• ROOFING APPLICATION STANDARD (RAS) No.127
    PROCEDURE FOR DETERMINING THE MOMENT OF RESISTANCE AND MINIMUM
    CHARACTERISTIC RESISTANCE LOAD TO INSTALL A TILE SYSTEM ON A
    BUILDING OF A SPECIFIED ROOF SLOPE AND HEIGHT

    1.Scope

    This standard covers the procedure for determining the Moment of Resistance (Mr) and Minimum Characteristic Resistance Load (F') to install a tile system on buildings of a specified roof slope and height. Compliance with the requirements and procedures herein specified, where the pressures (Pasd) have been determined based on Table 1 or Table 2 of this standard, as applicable, do not require additional signed and sealed engineering design calculation. All other calculations must be prepared, signed and sealed by a professional engineer or registered architect. Table 1 is applicable to a wind speed of 175 mph, risk category II buildings, and exposure category C. Table 2 is applicable to a wind speed of 175 mph, risk category II buildings, and exposure category D.

    2.How to determine the Moment Resistance (Mr) (Moment Based Systems)

    1. 2.1Determine the minimum design wind pressures for the field, perimeter and corner areas (Pasd1, Pasd2 and Pasd3, respectively) using the values given in Table 1 or Table 2, as applicable, or those obtained by engineering analysis prepared, signed and sealed by a professional engineer or registered architect based on ASCE 7.

    2. 2.2Locate the aerodynamic multiplier (λ) in tile Product Approval.

    3. 2.3Determine the restoring moment due to gravity (Mg) per Product Approval.

    4. 2.4Determine the attachment resistance (Mf) per Product Approval.

    5. 2.5Determine the Moment of Resistance (Mr) per following formula:

      Eqn1
    6. 2.6Compare the values for Mr, with the values for Mf, noted in the Product Approval. If the Mf values are greater than or equal to the Mr values, for each area of the roof [i.e., field Pasd(1), perimeter Pasd(2) and corner Pasd(3) areas], then the tile attachment method is acceptable.

    3.How to determine the Minimum Characteristic Resistance Load (F') (Uplift Based System)

    1. 3.1Determine the minimum design pressures for the field, perimeter and corner areas [Pasd(1), Pasd(2) and Pasd(3), respectively] using the values given in Table 1 or Table 2, as applicable, or those obtained by engineering analysis prepared, signed and sealed by a professional engineer or registered architect based on the criteria set forth in ASCE 7.

    2. 3.2Determine the angle (θ) of roof slope, from Table 1 or Table 2, as applicable.

    3. 3.3Determine the length (l), width (w) and average tile weight (W) of tile, per Product Approval.

    4. 3.4Determine the required uplift resistance (Fr) per following formula:

      Eqn2
    5. 3.5Compare the values for Fr with the values for F' noted in the Product Approval. If the F' values are greater than or equal to the Fr values, for each area of roof [i.e., field Pasd(1) perimeter (Pasd(2) and corner Pasd(3) areas], then the tile attachment method is acceptable.

    TABLE 1 — RISK CATEGORY II EXPOSURE CATEGORY “C”1 MINIMUM DESIGN WIND UPLIFT PRESSURES IN PSF FOR FIELD [Pasd(1)], PERIMETER [Pasd(2)] AND CORNER [Pasd(3)] AREAS OF ROOFS FOR EXPOSURE C BUILDINGS WITH A ROOF MEAN HEIGHT AS SPECIFIED3

    ROOF SLOPE> 2:12 to ≤ 6:12> 6:12 to ≤12:12
    Roof mean heightPasd(1)Pasd(2)Pasd(3)2Pasd(1)Pasd(2) & Pasd(3)
    ≤ 20'-39.1-68.1-100.7-42.8-50.0
    >20' to ≤ 25'-40.9-71.3-105.4-44.8-52.3
    >25' to ≤ 30'-42.4-73.9-109.3-46.4-54.3
    >30' to ≤ 35'-43.9-76.6-113.2-48.1-56.2
    >35' to ≤ 40'-45.1-78.7-116.3-49.4-57.8
    1. 1 Calculated in accordance with ASCE.

    2. 2 For Hip Roofs with slope ≤ 5.5:12, Pasd(3) shall be treated as Pasd(2).

    3. 3 Pasd = 0.6Pult

    TABLE 2 — RISK CATEGORY II EXPOSURE CATEGORY “D”1 MINIMUM DESIGN WIND UPLIFT PRESSURES IN PSF FOR FIELD [Pasd(1)], PERIMETER [Pasd(2)] AND CORNER [Pasd(3)] AREAS OF ROOFS FOR EXPOSURE D BUILDINGS WITH A ROOF MEAN HEIGHT AS SPECIFIED3

    ROOF SLOPE> 2:12 to ≤ 6:12> 6:12 to ≤ 12:12
    Roof mean heightPasd(1)Pasd(2)Pasd(3)2Pasd(1)Pasd(2) & Pasd(3)
    ≤ 20'-47.0-81.9-121.0-51.4-60.1
    >20' to ≤ 25'-48.8-85.0-125.7-53.4-62.4
    >25' to ≤ 30'-50.3-87.7-129.6-55.0-64.4
    >30' to ≤ 35'-51.5-89.9-132.7-56.4-65.9
    >35' to ≤ 40'-52.7-91.9-135.8-57.7-67.9
    1. 1 Calculated in accordance with ASCE 7.

    2. 2 For Hip Roofs with slope ≤ 5.5:12, Pasd(3) shall be treated as Pasd(2).

    3. 3 Pasd = 0.6Pult

    TABLE 3

    WHERE TO OBTAIN INFORMATION

    DescriptionSymbolWhere to find
    Design PressurePasd(1) or Pasd(2) or Pasd(3)Table 1 or Table 2, as applicable, or by an engineer analysis prepared, signed and sealed by a professional engineer based on ASCE 7
    Mean Roof HeightHJob Site
    Roof SlopeθJob Site
    Aerodynamic MultiplierλProduct Approval
    Restoring Moment due to GravityMgProduct Approval
    Attachment ResistanceMfProduct Approval
    Required Moment ResistanceMrCalculated
    Minimum Characteristic Resistance LoadF'Product Approval
    Required Uplift ResistanceFrCalculated
    Average Tile WeightWProduct Approval
    Tile Dimensionsl=length w=widthProduct Approval

    All calculations must be submitted to the building official at the time of permitting.

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