From Screw-down to Standing-seam Metal Roofing

Time to reroof an old screw-down metal roof? Are you thinking about upgrading to a new standing-seam roof? Great idea! Today’s new standing-seam roofs are truly state-of-the-art; available in many profiles and finishes; and, more importantly, address many of the issues encountered in older generation screw-down metal roofs.

Caulk, roof coating and tar patches were used to cover leaking fasteners and panel end laps.

Caulk, roof coating and tar patches were used to cover leaking fasteners and panel end laps.

The screw-down metal roof and wall panel has been the backbone of the metal building industry since its inception and still represents a significant part of the total market. Screw-down panels are lightweight, durable, inexpensive and strong enough to span up to 5 feet between structural supports. Screw-down roofs and walls also have a wonderful physical property: The panels can and frequently are used as “diaphragm bracing,” securely holding the building’s roof purlins and wall girts in position, adding rigidity to the structure in much the same way drywall strengthens stud walls. This is a huge material—and labor—cost saver!

The early systems were not without problems, however; much of the technology we take for granted today did not exist in the early years of pre-engineered buildings. Many roofs during the late ’60s thru early ’80s were installed using 10-year life fasteners to secure a 30-plus-year life roof.

The fastener issue seems crazy today given the numerous inexpensive, long-life, weathertight, self-drilling screws available. Back when I started in the metal building industry, you could have the newly developed “self-drilling” cadmium fasteners or “self-tapping” stainless. Self-tapping meant you had to pre-drill a hole in the panel and purlin to install it—a much slower and more expensive process. Most of us used the less expensive but (unknown to us at the time) fairly short-life cadmium-coated fasteners and often never provided the option of a stainless upgrade to our customers.

Another shortcoming with screw-down roof panels is that, generally speaking, screw-down panels on metal buildings should be a maximum length of about 80 feet. Longer roof-panel runs frequently suffered rips or slots in the metal caused by expansion and contraction. Metal panels expand and contract at a rate of about 1 inch per 100 feet of panel run. This is normally absorbed by the back and forth rolling of the roof purlin and some panel bowing, but after 80 feet or so they can no longer absorb the movement resulting in trauma to the panels and trim. I have frequently seen this 80-foot limit exceeded.

a rusted fastener has caused the surrounding metal to corrode and fail.

A rusted fastener has caused the surrounding
metal to corrode and fail.

Standing-seam panels eliminate both of these shortcomings. The panels are attached to “sliding clips”. These clips are screwed to the purlins and seamed into the side laps of the panels securing them and thus the panels have very few, if any, exposed fasteners. The clips maintain a solid connection with the structure of the building while still allowing the panels, which can be 150 feet or longer, to move with expansion and contraction forces without damage.

This is great news for the building owner: You’re providing a more watertight roof, few if any penetrations, and expansion and contraction ability. It does come with a catch, however; standing-seam panels, because they move, do not provide diaphragm strength. The building’s roof purlins must have significantly more bridging and bracing to keep them in their correct and upright position. This is automatically taken care of in new building design but when it comes time to reroof an older building, removing the existing screw-down roof could remove the diaphragm bracing it once provided and make the building structurally unsound. Yes, that’s bad!

PHOTOS: ROOF HUGGER INC.

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Vapor Retarders

The need for, use and design of a vapor retarder in the design of a roof system used to be a hotly debated topic. It appears now—when vapor retarders are needed more than ever—the design community seems to have lost interest, which is not good, considering how codes and standards (altered through concerns for energy savings) have changed how buildings are designed, constructed and operated. Most notably, positive building pressures are changing the game.

If not controlled, constructiongenerated moisture can have deleterious effects on new roof systems.

PHOTO 1: If not controlled, construction-generated
moisture can have
deleterious effects on new
roof systems.

A vapor retarder is a material or system that is designed as part of the roof system to substantially reduce the movement of water vapor into the roof system, where it can condense. Everyone knows that water in roof systems is never a positive. Typically, a vapor retarder has to have a perm rating of 1.0 or less to be successful. Through my recent observations, the lack of or poorly constructed vapor retarders contribute to ice under the membrane, soaked insulation facers, destabilized insulation, rusting roof decks, dripping water down screw-fastener threads, compromised fiber board and perlite integrity, mold on organic facers and loss of adhesion on adhered systems, just to name a few. Oh, and did I fail to mention the litigation that follows?

