How to check a rebar takeoff against the bar schedules

The bar schedules for every element type, the general notes (cover, laps, anchorage, hooks), the plans and sections, and the take-off you are checking, in Excel, sorted by element and bar mark.

Keep one formula at hand. A steel bar weighs d² ÷ 162 kilograms per metre, with d in millimetres: a 12 mm bar is 0.89 kg/m and a 16 mm bar 1.58 kg/m.

Make two lists of bar marks, one from the schedules and one from the take-off, and compare them both ways. A scheduled mark missing from the take-off is steel you have not priced. A mark in the take-off that is on no schedule was copied from another job, read from a superseded revision, or invented.

Then check the multiplier. Schedules often give bars per member and leave the number of members to the plan: four bars per column, and the plan shows twelve columns of that type. Most missing tonnes are a wrong count, not a wrong length.

A continuous run longer than the bars your supplier delivers needs a lap at every joint, and column bars need one wherever the drawings splice them. The general notes give the lap length, usually as a multiple of the bar diameter, sometimes as a table by diameter and concrete grade.

Say the bars come in 12 m lengths and the notes give a 0.8 m lap: a 30 m run needs three bars and two laps, 31.6 m of steel, not 30. Check that laps sit where runs exceed the stock length, at the length the notes give for that diameter, and only once: not in the schedule length and again in the take-off.

A bar is shorter than the concrete around it. The cut length of a straight bar is the member length less the cover at both ends, plus the hooks and bends the schedule shows. Say a footing is 2.0 m long with 75 mm cover: its straight bottom bar is 1.85 m before any bends.

Cover changes with exposure, so read it from the notes for each element: concrete cast against soil usually needs more than an internal slab. If a take-off used the concrete dimension as the bar length, every bar is long, and the short, numerous links and stirrups are wrong the most.

Divide the steel of each element type by its concrete volume and compare the result with bands built from your own accepted jobs of the same structural system: footings with footings, columns with columns. A column or a transfer beam typically carries far more steel per cubic metre than a lightly loaded slab, so one building-wide ratio hides more than it shows.

• Below the band: usually missing bars, such as a schedule never read or a top mesh left out.
• Above the band: usually double counting, such as a bar in both the beam and the slab, or laps added twice.

The ratio does not tell you which bar is wrong. It tells you where to look.

Total the take-off two ways, by diameter and by element: the two totals must be equal. Where a schedule prints its own total weight, the element total must match it. Then recompute a sample of rows by hand: number of bars × cut length × unit weight.

If the sample is right and the totals tie, the take-off is arithmetically sound; checks 1 to 4 tell you whether it is the right steel. Anything you cannot close goes on the query list with its sheet and schedule row. Do not average two schedules that disagree. Ask.

detumble reads the bar schedules from the structural DWG or DXF set, including tables drawn as blocks or embedded as objects, and turns them into bar sets in a material take-off per element. Each bar set carries the sheet and schedule row it came from, which is what checks 1 and 5 need: every bar set in the take-off is traceable to its row.

Nothing is final until an engineer accepts it, so run all five checks on its output too: the review gate is where a figure the drawings do not support gets corrected before it reaches the bill.

It reads bar schedules; it does not produce a fabrication bar bending schedule in shape-code format. Prices are on the pricing page, the QS workflow on the quantity surveyors page.