Glossary

Decode Your Own Estimate

Short answer

116 terms from the shop floor, defined plainly. If a line item on your estimate makes no sense, it is probably explained here.

116 definitions covering RV structure, body and paint, roof and seals, slides and awnings, electrical and power, plumbing, HVAC and appliances, chassis, insurance claims, and materials and process.

Updated 2026-07-29 by OCRV Center Editorial Team

Structure

Delamination: Separation of an RV sidewall from the substrate bonded behind it. Usually starts at an impact point or a leak and spreads outward for weeks. Shows as a bubble, a wave in a reflection, or a hollow sound when tapped.
Superstructure: The welded aluminum or steel cage inside a laminated wall that carries the load. Damage here is invisible from outside but determines whether the wall can be repaired or has to be sectioned and rebuilt.
Luan: Thin plywood laminated behind the fiberglass on many RV walls. Cheap, light and highly vulnerable to moisture. Once luan wicks water it delaminates and loses structural value permanently.
Azdel: A composite panel used instead of luan on better builds. It does not absorb water or rot, which is why a leak in an Azdel wall causes far less collateral damage than the same leak in a luan wall.
Outrigger: A short lateral member welded off the main frame rail to carry floor and sidewall load. Common failure point on fifth wheels and heavily loaded trailers, where fatigue cracks start at the weld toe.
Frame rail: The primary longitudinal steel member the whole vehicle is built on. Deflection here shows up later as tire wear, tracking pull and slide openings that will not stay square.
Sectioning: Cutting out a damaged length of structure and welding in a new piece at a manufacturer-approved location. Correct on many repairs, catastrophic if done at the wrong point in the load path.
Pin box: The forward structure on a fifth wheel that carries the kingpin and transfers tow load into the frame. Takes the worst of a jackknife and is a common hidden-damage location.
Kingpin: The vertical pin on a fifth wheel that locks into the truck hitch plate. Wear, bending or a cracked mount is a safety item, not a cosmetic one.
A-frame: The triangular tongue structure at the front of a travel trailer. Carries the coupler, the jack and often the propane and battery, which makes it a busy area for both damage and corrosion.
Subfloor: The structural floor deck under your finished flooring. When it goes soft from a leak, replacing the vinyl on top solves nothing. The deck has to come out.
Soft spot: A section of floor or wall that flexes underfoot or under hand pressure. Almost always rotted substrate from a slow leak, and almost always larger than it feels.
Unibody: Construction where the body panels carry structural load, as on a Sprinter or Transit. Requires measured pulling on a rack rather than panel replacement alone.
Belly pan: The sheet on the underside of an RV or trailer that protects tanks, plumbing and insulation. On an Airstream it is also structural and expensive.

Body and Paint

Gelcoat: The pigmented resin surface layer on a fiberglass panel. It is not paint. It oxidizes chalky under UV and it spider-cracks under flex rather than chipping.
Spider crack: A web of fine cracks in gelcoat radiating from a stress point. Cosmetic on the surface, but it marks where the laminate underneath has been flexing.
Chopped strand mat: Randomly oriented fiberglass reinforcement used to build thickness in a repair. Wets out easily and conforms to shape, which is why it is the workhorse of RV panel work.
Paint blend: Fading new color into the adjacent undamaged panel so the transition is invisible. Necessary on almost any repair, and one of the most commonly omitted line items on an outside estimate.
Base coat and clear coat: Two stage refinish where color goes on first and a separate clear provides gloss and UV protection. Repairs better than single stage and is standard on modern coaches.
Single stage: Refinish where color and gloss are in one product. Faster and cheaper, less repairable, and common on older or budget builds and on fleet units.
Orange peel: A dimpled paint texture from incorrect gun setup, reducer choice or booth temperature. Correctable by cut and polish if the film is thick enough.
Fisheye: A small crater in fresh paint caused by silicone or oil contamination on the surface. The only real fix is to sand it out and respray that area.
Oxidation: UV degradation of the surface layer, leaving a chalky dull finish. Coastal storage accelerates it. Often correctable by compounding rather than repainting.
Paint correction: Machine compounding and polishing that removes a measured amount of clear or gelcoat to level defects. Finite: a panel can only be corrected so many times.
Ceramic coating: A cured silica-based layer that adds gloss, chemical resistance and easier cleaning. It resists oxidation, it does not prevent impact damage.
Paint protection film: Clear urethane film applied to high-impact areas like a front cap or lower panel. Absorbs rock strikes that would otherwise chip through to substrate.
Vinyl wrap: Adhesive film applied over paint for color change or graphics. Faster than paint and reversible, but it needs sound paint underneath and it has a finite life in direct sun.
Paintless dent removal: Working a dent out from behind the panel without refinishing. Works on ductile metal with intact paint. Does not work on fiberglass or on creased damage.

