but who does it is the question.

When you have a mere inch without control of level or slope or the other components are close to 1 inch or larger, there is no room for redundancy. If one cannot provide a reasonable overlap or seal the bottom face, a much larger minimum makes sense. One inch is a throwback to the era of loose buildings.

We always use 3 to 4 inches as a minimum. The cost of the added metal is minimal. We also like to hang the metal out 1 to 2 inches so it will drip free of the wall.

In California, we typically see a shadow under the edge metal and below we see wall damage and rot. Although 1 inch may seem adequate, it is not reliable. My firm has seen millions of dollars in damage from short laps; they are one of the first things we look for during inspections. They may "pencil out," but they don't "pan out." They just make money for the repair and defect industries, which amply have supported me.

Karl Kardel
Karl Kardel Consultancy
Piedmont, Calif.

Following is Kirby's response to the letters:

Thank you for your comments. I had no idea my article would generate so much discussion within the design and consulting sectors of the roofing industry.

It certainly is within the purview of roof system designers to design roof system details specific to a project's construction type, requirements and location. In fact, NRCA wants design professionals to use its details as the basis for design and improve upon them as necessary. Therefore, I must emphasize NRCA's recommendation for a 1-inch overlap is a minimum recommendation.

As readers have pointed out, there are circumstances that may require a larger overlap of edge metal over a wall. Please realize larger overlaps will require a longer cleat if cleats are fastened into the wood blocking (as per NRCA's recommendation). A longer cleat fabricated from the same material and similarly fastened will likely reduce the wind resistance of the edge metal—be it a gravel stop or coping. This is a trade-off that must be addressed.

If a roof system designer believes it is important to seal the interface of edge metal and a wall, doing so takes away one path for air movement. If there are other paths for air movement and the subsequent removal of trapped moisture, perhaps installation of sealant at this location may be acceptable. Again, this is a trade-off.

As always, NRCA's recommendations are provided as a basis for good roofing practices throughout the U.S. NRCA does not provide geographic-specific recommendations.