How to Prepare a Bar Bending Schedule for a Slab (Step-by-Step)
Slabs are usually the simplest member to schedule — most of the bars are straight, running in two directions across the slab. This guide walks through identifying the bars in a typical slab, how they map to a bar bending schedule, and a worked example you can check your own numbers against.
The bars in a typical slab
Not to scale — illustrative only
- Main bars. Run in the primary span direction, spaced according to the design (e.g. 200mm centres). These are almost always shape code 00 (straight), cut to the slab span plus end cover and any anchorage.
- Distribution bars. Run perpendicular to the main bars, spaced more widely, and tie the main bars together while distributing load across the slab width. Also typically straight, shape code 00.
- Top bars (continuous/cantilever slabs). Where a slab is continuous over a support or cantilevers past one, top bars are added over the support — sometimes straight, sometimes with a single bend (shape code 11) if they need to turn down into a beam or wall.
Worked example
Take a simple one-way slab: 4.0m clear span, main bars 12mm at 200mm centres, distribution bars 10mm at 250mm centres, slab width 3.0m, 25mm cover.
| Bar mark | Shape | Size | Cutting length | No. | Total length | Weight |
|---|---|---|---|---|---|---|
| 101 (main) | 00 — straight | 12mm | 4050mm | 16 | 64.8m | ≈57.6 kg |
| 102 (distribution) | 00 — straight | 10mm | 3050mm | 13 | 39.65m | ≈24.5 kg |
- Cutting length. For a straight bar, cutting length is simply the span plus a small allowance for cover/anchorage at each end — here, 4.0m span + 2 × 25mm cover ≈ 4.05m for the main bars.
- Number of bars. Slab width ÷ spacing, plus one: 3.0m ÷ 0.2m + 1 = 16 main bars. Same logic for distribution bars across the 4.0m span at 250mm centres.
- Total length and weight. Multiply cutting length by number of bars, then apply the weight-per-metre for each bar size.
On a real slab, you'd repeat this for every panel and add top bars at any continuous or cantilevered edges — which is where doing this by hand across a whole floor plate gets tedious fast.
Build the slab schedule automatically
Enter the span, spacing and bar sizes and the calculator handles the cutting length, quantity and weight for every bar mark.
Open the BS 8666 calculator →Frequently asked questions
What bars go into a slab bar bending schedule?
A typical slab schedule includes main (span direction) bars, distribution bars running perpendicular to the main bars, and top bars over continuous supports where the slab is designed as continuous rather than simply supported.
What shape code is used for slab main bars?
Most slab main and distribution bars are straight bars, shape code 00, since a typical slab bar runs the full span without a bend. Bars that need to turn up at a slab edge or into a supporting beam use a single-bend shape such as code 11.
How do you calculate the number of bars in a slab?
The number of bars in a slab is calculated by dividing the slab width (in the direction perpendicular to the bar) by the bar spacing given on the drawing, then adding one, and rounding as needed to suit the actual layout and edge distances.
More member-specific guides
See how the same process works for other structural elements.
BBS for a beam → BBS for a column & footing →This is an illustrative worked example, not a substitute for a checked, engineer-approved bending schedule. Always take spans, spacing, cover and bar sizes from the actual structural design.