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RV, Van, Trailer and Fleet Repair Glossary

The short answer

Definitions for the terms that appear on estimates, supplements and repair orders for RVs, trailers, vans and fleet vehicles. Grouped by domain: structure and body, paint and finish, roof and seals, slides and awnings, electrical and systems, running gear, and insurance.

How To Use This

Most disputes on a repair order come from two people using the same word to mean different things. An adjuster writing delamination may mean a visible bubble. A shop writing delamination means a mapped area of separation that is usually several times larger. Neither is being dishonest. They are describing different scopes with one word, and the estimate reflects the smaller one.

These definitions are written the way the terms get used on an actual repair order rather than the way a manufacturer glossary would phrase them. If a term on your estimate is not here, ask the shop to define it in writing before you approve the line. A line item nobody can explain in a sentence is a line item worth questioning.

Structure and Body

These are the terms that decide whether a repair is cosmetic or structural, and therefore what it costs. The single most important concept in this group is the sandwich panel, because almost every expensive surprise on a coach or trailer traces back to what happened inside one. Read this group first if the word structural appears anywhere on your estimate, because that single word is what separates a refinish from a rebuild.

Laminated sidewall: A wall built as bonded layers of exterior skin, adhesive, substrate, insulation or framing, and interior panel, rather than a single sheet of material.
Sandwich panel: The general term for that layered construction, where the strength comes from the bond between the layers rather than from any one layer alone.
Substrate: The backing material directly behind the exterior skin, commonly luan or a composite board, that the skin is bonded to.
Luan: A thin plywood commonly used as substrate in RV walls, which loses structural integrity quickly once it gets wet.
Delamination: Separation of the bonded layers in a sandwich panel, showing as a bubble, wave, soft spot, or hollow sound when tapped.
Tap test: Assessment method where a panel is tapped across its surface to map separation by the change in sound, which is how the real extent gets measured.
Fiberglass layup: Building up structural fiberglass in layers of cloth and resin to a specified schedule, which is a repair that carries load, unlike filler.
Gelcoat: The pigmented resin surface layer on a molded fiberglass component, which is the finish rather than a coating applied over one.
Cap: The molded fiberglass front or rear end of a motorhome or trailer, structural in some areas and cosmetic in others.
Cage: The welded steel or aluminum framework that carries load in a motorhome house structure, distinct from the chassis underneath it.
Racking: Distortion of a rectangular structure into a parallelogram, which is what makes doors and slides bind even when nothing looks bent.
Chassis: The frame, suspension, and drivetrain the house structure is built onto, a separate structure that fails independently of the house.
Outrigger: A lateral frame member extending from the main rail to support the floor and body beyond the rail width.
Crossmember: A transverse frame member tying the main rails together and supporting the subfloor.
Subfloor: The structural decking between the frame and the finished flooring, and the most common casualty of long-term water intrusion.
Stick and tin: Construction using a wood or aluminum stud frame with aluminum sheet skin, where the skin is weather barrier rather than structure.
Monocoque: Construction where the skin itself carries the structural load, as on a riveted Airstream shell, so panel replacement is structural work.
Oil canning: Visible flexing or popping of a large flat panel under light hand pressure, indicating loss of tension or backing support.
Stress riser: A point where geometry concentrates load, such as a hole or an abrupt change in section, and therefore where cracks start.
Heat affected zone: The area adjacent to a weld where the base metal properties were changed by heat, and the usual location of a later crack.
Galvanic corrosion: Accelerated corrosion where dissimilar metals contact in the presence of moisture, common on coastal trailers at steel fasteners in aluminum panels.

Paint and Finish

Refinish terms show up on estimates as hours and materials, and the gap between a cheap paint estimate and an accurate one is almost always in preparation and blending rather than in the spraying itself. Color, blending, and graphics reproduction are the three lines owners question most often, and all three are labor rather than material. Knowing what each term describes makes a refinish estimate readable instead of arbitrary.

