In this issue...
Storm-Resistant Roofing: A Home's First Line of Defense
Nail spacing requirements for plywood or OSB roof deck.
With the Gulf Coast still reeling from the devastation wrought by Hurricane Katrina last year, it is difficult to believe that the onset of this year's hurricane season is right around the corner. Although no one can predict or mitigate Mother Nature, advances in building science now enable builders to construct homes that better withstand destructive storms.
During a storm, a strong roof is often a home's first line of protection. Likewise, a weaker roof can be its Achilles heel. A poorly-constructed roof will be susceptible to lift-off, which can compromise the entire building. However, most storm-related damage is actually caused by water penetration rather than structural failure. And even carefully-constructed traditional roofs can be vulnerable to water infiltration.
The Partnership for Advancing Technology in Housing (PATH) developed 11 recommendations for storm-resistant roofing that can help homes stay structurally sound and prevent water damage during storms. In addition, the Institute for Business & Home Safety's (IBHS) Fortified...for safer living® program provides a builder's guide that includes criteria for high-wind prone areas.
These recommendations are especially useful for areas that are at high-risk for strong winds. However, many can and should be used on homes outside of hurricane-prone regions to prevent damage during other storms. According to the IBHS, all of the continental United States are susceptible to hurricanes, tornados, or high winds.
Roof Design
Moderately-pitched hip roofs are the best choice for preventing uplift during a storm, unlike gable roofs, which are at risk from damaging horizontal and uplift forces unless adequately braced. A moderate pitch between 4/12 and 6/12 is best - roofs that are too flat (3/12 or less) can also be susceptible to uplift.
Builders should also reduce through-the-roof penetrations wherever possible in order to avoid unnecessary water intrusion. For example, tubular skylights with polycarbonate domes reduce the through-the-roof penetration size considerably compared with traditional skylights. Baffled ridge vents should also be used to help prevent airflow and wind-driven rain from entering the attic.
Sheathing
Roof sheathing installation can play a significant role in the amount of damage caused by a storm. Sheathing with a minimum thickness of 19/32 of an inch adds strength, as do improved nails and nailing techniques.
The Fortified...for safer living Builders Guide (www.ibhs.org/publications/downloads/468.pdf), developed by the Institute for Business & Home Safety, specifies using 2 1/2-inch ring shank nails and nailing at 4 inches on-center on panels adjacent to a gable end and 6 inches on-center everywhere else. According to Michael Redburn, president of RFB Homes, a Ft. Myers, Fla., builder who constructs to Fortified home guidelines, the ring shank nails are so strong that they cannot be pulled out. "If we make a mistake, we have to cut them," he said.
RFB Homes goes beyond the Fortified guidelines by taping all roof decking seams with 10-inch wide tape. According to Redburn, this allows the roof deck to act as a secondary water and wind barrier if the roof covering does blow off. "It won't last forever, but it gives enough time to get a new roof up," he explained.
PATH recommends using self-adhering asphalt/rubber (modified bitumen) tape that is at least 4 inches wide, or using a peel-and-stick roof membrane product over the entire deck.
Underlayment
The Florida Alliance for Safe Homes (FLASH) recommends installation of a layer of #30 felt paper underlayment with 2-inch minimum overlap over the wood roof sheathing and secondary water barrier tape. End laps should be a minimum of 6 inches. Nail spacing should be no greater than 6 inches along the laps and 12 inches in the interior of each strip using low-profile roofing nails with load distribution disks or capped-head nails. Roofs within 3,000 feet of salt water should have hot-dipped galvanized fasteners for attachment of all roof coverings, including underlayment. A layer of #90 underlayment is recommended for tile, slate, or metal roof coverings.
Connections
According to the Fortified builder's guide, "the building must have positive connections from the roof to the foundation as a means to transmit wind uplift and shear loads safely to the ground." Hurricane straps should be used to secure the roof to wall framing effectively. Straps should wrap over the top of the roof truss or rafter.
Cladding
Roof installation should be finished with a durable covering, such as wind and impact-resistant shingles, ceramic or concrete tiles, or standing-seam metal roofs. In high-wind zones, increasing the frequency of fasteners from four to six per shingle will increase the wind-resistance rating. Ceramic and concrete roof tiles should be mechanically attached to roof sheathing. Metal roofs should be installed in compliance with manufacturer's instructions for high-wind areas. In warm and moderate climates, choosing a light-colored cladding will reduce the amount of summer solar heat absorbed by the roof and extend its life.
