19761-Certification.pdf

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28357 Industrial Blvd

Hayward, CA 94545

1-800-227-9523

IronRidge.com

Attn: Corey Geiger, COO, IronRidge Inc.

Date: December 10th, 2018

Re: Structural Certification for IronRidge Knockout Tile Roof Attachment

This letter addresses the structural capacity of the IronRidge Knockout Tile for use as a tile roof attachment for

flush mounted PV solar systems. Knockout Tile assembly consists of an extruded aluminum base, a rail

mounting bracket (L-foot), and an aluminum tile replacement flashing fastened to the assembly. The base is

attached to an underlying roof rafter using one (1) 5/16” stainless steel lag bolt and the L-foot is secured to the

base by a 5/16" stainless steel threaded stud and nut. Assembly of Knockout Tile and accompanying hardware

shall be installed in accordance with IronRidge Knockout Tile Installation Manual. Full assembly details are

shown in Exhibit EX-0018.

The referenced uplift, compression and lateral capacities of Knockout Tile tabulated below are based on

mechanical load tests conducted along the four load directions shown in Figure 1, using a Universal Instron

Test Unit, conforming to the following standards:

ASTM D1761-12, Standard Test Methods for Mechanical Fasteners in Wood

ASTM B 557-15, Standard Test Method for Tension Testing Wrought and Cast Aluminum and

Magnesium-Alloy Products

NDS-2015, National Design Specification (NDS) for Wood Construction

ICC-428, Acceptance Criteria for Modular Framing Systems Used to Support Photovoltaic (PV)

Modules

For each load test, a Knockout Tile assembly was installed onto a preconditioned sample roof deck composed

of 15/32” OSB board and 2x4 Douglas Fir rafters. The measured moisture contents of the conditioned roof

decks ranged from 10% to 12%, and average specific gravity applying to uplift and lateral (across slope)

directions is 0.47. For each test, loads were applied at the highest slot position on the L-foot as shown in

Figure 1 and testing was performed to consider all orientations of L-foot and base as allowed per the Knockout

Tile Installation Manual. Table 1 below summarizes the average peak load, its associated failure mode, and

the calculated allowable capacity for the respective load direction. The listed average peak load reflects the

orientation of L-foot and base which results in the lowest capacity and can be applied to other allowable

orientations.

For wood species with specific gravity other than 0.47, capacities associated with lag pull out failure mode

(uplift & lateral across slope) shall be adjusted per American Wood Counsel (AWC) National Design

Specification Eq. (12.2-1). Adjusted results for various wood species are presented in Table 2 below.

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28357 Industrial Blvd

Hayward, CA 94545

1-800-227-9523

IronRidge.com

Table 1 Notes:

(1) Capacity applies to rafter size of 2x4 or greater at 24” O.C. or less, deck thickness 15/32” or greater, and are based on securing lag bolts within the

center 1/3 of rafter width with a minimum 2.5” end distance.

(2) For rafter specific gravity not equal to 0.47, uplift and lateral (across slope) capacities shall be adjusted and can be referenced in Table 2.

(3) Deviation reflects the variance of the highest or the lowest test value from the group mean for the respective load direction.

(4) Safety Factor is associated with the respective failure mode determined by the specific code referenced on Page 1.

(5) Allowable capacity is equal to Average Peak Load divided by its associated Safety Factor.

Table 2 Notes:

(1) Wood specific gravity is per NDS-2015 Table 12.3.3.A.

(2) Allowable Capacity = Table 1 Allowable Capacity x Adjustment Factor

Adjustment Factor = (Wood Density/0.47)3/2 per (AWC) National Design Specification Eq. (12.2-1)

Sincerely,

Gang Xuan, SE

Senior Structural Engineer

Load Direction Specimen Quantity Average Peak Load at

Failure (lbs)

Deviation of Test

Results (3) Critical Failure Mode Safety Factor (4) Allowable Capacity

(lbs) (5)

Uplift Load

Perpendicular to Roof

Surface(2)

4 1440 4% Lag Bolt Pull-out 3.0 480

Compression Load

Perpendicular to Roof

Surface

4 2385 7% OSB Deck Rupture 2.54 939

Lateral Load Parallel to

Rafter (Downslope) 4 461 2% Rupture of Base at

Lag Bolt Connection 1.95 237

Lateral Load

Perpendicular to Rafter

(Across Slope)(2)

4 592 9% Lag Bolt Pull-out 3.00 197

Table 1: IronRidge Knockout Tile Roof Assembly Allowable Capacities (1)

Wood Species NDS Assigned Specific Gravity(1) Allowable Uplift Capacity (lbs)(2) Allowable Lateral (Across Slope)

Capacity (lbs)(2)

Southern Pine 0.55 608 249

Douglas Fir-Larch 0.5 527 216

Douglas Fir-South 0.46 465 191

Hem-Fir (North) 0.46 465 191

Hem-Fir 0.43 420 172

Spruce-Pine-Fir 0.42 405 166

Table 2: Allowable Capacities Adjusted for Various Wood Species

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2.0

6.13

3.55

5.02

2 3

EXHIBIT: EX-0018

ITEM NO. DESCRIPTION

1 NUT, FLANGE, HEX, 5/16-18 SS

2 WASHER, EPDM BACKED

3 L-FOOT

4 BOLT, LAG 5/16 X 4"

5 ASSY, BASE

6 FLASHING, TILE REPLACEMENT, S-TILE

7 FLASHING, TILE REPLACEMENT, FLAT TILE

8 FLASHING, TILE REPLACEMENT, W-TILE Assy, Knockout Tile

DWG. NO. EX-0018