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Product ID: LAG-516-400-SS
5/16" x 4" Stainless Steel Lag Bolt
5/16" x 4" Stainless Steel Lag Bolt

Stainless steel lag bolts are used to fasten L-feet to the roof structure.  The length and diameter of the bolt depends on the pull-out strength needed, and the thickness of the non-structural material (shingles & sheeting) being passed through.

Because lag bolt requirements vary with design wind load and lumber used for the roof trusses, lag bolts are no longer provided with SolarMount L feet.

The table below (reproduced from Unirac's Technical Bulletin 103: Code Compliant SolarMount Installation) lists pull-out values for various roof truss lumber and lag screws.  To ensure code compliance, the lag pull-out value must exceed the installation's design live load per footing multiplied by an appropriate safety factor.

 Stainless steel lag bolts

Lag Pull-Out Values (lbs) in Typical Roof Truss Lumber

Lag Screw Specifications
Specific5/16" Shaft5/16" Shaft3/8" Shaft
 Gravity2 1/2" Thread Depthper 1" Thread Depthper 1" Thread Depth
Douglas Fir — Larch0.50665266304
Douglas Fir — South0.46588235269
Engelmann Spruce, Lodgepole Pine
(MSR 1650 f & higher)0.46588235269
Hem — Fir0.43530212243
Hem — Fir (North)0.46588235269
Southern Pine0.55768307352
Spruce, Pine, Fir0.42513205235
Spruce, Pine, Fir0.50665266304
(E of 2 million psi and higher
grades of MSR and MEL)
Sources: Uniform Building Code; American Wood Council.

The table below (reproduced from Unirac's SolarMount Canadian Code Compliant Installation Manual) lists lag bolt withdrawl resistance for some commonly available wood species in Ontario.

Lag Bolt Withdrawal Resistance
Wood Species5/16” Ø Lag Screw Specifications
Factored Withdrawal Resistance (kN/mm x 103)

Price: $1.34
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