Roof and Seals

EPDM: A rubber roof membrane, usually white, that chalks off a thin layer over time. Repairable in place, needs recoating on a cycle, and tears at seams rather than in the field.
TPO: A thermoplastic roof membrane that is heat weldable and holds gloss longer than EPDM. Stiffer and less forgiving of movement at terminations.
Filon: Fiberglass-reinforced panel used for hard roofs and sidewalls. Walkable, durable, and prone to spider cracking at fastener points.
Dicor: A common brand of self-leveling lap sealant used at roof penetrations. Flows out flat when applied and needs periodic inspection and topping.
Eternabond: Butyl-backed tape used to seal seams and repairs on a roof membrane. Excellent adhesion, effectively permanent, and difficult to remove cleanly later.
Self-leveling lap sealant: A pourable sealant for horizontal roof surfaces that flows into gaps. Not for vertical use, where it sags and pulls away.
Butyl tape: Non-curing sticky sealing tape used behind window frames, vents and trim. It stays flexible for years then hardens and shrinks, which is when the leak starts.
Termination bar: The metal strip that clamps the roof membrane edge to the sidewall and gets sealed over. The single most common origin point for roof-to-sidewall water intrusion.
Drip rail: Extruded trim at the roof edge that directs water away from the wall. If its sealant fails water runs behind the sidewall instead of off it.
Roof vent: A 14 by 14 inch opening with a lid, and often a fan. High-traffic penetration, common leak source, and the cheapest thing on the roof to get wrong.
Skylight: A domed acrylic panel over a shower or living area. Becomes brittle from UV and cracks, sometimes years before anyone notices the stain below.

Slides and Awnings

Schwintek: An in-wall slide system driven by vertical rack-and-pinion columns on each side. Compact and popular, sensitive to being out of sync, and it will chew a rack if run misaligned.
In-wall slide: Slide mechanism mounted inside the wall thickness rather than under the floor. Saves interior space and puts the drive hardware where water intrusion can reach it.
Hydraulic slide: Slide driven by hydraulic cylinders from a central pump. Strong, suited to heavy rooms, and its failures are usually pump, solenoid or hose rather than mechanism.
Cable slide: Slide moved by a cable and pulley arrangement, common on larger fifth wheel rooms. Needs periodic tension adjustment or the room stops sealing evenly.
Wiper seal: The flexible blade seal that sweeps the slide wall as the room moves. First line of defense against water, and it wears rather than fails suddenly.
Bulb seal: A hollow compressible seal that squashes flat when the room is retracted. When a slide opening racks out of square, this is the seal that stops sealing.
D-seal: A D-profile seal on the slide perimeter that provides the primary weather barrier when closed. Compression set over years is normal and it is a maintenance item.
Slide topper: A small fabric awning above a slide room that keeps debris and standing water off the roof of the slide. Cheap, and it prevents a very expensive problem.
Awning arm: The articulated support that extends and tensions an awning. Bends in wind, and a bent arm will destroy fabric on the next cycle if it is not corrected first.
Wind sensor: A motion sensor that auto-retracts a powered awning above a threshold. Needs calibration, and a miscalibrated one either retracts constantly or never at all.

Electrical and Power

Converter: Turns 120V shore power into 12V to run house circuits and charge batteries. When one fails, everything 12V dies while plugged in and people assume the batteries are bad.
Inverter: Turns 12V battery power into 120V for outlets and appliances. Sizing matters: an undersized inverter will trip under a real load rather than fail visibly.
Transfer switch: Automatically selects between shore power and generator. A stuck or arced transfer switch is a frequent cause of intermittent whole-coach power problems.
Shore power: Grid power delivered through a 30 or 50 amp cord. 50 amp service is two 120V legs, which is why a 50 amp coach on a 30 amp adapter has half the capacity people expect.
AGM battery: Sealed lead acid with absorbed electrolyte. Tolerant, heavy, and unhappy below about 50 percent depth of discharge, which shortens life fast if you boondock.
LiFePO4: Lithium iron phosphate battery chemistry. Usable to a much deeper discharge, far lighter, and it needs a charge profile and low-temperature protection the old converter will not provide.
Battery management system: The electronics inside or alongside a lithium bank that protect against over-charge, over-discharge and low-temperature charging. Not optional on lithium.
DC-DC charger: Charges a house bank from the alternator at a controlled rate. Required with lithium, because a raw alternator connection will either undercharge the bank or cook the alternator.
MPPT controller: Solar charge controller that tracks the panel maximum power point. Meaningfully more efficient than PWM, especially in partial shade and cold, and worth the cost on any real array.
PWM controller: A simpler and cheaper solar charge controller that pulls panel voltage down to battery voltage. Fine on small systems, wasteful on large ones.
Shunt: A precision resistor in the negative battery cable that lets a monitor measure real current in and out. Without one, a state of charge readout is an educated guess.
Parasitic draw: Current consumed while everything appears off. Propane detectors, control boards and stereo memory add up, and a stored coach with no solar will be flat in weeks.
Ground fault: Current returning through an unintended path. In a coastal-stored vehicle it usually traces to a corroded ground point rather than a damaged conductor.

