Structural collision repairs: why your shop must follow the automaker’s procedure
What the automaker’s repair steps protect and what to ask your body shop
Safety Behind the Wheel Foundation built this guide from NHTSA and Insurance Institute for Highway Safety (IIHS) research on how vehicles protect the people inside, repair guidance from I-CAR and the California Department of Insurance’s auto body repair consumer rights. Every source is listed at the end.
After a collision, most people judge a repair by what they can see. The paint matches, the gaps line up and the doors close well. But the parts that will matter most in the next crash sit under that paint.
Safety engineers use the word crashworthiness for how well a vehicle protects the people inside during a crash. Federal research on crashworthiness looks at vehicle design as well as safety equipment [1]. Seat belts and air bags are meant to control how your body moves during a collision [1].
The body structure has two jobs. The front section, between the bumper and the cabin, is built to crumple and soak up crash energy [2]. A longer crush zone gives the structure more room to collapse before the collision reaches the people inside [2]. The cabin, sometimes called the safety cage, is meant to keep its shape around you.
Air bags help, but they cannot do the job alone. Vehicles also need side structures that keep a collision from pushing deep into the cabin [3]. Air bag sensors start judging how severe a crash is the instant it begins [3]. Belts, bags and structure work best when the metal behaves as designed.
Structural parts are the load carrying pieces under the skin, such as frame rails and pillars. When they are damaged, the repair method matters as much as the finish.
What modern car bodies are made of
Industry sectioning guidance from the late 1980s was developed on cars made of mild steel, a softer, easy to shape metal [4]. Today’s vehicles contain far more high strength and ultra high strength steel [4]. A single body can mix several materials [5]:
- Mild steel. The traditional, softer body steel.
- High strength steel (HSS). Steel made to resist bending more than mild steel.
- Ultra high strength steel (UHSS). An even stronger grade. Its strength is often rated in megapascals (MPa), a unit engineers use to describe how much force a metal can take.
- Dual phase steel. Another advanced steel that technicians need to identify before they repair it.
- Aluminum. A lighter metal that needs its own repair methods.
The way parts are fastened has changed too. Factory joints can include laser welds, adhesive and self piercing rivets [6]. A self piercing rivet is a fastener pressed through layers of metal without a drilled hole.
These changes affect how a collision plays out. As cars gained more high strength steel, crash energy began to follow different paths and travel deeper into the vehicle [7]. Newer vehicles also tend to have tighter tolerances, so restoring the automaker’s exact dimensions matters more for how the car performs [7].
Our guide on measuring your car’s structure after a hard hit explains how shops check those dimensions. This article covers how the damage should then be fixed.
Why the automaker’s procedure is the rulebook
Each automaker publishes repair instructions for its own models. Shops often call them OEM repair procedures. OEM stands for original equipment manufacturer, the company that built the car.
Industry repair training guidance treats these procedures as specifications the repairer must meet, not friendly suggestions [8]. It sets out a clear order for finding the right method [8]:
- Start with the body repair manual for the exact year, make, model and damaged part, along with the automaker’s published position statements.
- If those do not cover the job, use the automaker’s general repair procedures.
- Only if the automaker is silent, turn to best practices developed and checked across the repair industry.
A position statement is a short notice in which an automaker states its rules on a repair practice.
A procedure for a damaged structural part can answer questions a technician should never guess at:
- May this part be straightened, or must it be replaced [5, 8]?
- Does this metal have heat or temperature limits [9]?
- May this part be cut and joined, and if so, exactly where [10, 11]?
- Which joint type and joining method should be used [6, 11]?
- How should the result be checked, such as by measuring [7]?
“Habit based” repair means doing the job the way it has always been done, instead of looking up the steps for that model. On a modern structure, a habit can quietly undo the engineering.
Straighten or replace: heat and stronger steels
Heat can make bent metal easier to pull back into shape. On a modern structure, though, using heat out of habit can cause harm.
Heat can do lasting harm to some metals. It breaks down the inner makeup that gives the metal its strength [9]. Weakened structural metal can leave the people inside at high risk in a collision [9]. Many automakers set heating and temperature limits based on the type of metal [9]. That is why the first step before straightening is knowing exactly what the part is made of [9].
