# RV Repair Terminology Glossary > This glossary defines 57 terms that show up on RV repair estimates, teardown reports, and insurance correspondence, grouped by the part of the job they belong to. Definitions are written the way an estimator would explain them at the counter, not the way a parts catalog states them. If a word on your estimate is not here, it is almost certainly a brand name for something that is. | | | | --- | --- | | Business | OCRV Center | | Service area | Westminster, Orange County, Southern California | | Facility | 23281 La Palma Ave, Yorba Linda, CA 92887 | | Phone | (949) 799-3387 | | Email | info@ocrvcenter.com | | Source | https://ocrv.online/resources/glossary/ | This RV repair terminology glossary exists because owners keep getting handed estimates full of words nobody explained. An estimate that reads clearly is an estimate you can question, and an owner who can question a line item usually ends up with a better repair. The 57 entries below are grouped by domain: structural and chassis, body and paint, fiberglass and laminate, roof and sealant, coach systems, and insurance. Read the section that matches your damage first. ## How to Use This Glossary Repair vocabulary is not decoration. The specific word an estimator chooses usually decides which labor operation gets billed, which is why two estimates on the same damage can differ by thousands of dollars while both look reasonable. When a line says structural repair rather than panel repair, an entire measurement and verification process comes with it. When a line says blend rather than refinish, the paint hours change. Owners get the most out of this page by reading their estimate with it open, term by term, and marking anything that does not match what they were told at drop off. Bring the marked copy back to the estimator. A shop that scoped the job honestly will walk each line without hesitation. A shop that cannot explain a line in plain language either did not look closely or is padding, and both are worth knowing before the deposit clears. ## Structural and Chassis Terms Structural work is the category that separates a cosmetic repair from a long one. Anything that carries load, resists twist, or holds an assembly in alignment belongs here, and damage to it changes the entire character of the job. A dented panel is a panel. A bent outrigger under that panel is a measurement job, a pull setup, and a verification record. Owners often assume that if the vehicle drives straight, nothing structural happened. That reasoning holds up better on unibody cars than on coaches, where a house structure sits on top of a chassis and the two can be damaged independently. A coach can track perfectly down the road while its rear wall separation grows every time the slide cycles. Alignment is the tell here, not appearance. - Chassis: The frame, axles, suspension, steering, and drivetrain the unit is built on. On motorhomes it arrives from a chassis manufacturer and the coach body is constructed on top of it. - Frame rail: The main longitudinal steel members carrying the load of the house structure. Bent, cracked, or twisted rails move a job from cosmetic repair into structural repair. - Outrigger: A lateral steel member welded to the frame rail to support floor width beyond the rail. A frequent casualty in side impacts and curb strikes, and usually invisible until the skirt comes off. - Crossmember: A transverse member tying the frame rails together. Controls chassis twist and carries tank, floor, and slide loads. - Sidewall stud: The vertical framing member inside a laminated wall, typically aluminum tube or wood, that carries wall load and provides attachment points for anything mounted through the skin. - Slide room: The extendable box section that travels out of the sidewall. It has its own floor, roof, walls, and seal system, and it is effectively a small structure inside a larger one. - Slide mechanism: The rack and pinion, cable, hydraulic, or rail drive assembly that moves the slide room. Damage to the opening usually shows up first as a slide that binds or racks. - Torsion axle: A trailer axle using rubber cords inside a square tube for suspension rather than leaf springs. A bent torsion axle is replaced, not straightened. - Frame rack and measuring system: A fixed anchoring setup with three dimensional measurement, used to pull structure back to published dimensions and to prove on paper that it landed there. - Kingpin: The pin on a fifth wheel trailer that locks into the tow vehicle hitch. The pin box and the structure around it are mandatory inspection points after any towing incident. ## Body, Panel, and Paint Terms Paint is where owners are most likely to feel overcharged and least likely to understand why. The surface area on a 38 foot coach is many times that of a passenger car, the panels are not flat, and a large portion of coaches built in the last fifteen years carry painted graphics rather than applied decals. Reproducing a multi color graphic across a repaired quarter is a pattern layout problem before it is a spraying problem. The second cost driver is transition. Color that matches perfectly on a spray out card can read differently against thirty feet of sun aged adjacent panel, so a correct repair extends color into neighboring surfaces until the eye stops finding the edge. That