Plumbing and Tanks

Fresh water tank: Onboard potable water storage. Strap failure and fitting cracks are common, and a slow tank leak is one of the hardest water sources to find because it soaks the floor from below.
Black tank: Toilet waste holding tank. Failures are usually the flange, the valve or the vent, and a bad seal announces itself long before it leaks visibly.
Gray tank: Sink and shower waste holding tank. Prone to biofilm and slow drains, and a cracked gray tank produces the classic mystery damp spot in a basement bay.
Macerator: A pump that grinds and moves waste through a small hose. Useful where gravity dumping is impractical, and unforgiving of anything that should not have gone in.
PEX: Flexible cross-linked polyethylene tubing used for water lines. Freeze tolerant compared with rigid pipe, and repiping in PEX is often cheaper than chasing leaks in old lines.
City water inlet: The external connection that pressurizes the system from a park spigot. Unregulated park pressure is a common cause of burst fittings inside a wall.
Water heater bypass: Valves that route water around the heater tank for winterizing. Left in the wrong position after storage, you get no hot water and a confusing service call.
Anode rod: A sacrificial rod in a steel water heater tank that corrodes so the tank does not. A consumable. Ignore it and you replace the heater instead of a $25 part.

HVAC and Appliances

Absorption refrigerator: Cools using heat and ammonia rather than a compressor, running on propane or 120V. Silent, slow, sensitive to being off level, and its cooling unit is the usual failure.
Cooling unit: The sealed heat exchanger assembly inside an absorption fridge. Replaceable as a unit, and often the deciding factor between repair and a 12V compressor conversion.
12V compressor refrigerator: A modern residential-style fridge running on DC. Cools faster, tolerates being off level, and needs real battery capacity behind it.
Hard start capacitor: A capacitor that helps a roof air compressor start against a weak supply. Cheap, and often the difference between an AC that runs on a generator and one that will not.
Soft start: Electronics that ramp an air conditioner compressor up gradually, reducing inrush. Lets a smaller generator or inverter run an AC that otherwise trips.
Ducted air conditioning: Roof air distributed through ceiling ductwork to multiple vents. Quieter and more even, and harder to diagnose because airflow loss can be anywhere in the run.
Hydronic heat: Heating by circulating hot fluid through exchangers rather than blowing hot air. Comfortable, complex and expensive to repair when the boiler side fails.
AquaHot: A common brand of diesel-fired hydronic system providing both heat and unlimited hot water. Excellent when maintained, and a significant service item when it is not.
Sail switch: An airflow-sensing safety switch in a furnace that prevents ignition without adequate air movement. A dirty or stuck sail switch is a classic no-heat cause.
ECO switch: An energy cut off thermal switch that shuts a water heater down on over-temperature. Tripping repeatedly is a symptom, not the problem.
LP regulator: Steps propane tank pressure down to appliance working pressure. Aging regulators drift out of spec and produce lazy yellow flames and unreliable ignition.

Chassis and Suspension

Torsion axle: Suspension using rubber cords inside the axle tube instead of springs. Independent, quiet, and not rebuildable: when the rubber takes a set, the axle gets replaced.
Equalizer: The pivoting link between leaf springs on a tandem axle that shares load over bumps. A worn equalizer is behind most trailer tire scrub and uneven wear.
Wet bolt: A greaseable suspension bolt with a zerk fitting. An inexpensive upgrade that dramatically extends the life of shackles and equalizer bushings.
Bearing repack: Cleaning, inspecting and regreasing wheel bearings on a schedule. Skipped repacks are the single most common cause of trailer wheel-off failures.
Auto-level calibration: Teaching a leveling system where true zero is. After frame work or a jack replacement, an uncalibrated system will level the coach to the wrong reference.
Air bag suspension: Air springs providing adjustable ride height and load support. Leaks are usually fitting or line rather than bag, and a slow leak looks exactly like a bad compressor.
ADAS: Advanced driver assistance systems: cameras, radar and sensors behind bumpers and glass. Post-collision recalibration is required, not optional, and it is frequently left off estimates.

