Fender and Quarter Skin Repair on Motorhomes, Vans and Box Trucks
Written by Structural Repair Lead, Structural and Frame Lead, OCRV Center. Reviewed by Refinish Department Lead
In shortOn a motorhome the fender is molded fiberglass screwed into a skirt. On a Sprinter it is stamped steel with a factory seam. Two trades, one page, $750 to $8,500+.
How does fender and quarter skin repair differ between an RV and a van?
Fender and quarter skin repair on a motorhome is fiberglass work: grinding, laminating, fairing and refinishing a molded skirt. On a Sprinter or box truck it is metal work with sectioning, welding or riveting. Our Yorba Linda shop runs both, and Rancho Santa Margarita owners get told which one they have at estimate.
- Motorhome fenders are molded fiberglass, not bolt on stampings
- Sprinter rear quarters section at factory seams to OEM procedure
- Box truck corners are riveted skins over formed posts
- Cracks on RV skirts usually start at a screw hole, not at the impact
- Price range
- $750 to $8,500+4 to 40 labor hours at $210 per hour
- Labor rate
- $210 per hourBody and paint department
- Typical turnaround
- 3 to 12 shop daysMetal sectioning and corrosion protection add days over a fiberglass repair
- Materials
- $55 per paint hour, $5 per body hourWeld through primer and cavity wax included on metal sectioning
- Written estimate
- $150Credited in full against an authorized repair
Last verified
Curb contact is the most common way this damage arrives. A tight canyon turn off Santa Margarita Parkway, a driveway apron taken at the wrong angle, a fuel island kerb that was closer than the mirror suggested. The tire clears, the skirt does not, and the result is a scrape running the length of a wheel opening with cracks fanning out from the screw line above it.
What happens next depends entirely on what that skirt is made of. Motorhomes, fifth wheels and trailers carry molded fiberglass or filon over the wheel opening, screwed into the sidewall through a trim insert. Sprinters, cargo vans and chassis cabs carry stamped steel or aluminum with real flanges and factory seams. Box and reefer bodies carry riveted skins over formed corner posts. Three materials, three trades, and the estimate looks different for each.
The word fender means two unrelated parts here
On a motorhome, a fifth wheel or a travel trailer, the fender is a molded fiberglass skirt or a section of laminated filon covering the wheel opening. It is screwed into the sidewall through a trim channel and it carries no structural load. Nothing bolts off. Repair is a composite trade: grinding, scarfing, laminating, fairing and refinishing.
On a Sprinter, a cargo van or a chassis cab, the front fender is a stamped panel bolted to the body with a sealer bead at the flange, and the rear quarter is welded structure that forms part of the body shell. Repair is a metal trade with published section locations, specified weld processes and a corrosion protection sequence that is not optional. On a box or reefer body it is a third thing again: a riveted skin over formed posts, where the fastener pattern is the joint.
| Vehicle | Fender or quarter material | Repair trade |
|---|---|---|
| Class A and Class C motorhome | Molded fiberglass skirt over sidewall | Composite laminating and refinish |
| Travel trailer and fifth wheel | Filon skirt bonded to substrate | Rebond, fair and refinish |
| Sprinter and cargo van | Bolt on steel fender, welded rear quarter | Metal sectioning and corrosion protection |
| Box and reefer body | Riveted aluminum or FRP over posts | Skin replacement and fastener renewal |
Why the crack rarely starts where the curb hit
Composite skirts fail at their fasteners far more often than at their impact points. A screw driven a quarter turn too far dishes the washer and puts a permanent compressive stress into a brittle laminate. Road vibration then does the rest, and a hairline appears at the hole and travels. When a curb strike happens later, the panel breaks along the path that was already prepared.
That is why our repair includes stop drilling every crack terminus and changing the hardware at reassembly. Fender washers spread the clamp load and a controlled torque means the panel is held rather than crushed. It costs almost nothing and it is the difference between a repair that lasts and a repair that reappears at the same screw in eighteen months.
Sectioning metal quarters to manufacturer procedure
A modern van body is engineered to fold in a specific way, and the panel joints are part of that design. Manufacturers publish where a quarter may be sectioned, what weld process is required at each flange, and where structural adhesive substitutes for or supplements a weld. Squeeze type resistance spot welding is specified at many of those joints because it reproduces the factory nugget rather than approximating it.
Cutting outside those locations produces a body that looks correct and behaves differently under load. We follow the published procedure, and where a job calls for it, we would rather replace a full quarter than section one in a location the manufacturer does not sanction. For a fleet running Sprinters on daily routes, that is not a philosophical point, it is the difference between a repaired van and a compromised one.