Installation
Correctly installing materials can also make a huge difference in roof durability. Using grid-marked sheathing can ease cutting, ensure the correct fastening pattern, and facilitate the layout of shingle underlayment.
Use proper flashing and starter strip techniques; for example, installing flashing wherever there is a change in surface plane or cladding material will channel water runoff during storm events and provide another level of water intrusion protection.
Because fastener or nailing schedules tend to change with the product and wind zone, consult the manufacturer's specifications so that fasteners are installed to the proper embedment depth into framing members or sheathing.
Cost Considerations
Most of these techniques add minimally to the finished cost of a roof. According to Redburn, the biggest costs come from the learning curve in getting contractors to change their practices. "It took about an extra day for [our contractors] to learn," he said. "After that, it doesn't add that much to the costs." Redburn estimates the additional labor and materials costs at 15 to 18 percent over a traditional roof.
Although the roof may cost homeowners a little more, it is well worth the savings they can receive from insurance companies. For example, through the Fortified program, First Floridian Insurance (a Travelers Company) has offered discounts.
More information on storm resistant roofing is available in PATH's Tech Set #5, Storm-Resistant Roofing - visit www.toolbase.org for this and other PATH Tech Sets.
Pan Flashing/Sill Protection Installations Effective in Reducing Water Intrusion
Water intrusion in walls is an ongoing problem for the home building industry. Intrusion can occur in all types of buildings and in most climates, often through windows, doors, and other through-the-wall penetrations. One of the most critical paths for water intrusion is below window units in typical wall assemblies. This area is often poorly addressed, detailed, and executed in the construction process. In the past few years, manufacturers have introduced numerous new flashing products that can help builders with this problem.
In order to test the effectiveness of new techniques in reducing water intrusion, the NAHB Research Center teamed with Williams Building Diagnostics, Inc. (WBD) to conduct laboratory and field evaluations of various types of pan flashing systems over wood framing for the PATH Program. Although the project tested only a few of these products under specific circumstances and cannot guarantee the performance of all similar products, pan flashing demonstrated the potential to greatly improve the moisture resistance of the window/wall interface.
Pan flashing is a water-impervious material that is installed on the sill within the rough opening of a window or door, and is lapped over the weather-resistive barrier (WRB). It is designed to direct water entering the window cavity out of the wall without penetrating the WRB. This type of flashing commonly has upturned legs on the back and sides, and is usually sloped toward the exterior of the home to drain water.
As the first step in this project, researchers identified the range and attributes of available pan flashing products on the market. After reviewing their characteristics, various types of tests were conducted to determine how well these products worked in the laboratory and the real world.
Because several of the surveyed products used self-adhesive membranes, an outdoor weathering test helped determine how well they adhered to the flashing when exposed to the elements over an extended period. Simultaneously, a pan flashing was tested with two kinds of WRBs and two installation approaches to ensure that the flashing systems were robust enough to function well under different usage scenarios. Finally, technicians retrofitted pan flashing products in several field locations where moisture intrusion at windows had been a problem. Moisture sensors installed behind the flashing detected any water penetration.
In both the laboratory and the field tests, the pan flashing systems effectively prevented the intrusion of water into the wall cavity at the window sill. The adhesive systems showed slight wrinkling, but did not admit any significant amount of water. The use of a heat gun or primer during installation reduced these wrinkles. The different WRBs and installation techniques tested on the panels in the laboratory also resulted in no water intrusion, demonstrating the system's durability over a wide range of weather conditions. After several months of exposure, two field trials - one in a residential building and one in a commercial building - showed only slight moisture penetration that is well within the acceptable range. Monitoring of these two sites is ongoing.
Taken together, these tests found that durable pan flashing products used with other water management techniques can greatly reduce water intrusion at window/wall interfaces.
For best results, builders should slope the sill pans or use products with an integral slope to ensure not only that water does not reach unprotected wood, but that it also drains away to the exterior of the wall. Using supplementary heat or a primer will improve adhesion of membrane products.