The codes’ “air-barrier requirements” have confused roof system designers. Codes and standards are being driven by the need for energy savings and, as a consequence, buildings are becoming tighter and tighter, as well as more sophisticated. This article will discuss preventing air and vapor transport of interior conditioned air into the roof system and the need for a vapor retarder. The responsibility of incorporating a vapor retarder or air retarder into a roof system is that of the licensed design professional and not that of the contractor or roof system material supplier.

It should be noted that all vapor retarders are air barriers but not all air barriers are vapor retarders. In so much that the roof membrane can often serve as an air barrier, it does nothing to prevent this interior air transport.

WHEN TO USE A VAPOR RETARDER

So the question arises: “When is it prudent to use a vapor retarder?” This is not a simple question and has been complicated by codes, standards, costs and building construction, changing roof membranes and confusion about air barriers. Then, there is the difference in new-construction design and roof removal and replacement design. Historically, it was said that a vapor retarder should be used if the interior use of the building was “wet”, such as a pool room, kitchen, locker shower rooms, etc.; outside temperature in the winter was 40 F or below; or when in doubt, leave it out. In my experience, changes in the building and construction industry have now made the determination criteria more complex.

I find there are typically three primary scenarios that suggest a vapor barrier is prudent. The first is the interior use of the building. The second is consideration for the control of construction-generated moisture, so that the roof can make it to the building’s intended use (see photo 1). The third consideration is the sequence of construction. In all three situations I like to specify a robust vapor retarder that “dries in” the building so that interior work and construction work above the vapor retarder can take place without compromising the finished roof. Consider the following:

BUILDING USE

This characteristic is often the most determinant. If the interior use of the building requires conditioned air and has relative-humidity percentages great enough to condense if the exterior temperatures get cold enough, a vapor retarder is needed to prevent the movement of this conditioned air into the roof system where it can condense and become problematic.

Most designers consider building use only in their design thinking, and it is often in error as the roof system can be compromised during construction and commissioning (through interior building flushing, which can drive moist air into the roof system) before occupancy.

To seal two-ply asphaltic felts set in hot asphalt on a concrete roof deck, an asphaltic glaze coat was applied at the end of the day. Because of the inherent tackiness of the asphalt until it oxidizes, Hutch has been specifying a smooth-surfaced modified bitumen cap sheet, eliminating the glaze coat.

PHOTO 2: To seal two-ply asphaltic felts set in hot asphalt on a concrete roof deck, an asphaltic glaze coat was applied at the end of the day. Because of the
inherent tackiness of the asphalt until it oxidizes, Hutch has been specifying a smooth-surfaced modified bitumen cap
sheet, eliminating the glaze coat.

CONTROL OF CONSTRUCTION-GENERATED MOISTURE

I have seen roof systems on office buildings severely compromised by construction- generated moisture caused by concrete pours, combustion heaters, block laying, fireproofing, drywall taping and painting. Thus, a simple vapor retarder should be considered in these situations to control rising moisture vapor during construction, which includes the flushing of the building if required for commissioning.

CONSTRUCTION SEQUENCING AND MATERIALS

Building construction takes place year round. It is unfortunate decision makers in the roofing industry who are pushing low-VOC and/or water-based adhesives do not understand this; problems with their decisions are for another article. If the roof is to be installed in late fall (in the Midwest) and interior concrete work and/or large amounts of moisture-producing construction, such as concrete-block laying, plastering, drywall taping or painting, are to take place, a vapor retarder should be considered.

How will the building, especially the façades, be constructed? Will they be installed after the finished roof? This creates a scenario for a damaged “completed” roof system.

PHOTOS: Hutchinson Design Group Ltd.

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New VOC Regulations Threatened the Quality of Roofing Assemblies until the Roofing Industry Became Involved

Ellen Thorp, associate executive director of the EPDM Roofing Association, makes it a point to be responsive to the many inquiries she gets. Most deal with routine requests for information about EPDM, but one phone call Thorp fielded six years ago from one of ERA’s member companies stood out from the rest. Ultimately, it changed the way ERA and the roofing industry do business.

A manufacturer’s rep had heard from a customer in Connecticut that the state was about to implement VOC regulations. The problem: The new regulations would ban some of the adhesives, sealants, and primers essential to installing EPDM and other roofing products, and there were no substitute products available to meet the new standards. If the new regulations went into effect as scheduled, they threatened to negatively impact the safety and quality of roofing assemblies in the affected area and the roofing industry as a whole.

