Agree on the complete section
Ask for the proposed valley detail with the selected tile, membrane, metal and supporting deck identified. A photograph of a neat cut line cannot show those relationships. PNNL emphasizes continuous protection at valleys and integration with adjoining water-control materials. Use its principles as background, then follow the actual tile system’s requirements for the finished assembly.
Protect the water-carrying metal
Ask how small cut tiles will be retained without puncturing the water-carrying metal. Ludowici’s Flat Slab prototype uses wire tied to a fastener outside that metal. Obtain the corresponding detail for your product, and request a photograph before neighboring pieces conceal the connection.
Resolve the opening before cutting
Do not choose valley width solely for appearance or assume one width works along every run. The relevant manufacturer detail and roof geometry govern. As a review exercise, mark the valley’s start, changes of direction and outlet on the plan. Ask where runoff is concentrated and whether surrounding cuts, support or accumulated debris could obstruct its intended route.
Inspect while the layers are visible
Request a checkpoint before cut tiles conceal the valley perimeter. Useful photographs show membrane preparation, metal laps, support and how short pieces are retained. Discuss access for later debris removal without adding exposed fasteners or improvised dams. If the requested appearance conflicts with the planned drainage detail, resolve the design before the installer cuts the remaining tile.
Related questions
Further reading & technical sources
- Roof Valleys and Penetrations Sealed ↗
- Flat Slab Tile — Section at Field Cut Valley ↗
- Gutters and Downspouts ↗
Consult the current product documentation and local requirements for your project. These introductions are not installation specifications.
Tile Roofing USA editorial guide · Published October 26, 2026.