Why Nailers in Low Slope Roofing Systems are so important

Roofers in DFW - Roofing Company Dallas - CMAC Roofing (3)

ANSI SPRI ES1 has been in place since 2003 to assist designers, producers, owners and contractors in preventing perimeter edge metal assemblies from failing in low-slope roofing systems. Edge metal is also the primary form of membrane securing, a visible indicator of performance or loss, and is needed in a high wind event to withstand the primary effect on the roof. What are we doing to ensure that these tested and code-compliant assemblies transfer load to other stable and sustainable components that absorb the transfer of load at the very least?

The dominant choice in commercial building perimeter joinery continues to be nailers made from wood. This is largely due to initial expense, availability, and normal practice. As we begin to assess how best to protect a facility’s perimeter, there are numerous considerations. Is the design suspicious of condensation and water intrusion for moisture, mold and rot? Will the chosen component warp over time to generate uneven and weak connection points? Will the type of fastener used react, causing rust or decay, with the substrate? The labor required to create the nailer is economically viable with radius, convex/concave, or a high nailer condition of construction. It is not uncommon to find tapered insulation in roof assemblies with nailer constructions that exceed 12′ in height at the perimeter with the current insulation requirements in code. Many of these questions fall back on the designer to address, and it can be helpful for designers to have wind uplift and attachment reference resources as well as proper designs in their design for tying in thermal, air, and vapor barriers.

We find a coping that has remained attached to a shimmed nailer made of parts of wood. The assembly released not only under wind power from the substrate, but also suffered a deformation of the torsion load, twisting the wood components as it sheared off the edge of the house.

We are discovering a suspicious design multi-component nailer with many potential current and future flaws. This perimeter offered a small solid surface to protect a membrane, left a flexible and volatile potential for load durability and posed a weakness in the ability of the installer to avoid penetration of air and water. Esthetically, there was also significant scope for any completed assembly to mimic the wavy substrate look.

We found plywood used to manufacture a radius condition that produced an extremely volatile load consistency, considerable height variance to work with by the installer, and reflected the capacity for faster condensation degradation in air pockets and gaps.

The good news is that there are different services that deal with nailers and their value in commercial buildings. These specifications are designed to provide specifiers and installers with a baseline reference to reduce the incidence of a concealed flaw at the perimeter of your roof assembly.

The most current of these publications, the ANSI SPRI ED1 Design Specification for Edge Structures Used for Low Slope Roofing Systems, which was accepted by ANSI on June 3, 2019, is addressed to a designer with tables A6 and A7 that include Nailer Connection Fastener Loads for buildings above and below 60 ‘in height. Relevant information for fastener spacing and perimeter fastener load is given to the builder on the basis of the Area of Roof Pressure psf (kPa) in an easy to use format. For models needing to fix complex situations and heights of nailers, this becomes important and can be a valuable reference for ensuring perimeter cohesion.

Furthermore, where alternative nailers or no nailers need to be used, ED1 offers the designer instructions. Additional advice on non-wood nailers and the addition of fasteners to light weight concrete and gypsum decks is given on pages 24 and 25. The architecture of this device should not be underestimated as a secret component in an assembly that could bear a considerable amount of load transfer liability.

The single ply roofing industry continues to see improvements in masonry fastening solutions that can sometimes totally remove the nailer and enable termination components to be firmly installed without the use of wood. Time must be taken to ascertain the consistency of the masonry substrate, frequently doing a pull evaluation of the current state. Designers include air room, EIFS, and ACM panels in certain exterior envelope solutions, which can generate problems for proper Dallas roofing membrane protection if not tackled during develop. In an effort to match surfaces that may not be sufficient for load transfer and securing, these variances may decrease the efficacy of tested fastening patterns and may produce additional opportunities for torque failure from longer screws or nails poorly secured.

As the building industry progresses with continuity into continuous insulation and construction envelope solutions, multiple nailer alternates give designers the opportunity to stretch insulation or lightweight concrete beyond which these elements have been prevented by conventional wood nailers in the past.

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