is a technique, not an upsell, and it is the difference between a repair you cannot find and one you spot from the campsite next door. - Front cap and rear cap: The molded fiberglass end sections of a coach. Usually a single large part, often expensive, and frequently on a long lead time from the manufacturer. - Filon: A thin fiberglass reinforced panel used as the outer skin on many laminated sidewalls. Smooth, light, and bonded rather than fastened. - Aluminum siding: Corrugated or flat aluminum exterior skin used on stick and tin construction. Unlike laminate, it can often be replaced in discrete panel sections. - Blend panel: An adjacent panel sprayed partway so the color transition disappears. Required on metallics and pearls, and standard practice on any large surface. - Clearcoat: The unpigmented top layer carrying gloss and ultraviolet protection. Clearcoat failure looks like chalky, peeling patches rather than fading. - Full body paint: A coach finished in painted graphics instead of applied vinyl. Repairs cost more because both color and pattern must be reproduced and aligned. - Gelcoat: The pigmented resin surface layer of a molded fiberglass part. It is the finish itself, not a coating applied over one, which is why it is repaired differently than paint. - Orange peel: A textured, dimpled finish caused by spray or flow conditions. Corrected by sanding and polishing rather than respraying. - Featheredge: Tapering the edge of a repair so that filler, primer, and paint step out gradually and never telegraph a ring through the finish. - Cut and buff: Wet sanding and machine polishing fresh paint to remove texture and bring gloss in line with the surrounding original finish. ## Fiberglass and Laminate Terms Most modern coach and trailer sidewalls are laminated sandwiches: an outer skin, an adhesive layer, a foam or plywood core, framing members, and an interior surface. The assembly is strong when bonded and weak the moment the bond fails, which is why delamination is treated as a structural condition rather than a cosmetic one. Repairing it means restoring the bond across the affected area, not filling the visible symptom. The other half of this vocabulary comes from molded parts: caps, fenders, and skirts made of layered glass reinforcement in cured resin. These fail by cracking rather than denting, and a crack tends to keep running under flex until the stress that caused it is addressed. A repair that only fills the crack line usually reappears within a season. Finding and relieving the stress that opened it is part of the repair, not an extra. - Delamination: Separation of the outer skin from the core in a laminated wall. Shows as bubbles, long waves, or a hollow sound when the surface is tapped with a knuckle. - Lauan: A thin plywood layer bonded inside many laminated walls. It absorbs water readily and loses structural value quickly once wet, which is why leaks turn into wall replacement. - Vacuum lamination: The factory process pressing skin, adhesive, core, and framing together under uniform pressure. Field repairs re-create it with clamping, weight, and controlled cure conditions. - Core: The insulating layer inside a laminated panel, usually block foam or a honeycomb material, which also carries shear load between the skins. - Resin: The liquid that cures to bind fiberglass reinforcement. Polyester, vinyl ester, and epoxy differ in strength, cost, adhesion, and how they behave against an existing repair. - Chopped strand mat: Random fiber reinforcement used to build thickness and conform to curved shapes. - Woven roving: Woven fiberglass fabric used where directional strength matters, such as around a repaired opening or a load path. - Print through: The pattern of the reinforcement weave appearing through the finished surface after the resin cures and shrinks. A finishing defect, and a sign of insufficient cure time before topcoat. - Spider cracks: Fine radiating cracks in gelcoat, usually from impact or repeated flex. Isolated ones are cosmetic. Clusters are a flag for damage in the substrate below. ## Roof, Sealant, and Water Intrusion Terms Almost every serious water intrusion job we open started at a roof penetration that was sealed correctly at the factory and never maintained afterward. Sealant is a consumable. It has a service life measured in a few years under Southern California sun, and once it opens, water travels sideways along the substrate rather than dripping straight down into view. By the time it shows up inside, it has usually been traveling for a long while. That lateral travel is why owners are surprised by scope. A stain above a bedroom window can originate from an air conditioner gasket eight feet away, and the wet zone between them has been quietly losing strength the whole time. Moisture mapping before scope is written is what keeps the repair from being opened twice. Owners who insist on mapping before repair almost never see the same job come back a second time. - EPDM: A synthetic rubber membrane roofing material. Flexible, chalky as it ages, and patchable when damage is localized. - TPO: A thermoplastic membrane roof. Heat weldable at seams, generally brighter and stiffer than EPDM, and less forgiving of movement. - Fiberglass roof: A molded or laminated single piece hard roof. Walkable and durable, but it cracks