The results of these tests are detailed in the new report "Laboratory and Field Evaluation of Pan Flashing/Sill Protection and Water Resistive Barriers," which is available on the ToolBase website. The report includes a detailed listing of the pan flashing products identified as part of this PATH project. Visit www.ToolBase.org/panflashingeval to download the report.
Best Practices Guide to Residential Construction Materials, Finishes, and Details
This comprehensive guide, compiled by former Journal of Light Construction editorial director Steven Bliss, is a practical resource for building professionals seeking current information on construction materials, finishes, and details. In this resource, Bliss draws on his extensive knowledge as a practicing builder, designer, and construction editor to help other building professionals select the right materials and install them with confidence. Builders, designers, and contractors will find it extremely helpful in making informed material selections, quick on-site product comparisons, and for resolving questions about product performance when planning residential projects.
The Guide is organized in a textbook format with seven chapters, making it very reader friendly. Each section offers field-tested installation details and practical solutions for a variety of building products and systems that readers will wish they'd known sooner. Many of these include technologies or practices that have been recently introduced in the marketplace and/or proven to be durable, affordable, energy efficient, and sustainable.
Chapter topics include: Exterior Finishes; Roofing; Windows and Doors; Decks and Porches; Interior Finishes; Kitchen and Bath; and Indoor Air Quality. Descriptions of materials, components, and elements within the chapters are accompanied by helpful graphics and photographs that guide a reader through installation. For example, Chapter One - Exterior Finishes includes a thorough discussion of all components of exterior walls that provide a durable and weather-resistant envelope. Bliss addresses relevant code requirements, performance measures, critical installation details, and recommendations for siding, veneers, weather-resistive barriers, sheathing, trim, flashing, caulks, sealants, adhesives, and finishes. Beyond the concepts and helpful hints, the chapter also lists product suppliers and their websites or contact information. The Guide's Resource and Subject Index pages offer additional practical resources.
By using the Guide, residential building professionals have access to a source of objective information that takes the guesswork out of selecting products and materials that can influence the design and durability of their projects. The Guide can be purchased online from the publisher at www.wiley.com or from Amazon.com. More information on many of the products and technologies described in the Guide can be found in the PATH Technology Inventory as well - visit www.ToolBase.org/techinv.
From Concept to Reality
Artist's rendition of a community of PATH Concept Homes.
The Partnership for Advancing Technology in Housing (PATH) recently announced that the first demonstration PATH Concept Home will be built by Brighton Construction, a Nebraska-based construction firm that builds affordable housing and designs homes that fit the preferences of a wide range of cultural demographics. Brighton will build the demonstration home within an existing neighborhood in Omaha overlooking the Creighton University campus. Construction is expected to begin this summer.
Timing for the Concept Home becoming a reality coincides with new research results that indicate builders and architects are ready to embrace the innovative features offered by this home. According to a recent PATH-sponsored survey, builders and architects agree that greater energy efficiency, increased affordability, and design flexibility are the most important features for homes of the future. More than half of builders and architects surveyed said they would introduce a new building system or design element into the homes they build if they had an adequate comfort level with the expected performance.
The Concept Home program is an initiative to develop high-quality, affordable homes that easily adjust to changing lifestyles and technological advances. The concept incorporates flexible floor plans that allow the home to accommodate lifestyle changes. Homeowners can rearrange the home over time to fit their work habits and family needs, or to help them age in place.
While the design flexibility equips the home and its owners for the future, the Concept Home also offers more immediate benefits. During construction, it combines functions that make optimal use of labor, materials, time, and money. Improved production methods will speed construction and enhance the home's long-term durability. And its customizable designs will give the home the quality and curb appeal of a custom-built house without the high cost.
Six principles create the foundation for the Concept Home: (1) flexible floor plans; (2) organized and accessible systems; (3) improved production processes; (4) alternative basic materials; (5) standardization of measurements and component interfaces; and (6) integrated functions.
The Concept Home Design Guide is now available to be downloaded for building professionals who want to learn more about how these homes will work. The Guide includes designs for both attached and detached Concept Homes, as well as examples of how to incorporate the six design principles. Builders and designers who want more detail on the technologies, systems, and design approaches can also access detailed technical reports for each of the principles. Both the Design Guide and reports are available at www.pathnet.org/concepthome.