Corrosion protection is most of the difference in a metal repair
Cheap quarter and fender repairs come back as rust, and they come back from the inside. Any time metal is cut, welded or drilled, bare steel is exposed inside a cavity that will never be seen again. Weld through primer at the joint, cavity wax injected into the closed section, and isolation between aluminum and steel are what keep that from becoming a problem two winters later.
The coastal air in this part of Orange County is not kind to a poorly protected seam, and units that spend time near the water accelerate it further. We treat this sequence as part of the repair rather than as an upgrade, and it is written into the estimate as its own operation so nobody has to guess whether it happened.
Before you proceed
If an estimate for a welded quarter repair has no line for cavity wax or weld through primer, ask why. Those two operations are the difference between a ten year repair and a three year one.
Graphics that run across a wheel opening
Wheel arches are exactly where coach designers like to put a sweep, and that turns a modest skirt repair into a layout exercise. We measure the stripe geometry off the undamaged side of the unit before any sanding starts, because once the graphic is gone there is nothing left to reference except photographs and hope.
On decal schemes the fix may be reproduction vinyl. On sprayed schemes it is masking and multi stage color, which is slower and carries more paint hours. Either way it is called out separately in the estimate, because an owner comparing two quotes deserves to know which one included the stripe.
Wheel well liners, clearance and what happens after the repair
The liner behind a fender is not trim. It is what stops road grit, water and thrown stones from blasting the back of the panel at highway speed. A missing or torn liner is why plenty of skirts fail from the inside years before anything hits them from the outside, and it is one of the most common items left off a cheap repair because it is invisible once the wheel goes back on.
Clearance is the other post repair check. A skirt or arch pushed inward by an impact can sit close enough to a tire that it only makes contact under load or in a turn, which produces a rub mark an owner discovers weeks later. We measure clearance at full lock and at ride height before releasing the vehicle, and on dual rear axles we check between the tires as well, because that gap is where a heat damaged repair usually shows up first.
Note
Ask whether the wheel well liner is included. It is the least visible line on a fender estimate and the one that most affects how long the repair lasts.
Tire failures, curb strikes and how carriers see them
A blown dual on a diesel pusher does remarkable damage in a very short distance. The casing takes the skirt, the wheel well liner, frequently a section of the laminated wall above it and sometimes the wiring loom routed along the frame. That is a covered event on most policies and it should be documented as one incident with a full scope, not repaired piecemeal as it is discovered.
Curb strikes are more contested. Single vehicle contact with a fixed object generally falls under collision coverage, and a deductible often makes a modest skirt repair not worth filing. We will tell you honestly which side of that line an estimate lands on, because sending an owner into a claim that costs them more than the repair helps nobody.
What is included
- Material identification at the wheel opening
- We establish whether the skirt is molded fiberglass, laminated filon over substrate, stamped steel or riveted aluminum before writing a single line of the estimate.
- Crack termination and scarf preparation
- Every crack end is stop drilled and the repair area is scarfed to a proper taper so the laminate has something to key into rather than a butt edge.
- Structural laminating or metal sectioning
- Fiberglass repairs are laminated with matched cloth and resin. Metal repairs are sectioned at approved seams with the joining method the manufacturer specifies.
- Corrosion protection at every new joint
- Weld through primer at the weld, cavity wax inside the closed section, and isolation between dissimilar metals. Skipping this is why cheap quarter repairs come back.
- Wheel well liner and splash shield refit
- Liners are reinstalled or replaced. A missing liner lets grit blast the back of a fresh repair, which is a slow way to redo the work.
- Fastener hardware upgrade on fiberglass skirtswhere applicable
- Fender washers and controlled torque replace the original point loading so the same crack does not start again at the same hole.
- Graphic reproduction across the repair areawhere applicable
- Wheel openings frequently carry a sweep or stripe. Layout is measured off the undamaged side before anything is sanded.
How the work runs
Sort the panel by material and construction
0.5 to 1 hour
Fiberglass, filon over substrate, steel and aluminum all get separated at intake. This is the single decision that sets the trade, the tooling, the hour count and the parts strategy for the entire job, and getting it wrong wastes a day.
Find the true edge of the damage
0.5 to 2 hours
On composite we tap test outward until the sound tightens. On metal we probe the flange and check for corrosion behind sealant. On riveted bodies we push the panel and watch the fastener line. The visible scar is rarely the boundary.
Remove trim, liners and hardware
1 to 4 hours
Insert trim, screw covers, flares, wheel well liners and lights come off and get labelled. On a Sprinter the front fender is a bolt on with a sealer bead at the flange, and that bead has to be cleaned rather than smeared back together.
Repair the structure
2 to 20 hours
Composite panels are scarfed and laminated from the back where access exists. Metal is sectioned at approved seams and joined with the specified process. Riveted skins are replaced and refastened on a fresh pattern rather than into the old holes.
