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.
- 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.