Steep-slope Roof System Mockup Characteristics

Steep-slope mockups must provide characteristics similar to those typically found on most steep-slope roofs. These characteristics are essential to ensure standard testing conditions are achieved and fair performance exams are administered. All steep-slope mockup designs should include the following characteristics:

  1. Deck material must be one of the following:
    • A minimum of four-ply, nominal thickness of ½ -inch-thick (actual thickness of 15/32-inch thick) plywood installed over supports spaced no more than 16 inches on-center
    • A minimum four-ply, nominal thickness of ⅝-inch-thick (actual thickness of 19/32-inch-thick) plywood installed over supports spaced no more than 24 inches on-center
  2. A slope of no less than 4:12 and no greater than 8:12

  3. A total field area of no less than 120 square feet

  4. A minimum of 10 lineal feet of hip and ridge in any combination that must include a minimum of 4 lineal feet of hip and 4 lineal feet of ridge. The decking at the ridge must include a 1-inch opening on each side of center to accommodate the installation of continuous ridge vent materials.

  5. The mockup must remain stationary and secure always for the duration of any performance exam

  6. One rake edge

  7. One hip roof area

  8. One valley no less than 4 lineal feet in length

  9. One chimney penetration no less than 12 inches and no more than 16 inches square extending above the roof deck no more than 18 inches on its tallest side. Chimney penetration design should allow for detaching and reattaching at various mockup locations.

  10. One plumbing vent pipe penetration not exceeding a 5-inch diameter and not exceeding a 12-inch height on its tallest side. Pipe penetration design should allow for detaching and reattaching at various mockup locations.

  11. Penetrations must never be placed within 12 inches of a ridge, hip, another penetration or a valley's center.

  12. A minimum 4-inch (nominal) fascia board on all lower drip edges

  13. Lower drip edge must be less than 36 inches above ground

NRCA also recommends a separation sheet, such as rosin building paper, be affixed on steep-slope mockup wood decks for performance assignments requiring use of self-adhering ice and water protection membrane for easier material removal after exam completion.

*NRCA's mockup designs shown in the drawings represent minimum characteristic requirements. Actual mockups can be larger and more elaborate, if desired, providing they meet the minimum characteristics listed such as size, slope and types of penetrations and/or details. NRCA's mockups are designed as portable, moveable units, but these qualities are not required.

Steep Slope 1
Steep Slope 2



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