Some parts should not be straightened at all. Where an automaker gives no guidance, an industry best practice says damaged parts rated above 600 MPa should not be straightened. Replacement is the only option [8].
The repair or replace decision also depends on the damage itself. Technicians weigh the part’s material and heating limits, damage near factory welds, and signs such as kinks, cracks, tears or stretched metal [5]. A kink is a sharp fold in the metal, not a smooth bend. They also check the automaker’s manual for any repair limits [5].
If a shop plans to heat a structural part, it is fair to ask whether the automaker allows it and what limit applies.
Sectioning: cutting only where the automaker allows
Sometimes only part of a damaged piece needs to be replaced. There are two ways to do this [10]:
- Partial replacement swaps out part of a component at a seam where the factory joined it.
- Sectioning cuts through a part away from any factory seam and joins in a new piece.
Sectioning creates a joint that was not in the car before [10]. Where that joint sits, and how it is built, shapes how the part behaves in a later collision. The automaker chooses whether a part may be sectioned, where, and with which joint type, to keep the vehicle safe in a future collision [11].
General sectioning guidelines were written in the late 1980s for cars made of mild steel [4]. They have never been tested on vehicles rich in high strength and ultra high strength steel [4]. In modern designs, it is very hard to tell by eye which areas are built to pass crash energy along and which are built to crush and absorb it [4].
So the guidance is direct. When the automaker has not published a way to section a part, do not cut it [4]. For a structural or UHSS part with no specific procedure, the answer is most likely not to section it [12]. Some automakers add that when damage runs past their approved cut points, a full new part is the only acceptable fix [12]. Safety Behind the Wheel Foundation encourages drivers to expect this standard on every structural repair.
Putting it back together: welds, adhesives and rivets
A body shop cannot always join parts the same way the factory did [6]. Some factory joints, such as laser welds, cannot be copied in a repair shop [6]. In those cases, the automaker’s procedure names a substitute, which may be spot welds, plug welds or adhesive [6].
A few terms help here:
- Squeeze type resistance spot welding. A welder clamps the panels between two tips and passes electric current through them to fuse a small spot.
- Plug weld. The technician makes a hole in the top layer and fills it with weld metal to join it to the layer below.
- Rivet bonding. Rivets used together with a structural adhesive.
- MIG brazing. A joining method in which a filler metal melts and bonds the parts while the steel itself does not melt.
Most automakers favor squeeze type spot welding to attach panels because their bodies use high strength and ultra high strength steels [13]. Fewer automakers are expected to allow conventional wire feed (MIG) welding for attaching panels on advanced structures [13]. It will likely still be used for sectioning where allowed [13].
The substitutes are specific to each model. When a spot welder cannot reach a joint, an automaker may call for rivet bonding or MIG brazing instead [6]. A factory self piercing rivet is not always replaced with the same kind of rivet. The procedure may call for a blind rivet or a plug weld [6]. Where the factory used adhesive on a hem flange, a folded over panel edge, the procedure may call for a seam sealer or urethane instead [6].
Comparison compiled by Safety Behind the Wheel Foundation
Factory joints and what a repair procedure may call for
| Factory joint or situation | What a repair procedure may call for |
|---|---|
| Laser weld | Spot welds, plug welds or adhesive [6] |
| Panels on high strength steel bodies | Squeeze type spot welds, which most automakers prefer [13] |
| Self piercing rivet | The same rivet, a blind rivet or a plug weld [6] |
| Hard to reach joint | Rivet bonding or MIG brazing [6] |
| Factory adhesive on a hem flange | Seam sealer or urethane, as the procedure names [6] |
Careful shops also test before they weld on your car. A technician makes practice welds on scrap metal, then tears and twists them apart to inspect the result [14]. Skipping that step leaves no way to know whether the machine settings and technique will make a sound weld on the vehicle [14].
How shortcuts can change crash performance
Every shortcut below can leave a repair that looks finished. The difference shows up only when the structure is asked to do its job again.