Insurance and Claims

Supplement: An addition to an approved estimate covering damage found after work began. Routine on RV claims because the original estimate was written from outside the panel.
Betterment: A charge to the owner when a repair leaves the vehicle better than before, typically on wear items. Legitimate in narrow cases, frequently applied too broadly.
LKQ parts: Like kind and quality, meaning used salvage parts. Reasonable for some cosmetic components, and inappropriate for structural components where history is unknown.
Aftermarket parts: Non-original replacement parts. Quality ranges from excellent to unusable, and fit on RV panels is far less consistent than on automobiles.
Diminished value: The reduction in market value that persists after a proper repair. Recoverable in some third party situations, and rarely raised unless the owner raises it.
Actual cash value: What the vehicle was worth immediately before the loss. The comparables chosen drive this number, and RV comparables are genuinely hard to select well.
Total loss threshold: The ratio of repair cost to actual cash value at which a carrier declares a total loss. Varies by carrier and by state, and it is arithmetic rather than judgment.
Appraisal clause: A provision in many policies allowing an independent appraisal when the owner and carrier disagree on value. Present in more policies than owners realize.
Direct repair program: A carrier network of pre-approved shops. Can streamline a claim, and does not override your right in California to choose the facility.
Subrogation: Your carrier pursuing the at-fault party to recover what it paid. Successful subrogation is often what gets a deductible refunded.
Loss of use: Coverage for the cost of being without the vehicle. On an RV this is not a rental car, and the terms differ significantly from an auto policy.
Teardown: Removing panels and components to expose and document the true extent of damage before finalizing a repair plan. The step that determines whether a claim is paid correctly.
Blueprinting: Writing the complete repair plan after teardown, with every operation, part and hour identified before work starts. Reduces mid-job surprises to near zero.

Materials and Process

Body labor: Time spent on metal, panel and structural work, billed at the body and paint rate. Distinct from paint labor even though both appear under the same rate.
Paint labor: Time spent on preparation, spraying and finishing. Drives the paint materials charge, which is calculated per paint hour rather than estimated separately.
Materials rate: A per-hour charge covering consumables. Ours is $55 per paint hour and $5 per body hour, which is how the industry avoids itemizing every roll of tape.
Cycle time: Total calendar days from intake to delivery, including waiting on approval and parts. Always longer than labor hours suggest, and the honest number to ask a shop for.
Frame rack: A fixed bench with anchoring and pulling towers used to measure and correct structure against factory specification. Not something that can be replicated in a driveway.
Downdraft booth: A spray booth that pulls air down through the floor, carrying overspray away from the panel. Produces materially cleaner finishes than a crossdraft booth.
Bake cycle: Controlled elevated-temperature cure after spraying. Speeds cure and improves final hardness, and it is one reason booth work outperforms outdoor spraying.
MIG welding: Wire-fed welding used on most steel structural repair. Fast and strong, and requires correct settings for the specific steel to avoid a brittle joint.
TIG welding: Precise hand-fed welding used on aluminum and thin material. Slower, cleaner, and what aluminum sidewall and Airstream structural work requires.
Buck rivet: A solid rivet set by bucking the tail, used on Airstream and aircraft-style aluminum construction. Stronger than a pop rivet and it takes two people to install correctly.
Olympic rivet: A blind rivet that mimics the appearance of a solid buck rivet on the outside. The accepted repair fastener where the interior side cannot be reached.
Moisture meter: A pin or pinless instrument that reads moisture content in a substrate. Used on a grid to map how far a leak has actually traveled.
Thermal imaging: Infrared survey that shows temperature differences from trapped moisture and lost insulation. Finds wet areas behind an intact wall without opening it.
BAR license: California Bureau of Automotive Repair registration required for any repair facility in the state. Ours is ARD00288521 and every shop you consider should give you theirs.
VOC regulation: California limits on volatile organic compounds in coatings. Constrains which products can legally be sprayed here and is part of why California refinish work costs what it does.

Something missing? Ask us and we will add it. See also the answers section and the rate card.