Manual Elements

Some users of The NRCA Roofing and Waterproofing Manual, Fifth Edition, may not be aware of the tables located after the low-slope roof system construction details. A majority of these tables cover topics that apply to most low-slope roof systems, such as sheet-metal fascia edges and counterflashing options. However, there also are two tables that feature the perimeter base securement options for single-ply roof membrane systems. This column will focus on Single Ply Table 7.1—Options for perimeter base securement (roof-to-wall and roof-to-curb intersections).

There are two categories of single-ply membrane roof systems—thermoplastic and thermoset. Installation guidelines for single-ply roof systems offer a variety of base-securement options for roof-to-wall or roof-to-curb intersections. However, one method is shown for each roof system in the construction details. The available options are shown in Single Ply Tables 7.1 and 7.2. The securement options shown in Table 7.1 can be used for thermoplastic and thermoset roof systems.

Table 7.1 from The NRCA Roofing and Waterproofing Manual, Fifth Edition

Options 1-A and 1-B illustrate a fastening strip (bar) on top of the field sheet with mechanical fasteners securing the roof membrane field sheet to the wall/curb or roof deck. A flashing membrane strip then is installed over the fastening strip. Some roof systems require that the exposed edges of a flashing membrane be sealed with appropriate sealant.

Options 2-A and 2-B show a reinforced membrane attachment strip fastened with seam plates and fasteners; note the attachment strip is installed under the roof membrane field sheet. Again, there is an option of installing the seam plates and fasteners on the vertical or horizontal surface.

It is important to note that fasteners for use with thermoplastic or thermoset roof membranes can vary with the systems specified. Some manufacturers will allow the use of readily available screws and plates, but other manufacturers require specialized, preassembled fastening components where needed. Specific deck types and warranty requirements should be considered when selecting a proper fastener.

Joan P. Crowe, AIA, is an NRCA manager of technical services.