The proposed regulations were part of an effort by the Ozone Transport Commission, or OTC, to achieve federally mandated air-quality standards in the Northeast and Mid-Atlantic. The OTC was created under the Clean Air Act to develop solutions for the New England states, as well as Delaware; Maryland; New Jersey; New York; Pennsylvania; Virginia; and Washington, D.C. At the time of OTC’s creation, most of these states had not attained federally mandated ozone standards, and the region lagged behind other parts of the U.S. in achieving compliance.

As part of its initial work, OTC developed a Model Rule for Adhesives and Sealants, based on regulations used in California, incorporating provisions effective in the climactic and market conditions of that state. At the time of the phone call to Thorp, the OTC had released the model rule, and states were beginning to draft their own regulations that included implementation dates within the next year. “The VOC limits the OTC was proposing would have required products that did not exist in the Northeast and Mid-Atlantic,” Thorp explains. “It was also concerning that they were basing the limits on California regulations. The climate in the Northeast is very different than in California, so we didn’t feel it was good science to be creating a model rule based on a place that had a completely different climate.”

Thorp and the ERA member companies were very interested in working with state regulators. “It certainly is our priority to reduce VOC emissions wherever possible, but it also is important to us to have regulations that our industry could work with and are based on the best available science,” she says. In fact, products that would meet the new regulations were in development but were not yet available. In addition, the new adhesives and sealants would require new or modified application techniques. That meant the roofing industry needed time to train thousands of roofing contractors.

ERA’s first step was to support its assertion that the climate of the Northeast differed dramatically from that of California. ERA hired Jim Hoff of Tegnos Research Inc. to review weather data and the effects the weather has on low-VOC products. “At ERA’s expense, we assembled relevant scientific data and provided it to the state regulators,” Thorp adds.

ERA worked with regulators in each state, sharing the results of its research. ERA provided the state environmental protection and air quality bureaus with detailed information about what sealants were available and explained the time needed to train roofing contractors. Working together, the regulatory bodies and ERA were able to agree on a phased-in or seasonal approach. For instance, in a majority of the states, the new low-VOC products were required initially only in the summer for three months. The year after, they were required for five months. Then, the following year, they were required year-round. Once these states had found success with this approach, others followed suit. “We explained to the regulators the importance of being consistent since many roofing companies do work across multiple states, especially in the Northeast where the states are small and roofing companies are likely to work across state lines,” Thorp notes.

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A Roofer’s Guide to Safely Navigating an OSHA Inspection

Almost every American can recite his or her Miranda rights. We have all seen enough cop dramas and world’s wildest police chases on prime-time television to know that when the police, FBI or other law-enforcement agencies get involved that we have the right to remain silent, and we know that everything we say can and will be used against us in a court of law. Unfortunately, many roofing contractors in the construction industry do not remember their rights when an OSHA inspector arrives at their job sites, and this can lead to hefty fines. It is very important for residential and commercial roofing contractors to remember OSHA inspectors are adversaries when they visit your job site, and they are not inspecting your equipment and interviewing the crew out of curiosity. When an OSHA inspector arrives onsite, he or she is usually there to gather evidence to issue a citation.

One of the most discouraging situations that we have seen from OSHA’s recent push for larger fines and more citations occurs when honest men and women in the roofing industry open their arms to OSHA inspectors who arrive at the job. Roofing contractors and their crews are not criminals, and most truly have nothing to hide. The majority of contractors in the industry are hesitant to take a firm stance against an apparently well-to-do government agent on their job site. However, a roofer who opens up and allows OSHA inspectors free and unlimited access to a construction site is making a costly mistake. Therefore, it is important to remember that when OSHA visits on your next project, there are a few key questions that every roofing contractor needs to be able to answer about the inspection.

WHY IS OSHA ON MY JOB SITE?

OSHA will investigate a job site for a number of reasons. Inspectors will show up if an employee has issued a complaint against you, if there is a recent fatality or if there is an imminent threat identified. However, in recent months, OSHA has been after
the residential and commercial roofing industry through a systematic targeting method. The dangers of fall-related injuries in the industry have been well-documented, and this has prompted inspectors in your area to be on the lookout for roofers. Additionally, roofers are the easiest to cite due to the fact that roofing is a highly visible construction trade and an inspector does not have to use much effort to determine the likelihood of a dangerous situation that needs inspecting.