Basecoat: The pigmented color layer, which carries the color but not the gloss or the durability.
Clearcoat: The transparent protective layer over the basecoat, which provides gloss and UV protection and is what fails first in the sun.
Blending: Fading new paint into adjacent undamaged panels so the transition is invisible, which is why a refinish estimate covers more panels than the damaged one.
Color match: Matching against the actual panel under multiple light sources rather than against a paint code, because sun exposure moves a color away from its code.
Variance: Factory color variation between production runs of the same code, which is why a code alone is not sufficient for a match.
Full-body paint: Refinishing the entire vehicle rather than a repair area, typically required when a discontinued scheme has to be reproduced across large sections.
Graphics reproduction: Recreating a factory decal scheme in masked multi-stage paint when the original decal is discontinued and cannot be purchased.
Oxidation or chalking: UV degradation of gelcoat or paint into a dull, powdery surface, which is wear rather than event damage on most claims.
Crazing: Fine surface cracking in gelcoat, which can be cosmetic or can indicate that the laminate underneath flexed.
Feather, prime and block: The preparation sequence of tapering a repair edge, applying primer, and sanding it flat so the repair does not telegraph.
Telegraphing: A repair becoming visible through the finish later, usually after heat cycling, because the underlying repair moved or was never structural.
Orange peel: A textured finish resembling citrus skin, caused by spray, viscosity, or flash time problems.
Fisheye: A circular void in wet paint caused by contamination such as silicone or oil on the surface.
Flash time: The interval a coat needs before the next coat is applied, and a schedule that cannot be compressed to hit a delivery date.
Mil thickness: Coating thickness measured in thousandths of an inch, used to verify adequate build and to detect prior refinish work.

Roof and Seals

Roof terminology matters because the difference between a patch, a recoat, and a membrane replacement is a large difference in price, and the words get used loosely on estimates. Membrane type also changes the repair method, so an estimate that never names the material is describing a job nobody has actually scoped. Decking condition is the finding that moves a roof from maintenance into structural work, and it is the one worth asking about first.

EPDM: A synthetic rubber roof membrane, common on RVs, which chalks as it ages and is identified by the residue it leaves on a hand.
TPO: A thermoplastic roof membrane, generally more puncture resistant than EPDM and heat weldable at seams.
Fiberglass roof: A molded one-piece roof, more durable than membrane but repairable only by layup rather than by patching.
Decking: The structural sheet material under the roof membrane, which goes soft when water gets past the membrane and turns a roof job into structural work.
Lap sealant: The flexible sealant applied over seams and around penetrations on a membrane roof, which requires periodic inspection and renewal.
Self-leveling sealant: A lap sealant formulated to flow flat on horizontal surfaces, used on roofs and not appropriate on vertical seams.
Butyl tape: A non-hardening sealing tape used under mounting flanges of windows, vents, and roof components as the primary water seal.
Penetration: Any opening through the roof for a vent, skylight, antenna, air conditioner, or fixture, and the origin of most roof leaks.
Termination bar: A metal strip mechanically fastening and sealing the membrane edge at a roof perimeter or transition.
Ponding: Standing water that does not drain off a roof, which accelerates seam and sealant failure at the low point.
Recoat: Applying a new coating over a sound, adhered membrane, which is maintenance rather than replacement.
Membrane replacement: Removing the old membrane entirely, repairing decking as needed, and installing new material, which is the correct call once a membrane is brittle or separated.
Water test: Controlled application of water to a repaired area and every disturbed penetration to verify the seal before delivery.
Moisture meter: Instrument used to detect water content in wall and floor structure, which is how the actual extent of water damage gets mapped.

Slides and Awnings

Slide rooms are the highest-complexity moving assembly on most coaches and the most common source of leaks and misdiagnosis, because a seal problem is usually a symptom of a geometry problem. Almost every slide complaint arrives described as a leak, and almost every one of them turns out to involve the rail, the drive system, or an opening that is no longer square. These terms let you follow that conversation on a repair order instead of taking it on faith.

Slide room: A section of the living space that extends outward on rails to increase interior space when parked.
Schwintek: An in-wall slide system driven by synchronized motors and toothed racks on each side, common on lighter rooms and sensitive to being out of sync.
Rack and pinion: A slide mechanism driving a toothed rack with a gear, typically under-mounted on heavier rooms.
Hydraulic slide: A slide driven by hydraulic cylinders from a central pump, used on the heaviest rooms.
Cable slide: A slide system using cables to pull the room in and out, requiring correct tension to stay square.
Flush floor slide: A slide design where the room floor sits level with the main floor rather than on top of it.
Slide rail: The structural track the room travels on, which bends in a collision and produces binding that no seal replacement will fix.
Wiper seal: The flexible blade seal that wipes the slide room surface as it travels, which is a moving seal rather than a static one.
Bulb seal: A hollow compressible seal that seats when the room is fully in or fully out, forming the primary weather seal.
Slide topper: A fabric awning mounted above a slide room to keep debris and water off the roof of the extended room.
Out of sync: A condition on a multi-motor slide where one side travels further than the other, racking the room and destroying seals and gear racks.
Awning roller tube: The tube the awning fabric rolls onto, which bends easily and is a common wind damage item.
Awning arm: The support structure extending the awning, either manual or powered, and the component that usually fails in a wind event.
Awning fabric: The vinyl or acrylic canopy material, which fails from UV and from being retracted wet.

