Increased Thermal Values Affect an Existing Roof Edge

Recent code and standard development has resulted in increased thermal insulation. This increase has required greater and greater insulation thicknesses, which are even thicker when
tapered insulation is added. This roof system thickness, especially in reroofing design, has thrown a curveball to many designers: How should they address existing rooftop conditions?

On a recent project in which the roof sustained a wind event, investigation for the design of the new roof edge and system found multiple concerns: open metal stud cavities to the parapet, open metal panel joints, wood and substrate boards attached with drywall wall screws and moisture drive concerns. This information led to the design of one of the author’s most complicated roof edges.

Photo 1: On a recent project in which the roof sustained a wind event, investigation for the design of the new roof edge and system found multiple concerns: open metal stud cavities to the parapet, open metal panel joints, wood and substrate boards attached with drywall wall screws and moisture drive concerns. This information led to the design of one of the author’s most complicated roof edges (see Figure 1).

I have successfully dealt with this for more than three decades and mostly with ease. However, based on the fight being put up by the Chicago Roofing Contractors Association (CRCA), you would think it is putting contractors out of business rather than having the potential to increase their bottom lines.

Consequently, this will be the first of several articles discussing how designers can deal with existing conditions on the roof when increased thermal values are required. This article will explain the roof edge—the first defense against wind uplift and often an aesthetic concern. Future topics will include drains, roof curbs, access doors, windows, RTUs and plumbing vents.

WHY THE NEED

Twenty-five or 30 years ago, insulation was what you placed on the roof deck to act as a separator between the roof cover and roof deck, especially with the increased use of fluted steel decks instead of monolithic-type decks, like concrete, gypsum, wood and cementitious wood fiber. Prior to that, roof covers were often placed directly on these monolithic roof decks sans insulation.

On a recent project in which the roof sustained a wind event, investigation for the design of the new roof edge and system found multiple concerns: open metal stud cavities to the parapet, open metal panel joints, wood and substrate boards attached with drywall wall screws and moisture drive concerns. This information led to the design of one of the author’s most complicated roof edges.

Figure 1: On a recent project in which the roof sustained a wind event, investigation for the design of the new roof edge and system found multiple concerns: open metal stud cavities to the parapet, open metal panel joints, wood and substrate boards attached with drywall wall screws and moisture drive concerns. This information led to the design of one of the author’s most complicated roof edges (see Photo 1).

It has only been within the last 25 to 30 years that insulation has become an integral component of the roof system, often changing how the roof cover behaved. As energy and the conservation of energy became vogue, codes and standards became more stringent in regard to thermal insulation values. With the increase in R-value came an increase in the thickness of insulation. This in turn requires roof edges be higher to accommodate the increases in insulation, ultimately changing how the roof edge on buildings without parapets are designed.

Stacking wood to raise the roof edge is old school. Here you can see the new wood blocking is the second stacking over previously installed wood on a previous reroof.

Photo 2: Stacking wood to raise the roof edge is old school. Here you can see the new wood blocking is the second stacking over previously installed wood on a previous reroof.

The use of tapered insulation with thicknesses often above 12 inches changed how the roof edge is treated, especially in reroofing situations, which has resulted in design challenges. Add to this, modern building design that forewent parapets for gravel stop; the challenge of raising the roof edge to accommodate new insulation heights has dramatically increased.

The Washington, D.C.-based American Institute of Architects has issued a challenge to the design community to make all new construction Zero Energy Buildings (buildings that produce as much energy as they use) by 2030. Intuitively, more insulation (and perhaps fewer windows) will result in a building that uses less energy and, thus, more easily achieves a balance point.

To strengthen the multiple stacks of 2xs, 3/4-inch plywood is being added on the exterior.

Photo 3: To strengthen the multiple stacks of 2xs, 3/4-inch plywood is being added on the exterior.

This altruistic, far-reaching goal is being fought. CRCA, for example, is fighting the new code increases in roof insulation. Although the organization states a variety of reasons, it appears that the fear of owners delaying work that costs more because of increased insulation thickness is the greatest concern. This is interesting because design—by state mandate—is the purvey of licensed design professionals. Is the CRCA advocating design by non-licensed designers? I believe the CRCA’s position is foolish. Why would a predominately union-based contractor organization fight a code mandate that allows their members to increase profits? Perhaps the challenge by “right to work contractors” is greater than believed.

CONCERNS: LEGITIMATE OR NOT

There are a number of concerns, or design challenges, as I like to say, to raising the roof edge. For us architects, respecting the architect’s vision and design intent is often in conflict with what may need to be accomplished. I have worked with clients in buildings of note, designed by well-known architects, and have been able to respect every detail of the roof-edge vision. It is very difficult and challenging.

When stacking, wood joints should be offset and scarfed at 45 degrees.

Photo 4: When stacking, wood joints should be offset and scarfed at 45 degrees.

Another concern can be cost. Historically, a dimensional 2x was set at the roof edge and nailed; now we often raise the roof edge with prefabricated insulated curbs. Costs are always a concern but when budgeted correctly and the client is informed during the process, the project has always been realized within a year or two.

Another concern I often hear voiced is, “It’s difficult” or “I cannot figure it out”. When one considers that the roof edge must be (let’s say should be) tied to the building structure to resist wind loads, these are true concerns. These types of conditions often call on years of experience. Therefore, I say the challenge is on!

On this detail from an older project, the roof edge is being raised with multiple layers of 2 by 12s—a bit old school but easily performed. It is recommended to not specify preservative- treated wood, coated screws and off-set joints.

