Wood Nailers for Roofing
January 22, 2020

Wood nailers are often overlooked, but they are a very important component of a successful roof assembly. A horizontal wood nailer is used to provide an effective substrate for some installation details and for other roof accessories. In addition, it is used to provide solid protection for the edge of the membrane underlayment. At a minimum, wood nailers must be thick enough that the top of the nailer is flush with the top of the membrane underlayment.

General Criteria:

  • The width of the nailers must exceed the width of the metal flange of edgings, scuppers, etc.
  • When treated lumber is specified, it is recommended that only lumber that has been pressure treated with salt preservatives be specified. Lumber treated with any of the wood preservatives such as, Creosote, Pentachlorophenol, Copper Naphthenate, and Copper 8-quinolinolate will adversely affect the membrane when in direct contact and are, therefore, unacceptable.
  • If non-treated lumber is to be specified, it must be stored to protect from moisture sources. A seal should be provided between the non-treated lumber and a concrete or gypsum substrate.
  • Methods used to fasten the nailer vary with building conditions; however, it is essential that secure attachment of durable stock be accomplished. Factory Mutual Loss Prevention Data Bulletin 1-49 (Perimeter Flashing) contains options for the spacing and sizing of fasteners based on the project wind zone.
  • Wood nailers that are anchored to steel, wood, or masonry decking should not be less than 2" x 6" nominal (minimum 1-1/2" x 5-1/2").
  • Wood nailers should be Douglas Fir, Southern Yellow Pine, or of wood having similar decay-resistant properties.

The American Wood Protection Association (AWPA) publishes the AWPA Book of Standards and is the industry standard for wood treatment. U1 is the specification for treated wood and outlines wood species, preservatives, and specifications for their Use Category System. This is a great resource when you have questions of when and where you should treat wood and what are the recommendations for various treatments.

Carlisle SynTec publishes some topics in the Design References portion of our product binder, which can also be accessed on the Carlisle SynTec website. For more information on wood nailer attachment, including some drawings, click here.

Contact Craig Tyler at [email protected] with further questions.

February 19, 2020
FM’s VSH Testing – Very Severe Hail

FM Global, a leading commercial building insurer, and its code-approved testing agency subsidiary, FM Approvals, have created a Very Severe Hail (VSH) impact resistance classification that could affect design professionals. FM Global Guidelines Traditionally, FM Global has recommended its insured building owners use moderate hail (MH) and severe hail (SH) classified roof systems for buildings located in areas FM Global considers to be susceptible to moderate or severe hail impacts. FM Loss Prevention Data Sheet 1-34 ("Hail Damage") provides a map identifying these regions. In recent years, the insurance industry in the United States has seen an uptick in losses from hail in terms of the number of claims experienced and costs of those claims. A majority of the hail damage occurs to roof systems and other rooftop components. In the latest version of FM 1-34 (April 2019), FM Global identified a new VSH region encompassing Oklahoma, Kansas, Nebraska, South Dakota, most of Texas, and parts of Montana, North Dakota, Minnesota, Iowa, Missouri, Arkansas, Wyoming, Colorado, and New Mexico.  Per FM Global, this area was classified as a VSH region based on data from the National Oceanic and Atmospheric Administration's National Weather Service and National Center for Environmental Protection's Storm Prediction Center. This data shows a concentration of reports of hail greater than 2 inches in diameter in this geographical region. Until recently, FM Approvals did not have VSH-classified roof systems available to satisfy its recommendation in the VSH region. In the interim, FM 1-34 recommended using assemblies tested to a Class 4 rating using FM 4473 ("Specification Test Standard for Impact Resistance Testing of Rigid Roofing Materials by Impacting with Freezer Ice Balls"). FM 1-34 indicates aggregate- and paver-ballasted roof systems can be substituted for MH- and SH-classified roof systems in the MH and SH regions. However, FM Global restricts the use of aggregate-ballasted roof systems on buildings taller than 150 feet, or in areas where the design wind speed is 100 miles per hour or greater. FM has indicated only paver-surfaced roof systems can be substituted for a VSH-classified roof system. FM 1-34 also contains recommendations for skylights, rooftop HVAC equipment, and other critical outdoor equipment in the MH, SH, and VSH regions. Hail Classifications FM Approvals traditionally has tested and classified membrane roof systems for MH and SH impact resistances using FM 4470 ("Approval Standard for Single-Ply, Polymer-Modified Bitumen Sheet, Built-Up Roofs (BUR) and Liquid Applied Roof Assemblies for use in Class 1 and Noncombustible Roof Deck Construction). This is the same test method on which many FM Approvals roof system classifications are based. Using FM 4470's procedure, MH-classified roof systems withstand a 2-inch-diameter steel ball weighing 1.19 pounds dropped from a height of 81 inches in a section of tubing. This results in an impact energy of about 8 foot-pounds (ft-lbs.) on the surface of the roof system test specimen. SH-classified roof systems withstand the same 2-inch-diameter steel ball dropped from a height of 141.5 inches, resulting in an impact energy of about 14 ft-lbs. on the surface of the roof system test specimen. FM Approvals recently updated its impact-resistance test method to include testing for the VSH classification. The new testing involves propelling 2-inch-diameter preformed ice balls at roof system test specimens using an ice ball launcher. The ice balls are propelled at 152 to 160 feet per second, resulting in an impact energy of 53 to 58 ft-lbs. on the surface of the roof system test specimen. With these higher test standards, new materials and assemblies are being developed and tested to meet the new ratings. Carlisle has introduced a new coverboard, EcoStorm, that can achieve the VSH rating. Carlisle currently has 133 approved VSH approved assemblies. For more information on EcoStorm VSH Coverboard, click here. Contact Brian Emert at [email protected] with further questions.

