GAF Open-Valley Fasteners: The Metal Needs Room to Move
Bulletin dated: February 1, 2021 revision
GAF describes fastening along valley-metal edges so the metal can expand and contract. Its alternative through-metal fastening detail has specific conditions for leak barrier, valley shape and width, shingle overlap and roof slope
GAF technical bulletin: Nailing metal flashing in open valleys.
What this means for your roof
GAF describes fastening along valley-metal edges so the metal can expand and contract. Its alternative through-metal fastening detail has specific conditions for leak barrier, valley shape and width, shingle overlap and roof slope. It is not general permission to nail through any open valley.
A useful question for your contractor
Which approved valley-fastening detail is being used, and are all its conditions met?
Ask for the answer to be tied to the actual roof condition and the exact product being installed. Keep the agreed repair or installation detail with your estimate and project photos.
Bulletin dated: February 1, 2021 revision. The date shown identifies the manufacturer document used for this summary.
Read GAF: Nailing metal flashing in open valleys
This homeowner summary explains the cited bulletin. The complete manufacturer document and current product instructions govern the installation details. A requirement for one manufacturer or product should not be transferred to another without checking.