DO I HAVE TO COMPLY? HOW SHOULD I COMPLY? WHAT HAPPENS IF I REFUSE OSHA ACCESS?

First and foremost, you need to know that OSHA has a legal right to inspect your job site. OSHA has what is called “administrative probable cause” to inspect and investigate your project. OSHA’s probable cause is more easily obtained than that of other agencies. An officer of city, state or federal law enforcement needs a much more specific probable cause to enter a private citizen’s property. When an active construction job is taking place, there is an inherent risk of danger and injury, and this gives OSHA all the administrative probable cause it needs.

This is not to say that you or your site superintendent does not have the right to deny OSHA access to the project and demand that the inspector get a warrant. The site superintendent has the option to consent to OSHA’s inspection or deny the inspector access to the project. The superintendent is well within his or her rights to tell the inspector to get a warrant. This is not an easy fix, however. If you tell OSHA to get a warrant, it most certainly will. Because of OSHA’s broad power to oversee safety within the U.S., the agency can obtain a warrant from a judge or magistrate. Once OSHA obtains a warrant for a site inspection, its inspection can become much more invasive. This means OSHA inspectors can get permission from a judge to examine documents; conduct extensive interviews; and also perform scientific tests on items, such as air quality, presence of combustible material or any other danger.

The bottom line is that it is rarely a good idea to tell an OSHA compliance officer to get a warrant. The reasoning behind this has to do with the scope of OSHA’s inspection rights under the Code of Federal Regulations (CFR). The CFR demands that OSHA’s inspection be “reasonable.” This essentially means that the agency is limited to inspect only the men, equipment and materials that are within “plain sight.” “Plain sight” is a doctrine borrowed from criminal law and the Fourth Amendment, which says that a government agent may not sample or manipulate anything that is not within his or her reasonable line of sight. If an agent violates this doctrine, it is possible all the information he or she obtained during the inspection may be suspect.

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Substrate Boards

The third installment in my series on the roof system is about the substrate board. (To read my first two articles, “Roofs Are Systems” and “Roof Decks”, see the January/February issue, page 52, and the March/April issue, page 54, respectively.) For the purpose of this article, we will define the substrate board as the material that is placed upon the roof deck prior to the placement of thermal insulation. It often is used in part to support vapor retarders and air barriers (which will be discussed in my next article in the September/October issue).

The type of substrate board should be chosen based on the roof-deck type, interior building use, installation time of year and the cover material to be placed upon it.

The type of substrate board should be chosen based on the roof-deck type, interior building
use, installation time of year and the cover material to be placed upon it.

Substrate boards come in many differing material compositions:
• Gypsum Board
• Modified Fiber Reinforced Gypsum
• Plywood
• High-density Wood Fiber
• Mineral Fiber
• Perlite

Substrate boards come in varying thicknesses, as well: 1/4 inch, 1/2 inch, 5/8 inch and 1 inch. The thickness is often chosen based on the need for the board to provide integrity over the roof deck, such as at flute spans on steel roof decks.

TOUGHNESS

The type of substrate board should be chosen based on the roof-deck type, interior building use, installation time of year and the cover material to be placed upon it. For example, vapor retarder versus thermal insulation and the method of attachment. Vapor retarders can be adhered with asphalt, spray foam, bonding adhesive, etc. The substrate board must be compatible with these. You wouldn’t want to place a self-adhering vapor retarder on perlite or hardboard because the surface particulate is easily parted from the board. Meanwhile, hot asphalt would impregnate the board and tie the vapor-retarder felts in better. The substrate board must have structural integrity over the flutes when installed on steel roof decks. The modified gypsum boards at 1/2 inch can do this; fiberboards cannot. If the insulation is to be mechanically fastened, a substrate board may not be required.

It should be more common to increase the number of fasteners to prevent deformation of the board, which will affect the roof system’s performance.

It should be more common to increase the number of fasteners to prevent deformation of the board, which will affect the roof system’s performance.

The substrate board should be able to withstand construction-generated moisture that may/can be driven into the board. Note: In northern climates, a dew-point analysis is required to determine the correct amount of insulation above the substrate board and vapor retarder, so condensation does not occur below the vapor retarder and in the substrate board.