Comparison compiled by Safety Behind the Wheel Foundation
Repair shortcuts and what the procedure does instead
| Habit or shortcut | Why it is a concern | What the procedure does instead |
|---|---|---|
| Heating a bent part to pull it | Heat can permanently weaken some metals [9] | Sets heat limits or requires replacement [8, 9] |
| Cutting wherever is handy | The new joint may land where the car is meant to crush or carry energy [4] | Names approved cut points, or says not to section [4, 12] |
| Using the shop’s usual welder for everything | Stronger steels may call for a different method [13] | Names the joining method for each joint [6] |
| Skipping test welds | No way to confirm the weld settings work [14] | Tests first, then welds on the car [14] |
| Judging fit by eye | Newer cars have tighter tolerances [7] | Measures before and after the repair [7] |
The common thread is that structural repair choices are made with the next collision in mind [11]. The goal is a car that behaves the way its designers intended, not just one that looks the way it did.
Once a car is sealed and painted, you cannot see the welds or joints. The procedure, the measurements and the shop’s notes are your best evidence of what was done.
Questions to ask before and after structural work
You do not need to know how to weld to protect your family. You need clear questions and written answers. Bring this list at drop off and again at pickup.
Some states spell out the paperwork you are owed. California’s consumer rights include an itemized written estimate and, after the work, a detailed invoice [15]. Both must list parts and labor and identify each part as new, used, aftermarket, reconditioned or rebuilt [15]. Rules differ by state, so check with your state insurance department.
Structural work often leads to other steps, such as electronic scans, wheel alignment, corrosion protection and camera and sensor checks. For help choosing a capable shop, see how to pick a collision repair shop after a crash.
When the estimate and the procedure do not match
The first estimate is often written before the car is taken apart. Once panels come off, the shop may find more damage or learn that the automaker requires a part to be replaced rather than repaired. That can lead to a revised estimate, explained in hidden crash damage and the revised repair estimate.
If the estimate seems to skip a step the automaker requires, try this order:
- Ask the shop which procedure supports the added step or part.
- Ask the shop to share that procedure with the insurer, and keep a copy yourself.
- Get the insurer’s position in writing if it disagrees.
- Do not authorize a structural shortcut just to speed things up.
- If the dispute stalls, contact your state insurance department.
In California, you may also get your own estimate from a registered body shop while a claim is open [15]. Concerns can go to the Bureau of Automotive Repair or the Department of Insurance [15].
If the shop and insurer cannot agree, see what to do when your repair shop and insurer don’t agree. The goal is not to win an argument. It is a car that can protect your family the way it was built to.
Frequently asked questions
Can a bent frame rail ever be straightened?
Sometimes. It depends on what the rail is made of, how badly it is damaged and what the automaker allows. Damage such as kinks, cracks and tears weighs toward replacement [5]. Some very strong steels should not be straightened at all [8]. Heat limits also vary by metal [9]. Ask the shop to show you the automaker’s guidance for that exact rail before work starts, and keep a copy in your file.
Is wire feed (MIG) welding always wrong on a newer car?
No. Most automakers prefer squeeze type spot welds for attaching panels on cars with high strength and ultra high strength steels [13]. But conventional wire feed welding is still expected for sectioning where the automaker allows it [13]. Some procedures also call for plug welds or MIG brazing at certain joints [6]. The right answer is whatever the procedure for your model says for that joint.
Can I get a copy of the repair procedures used on my car?
You can ask. Request copies of the procedures, the before and after measurements and any test weld notes along with your final invoice. If a shop will not explain which procedures it followed, treat that as a reason to ask more questions before you accept the car.
I bought a used car that had a structural repair. What should I do?
Ask the seller for any repair records, including the estimate, invoice and measurement reports. An inspection by a collision repair facility can look for signs of past structural work. If records exist, ask whether the repair followed the automaker’s procedure. A structural measurement can also show whether key dimensions are where they should be.
Will following the automaker’s procedure make the repair cost more?
It can change the estimate. A procedure may call for replacing a part that a shop might once have straightened, or for extra steps such as test welds [8, 14]. Costs vary by vehicle and damage. If you are concerned, ask the shop and insurer to explain each added line. For a structural repair, the cheaper path is not a savings if the car no longer protects you as designed.
The bottom line
Recommendation from Safety Behind the Wheel Foundation
Safety Behind the Wheel Foundation urges drivers to insist on the automaker’s procedure for any structural repair. A modern car body is engineered to crush in some places and hold firm in others. Repairing it by habit can change that balance in ways no one can see. The automaker’s procedure for your exact model is the best guide to which parts can be fixed, where cuts may go and how new parts are joined.
