Yes, loose steel rebar can be bent and cut on site, but only within limits. 10M bends easily with a hand bender, 15M is hard work by hand, and 20M and larger need powered equipment. Bars can be cut with a portable rebar cutter, an abrasive saw or, for plain black bar, a torch. What you should not do without the engineer's approval is bend bars already cast into concrete, cut bars in place to clear an obstruction, or heat bars to bend them. Epoxy-coated and fibreglass (GFRP) bar have stricter rules again.
This post is about what is practical on site. For why a correct bend doesn't hurt the bar, and why rebending does, see does bending rebar weaken it.
What you can and can't do on site
| Job | On site? | Condition |
|---|---|---|
| Bend loose 10M bar | Yes | Cold, around the correct pin diameter, bent once |
| Bend loose 15M bar | Possible | Hard to do accurately by hand; a powered bender is better |
| Bend 20M and larger | Rarely practical | Needs powered equipment and the right mandrel |
| Bend dowels or bars already in concrete | Only with engineer approval | Or where the drawings show it |
| Heat a bar to bend it | Only with an engineer-approved procedure | Heat changes the steel |
| Cut loose black bar to length | Yes | Shear, saw or torch |
| Cut bars in place to clear an obstruction | Only with engineer approval | Reduces strength at that point |
| Cut or bend epoxy-coated bar | Cut yes, bend with care | No torch; patch every cut end and damaged spot |
| Cut or bend GFRP bar | Cut straight bar only | High-speed saw; no field bending at all |
How to bend 10M and 15M rebar on site
The right tool is a lever bender with a pin of the correct diameter for the bar size and grade, mounted on a bench or base so the bar can't slip. Portable electric benders do the same job faster and more consistently.
The pin matters because the bend diameter is a code minimum, not a preference. Under CSA A23.1, as reproduced in the RSIC Manual of Standard Practice, the finished bend diameter for main bar hooks is:
| Bar size | Grade 400R or 500R | Grade 400W or 500W |
|---|---|---|
| 10M | 70 mm | 60 mm |
| 15M | 100 mm | 90 mm |
| 20M | 120 mm | 100 mm |
Stirrups and ties bend tighter: RSIC lists a finished bend diameter of 45 mm for 10M and 65 mm for 15M. The full set of values is in our rebar bending chart.
Bending rebar without a bender usually means a pipe slipped over the bar as a lever, or the bar bent over a form edge or another bar. Both tend to make the bend far tighter than the minimum, and it is easy to overshoot and bend back. If the bar is structural, get a proper bender or order the shape.
Practical points for a field bend:
- Mark the bar first. Measure to the point of the bend, allowing for the fact that the bend uses some of the length.
- Bend once, to the final angle. Don't straighten and rebend.
- Check the first piece against the drawing before bending the rest.
- Bend loose bars only. Embedded dowels and starter bars need the engineer's say-so.
- Watch the cold. CSA A23.1 has set a temperature range for bending (10 °C to 100 °C in the 2004 edition) unless the owner permits otherwise. In an Ontario winter, ask the engineer before bending bars outdoors.
Bending 20M and larger
From 20M up, bending by hand is not realistic. Field bending needs a powered bender sized for the bar and a mandrel matching the minimum bend diameter, and even then the shape will be less consistent than a shop bend. RSIC estimating practice expects field fabrication only where it is genuinely needed, for example when founding elevations aren't known until excavation, or when it keeps the schedule moving. Otherwise, larger bent bars should come from the shop.
How to cut rebar on site
Several tools cut rebar well. Pick by bar size, quantity and whether the bar is coated:
- Portable rebar cutter. Hydraulic or electric shears that cut common sizes cleanly in seconds with no sparks. Many combine a cutter and a bender.
- Abrasive chop saw. Good for repeat cuts to length on a stand. Throws sparks and needs a guard and eye protection.
- Angle grinder with a cut-off wheel. Handy for a few cuts or awkward spots. Keep the guard on and both hands on the tool.
