Cutting and Bending on Site Without a Bending Schedule
You are working on a small residential extension. The drawing shows a cantilever slab with top bars, but the bending schedule is missing and the engineer is unavailable until Monday. It is Friday afternoon and the concrete is booked for Saturday. A stack of N12 straight bars is on site. The cantilever projects 1.2 m and the slab is 150 mm thick. The leading hand sketches a bar with a 90-degree hook at the outer end and asks you to cut and bend 40 bars to suit. The site bender is a manual machine with a capacity of N16. The slab edge form is already set.
1. Decide whether to cut and bend to the leading hand's sketch or to stop. Justify your decision.
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Stop. Cutting and bending structural reinforcement without an approved bending schedule or engineer's detail is not a decision for the leading hand or the steelfixer, even on a small job. The bar shape, hook type, bend diameter, and anchorage length all affect whether the cantilever works.
A 1.2 m cantilever with top bars relies on correct anchorage into the back span. A 90-degree hook at the outer end may not be the specified detail, and the bend diameter for N12 must meet the minimum to avoid cracking or splitting the bar. The manual bender can physically bend N12, but capacity is not the same as suitability.
The correct action is to stop, record the missing information, and escalate. Options include getting the engineer to issue a detail by email, using a standard detail from the drawings if one exists, or delaying the pour. A Saturday pour is not worth an unverified cantilever.
2. If the engineer later confirms a standard 90-degree hook, describe the checks you would make before bending.
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Before bending, confirm the bar grade and the minimum bend diameter from the engineer's detail or the relevant standard. Check that the manual bender's tooling matches the required diameter, because an undersized former will crack the bar.
Check the hook length and the anchorage into the back span, not just the cantilever portion. Confirm the bar will fit within the 150 mm slab thickness with the required top cover, allowing for the hook and any crossing bars.
Check the cut length against the detail, allowing for bend deductions, and mark each bar before bending. Bend a trial bar and check the dimensions and the absence of cracking before running the batch of 40. Record the approved detail and keep it with the delivery docket so the inspector can verify the work.