Substrate boards are often placed on the roof deck and a vapor retarder installed upon them. This condition is often used to temporarily get the building “in the dry”. This temporary roof then is often used as a work platform for other trades, such as masonry, carpentry, glazers and ironworkers, to name a few. The temporary roof also is asked to support material storage. Consequently, the substrate board must be tough enough to resist these activities.

The most common use of a substrate board is on steel and wood decks. On steel roof decks, the substrate board provides a continuous smooth surface to place an air or vapor retarder onto. It also can provide a surface to which the insulation above can be adhered. Substrate boards on wood decks (plywood, OSB, planking) are used to increase fire resistance, prevent adhesive from dripping into the interior, provide a clean and acceptable surface onto which an air or vapor retarder can be adhered, or as a surface onto which the insulation can be adhered.

PHOTOS: HUTCHINSON DESIGN GROUP LTD.

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The NRCA ProForeman Certificate Program Helps Roofing Contractors Invest in Their Foremen

High Life Speedboats was experiencing a problem with its newest model speedboat engine, which, when hitting top speeds, would frequently cut out. This resulted in boats that were traveling 60 mph to be almost dead in the water within seconds. More than once, someone had been seriously injured by being thrown off balance, crashing into onboard components or being thrown overboard.

Panache Speedboats also was trying to improve its engines. The company had been in business for two decades and was known for building reliable boats. With operations systematized and production running in turnkey mode, company engineers wanted to explore the possibilities of building a higher-performance engine and securing Panache a spot in the elite racing market.

There are two equal and opposite drives for improvement in both of these cases. High Life needs to improve; its product is unreliable and the company will ultimately go out of business—not to mention people may be hurt and killed if steps are not taken. Panache wants to improve; it has a reliable product but it’s not as good as it could be.

So, now you may be asking, “How does this relate to the roofing industry?”

Most reputable roofing contractors are not like High Life. Their roof systems don’t fail outright, causing damage and ruining companies’ reputations. Most roofing contractors are Panache engines. They are reliable and their roof systems serve customers well.

But if you have the itch, like Panache, to increase performance, then you have a drive to improve for the best reason— because you want to be better. You are not panicking. You are planning. You want to see whether you can shape your company to become an elite contracting company, known for its excellence.

Thoughtful contractors will consider what investments will yield the most significant returns for their companies. New equipment? A better facility? Increasing the types of systems they install?

Consider the following statement from Ethan Cowles of Raleigh, N.C.-based management consultant FMI: “World-class contractors all have incredible talent at the foremen level. That is not to say company leadership, business strategy, project management, etc., are not important, but operations without great foremen always struggle to achieve anything but mediocrity.”

HIGH-PERFORMANCE FOREMEN

Cowles’ quote resonates with what the Rosemont, Ill.-based National Roofing Contractors Association (NRCA) has heard from its contractor members, as well. Tom Shanahan, NRCA’s associate executive director of risk management, states that after asking hundreds of contractors over the years how much of each dollar flowing through a company is affected directly by foremen, he has safely landed on 85 cents. Eighty-five cents of every dollar.

Foremen drive your trucks, use your equipment, manage your labor, direct quality control, affect insurance rates and often are the face of your company for customers.

EIGHTY-FIVE CENTS OF EVERY DOLLAR.

It makes you want to ensure your foremen are high-performance engines, doesn’t it?

NRCA has been focused for years on providing education for roofing foremen. Recognizing that most foremen are promoted into their positions because of their roofing skills and work ethic, rather than for their leadership prowess, For Foremen Only has provided a venue for training thousands of foremen about leadership and communication during the past 15 years. Now, packaged within this larger ProForeman initiative, the classes provide a cornerstone for a well-rounded experience aimed at helping roofing-contractor operations to achieve world-class excellence.

Foremen need to be leaders, not just crew managers; therefore, they need to understand the whole picture—the process of selling and installing roof systems, their role in keeping employees safe, outside forces that necessitate compliance and more—if they are to understand the importance of their role.

The ProForeman program is designed to help roofing foremen shift their perspectives of their role from being roofing installation managers to company leaders. As leaders, the burden of responsibility is greater and, when understood, frees them to think differently about how to work with their crews and their supervisors.