Protect, fair and refinish
3 to 14 hours
Corrosion protection goes in before anything closes up. Fairing is blocked to the arch contour with a curved board so the wheel opening keeps its radius, then color and any graphic are laid in and blended to a break.
What this costs
$750 to $8,500+
4 to 40 labor hours at $210 per hour, body and paint.
- Paint supplies at $55 per paint hour.
- Body supplies at $5 per body hour.
- Parts at $100 or less carry 100 percent markup. Parts over $100 carry 35 percent. Special order parts require a full non refundable deposit at order.
- Sales tax of 7.75 percent applies to parts and materials. Labor is not taxed.
- A 50 percent deposit is taken at authorization on any job over $2,000, with an additional 25 percent when parts arrive on any job over $10,000. Final balance is due at pickup.
- A cracked fiberglass skirt on a solid color coach, laminated and refinished, sits near the bottom.
- A sectioned steel quarter on a Sprinter with full corrosion protection and a graphic sweep sits at the top.
- Bolt on van fenders land low in the range because the part exists and the flange is accessible.
How estimating is billed
- Written repair estimate: $150, credited in full against an authorized repair.
- In depth diagnostic, scan and programming: $285 per hour, one hour minimum, credited in full against an authorized repair.
- In shop pre purchase inspection: $400 to $1,200 depending on unit size and systems count.
- Insurance walk ins are accepted during posted hours. All inspection and estimating work is performed in shop at the Yorba Linda facility.
What you will notice first
- A scrape along the lower wheel opening with the gelcoat cut through to the laminate
- Cracks radiating upward from screw holes along the top of a fender skirt
- A fender flare that has pulled away at one end and now catches wind at speed
- Rust bubbling along the bottom flange of a steel van fender
- A rear quarter with a crease that runs into the wheel arch on a Sprinter
- A box body corner where the skin has separated from the post and moves in the wind
- Tire rub marks inside the arch after a hit pushed the skirt inward
- Sealant squeezed out along a fender to body flange with dirt packed into the gap
How this fails, and what we do about it
| Failure mode | How we diagnose it | The fix |
|---|---|---|
| Screw hole crack propagation in a fiberglass skirt | Cracks start at fastener holes along the top trim line and run down. Look for a washer that has dished or a screw that has been driven past flush. The impact damage below is often secondary to this. | Stop drill each crack end, grind a scarf from the back where access exists, laminate with matched cloth, then reinstall with fender washers and a controlled torque so the panel is clamped rather than crushed. |
| Delaminated filon skirt after a curb strike | The skin around the scrape sounds drummy and lifts slightly at the edge. The strike sheared the bond over a wider area than the visible scar. | Cut back to sound bond, replace the substrate section if it is crushed, and rebond new skirt stock with structural adhesive under clamp pressure. Filling over a released bond leaves the repair sitting on nothing. |
| Rusted lower flange on a steel van fender | Bubbling paint along the bottom edge with a soft spot when probed. Peel the sealant bead and you will find the corrosion started behind it where water wicked into the seam. | Cut the flange back to clean metal, weld in new metal with weld through primer at the joint, treat the cavity with wax, and reseal. Grinding and filling a rusted flange returns it within a year. |
| Creased rear quarter on a Sprinter or chassis cab | The crease crosses the wheel arch and the panel is stretched. Check the OEM procedure for allowable section locations before deciding between a partial and a full quarter. | Section at a manufacturer approved seam using squeeze type resistance spot welds where specified, bond and rivet flanges where the procedure calls for it, then restore corrosion protection inside the cavity. |
| Separated skin at a box body corner post | The aluminum or FRP skin moves against the post and the fastener line shows elongated holes. Water staining inside the box at the same corner usually confirms it. | Replace the skin section and refasten with Huck bolts or structural blind fasteners at a fresh pattern, with isolation between the aluminum skin and any steel structure behind it. |
Why it happened
- Curb and kerb strikes on canyon roads, which land on the leading lower corner of a wheel opening rather than on the middle
- Overtightened screws through a fiberglass skirt, which start a stress crack at the hole and let road vibration finish it
- Tire failure on a dual rear axle, where the shredded casing takes the skirt and the wheel well liner with it
- Road salt and coastal air on steel van fenders, which corrodes the bottom flange from behind the sealant bead
- Loose or missing wheel well liners, which let grit blast the back of a panel until it fails from the inside
- Improper prior repair with rigid filler on a flexing skirt, which cracks along the repair boundary within a season
Parts and brands we work with
- Molded fiberglass fender skirts and wheel flares through OEM channels for Winnebago, Tiffin, Thor and Newmar coaches
- Crane Composites Filon skirt stock and gelcoat repair resin for laminated sidewall skirts
- Mercedes and Freightliner Sprinter bolt on front fenders, flange sealer and wheel arch liners
- Stamped steel quarter panel sections and factory seam locations per OEM repair procedure
- Huck bolts, Avdel structural blind fasteners and aluminum corner post stock for box and reefer bodies
- Weld through primer, cavity wax and dissimilar metal isolators for corrosion protection at new joints
What not to try yourself
- Filling a crack in a fiberglass skirt without stop drilling the ends first. The crack keeps running under the filler and reappears as a line through the finish within months.
