Calculate lag bolt pullout strength and required embedment for roof-mounted PV attachment points.
Input Parameters
Results
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Pullout per Bolt
lbs
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Total Capacity
lbs
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Safety Factor
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Connection Status
Note: NDS (National Design Specification for Wood) governs lag screw withdrawal. Minimum embedment is typically 6D. Pre-drill to 60-75% of shank diameter.
Reference
W = 1800 × G^1.5 × D × p (NDS Eq 12.2-3)
G = specific gravity (SPF=0.42, DF=0.50, SYP=0.55)
D = bolt shank diameter
p = embedment depth
W_adj = W × 0.625 (load duration factor)
SF = capacity / design load