The Measure of Success
Establishing a formal system for measuring performance can be a powerful catalyst for achieving business goals, and can play a vital role in pinpointing areas of inefficiency. However, fewer than half of trade contracting companies in business today have formal evaluation measures in place to help track performance statistics.
Tracking performance means more than checking off a task list at the end of each day. Performance statistics should be valid measures of success in terms of quality. Companies should identify a manageable number of performance measures - at least two and no more than five - and set annual goals for each. When setting these goals, it is important to consider trade-specific measures that will be most effective for the company.
It's equally important to have the proper means in place to effectively track these statistics. Each month, companies generate a number of sources of raw performance data. For example, statistics captured in inspection reports, customer satisfaction surveys, and punch lists from builders can illustrate positive and negative trends. With these readily accessible tools, monthly or quarterly performance tracking can be used to devise a strategy to improve performance. Typical examples of useful jobsite performance statistics include:
- Percentage of code inspections passed the first time
- Average number of trips required to complete each home
- Average number of builder punch items per home
- Average number of inspection items per home found by the trade supervisor
- Average number of warranty items per home
- Percentage of homes with zero "hot spot" items found
Companies with sophisticated databases can input data from inspection forms and track the trends with various cross-tabulations, while smaller companies without such databases may need to sample data by reviewing 10 to 20 percent of forms manually. Sample data should be representative of all of the work that a company does to ensure statistics that are 90 percent accurate or better.
Overall, establishing standards that can be measured leads to greater accountability at all levels, and increases awareness of company successes and setbacks. When used effectively as part of a quality assurance management system, performance measurement helps to ensure that your company's efforts are focused on improving in the most important areas and keeps the company on target to meet or exceed the expectations of builder customers and consumers.
For more information on performance measurement as part of a documented quality management system, visit www.nahbrc.com/quality.
PATH Resources: A Good Thing Keeps Getting Better
ToolBase.org and PATHnet.org are leading sources of practical information on building technology and the advances of the PATH program. Below is just a sampling of the kinds of information found on the two sites, both of which have recently been updated or expanded to simplify the process of technology selection and implementation, and keep pace with the changing needs of today's building professionals and consumers.
PATH Technology Inventory. Long recognized as a repository of reliable technical information for builders and remodelers, the PATH Technology Inventory was recently revamped to improve its utility, design, and navigation. Among the Technology Inventory's new features are downloadable Computer Assisted Design (CAD) drawings for over 40 technologies that builders and architects can add directly to plans. And, new online videos further explain product benefits and demonstrate installation.
The Inventory is continuously infused with up-and-coming technologies - wind power generators, translucent wall and ceiling panels, attic access insulation and seal systems, and advanced lighting controls, to name a few recent additions - that have the potential to improve the affordability, durability, quality, and efficiency of housing. The goal of the Inventory is to help these kinds of practical innovations gain market awareness and penetration like some of their predecessors on the listing, such as optimum value engineering and air admittance valves, which have graduated to the mainstream. To check out the Technology Inventory, visit www.ToolBase.org/techinv.
PATH Case Studies. Developed to promote a wide range of advanced, PATH-profiled technologies, these recently introduced "straight talk" case studies highlight builders' and remodelers' experiences with specific technologies in the field. Presented in their own words, these accounts reflect not only the details of the experience with the technology, but also what might be done differently the next time, and allow building professionals to learn from their peers. Case studies are posted on the PATHnet.org website, promoted at trade shows, and are uniquely designed to function as educational and marketing tools to increase the exposure for featured companies as leaders in housing innovation. Find out more about Case Studies and read or download the first one by visiting www.pathnet.org/sp.asp?mc=about_projects.
ToolBase TechNotes. These technical write-ups featured on ToolBase.org offer fundamental narratives on common issues builders want to know more about. Some recently introduced TechNotes focus on topics of interest such as copper pinhole leaks; termite protection for EIFS; the benefits of structural insulated panels (SIPS); and residential building diagnostic tools that can help builders improve the quality of their new homes. Each fact sheet includes a subject synopsis provided by NAHB Research Center experts and additional resources for more detailed information. Find these and other TechNotes by visiting www.ToolBase.org/.