NRCA Metal Flashings flashcards
NRCA Metal Flashings · 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.
- Galvanic series
- A ranking of metals by electrochemical potential in a given electrolyte. Metals farther apart on the list corrode faster when coupled in moisture.
- Sacrificial anode
- The less noble metal in a galvanic couple that corrodes to protect the cathode. Zinc coatings on steel act this way at cut edges and scratches.
- Copper runoff staining
- Water carrying dissolved copper salts stains light masonry and accelerates corrosion of zinc and aluminum below. Route drainage away from those metals.
- Bend allowance
- The length of neutral axis consumed by a bend, calculated as (π/180) × angle × (inside radius + K × thickness). Subtract it when laying out flat patterns.
- Ounce weight copper
- Copper sheet thickness stated as weight per square foot. 16 oz copper is 0.0216 in thick; 20 oz is 0.027 in.
- Reglet
- A groove cut or cast into masonry or concrete to receive the turned edge of flashing. Depth is typically a minimum of 3/4 in.
- Counterflashing
- Metal lapping over the top of base flashing to shed water and hide the joint. It must lap at least 4 in and terminate in a reglet or sealed surface mount.
- Through-wall flashing
- Flashing installed within a wall cavity to divert water to the exterior. It laps shingle-style and ends with a drip beyond the wall face.
- Weep hole spacing
- Openings above through-wall flashing that let cavity moisture escape. Typical spacing is 24 to 32 in on center, with end dams at terminations.
- Coping drip
- A formed edge on parapet coping that sheds water clear of the wall face. Coping needs a drip on both faces and clips allowing thermal movement.
- Base flashing height
- The vertical dimension of flashing above the roof surface. Common minimum is 8 in, with at least 4 in of lap over the membrane.
- Drip edge standoff
- The projection of edge metal past the fascia that keeps water off the wall. A minimum 1/4 in kick-out is typical.
- Gravel stop
- Edge metal that retains ballast and finishes the roof perimeter. It requires a continuous cleat and sealed corner laps.
- Termination bar
- A clamped metal bar that secures membrane or flashing edges. Fasteners are staggered and the bar is sealed to prevent a continuous split.
- Roof-to-wall cant
- A triangular fillet at the base of a wall that supports the flashing and avoids a sharp bend. Flashing must not bridge a gap.
- Expansion joint allowance
- Thermal movement accommodated in long metal runs. Copper moves roughly 1/8 in per 10 ft of length over normal temperature swings.
- Overflow scupper
- A secondary drainage opening through a parapet set above the primary drain. It must be independent and discharge visibly so blockage is noticed.
- Rational method
- Q = C × I × A estimates peak runoff from runoff coefficient, rainfall intensity, and area. It sizes gutters, leaders, and scuppers.
- Leader capacity
- The roof area a downspout can drain at design rainfall. A 3 in round leader handles roughly 1,000 to 1,200 sq ft at 1 in/hr.
- Gutter hanger spacing
- Bracket or strap spacing along a gutter run. Typical is 24 to 36 in on center, closer in snow-load regions, with room for thermal movement.
- Pitch pan
- A sealant-filled pan around a penetration, used where a manufactured boot will not fit. It is a last resort requiring periodic replenishment.
- Curb height minimum
- The height of a skylight or equipment curb above the finished roof. Common minimum is 8 in, increased in snow country.
- Step flashing
- Individual pieces lapped shingle-style along a chimney or wall, each set into the masonry or siding course. It works with base and cap flashing.
- Condensation gutter
- A channel inside a skylight curb that collects interior condensation and routes it outside, preventing water staining below the unit.
- Vent stack boot
- A two-piece flashing with a base flange lapped over the membrane and a collar clamped to the pipe. The top must be sealed to the stack.
- Dissimilar metal isolation
- Separating unlike metals with bituminous coating, EPDM tape, plastic washers, or insulated fasteners to break the galvanic cell.
- Dezincification
- Selective leaching of zinc from brass in aggressive water or soil, leaving a weak porous copper structure. Specify resistant alloys in these conditions.
- Neutral-cure silicone
- A low-modulus sealant for moving joints that does not corrode metal. It is not a substitute for proper laps in concealed flashing.
- Soldering copper
- Joining copper with 50/50 or 95/5 tin-antimony solder and flux. Joints must be clean and tight-lapped, and flux residue removed to stop corrosion.
- Fall protection threshold
- OSHA requires guardrails, nets, or personal fall arrest at 6 ft above a lower level in construction. Roof work must comply before access.
- Hot work permit
- Authorization required for soldering and brazing, with a fire watch and clearance from combustibles. A heat shield protects membrane near the work.
- Manufacturer instructions
- Published installation requirements for fasteners, spacing, sealant, and substrate preparation. Deviating from them typically voids the material warranty.