Electrical and Systems

Electrical terms appear on body estimates more often than people expect, because structural repair disturbs wiring and because modern chassis carry driver assistance systems that must be recalibrated after body work. Owners are frequently surprised to see wiring and calibration lines on a body invoice, and both are legitimate. Structural repair disturbs harnesses, and any repair that changes ride height or sensor mounting invalidates the aim of every camera and radar on the vehicle.

Shore power: External alternating current supplied by a campground pedestal or a home outlet through a power cord.
Converter: A device changing incoming alternating current into direct current to run 12 volt systems and charge the house batteries.
Inverter: A device changing 12 volt direct current from the batteries into alternating current to run household devices without shore power.
Transfer switch: A device that automatically selects between shore power and generator power and prevents both from being connected at once.
House battery: The battery bank powering interior systems, separate from the chassis starting battery.
LiFePO4: Lithium iron phosphate battery chemistry, common in modern house banks, requiring different charging profiles than lead-acid.
Shunt: A precision resistor in the battery negative path allowing a monitor to measure actual current in and out of the bank.
Parasitic draw: Current consumed while everything is nominally off, which is what flattens a bank in storage.
30 amp and 50 amp service: The two common shore power configurations, where 50 amp provides two separate legs and substantially more total capacity.
Ground fault interrupter: A protective device that opens the circuit on detecting current leaking to ground, required at exterior and wet-location outlets.
ADAS: Advanced driver assistance systems, meaning camera and radar based features such as lane keeping, adaptive cruise, blind spot monitoring, and automatic emergency braking.
Static calibration: ADAS calibration performed in shop against physical targets on a level surface to manufacturer specification.
Dynamic calibration: ADAS calibration performed by driving the vehicle under specified conditions, required by some platforms in addition to static.
Pre-repair scan: A full diagnostic scan performed before work begins so existing faults are recorded and not attributed to the repair.
Post-repair scan: A full diagnostic scan after repair to identify systems requiring calibration and to document a clean result.

Running Gear and Towing

Running gear terms come up on trailer structural jobs constantly, because suspension mounting points are where frame cracks start and because towing hardware is where load enters the structure. On towables the frame and the suspension are one problem rather than two, and a crack at a hanger is a structural finding rather than a maintenance item. Weight ratings belong in this group as well, because a frame reinforced for the wrong load fails again in the same place.

Leaf spring: A layered steel spring used on most towable trailer suspensions, mounted to hangers welded to the frame.
Equalizer: The pivoting link between leaf springs on a tandem axle that distributes load between the two axles.
Wet bolt: A greaseable suspension bolt used at spring and equalizer pivots, which prevents the wear that causes wandering under load.
Hanger: The bracket welded to the frame that the suspension attaches to, and a frequent crack location on heavier trailers.
Torsion axle: An independent suspension axle using rubber cords inside a tube instead of springs, mounted directly to the frame.
Kingpin: The pin on a fifth wheel trailer that engages the tow vehicle hitch, carrying vertical and horizontal load.
Pin box: The structure connecting the kingpin to the trailer frame, a high-stress assembly and a common inspection point after any impact.
Coupler: The forward fitting on a conventional trailer that engages the tow ball.
Weight distribution hitch: A hitch system using spring bars to transfer tongue weight forward onto the tow vehicle front axle.
Sway control: Hardware or electronics that resist trailer yaw at speed, either friction based or integrated with the hitch.
GVWR: Gross vehicle weight rating, the maximum a single vehicle is rated to weigh fully loaded.
GAWR: Gross axle weight rating, the maximum load a single axle is rated to carry.
CCC: Cargo carrying capacity, meaning what is left for people, fluids, and belongings after the vehicle is weighed as built.
Brake magnet: The electromagnet in an electric trailer brake assembly that engages the drum surface, a routine wear item.
Bearing repack: Cleaning, inspecting, and regreasing wheel bearings, standard maintenance on any towable.
Tire date code: The four digit week and year stamp on a tire sidewall, which matters more than tread depth on trailer tires because they age out before they wear out.
Air suspension: A chassis suspension using air springs and a leveling system, common on diesel pushers and sensitive to damage in a collision.

Insurance and Claim Terms

These are the words that decide what gets paid. If any of them appear on your settlement worksheet and you cannot explain what they mean, that is the line to ask about first. Most of these words describe deductions or process steps rather than repairs, which is how a settlement shrinks without anything changing on the estimate itself. Each one is worth asking about before you sign.

