Lap Joint Minimum Overlap Calculator

Calculate minimum overlap distance and fillet weld sizing for lap joints per AWS D1.1 and AISC standards

Input Parameters

Results

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Minimum Overlap
in
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Recommended Fillet Size
in
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Joint Capacity per Inch
lb/in
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Required Weld Length
in
Note: Lap joints should have overlap of at least 5x the thinner member thickness to prevent rotation. Single-sided fillet welds on lap joints create eccentricity - use both sides when possible for structural applications.

Reference

AWS D1.1 / AISC Lap Joint Requirements: Min overlap = 5 x thinner plate thickness (min 1 in) Fillet weld throat = 0.707 x fillet size Allowable shear = 0.30 x FEXX per weld Max fillet = plate thickness - 1/16 in (for t > 1/4 in) Min weld length = 4 x fillet size or 1.5 in (whichever is greater)