- Oxy-fuel torch. Fast on plain black bar, especially larger sizes, but it leaves a rough, heat-affected end. Never use a torch on epoxy-coated bar.
- Band saw. Clean, square cuts, mainly a shop tool.
A shop shears straight bars to length within a standard tolerance of plus or minus 25 mm under RSIC practice. Bars cut on site should be measured just as carefully, because a short bar can lose its lap or cover. Where bar ends must bear on each other in a compression splice, RSIC practice is to saw cut them square, which is a special shop operation.
Once bars are cut and placed, cap any exposed vertical ends to protect workers. Our guide to rebar caps in Ontario covers the options.
Cutting bars that are already in place
This is the cut that needs the most care. The RSIC manual is direct: cutting bars to clear obstructions reduces the strength of the structure at that point and may only be done with the engineer's approval. Common situations:
- A sleeve, pipe or box-out lands on a bar after the steel is placed.
- A dowel or starter bar is in the wrong location.
- Coring or saw cutting existing concrete for an opening, which almost always cuts reinforcement.
In each case the engineer decides whether the bar can be cut, moved, or replaced with added bars around the opening. For new connections into existing concrete, see how to dowel rebar into existing concrete.
Coated and fibreglass bar
- Epoxy-coated bar is cut with a saw or shear, never a torch, and every cut end and damaged spot is patched with the approved repair material. Field bending is best avoided. Our post on bending and cutting epoxy-coated rebar has the details.
- GFRP bar can't be bent on site at all. RSIC states that field cutting should be done with a high-speed cutter, that shear cutting is not permitted, and that proper PPE should be worn. Every bent piece has to be ordered from the manufacturer.
Field or shop: how to decide
Field cutting and bending make sense for:
- A few replacements or pieces damaged in handling.
- Field fit where a dimension is only known once the forms or excavation are done.
- Very small jobs, such as a single pier or a short repair with a few 10M bars.
For everything else, shop fabrication wins:
| Field | Shop | |
|---|---|---|
| Accuracy | Depends on the operator and tool | Machine set to the bar list; RSIC tolerances apply |
| Crew time | Spent cutting and bending | Spent placing |
| Waste | Offcuts on site | Cutting planned from stock lengths |
| Identification | Pieces sorted by hand | Bundled and tagged by mark |
| Larger bars | Hard or impractical | Routine |
The usual reason contractors bend on site is that the order was missing a shape or a dimension changed. A complete bar list fixes most of that before it starts; see how to order cut and bend rebar.
Get it cut and bent in the shop
We shear bars to length, bend them to all standard shapes from 10M to 55M, and tag and bundle each mark so your crew can place them without sorting or bending on site. We also prepare bar lists and placing drawings from your structural drawings, supply fabricated dowels and stirrups, and supply GFRP rebar.
Send your drawings or bar list for a free quote, or see our services.
Frequently asked questions
Can rebar be bent by hand?
10M bar can be bent by hand with a lever bender that has the correct pin. 15M is possible with a long-handled bender but hard to do accurately, and 20M and larger need a powered bender. Bending over a sharp edge or with a pipe as a cheater bar usually makes the bend too tight.
What is the best way to cut rebar on site?
A portable rebar cutter (hydraulic or electric shear) gives clean, fast cuts on common sizes. An abrasive chop saw or a grinder with a cut-off wheel also works. A torch can cut plain black bar, but never epoxy-coated bar, and GFRP must be cut with a high-speed saw, not sheared.
Can you cut rebar that is already in place?
Not without the engineer's approval. The RSIC Manual of Standard Practice notes that cutting bars to clear obstructions reduces the strength of the structure at that point. The same applies to coring or cutting through bars in existing concrete.
Is it cheaper to cut and bend rebar yourself?
Only for a handful of pieces. Once crew time, waste, tools and rework are counted, shop cut and bent bar delivered tagged by mark is usually the better deal for anything beyond small repairs.