First notice of loss: The initial report that opens a claim and generates a claim number.
Adjuster: The person assigned to evaluate the claim, determine coverage, and approve scope, typically working with authority limits and a queue.
Scope: The complete list of what will be repaired and how, which is what most claim disputes are actually about.
Teardown: Authorized disassembly performed to discover hidden damage before a final scope is written, billed as its own line item.
Supplement: A documented request to add scope and cost after the original estimate, supported by photographs and findings.
Reinspection: A second physical inspection, often requested when a supplement is disputed, ideally performed with the vehicle open.
Actual cash value: Replacement cost minus depreciation, meaning what the item was worth immediately before the loss.
Agreed value: A policy structure where the payout amount is set when the policy is bound rather than calculated at the time of loss.
Stated value: A policy structure where the owner declares a value, which may still be settled at the lesser of stated value or actual cash value.
Replacement cost: Coverage paying what it costs to replace the item today, without deduction for age or wear.
Betterment: A deduction applied when a repair genuinely leaves the vehicle in better condition than before the loss, such as a new tire replacing a worn one.
Depreciation: Reduction in value reflecting the service life a component has already consumed.
Recoverable depreciation: Depreciation withheld from the first payment on a replacement cost policy and released after the repair is completed and invoiced.
Total loss: A determination that documented repair cost exceeds the carrier threshold against vehicle value, resulting in settlement rather than repair.
Salvage value: What the damaged vehicle is worth to a salvage buyer, deducted if the owner retains the unit after a total loss.
Owner retained salvage: Keeping a totaled vehicle by accepting a reduced settlement, typically resulting in a branded title.
Diminished value: The reduction in market value of a repaired vehicle relative to an identical one with no claim history.
Subrogation: The carrier process of recovering paid amounts from an at-fault party, which is also how a deductible can come back to you.
Loss of use: Coverage for the cost of being without the vehicle, including rental or documented downtime on a commercial unit.
Sudden versus gradual: The classification that determines whether water damage is covered, since gradual seepage is generally excluded and sudden intrusion generally is not.
Appraisal clause: A policy provision providing a formal process for resolving valuation disputes without litigation.
Release: The document closing a claim, which should not be signed until the vehicle is delivered, tested, and confirmed to have no open items.

Questions

What is the difference between delamination and water damage?

Delamination is the separation of bonded layers in a wall or roof panel. Water damage is one of the two things that causes it, the other being heat. They are not the same finding and they are not the same claim. In the low desert we regularly see purely thermal delamination with no moisture present anywhere in the wall. The repair path differs as well, so the finding has to be named correctly.

What does teardown actually mean on an estimate?

Authorized disassembly performed to find hidden damage before a final scope is written. Trim, exterior skin, or interior panel comes off so the structure and substrate can be assessed and photographed. It is billed as its own line item, and on laminated construction it is the step that converts guesses into documented, approvable findings. Carriers routinely authorize it when the request explains what is being opened and why.

What is a supplement?

A documented request to add scope and cost after the original estimate, supported by photographs, moisture readings, measurements, and part numbers. Two or three supplements on a structural RV job is normal rather than a warning sign, because the construction hides damage until the vehicle is opened and again during reassembly. What matters is whether each one arrives with photographs and part numbers attached.

What is the difference between actual cash value and agreed value?

Actual cash value pays what the unit was worth immediately before the loss, which on a depreciating motorhome can be far below what you paid. Agreed value fixes the payout amount when the policy is bound. Which one you have is on your declarations page, and the time to find out is now rather than during a total loss conversation.

What does betterment mean on my estimate?

A deduction the carrier applies when a repair leaves the vehicle better than it was before the loss, such as a new tire replacing one with twenty percent of its tread left. It is defensible on wear items. It is much harder to defend on structural components or on labor that simply return the vehicle to its prior condition. Ask in writing what specific improvement you received on each line it appears.

What is the difference between EPDM and TPO?

Both are RV roof membranes. EPDM is a synthetic rubber that chalks visibly as it ages and leaves residue on your hand. TPO is a thermoplastic, generally more puncture resistant, with heat-weldable seams. The repair and replacement approach differs between them, which is why the estimate should name which one your vehicle has. If it does not, ask before you approve the roof line.

Why does my estimate list panels that are not damaged?

Blending. New paint has to be faded into adjacent undamaged panels or the transition line will be visible under direct sun, particularly on metallics. Blend labor on neighboring panels is standard refinish practice rather than padding, and an estimate that omits it is describing a repair that will show where the new paint stops. That line reads far more obviously on metallic colors than on solids.

Where the work happens

Location: All work is performed at our Yorba Linda facility. We do not offer mobile, roadside, or fleet route service.