What Is a Bar Bending Schedule?
A Bar Bending Schedule (BBS) is a detailed list of every reinforcement bar in a concrete structure, specifying its shape, diameter, length, quantity, and total weight. It's the critical link between structural drawings and the actual cutting, bending, and placement of steel on site.
A well-prepared BBS:
- Eliminates over-ordering (typical waste without BBS: 8-15%)
- Prevents site delays from missing bars
- Enables accurate cost estimation
- Provides clear instructions for the bar bending yard
Essential Columns in a BBS
| Column | Description | Example |
|---|
| Member | Structural element name | Beam B-12 |
|---|---|---|
| Bar Mark | Unique bar identifier | B12-a |
| Diameter | Nominal diameter (mm or #) | 16 mm |
| Shape Code | Standard shape reference | Shape 38 (BS 8666) |
| Total Length | Developed bar length | 4,850 mm |
| Dimensions | Each leg of the shape | a=2500, b=350 |
| Number | Count of identical bars | 4 |
| Unit Weight | kg/m for the diameter | 1.578 |
| Total Weight | Qty × Length × Unit Wt | 30.65 kg |
Step 1: List All Structural Members
From the structural drawings or BIM model, inventory every element:
- Foundations: footings, grade beams, pile caps, mat foundations
- Vertical: columns, shear walls, piers
- Horizontal: beams, slabs, lintels, staircases
- Special: retaining walls, ramps, curved elements
Step 2: Read Reinforcement Details
For each member, identify:
- Longitudinal bars: main flexural reinforcement
- Transverse bars: stirrups, ties, hooks
- Distribution bars: temperature and shrinkage steel
- Special reinforcement: confinement ties at beam-column joints
Bar Weights Reference (ASTM)
| Bar # | Diameter (in) | Diameter (mm) | Weight (lb/ft) | Weight (kg/m) |
|---|
| #3 | 0.375 | 9.5 | 0.376 | 0.560 |
|---|---|---|---|---|
| #4 | 0.500 | 12.7 | 0.668 | 0.994 |
| #5 | 0.625 | 15.9 | 1.043 | 1.552 |
| #6 | 0.750 | 19.1 | 1.502 | 2.235 |
| #7 | 0.875 | 22.2 | 2.044 | 3.042 |
| #8 | 1.000 | 25.4 | 2.670 | 3.973 |
| #9 | 1.128 | 28.7 | 3.400 | 5.060 |
| #10 | 1.270 | 32.3 | 4.303 | 6.404 |
| #11 | 1.410 | 35.8 | 5.313 | 7.907 |
Step 3: Calculate Bar Lengths
Total bar length includes:
- Straight length between supports
- Standard hooks (90° or 180°): add development per ACI 318 Table 25.3
- Lap splices: splice length = ld × factor (1.0 for Class A, 1.3 for Class B)
- Bends: minimum bend radius per ACI 318 Table 25.3
For rectangular stirrups:
`L = 2(a + b) + 2 × hook length`
where a and b are the inside dimensions plus cover.
Step 4: Calculate Quantities and Weights
For each bar mark:
1. Count bars per element
2. Multiply by number of identical elements
3. Calculate: `Weight = Quantity × Length (m) × Unit Weight (kg/m)`
Step 5: Add Wastage Factor
Stock lengths are 20 ft (6 m) or 40 ft (12 m). Cutting always produces offcuts:
- 5% wastage for projects with mostly long bars
- 8% for projects with many short bars and complex shapes
- 3% if using cutting optimization software
Step 6: Create Summary Table
At the end of the BBS, include a summary by diameter:
| Diameter | Net Weight (kg) | Wastage (%) | Total Weight (kg) |
|---|
| #4 | 2,480 | 5% | 2,604 |
|---|---|---|---|
| #5 | 5,120 | 5% | 5,376 |
| #6 | 8,350 | 5% | 8,768 |
| #8 | 4,200 | 5% | 4,410 |
| #10 | 1,850 | 5% | 1,943 |
| Total | 22,000 | — | 23,101 |
Common BBS Mistakes
- Forgetting lap splices — especially in continuous slab and wall bars
- Missing confinement ties — extra stirrups at beam-column joints
- Wrong unit weight — always verify against the bar manufacturer's data
- Confusing bar sizes — #5 and #6 look similar on small-scale drawings
- Omitting support bars — top bars in beams used for stirrup support
Automate with IronBid
Creating a BBS manually for a 10-story building can take 40-80 hours. IronBid imports BIM/IFC models and generates the complete BBS with shapes, weights, and summaries in minutes. Lap lengths and hooks are calculated automatically per your selected code (ACI 318, BS 8666, or Eurocode 2).
Frequently Asked Questions
How many columns should a bar bending schedule have?
A professional BBS needs at minimum 9 columns: member, bar mark, diameter, shape code, total length, shape dimensions, quantity, unit weight, and total weight. Optional columns include floor level, pour phase, and remarks.
What software is used for bar bending schedules?
Options range from Excel (manual), through RebarCAD and ASA Rebar (semi-automated), to BIM-based solutions like IronBid that generate the BBS directly from the 3D model.
Does the BBS include welded wire mesh?
Typically no. Wire mesh is scheduled separately in m² or ft² by mesh type, since it doesn't have individual bar shapes.