You do not need to inspect welds yourself. Ask which procedures apply, ask for the records, and do not accept a structural shortcut to save time. That paper trail is your best evidence that the car carrying your family was repaired to protect them.
Related articles
- Why a hard hit may call for measuring your car’s structure
- How to pick a collision repair shop after a crash
- Hidden crash damage and the revised repair estimate
- What to do when your repair shop and insurer don’t agree
- What to look over before you drive your repaired car home
- Restoring corrosion protection after structural repair: the hidden step in a safe fix
Sources and further reading
- 1National Highway Traffic Safety Administration. Crashworthiness. Accessed October 2026. nhtsa.gov/research-data/crashworthiness
- 2Insurance Institute for Highway Safety. Vehicle size and weight. Updated August 2026. iihs.org/research-areas/vehicle-size-and-weight
- 3Insurance Institute for Highway Safety. Airbags. Updated July 2026. iihs.org/research-areas/airbags
- 4I-CAR Repairability Technical Support. Update: Are General Sectioning Guidelines Still Applicable? Posted October 30, 2015. rts.i-car.com/crn-304.html
- 5I-CAR Repairability Technical Support. Back-To-Basics: Repair Vs. Replace Considerations. Posted October 10, 2025. rts.i-car.com/crn-2332.html
- 6I-CAR Repairability Technical Support. Factory Built vs. Repair Procedure. Posted August 24, 2017. rts.i-car.com/crn-656.html
- 7I-CAR Repairability Technical Support. Three-Dimensional Measuring Equipment – Is It Really Necessary? Posted September 8, 2011; validated 2024. rts.i-car.com/crn-20.html
- 8I-CAR Repairability Technical Support. Always Follow Vehicle Maker Procedures. Posted July 7, 2016. rts.i-car.com/crn-418.html
- 9I-CAR Repairability Technical Support. Straightening And Heat. Posted May 20, 2020. rts.i-car.com/crn-1359.html
- 10I-CAR Repairability Technical Support. What’s The Difference Between Sectioning And Partial Replacement? Posted August 28, 2015. rts.i-car.com/crn-274.html
- 11I-CAR Repairability Technical Support. Do I Really Have To Follow Vehicle Maker Recommendations? Posted May 29, 2014. rts.i-car.com/crn-65.html
- 12I-CAR Repairability Technical Support. When There Are No Specific Sectioning Procedures. Posted September 2, 2026. rts.i-car.com/crn-2423.html
- 13I-CAR Repairability Technical Support. Is A Spot Welder A Required Tool? UPDATE. Posted April 15, 2022. rts.i-car.com/crn-1823.html
- 14I-CAR Repairability Technical Support. Back-To-Basics: Destructive Weld Testing. Posted December 3, 2018. rts.i-car.com/crn-995.html
- 15California Department of Insurance. Auto Body Repair Consumer Bill of Rights. Undated; accessed October 2026. insurance.ca.gov/…/AutoRepairConsumerBillofRights_Final-3…
This article reflects the safety priorities of collision repair quality and vehicle occupant protection. It is general education, not legal, insurance or engineering advice for your vehicle. Repair guidance changes as vehicles change, and the right method depends on your exact make, model and damage. For your own situation, talk with a qualified collision repair facility, the vehicle maker or dealer, your insurer, or your state insurance department or consumer protection agency. Reviewed October 2026.
Cite this article: Safety Behind the Wheel Foundation. “Structural collision repairs: why your shop must follow the automaker’s procedure.” drivewithcare.org, https://drivewithcare.org/structural-repairs-follow-automaker-procedures/. Reviewed October 2026.
Special thanks to our contributors
We appreciate the professionals, experts, and community members who share their knowledge and perspectives to help make this resource better. Your insights are always welcome and appreciated.
Have professional expertise, firsthand experience, or a perspective that could make this resource better?
We welcome your input. Your knowledge and experience can help us make this resource more useful, accurate, and meaningful to the people who rely on it.
Thank you. Your contribution is on its way.
We’re grateful you took the time to share your knowledge with us. Our team reviews every contribution with care. If it helps improve this resource, we’ll update the page and recognize you the way you chose.
Keep learning
Safe Driving Resource Center
Guides, self-checks and articles for drivers, parents of new drivers, and families recovering after a crash.
