Rebar Lap-Splice Length
The tension lap-splice length as a multiple of the bar diameter (the jobsite 40-48 bar-diameter rule).
Example
You enter
- Bar size #5
- Lap factor (bar diameters) 48
- Minimum lap (in) 12
You get
- Bar diameter 0.625 in
- Lap length 30.0 in (2 ft 6 in)
Checked against published worked examples from: CMACN Masonry Chronicles (Huang and Ekwueme).
Details, formula, and sources
ScopeWith a 12 in floor and a feet-and-inches readout. The engineer of record and the drawings govern.
Formula or tableLap = max(lap factor x bar diameter, 12 in); db from the #3..#11 table (bar number / 8 in for #3..#8).
Source and editionACI 318 development-and-splice basis (Class B tension lap ~1.3 x development length, by name).
Free accessACI 318 licensed; the bar-diameter field rule is public practice.
What governsEstimate. AHJ and licensed structural engineer govern.
API field namesbar_size, lap_factor, min_lap_in, db, lap_in
- Lap factor 40-48 bar diameters for Grade 60 in 4,000 psi normalweight, never less than 12 in (editable)ACI 318