This bulletin describes a particular Timberline valley method with slope and assembly limitations. The vertical shingle course and protected centerline require deliberate layout.
GAF technical bulletin: California valleys closed cut.
What this means for your roof
This bulletin describes a particular Timberline valley method with slope and assembly limitations. The vertical shingle course and protected centerline require deliberate layout.
A useful question for your contractor
Ask the installer to identify the exact approved detail rather than relying on the name alone.
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 revision: February 1, 2021. This is the date of the manufacturer source, not a claim that this website guide existed on that date.
Read GAF: California valleys closed cut
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.