01
Normalize the material description
Require quarry or product, size, thickness, color, finish, testing and quantity assumptions. Substitutions should follow a written review process.
02
Compare every hidden component
List deck repairs, underlayment zones, fasteners, starters, valleys, wall flashings, ridges, ventilation, snow retention, staging and protection side by side.
03
Review qualifications and process
Ask who performs the slate work, how mockups and deliveries are approved, and how concealed conditions are documented. References should involve comparable natural-slate projects.