- Sectioning a modern van quarter wherever it is convenient. Manufacturers publish allowable section locations for a reason, and cutting outside them compromises the crash path of the body.
- Grinding and filling a rusted lower flange. The corrosion started behind the sealant on the inside of the seam, and covering the outside changes nothing about what is happening in there.
- Reusing the original holes when refastening a riveted box body skin. Elongated holes give a fastener nothing to clamp, and the joint works loose again on the first freeway run.
Which vehicles we do this on
Vehicles we perform Fender and Quarter on
Diesel PusherDiesel pusher repair means working on a rear engine coach built on a welded Freightliner XC or Spartan rail, with a full body painted fiberglass shell and large basement baysClass A GasClass A gas motorhome repair covers the molded front and rear caps, the vacuum bonded laminated sidewalls, the EPDM roof and the F53 chassis underneathClass CClass C motorhome repair centers on the cabover bunk, the joint where the coach body meets the factory van cab, and the stick built or laminated house behind itSprinterSprinter van collision repair covers the unitized steel shell, the rear and sliding door openings, the roof structure and the upfit that hangs off all of itCargo VanCargo van body repair covers ribbed steel sides, sliding and rear door openings, roof panels and the front structure of standard wheelbase work vansBox TruckBox truck body repair covers roll up doors and their tracks, rear frames and liftgate mounts, sheet and post sidewalls, hardwood floors over steel crossmembers and the subframe holding the body to the chassisStandardStandard fifth wheel repair concentrates on the pin box and upper deck welds, the floor at the step up transition, the front cap above the pin and the roof front radius seamFood TruckFood truck repair covers the step van body, the serving window aperture and its header, the roof hood curb, the coved floor under the cooking line and the generator compartmentNine out of ten fiberglass skirts that come in cracked, the crack did not start where the curb hit. It started at a screw somebody drove home with an impact driver at the factory or at a previous shop. You can see it: the washer is dished and there is a little star around the hole. So I stop drill, laminate the back, and then I put it together with a fender washer and a torque I can actually control. If you skip that last part you are going to see the same coach again in eighteen months with the same crack in the same place.
Appendix: questions and answers
- Is an RV fender the same kind of part as a car fender?
- No. On a motorhome or trailer it is a molded fiberglass or filon skirt screwed into the sidewall through a trim channel, carrying no structural load and offering nothing to unbolt. On a Sprinter or chassis cab it genuinely is a stamped panel with a bolt pattern and a flange sealer bead.
- Why does the crack in my fender skirt keep coming back?
- Usually because the crack ends were never stop drilled and the fastener that started it went back in the same way. A hairline under filler keeps travelling. We drill each terminus, laminate from behind, then reassemble with fender washers and controlled torque so the panel is clamped instead of crushed.
- Can you section my Sprinter quarter anywhere convenient?
- No. The manufacturer publishes allowable section locations and specifies the joining process at each one, including where squeeze type resistance spot welds are required. Cutting outside those locations changes how the body behaves under load, so we either section where permitted or replace the full quarter.
- A rear dual blew out and tore up the skirt. What is the real scope?
- Usually more than the skirt. A shredded casing at highway speed typically takes the wheel well liner, a section of laminated sidewall above the arch, and often wiring routed along the frame rail. It should be documented and claimed as one incident rather than repaired as each item is discovered.
- The corner of my box body flexes in the wind. Is that just rivets?
- It is the fastener pattern giving up. Holes elongate, the skin works against the post, and water tracks in at the same corner. The fix is a new skin section refastened on a fresh pattern with Huck bolts or structural blind fasteners, plus isolation between aluminum skin and steel structure.
- Is a curb scrape on the skirt worth filing on insurance?
- Often not. Single vehicle contact with a fixed object generally falls under collision, and a typical deductible can approach or exceed the repair. We write the estimate first so you can see the number before deciding, and we will say plainly when filing would cost you more than paying.
Open a file on this repair
Tell us the vehicle, what happened and whether a claim is open. We will tell you what the scope looks like and what it takes to get you back on the road.
Or call (949) 799-3387