Figure 2: On this detail from an older project, the roof edge is being raised with multiple layers of 2 by 12s—a bit old school but easily performed. It is recommended to not specify preservative- treated wood, coated screws and off-set joints.

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A Continuous Metal Piece Levels, Lowers or Pitches Any Standard Gutter or Screen Along the Roof’s Edge

Today’s roofing contractors have more product choices than ever before. Design innovations, high-quality materials and extended life expectancy are the norm. Most manufacturers have developed coordinated packages that include accessories, which not only results in better installations, but also provides enhanced solutions to present to any homeowner.

Following in my father’s footsteps, I have been a roofing contractor for 36 years. As my company grew, the challenge of organizing employees and providing systems to make the company more profitable became essential. One of my frustrations was waiting for gutter subcontractors to show up before we could start shingling. This was especially aggravating during winter when every roof is required to be watertight by the end of the day.

The High Back Adapter was designed to be installed with any manufacturer’s roofing package, regardless of what roof or gutter and accessories your contracting firm prefers to use.

The High Back Adapter was designed to be installed with any manufacturer’s roofing package, regardless of what roof or gutter and accessories your contracting firm prefers to use.

Consequently, I invented the High Back Adapter, which gives any roofer the flexibility to start the roofing application any time and gives the gutter installer the freedom to show up at any point in the roofing process. The High Back Adapter was designed to be installed with any manufacturer’s roofing package, regardless of what roof or gutter and accessories your contracting firm prefers to use.

The Solution

The High Back Adapter’s continuous one-piece design provides your company with enclosed insert pockets to independently level, lower or pitch any standard gutter or screen along the roof’s edge. It is available in steel, aluminum or copper in standard colors of white, brown and gray and is compatible with most metal, tile and all composite roof types. The product is designed to pitch gutters toward downspouts. It also allows gutter or screens to be installed any time in the future without breaking the manufacturer’s sealed edge you provided.

You may ask how this is possible. The gutter and screen slots provided in the High Back Adapter gave me the confidence that any manufactured seal would not be disturbed no matter when the gutter or screen was applied in the future. As a bonus, we found as the roofing materials got older, any replacement of these items can be done quickly without ever opening the edges.

Fortunately, the High Back Adapter’s gutter slot provides a way to level the gutter independently of the roof edge or structure, and all water is directed off the roof, into the gutter and to the ground.

Fortunately, the High Back Adapter’s gutter slot provides a way to level the gutter independently of the roof edge or structure, and all water is directed off the roof, into the gutter and to the ground.

Benefits of Lowering the Gutter

Typically, the gutter screen tucks under the first row of roofing material and screws into the gutter’s front lip. My crew and I noticed the screen’s final position lay relatively flat, producing a virtual shelf for any debris coming down the slope to settle. This debris would sit level with the wood substrate and roof edge, allowing any water flowing down the roof to literally dam up, eventually backing under the roofing material and wicking water back over the felt and into the wood substrate. This caused leaks, dry rot and felt deterioration in just a few years.

Fortunately, the High Back Adapter’s gutter slot provides a way to level the gutter independently of the roof edge or structure, and all water is directed off the roof, into the gutter and to the ground. Now installers can provide positive forward slope while preventing a virtual shelf.

The product provides standard 3 inches of protection on the roof and more than 2 inches in the gutter. Additionally, it gave us a way to level the roof deck on any existing home where dips or wavy edges were present. With the High Back Adapter, the roof has the appearance of a level edge even if the structure is not.

The notion of a gutter being limited by how level the building perimeter was or the inability to pitch the gutter in one or both directions is no longer an issue. The High Back Adapter’s enclosed slots give installers a way of pitching or lowering any standard gutter in one or both directions. Downspouts are no longer required to be placed in the lowest spots; gutters now can be pitched toward the best downspout location instead of the most convenient one.

The High Back Adapter has been our way of dealing with some common problems in about 75 percent of our roofing and gutter projects. We offer it as a benefit to our customer base and it is selling extremely well once a homeowner sees it. My hope is you will see your own opportunities and potential as you work in your respective fields. When you come up with the next best thing, don’t be afraid to implement it.

Brochure from Drexel Metals Offers Watertight Solutions for Perimeter Edge Systems

Engineered Commercial Roof Edge Systems, a brochure from Drexel Metals, offers architects and contractors an array of watertight solutions for specifying and installing perimeter edge systems.

Engineered Commercial Roof Edge Systems, a brochure from Drexel Metals, offers architects and contractors an array of watertight solutions for specifying and installing perimeter edge systems.

Engineered Commercial Roof Edge Systems, a brochure from Drexel Metals, offers architects and contractors an array of watertight solutions for specifying and installing perimeter edge systems.

“Roof edge systems typically represent only about one percent of a building’s overall cost,” says Brian Partyka, Drexel Metals’ executive vice president of business development. “Yet the importance of a properly designed roof edge system cannot be underestimated or ignored, as 60 percent of all roof warranty claims are attributed to metal edge failures.”

Drexel Metals has applied its expertise in the details of metal roofing to produce low-slope roof edge systems, or ES-1 Rated Roof Edge Systems. ES-1 is a reference for those who design, specify, fabricate or install low slope roof edges and it’s based upon information in ASCE 7-02 Minimum Design Loads for Buildings and Other Structures.

In Engineered Commercial Roof Edge Systems, Drexel Metals offers solutions for five coping solutions, two fascia cover designs, three gravel stop details and two solutions for drip edges. The brochure also has two methods for gutter specification and installation.