The ProForeman program comprises six main topics:

    • General education
    • Roofing technology
    • Construction/business practices
    • Leadership
    • Safety
    • Training others

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Wind Loading on Rooftop Equipment

I recently attended a continuing-education conference for civil/structural engineers that discussed changes in the 2012 International Building Code (IBC) and the referenced ASCE 7-10 “Minimum Design Loads for Buildings and Other Structures”. During the seminar, the question was asked: “Who is responsible for the design of wind loading to rooftop equipment as defined in the IBC and Chapter 29 of ASCE 7-10?” The most accepted response was to add a section in the structural general notes that wind design on rooftop equipment is to be designed “by others”.

A structural engineer designed the metal support system and load transfer from the new HVAC unit down through the structure.

A structural engineer designed the metal support system and load transfer from the new
HVAC unit down through the structure.

The design requirements for wind loading on rooftop equipment have been included in previous editions of the IBC and ASCE 7, but significant changes have been included in ASCE 7-10. The increased attention is in part because of more severe wind events in recent years. While it is not the primary responsibility of the roofing consultant or contractor to evaluate the systems being placed on the roof, it is good to understand the code’s requirements for loading to rooftop equipment, how the load is determined and applied, and how the load is transferred to the building structure.

CODE REQUIREMENTS

The primary focus of the roofing professional in the IBC is concentrated on Chapter 15 (Roof Assemblies). While there are requirements in Chapter 15 addressing rooftop structures, these requirements, particularly in relation to wind loading, extend beyond Chapter 15. It is therefore imperative to be familiar with other sections of the code.

For instance, Section 1504 (Performance Requirements) refers the user multiple times to Chapter 16 (Structural Design) for wind-loading-design requirements. While roof manufacturers typically prequalify their systems based on various industry standards (ASTM, FM, ANSI, etc.), rooftop equipment supports are not typically prequalified because of the variability of placement and conditions. Similarly, new to this code cycle, Section 1509.7.1 includes the requirement for wind resistance for rooftop-mounted photovoltaic systems per Chapter 16 of the IBC. Other industries or trades have similar requirements. Section 301.15 of the 2012 International Mechanical Code and Section 301.10 of the 2012 Fuel and Gas Code require “equipment and supports that are exposed to wind shall be designed to resist the wind pressures in accordance with the IBC”.

Section 1609 of Chapter 16 (Wind Loads) applies to wind loading on every building or structure. Section 1609.1.1 provides two design options. The designer can use chapters 26 to 30 of ASCE 7-10 or Section 1609.6 of the IBC. Note however that Section 1609.6 is based on the design procedures used in Chapter 27 of ASCE 7-10, which does not address wind loading on rooftop equipment and thus is not applicable. Chapter 29 of ASCE 7-10 (Wind Loading on Other Structure and Building Appurtenances) contains the procedures used to determine wind loading on rooftop structures and equipment.

DETERMINING AND APPLYING WIND LOADING ON ROOFTOP EQUIPMENT

Properly specified ballasting blocks are designed and formed to better address the freeze/thaw cycle.

Properly specified ballasting blocks are designed and formed to better address the freeze/thaw cycle.


To determine wind loading on rooftop equipment, the first step is to identify the building Risk Category (formerly the Occupancy Category) and the building location. The Risk Category is determined from Section 1604.5 and Table 1604.5 of the IBC or Table 1.5-1 of ASCE 7-10. There are slight variations in the two codes but typically each will produce the same Risk Category.

The Risk Category and the location are then used to determine the design wind speed based on published wind-speed maps, available in Section 1609.3, figures 1609 A to C of the IBC, or Section 26.5.1, figures 26.5-1 A to C of ASCE 7-10. It can be difficult to read these maps to select the appropriate wind contour line, specifically along the East Coast. The Redwood City, Calif.-based Applied Technology Council (ATC), a non-profit that advances engineering applications for hazard mitigation, has digitized the maps providing a valuable resource for determining design wind speeds by GPS coordinates or the building’s address. Visit ATC’s wind-speed website. Note however that it is always advisable to cross check this design wind speed with the maps in the adopted code or with the local building authority.

PHOTOS: MIRO INDUSTRIES INC.

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The Success of Your New (Replacement) Roof Depends on Adjacent and Connected Elements, including Masonry

Although the name of this publication is Roofing, the roofing/waterproofing/construction industry recognizes more and more that the building envelope is a fully integrated and interrelated assembly of systems.

masonry cracks due to freeze thaw

Click to view larger version

As such, I feel the need to discuss the importance of water resistance and structural integrity in existing wall surfaces, which are adjacent and connected to your project’s new (replacement) roof system. The focus of this article is not how to design a replacement roof system but how to address adjacent masonry to ensure it doesn’t work against the success of the new roof.

