NRCA Slate flashcards
NRCA Slate · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Fissility
- The property of slate that allows it to split into thin, flat sheets along cleavage planes formed during metamorphism; it is the defining characteristic of commercial roofing slate.
- Headlap
- The overlap between the head (top) of a lower slate and the butt of the slate above it. Minimum is typically 3 in for slate up to 3/8 in thick and 4 in for 1/2 in and thicker.
- Exposure
- The exposed length of a slate, calculated as slate length minus headlap. A 12 in slate with 3 in headlap has 9 in exposure and determines how many courses cover a given roof area.
- Slate square
- A unit of roof area equal to 100 sq ft. Because of headlap and side lap, one square of roof requires more than 100 sq ft of slate, commonly 1.10–1.30 times the area.
- ASTM C406
- The standard specification that classifies roofing slate by grade (S1, S2, S3) and type based on uniformity, harmful mineral content, and weathering characteristics.
- Slate ripper
- A long flat bar with a hooked end used to reach under a broken slate and cut or pull its nails so the slate can be removed without damaging adjacent slate.
- Slate hook
- A copper or stainless steel hook driven into the deck above a repair and bent over the head of a replacement slate, used where the slate cannot be nailed conventionally.
- Step flashing
- Individual L-shaped metal pieces interwoven with each slate course along a sidewall, extending at least 2 in under the slate and 4 in up the wall, lapped about 2 in.
- Counterflashing
- Metal set into a reglet cut at least 1 in deep in masonry, overlapping the base flashing below, with a 1/4 in gap at the bottom to allow for movement.
- Chimney cricket
- A small sloped flashing structure on the uphill side of a chimney wider than 30 in (some codes 24 in), typically sloped at least 1/4 in per foot to divert water.
- Open valley
- A valley lined with 16–20 in wide metal (copper, lead-coated copper, or stainless) with a W-shaped center, where slate is cut back 3–4 in from the valley centerline.
- Ice dam membrane
- A self-adhering waterproof membrane installed at eaves, valleys, and penetrations in cold climates, extending from the eave to at least 24 in inside the interior wall line.
- Double starter course
- Two layers of slate at the eave, with the lower layer set in mortar or on a cant strip, installed to shed water off the fascia and protect the underlayment edge.
- Cross joint
- A joint where four slate corners meet; it is avoided by offsetting joints in adjacent courses by at least 3 in so water cannot pass straight through the roof.
- Snug nailing
- Driving slate nails so the slate hangs loosely and can move with thermal expansion, rather than tight against the deck, which causes cracking.
- Slate weight per square
- Approximate dead load per 100 sq ft: 800 lb for 3/16 in, 1,000 lb for 1/4 in, 1,500 lb for 3/8 in, and 2,000 lb for 1/2 in slate.
- Ribbon slate
- Slate laid in bands of contrasting color, a design pattern that affects ordering and layout but not the durability or grade of the material.
- Graduated slate
- A pattern in which slate size increases toward the eave, requiring careful ordering and layout; it is a design choice, not a material grade.
- Pyrite staining
- Rust-colored stains on slate caused by oxidation of pyrite inclusions; it signals a harmful mineral content and is a durability concern under ASTM C406.
- Copper fasteners
- Solid copper or stainless steel nails and hooks preferred for slate because galvanized and electroplated copper products corrode and stain the slate surface.
- Underlayment laps
- Shingle-style lapping of underlayment with side laps of at least 6 in and end laps of at least 4 in, oriented to shed water down-slope.
- Deck sheathing
- Solid wood sheathing, typically 3/4 in nominal boards up to 8 in wide or plywood/OSB, that must be flat and sound to support slate without breakage.
- Reglet
- A groove cut at least 1 in deep into masonry to receive counterflashing; sealant alone is not a substitute for a properly set reglet.
- Snow guard
- A device anchored into the deck through the slate to hold snow and prevent sudden slides; it must not rely on the slate alone for anchorage.
- Moss removal
- Removing moss and lichen with a soft brush and approved cleaner, avoiding pressure washing and harsh chemicals that erode slate and force water beneath it.
- Restoration threshold
- The point at which spot repair is no longer economical, commonly when more than about 20–25% of slate is broken or underlayment has failed over large areas.
- OSHA fall trigger
- The height at which fall protection is required in construction, generally 6 ft above a lower level under 29 CFR 1926.501, with guardrail, net, or personal fall arrest.
- Ladder 4:1 rule
- The setup ratio for ladders: 1 ft out from the wall for every 4 ft of height, with the ladder extending 3 ft above the landing and secured.
- Silica dust
- Respirable crystalline silica released when cutting slate; controlled with wet cutting or dust collection and respiratory protection under OSHA 1926.1153.
- IRC Chapter 9
- The model code chapter covering roof assemblies and roof covering requirements, including underlayment, ice barriers, and flashing, as adopted and amended locally.
- Secretary's Standards
- Federal standards for historic rehabilitation that favor in-kind slate replacement and retention of original material on historic buildings.
- Slate condition survey
- A systematic mapping of broken or slipped slate, flashing condition, and attic-side evidence of deck and underlayment failure before planning repairs.