Slate roofing consists of thin sheets of natural slate stone, carefully selected for color, thickness, and splitting characteristics. Slate roofing provides exceptional durability and aesthetics, lasting 50 to 200 years depending on slate quality and climate. The weight of slate is significant, typically 10 to 15 pounds per square foot, requiring substantial roof structure. Roof framing must be designed for slate loads; undersized framing can sag or fail under the heavy load. Installation begins with proper roof underlayment. High-quality synthetic underlayment or quality felt prevents water leakage if slates crack or shift. Slate shingles are individually nailed with copper or stainless steel nails to the roof deck. Fastener selection is critical; improper fasteners can cause corrosion or rust staining on the slate. Each slate is typically nailed at the top edge, allowing the shingle below to overlay the nail holes and prevent water penetration. Proper nailing technique and spacing ensures shingles resist wind uplift. Skilled slate roofers are required for quality installation; improperly installed slate roofs leak and shift. Flashing at valleys, penetrations, and edges must direct water properly. Lead flashing is often used as it is long-lasting and compatible with slate. At roof edges and valleys, proper detailing is essential; these areas are common leak points. Maintenance of slate roofs includes periodic inspection for cracked shingles and moss or lichen growth. Cracked shingles must be replaced to prevent leaks. Moss or lichen should be carefully removed without pressure washing that could damage the slate. Slate roofs with proper installation and maintenance provide centuries of service.