These principles actually apply to any wall system that connects, generally above and adjacent, to your roof, but masonry poses some distinct concerns. Water intrusion, thermal movement and structural integrity of this masonry, along with locations of embedded flashing, all come into play as the new roof system is properly integrated into the adjacent rising wall, parapet wall or even perimeter edge wall beneath the roof.

COMMON MASONRY ISSUES

Thomas W. Hutchinson, AIA, FRCI, RRC, a regular Roofing contributor, has said, “long-term service life is the true essence of sustainability”. Moreover, designers specify (for owners to buy) warranties of 20, 25 years or more with new roof systems. It’s just good common sense that you can’t allow a new roof to be jeopardized by water intrusion from an adjacent system because of an oversight in the original analysis of the situation.

Many of us have been called by an owner who says his or her new roof is leaking, only to find roof-mounted equipment or an unrelated system is actually leaking. However, if the leak is stemming from another aspect of the building envelope, such as an adjacent parapet or rising wall, which is now jeopardizing the investment made on a new roof, that you (the designer) should have foreseen, it makes for a very difficult position. The roofing system manufacturer, who holds the warranty, and the owner are going to look at you as being responsible.

masonry

Click to view larger version

Let’s examine three common occurrences using actual case studies. All three situations, which occurred on schools in the Northeast, exemplify the condition of adjacent masonry was deficient and had to be corrected, adding a significant degree of scope and cost to the project to guarantee a roof design that would perform over the long haul. These three cases cover:
1. Repairing the masonry and covering it.
2. Altering the masonry to change the location of embedded flashings.
3. Replacing structurally unsound/failed masonry with another material.

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Spray Polyurethane Foam Has Structure-strengthening and Energy-efficiency Capabilities

A high-performance building material, spray polyurethane foam (SPF) is widely used as an effective, lasting roofing solution. With positive benefits, including versatility, thermal insulation, resistance to inclement weather cycling and storms, strengthening of the building envelope, long life span and durability, spray foam has enjoyed increased use among builders and roofing contractors alike.

A roof’s primary purpose is to protect the structure underneath it. As a roofing material, closed-cell SPF acts as a protective roofing mechanism and a thermal insulator. The lightweight material is ideal as a roofing solution when:

 As a roofing material, closed-cell SPF acts as a protective roofing mechanism and a thermal insulator.

As a roofing material, closed-cell SPF acts as a protective roofing mechanism and a thermal insulator.

  • the roof substrate has many penetrations.
  • the roof deck is an unusual shape or configuration.
  • the roof is being applied to a structure located in a severe-weather environment.
  • a lightweight option is needed.
  • a slope application is preferred to provide extra drainage capabilities.
  • keeping the existing roof cover is desired.

STRENGTH AND DURABILITY

SPF is considered a highly durable building material. The physical properties of the foam change little with time, accounting for a life span up to 30 years with regular care and maintenance. SPF roofing systems also strengthen the roof in multiple ways. Roofing spray foams possess a compressive strength of 40 to more than 60 pounds per inch. Spray foam’s adhesion strengthening capabilities are key, especially in locations where severe weather cycling, storms, wind, hail and other conditions are prevalent and commonly cause structure damage. Coastal and hurricane-prone regions are prime examples.

When applied to the interior side of a roof, closed-cell SPF can increase a building’s resistance to wind uplift during severe storms. When SPF is applied to built-up roofing and metal substrates, it increases resistance to wind uplift even further. A study conducted by the University of Florida, Gainesville, in 2007 found that applying closed-cell spray foam under a roof deck provides up to three times the resistance to wind uplift for wood roof sheathing panels when compared to a conventionally fastened roof.

Spray foam is a good solution for unusual configurations and areas with many penetrations.

Spray foam is a good solution for unusual configurations and areas with many penetrations.

Spray foam also is resistant to progressive peeling failure. Caused by wind, peeling happens at the roof’s edges when wind pulls flashings and copings away from their installed positions. Peeling looks like a tin can after it has been cut around the perimeter. When this happens, a chain reaction may occur and lead to catastrophic building failure. After the roof membrane, panels or tiles pull away, the board-stock insulation is exposed, often with less resistance to the lateral and uplift wind forces. Then the sheathing below and the substructure are subject to movement and wind or water damage, potentially leaving the entire building interior underneath open and vulnerable. SPF roofing is continuous, so it provides a water-resistant layer that is well adhered to the substrate.

