NRCA Metal Panel flashcards
NRCA Metal Panel · 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.
- Hydrokinetic vs hydrostatic panel
- Hydrokinetic (architectural) panels shed water by gravity and need about 3:12 slope; hydrostatic (structural) panels resist water at the seam and can go to 1/4:12 with double-lock seams.
- Standing seam seam height
- Common heights are 1, 1-1/2, 2, and 2-3/8 inches. Taller seams stiffen the panel, increase span capacity, and resist water siphoning at low roof slopes.
- Oil canning cause
- Elastic buckling of the flat panel pan caused by residual coil stress, wide pan widths, uneven substrate, or overdriven fasteners. Narrower pans, striations, and backer plates reduce its visibility.
- G90 galvanized coating
- A hot-dip zinc coating designation meaning 0.90 ounces of zinc per square foot of sheet. It is the common corrosion baseline for steel roof panels in moderate environments.
- OSHA low-slope fall trigger
- Under 29 CFR 1926.501(b)(10), fall protection is required when work is within 15 feet of the roof edge. A warning line plus safety monitor is allowed only on roofs 50 feet wide or less.
- Fall arrest anchorage strength
- Anchorage must support 5,000 pounds per worker, or be designed by a qualified person with a safety factor of at least two. Maximum arresting force is limited to 1,800 pounds.
- Steep roof fall protection
- Roofs steeper than 4:12 require fall protection at all times under 1926.501(b)(11), regardless of the distance from the edge. Warning lines alone are not acceptable.
- Ladder extension above landing
- Extension ladders must extend at least 3 feet above the roof landing, be set at a 1:4 angle, and be secured against displacement before the worker ascends.
- Purlin alignment tolerance
- Purlins must be straight and aligned within about 1/4 inch over any 10-foot run. Misalignment causes clip racking, loose seams, and visible panel distortion.
- Vapor retarder perm classes
- Class I is 0.1 perm or less, Class II is 0.1 to 1.0 perm, and Class III is 1.0 to 10 perms. Class I or II is typical on the warm side in cold climates.
- Eave ice dam membrane
- IRC R905.1.2 requires a self-adhering membrane from the eave edge to 24 inches inside the exterior wall line where the average January temperature is 25 degrees F or lower.
- Thermal break at purlin
- A foam block or high-density polyiso strip placed between the purlin and panel. It interrupts the conductive bridge that can cut effective insulation R-value by 20 to 40 percent.
- Panel coverage versus width
- Coverage is the net width after seam engagement, always less than the flat sheet width. Order quantity equals roof area divided by coverage, times one plus waste.
- Fastener penetration minimums
- Fasteners must penetrate steel purlins at least 1/2 inch and wood at least 1 inch. Overdriving crushes the washer; underdriving leaves the head proud and leaks.
- Thermal movement of panels
- A 40-foot aluminum panel moves about 0.55 inch over a 100 degree F swing. Slotted clips and fixed-free end conditions accommodate this movement without buckling.
- Uplift zone priority
- ASCE 7 components-and-cladding pressures are highest at corners, then edges, then the field. Fastener and clip density increases from field to edge to corner.
- Double-lock seam
- A seam folded twice by a powered seamer, producing the strongest and most water-resistant standing seam. It is commonly required for hydrostatic panels at slopes near 1/4:12.
- Seam sealant tape
- A butyl or urethane tape placed in the seam pan before closing. It supplements, but never replaces, a fully closed seam, and must not be stretched or left exposed to UV.
- Hose test for seams
- A water test applying a hose stream at about 5 psi for at least 5 minutes, working from the low side up. It is used to verify new seams and flashings before closeout.
- Counterflashing overlap
- Counterflashing is embedded at least 1 inch into the wall and overlaps the base flashing by at least 4 inches. The two are not fastened together so thermal movement is free.
- Curb height minimum
- A roof curb for a skylight or large penetration is typically at least 8 inches above the roof surface, flashed with a minimum 4 to 6 inch overlap onto the panel.
- Ridge cap fastening rule
- Ridge and hip caps are fastened on one side only, over a profiled closure, with at least a 6 inch end lap. Fastening both sides locks thermal movement and buckles the cap.
- Penetration size threshold
- Holes larger than 12 inches in any dimension require a structural curb and framed opening. Smaller penetrations may use a manufactured boot or field flashing.
- Vent area ratio
- IRC R806 requires 1 square foot of net free vent area per 150 square feet of attic floor, or 1:300 when a vapor retarder is present, split equally between intake and exhaust.
- Unvented hot roof strategy
- Seal a Class I or II vapor retarder on the warm side, seal all joints, and place rigid insulation above the deck so the deck stays above the interior dew point.
- Polyiso R-value per inch
- Polyisocyanurate provides roughly R-6.0 to R-6.5 per inch, the highest of the common rigid foams, and is often foil-faced for use above a metal deck.
- Minimum slope by panel type
- Architectural hydrokinetic panels need about 3:12. Structural hydrostatic panels can be listed to 1/4:12 (2 percent) when double-lock seams and sealant are used.
- Gutter slope and hangers
- Gutters slope at least 1/16 inch per foot toward the outlet, with hangers spaced no more than 24 inches on center and an expansion joint on long runs.
- Secondary drainage overflow
- Where a parapet can pond water, an overflow scupper or secondary drain is set at least 2 inches above the primary drain and sized for the 100-year storm.
- Backed-out fastener repair
- A fastener backed out about 1/8 inch or more is replaced in a new hole, not simply retightened. Retightening enlarges the hole and the fastener will loosen again.
- Metal-over-metal retrofit
- A new panel installed over an existing metal roof with a slip sheet and often new battens or purlins. It avoids tear-off and adds insulation and a new finish warranty.
- UL 580 uplift rating
- UL 580 is the standard uplift test for roof assemblies. The listed assembly requires the exact panel, clip, fastener, and substrate combination named in the listing.