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February 5, 2020
Spray Foam for Walls – The Perfect Wall

The challenge with every design is making sure that it will work in a specific environment. Through understanding the principles of a "perfect wall" - one which contains a water-shedding layer, an air control layer, a vapor control layer, and a thermal control layer - we can generate a wall solution that will work in every environment. The control layers are listed in order of importance. All are important, but not equally important. The ranking comes from historic experience and the underlying physics. Controlling water in the liquid form (rain and ground water) has been the focus of architects for generations. Controlling air is a much more recent focus - less than a century. The corollary, however, is too often true for many in the industry. There should be no doubt, the water control layer is much more important than the air control layer. Controlling vapor is even more recent - only a generation or two. Air movement transports significantly more water in vapor form than does vapor diffusion and therefore air control is more important than the control of molecular water vapor. "Air barriers" are more important than "vapor barriers". Thermal control dates back millennia - but getting it wrong has rarely led to durability failures. The thermal control layer failures have been typically limited to comfort issues and operating cost issues. Hence, thermal control layers are listed last on the control layer "priority" list. In the last decade we have been successful at combining the water control layer, air control layer, and vapor control layer into a single layer that can be a film, coating, membrane, or sheet goods. We have also had good success with wrapping the exterior of a building with all of these control layers and then enclosing those control layers with the fourth control layer - the thermal control layer. This configuration, with the thermal control layer outboard of the water, air, and vapor control layers, allows the assembly to be constructed in all climate zones: cold, mixed, hot and humid, or dry. Even better, this configuration allows this assembly to enclose virtually all interior environments in all climate zones: offices, commercial, residential, institutional, pools, museums, art galleries, and data processing centers. The sole exception being refrigerated buildings and cold storage facilities. In such assemblies the location of the thermal control layer is "flipped" with the other control layers - the thermal control layer now becomes located on the interior of the other three control layers. Utilizing spray foam technology, you can create the "perfect wall" with spray polyurethane (SPF) which meets; Water Control Layer - SPF is inherently moisture resistant. Air Control Layer - SPF has an Air Impermeability of <0.02 (L/s/m2) @ 1 inch of mercury. Vapor Control Layer - SPF has a water vapor permeability of 1.4 perm @ 1 inch of mercury. Thermal Control Layer - SPF has an R-Value per inch of 6.9. This also allows for thinner walls and continuous insulation without thermal breaks. Visit the Carlisle Spray Foam Insulation website at carlislesfi.com for more information on how your next project could utilize spray foam insulation as a "perfect wall" solution. Contact Brian Emert at [email protected] with further questions.

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January 8, 2020
Air and Vapor Barriers for Roofs

In 2012, the International Energy Conservation Code (IECC) introduced the continuous air barrier requirement for new commercial construction. This meant that air and vapor barriers were now required for walls, and they must be tied to both the roofing assembly and the foundation. For years, many architects and designers only utilized an air and vapor barrier on the roof deck for high-humidity occupancies, such as swimming pools or food processing facilities. But the new requirement meant taking a hard look at the needs of all buildings and what a roof assembly could do for the building envelope. A single-ply membrane, as stated in the IECC and as tested utilizing the ASTM E2178 standard, qualifies as an air barrier and can satisfy the requirement for an air barrier on any given project. So why would you consider adding an additional air and vapor barrier to the roofing assembly? There are a couple of very simple reasons: Reason 1: Air Intrusion. While a properly installed roofing system will not allow air leakage (e.g., conditioned indoor air from exiting the building thermal envelope), it does allow air movement within the roof assembly. As the single-ply roof membrane is on the top of the assembly, indoor conditioned air can infiltrate into the roofing system and travel into the layers of insulation or cover boards. Why is this an issue? See Reason 2… Reason 2: Moisture Migration. Adding a deck-level air and vapor barrier is a great solution to prevent air intrusion and moisture migration. This also allows the wall air and vapor barrier to be tied together at the deck level, which allows the roof to be replaced more easily in the future. The contractor will not be modifying the continuous air barrier when re-roofing, as the roof is no longer that barrier. Carlisle SynTec provides many options for deck level air and vapor barriers: VapAir Seal MD for steel deck construction, direct to deck; VapAir Seal 725TR for Concrete Decks; VapAir Seal Flashing Foam for sealing around penetrations such as pipes; Go to the Air and Vapor Barriers Product Page on the Carlisle SynTec website for more information, specifications, and details. Contact Craig Tyler at [email protected] with further questions.

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