When the Gaithersburg, Md.-based National Institute of Standards and Technology examined roofs following Hurricane Katrina, it found buildings with spray-foam roofs performed rather well without blow-off of the SPF or damage to flashings. The 2006 “Performance of Physical Structures in Hurricane Katrina and Hurricane Rita: A Reconnaissance Report” found that only one of the examined SPF roofs incurred notable damage, and that damage was confined to only 1 percent of the total roof system. The report concluded spray foam kept the roofs intact, prevented moisture from entering the buildings, and protected the structures from hail and debris.

Hurricane Katrina played a significant role in one of the largest reroofing projects ever on one of the largest metal-framed domed structures in the world: the Superdome in New Orleans. Katrina destroyed the dome’s second roof; the structure’s original roof was constructed with polyisocyanurate foam covered with a fluid-applied elastomeric coating but was replaced in 1989 with a single-ply EPDM roofing system. After the damages suffered during Katrina, the EPDM roof system was replaced with a spray foam roof system.

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Forum-selection Clauses and Their Impact on the Construction Industry

With the national housing market poised for slow but steady growth in 2014, U.S. contractors expect a good year for business, and the number of contracts and subcontracts for construction work is expected to increase. Many of these contracts will contain forum-selection clauses, and a recent U.S. Supreme Court ruling brings to light the importance of these clauses and coming changes in their enforceability.

WHAT IS A FORUM-SELECTION CLAUSE?

A forum-selection clause is a contractual provision in which the parties establish the place for specified litigation between them. These clauses have become increasingly common in construction contracts, particularly with general contractors who do business in two or more states. Often, general contractors have a form subcontract agreement they require or ask all subcontractors on a particular project to sign. If general contractors work in multiple states, forum-selection clauses can help them make potential litigation less costly and easier to manage by guaranteeing the litigation will take place in the company’s home state, where its executives and attorneys likely work.

An example is a general contractor based in New York but working on a North Carolina project and entering into a roofing subcontract with a North Carolina roofer. The general contractor can present the subcontractor with a forum-selection clause mandating any legal claims arising from the subcontract may only be brought in a New York court. For a North Carolina contractor, finding counsel and filing suit in New York will likely be more difficult and costly than doing so in North Carolina, especially when evidence and witnesses are located in North Carolina. In this example, the forum-selection clause makes litigation more predictable and cost-effective for the general contractor and also decreases the likelihood the subcontractor will actually be able to sue, so it most likely favors the general contractor.

To protect local contractors, many state laws have declared out-of-state forum-selection clauses unenforceable in construction contracts. These states include Arizona, California, Connecticut, Florida, Illinois, Louisiana, Minnesota, Montana, Nevada, New York, North Carolina, Ohio, Oregon, Pennsylvania, Tennessee, Utah, Virginia and Wisconsin. Additionally, state laws in Nebraska, Rhode Island, South Carolina and Texas make forum-selection clauses unenforceable in certain circumstances that sometimes, but do not necessarily, encompass construction contracts. In the first category of states, local contractors have been able to file suit locally despite forum-selection clauses because courts in these states can apply the state laws and disregard the clauses. However, the U.S. Supreme Court’s recent decision on these clauses will severely limit the reach of these laws and will ensure that forum-selection clauses are enforced in many more cases.

CASE BACKGROUND

In December 2013, the U.S. Supreme Court issued a unanimous decision in the case of Atlantic Marine Construction Co. v. United States District Court for the Western District of Texas. The court held that defendants in federal court can use forum-selection clauses to transfer their cases to the state specified in the clause, even if the suit is brought in a state with a law deeming these clauses unenforceable. Essentially, forum-selection clauses may be enforced by a venue transfer motion.

The case involved Atlantic Marine Construction (AMC) Co., a general contractor based in Virginia. AMC won a federal contract from the U.S. Army Corps of Engineers to construct a building at Fort Hood, Texas. AMC subcontracted with J-Crew Management, a local Texas company, to perform some of the work. AMC’s contract, which J-Crew Management signed, included a forum- selection clause dictating that any legal disputes between AMC and J-Crew Management arising from the contract had to be brought in state or federal court in Norfolk, Va.

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