rather than tears and repairs are refinishing work. - Lap sealant: The self leveling compound used at horizontal joints where roof penetrations meet the membrane. It flows to level as it cures, which is why it only works on horizontal surfaces. - Butyl tape: A soft, permanently pliable sealing tape installed under mounted components. It is the primary water barrier on most roof hardware, with the surface sealant acting as backup. - Roof penetration: Any opening cut through the roof for a vent, air conditioner, antenna, refrigerator stack, or skylight. Every penetration is a seal with a maintenance interval. - Substrate rot: Deterioration of the decking under a roof membrane. Found as soft spots underfoot and confirmed with a moisture meter before anything is opened. - Moisture meter reading: A pin or pinless measurement of moisture content in a wall or roof substrate, used to map how far intrusion has traveled from its entry point. - Slide topper: The fabric awning covering the top of an extended slide room. It sheds debris and water off the slide roof and is a wear item, not a permanent component. ## Coach Systems Terms A coach is a building with a drivetrain. Electrical, propane, water, waste, and climate systems all run through the same walls and floors that collision and water damage pass through, so systems vocabulary belongs on a repair page even when the original damage was purely structural. A wall repair that severs a run and does not restore it correctly is not a finished repair. Owners should also know these terms because systems faults are frequently the first symptom of damage nobody has looked for yet. A refrigerator that stops cooling, a slide that hesitates, or a converter that trips are all worth investigating rather than replacing outright. A converter that trips after an impact may be reporting a pinched conductor inside a wall rather than a failed converter, and swapping the unit would leave the actual fault in place. Symptoms are cheap information. Treat them as findings to report at drop off rather than problems to solve on your own. - Converter: Converts incoming alternating current from shore power or a generator into 12 volt direct current, and charges the house battery bank. - Inverter: Converts 12 volt direct current from the batteries into 120 volt alternating current for standard outlets. - Transfer switch: Automatically selects between shore power and generator power. A common failure point after any electrical event or surge. - Shore power: 30 or 50 amp alternating current supplied by an external pedestal or building outlet. - House battery bank: The batteries powering coach loads, kept separate from the chassis starting battery so that living in the vehicle does not strand it. - Absorption refrigerator: A propane or electric refrigerator with no compressor. Sensitive to being operated well off level, which is why leveling faults and cooling faults are related. - Grey and black tank: Holding tanks for sink and shower water and for toilet waste, respectively. Both are structural loads when full and both are inspection points after an impact. - LP system: The propane storage, regulator, and distribution plumbing. A pressure drop test is required after any repair that disturbs a line or a connection. - Leveling jacks: Hydraulic or electric jacks that level the unit at a site. Their mounting points are structural and get inspected after any impact near the corners. ## Insurance and Estimating Terms Claim vocabulary is where the money actually moves. Most disputes we watch owners lose are not disputes about whether damage exists, they are disputes about which defined term applies to it. Knowing what a supplement is, or what betterment means, changes what an owner can reasonably push back on and what they cannot. It also changes the tone of the conversation, because an owner using the same vocabulary as the adjuster is much harder to wave off with a general answer. None of this replaces reading your own policy, and none of it is legal advice. It is the working definitions used across estimates and adjuster correspondence, stated in the sense the industry uses them. Carriers vary, state law varies, and the exact wording on your declarations page controls what happens on your claim. Read these as the vocabulary you need in order to read your own policy productively, then go read it. Ten minutes with the policy before a loss is worth more than any glossary. - Estimate: The written scope and cost of repair based on damage visible before disassembly. It is a starting document, not a final number. - Supplement: An addition to the estimate submitted after teardown exposes damage that could not be seen. Supplements are normal on coach work and expected by most carriers. - Teardown: Controlled disassembly performed specifically to expose the true extent of damage before the final scope is set. - Betterment: A carrier deduction applied when a replacement part leaves the vehicle in better condition than it was before the loss. Most often applied to tires, roofs, and older components. - Depreciation: A reduction in claim payment reflecting age and wear. It may be recoverable or non recoverable depending on the exact policy language. - Actual cash value: Replacement cost minus depreciation. The default settlement basis on many recreational vehicle policies. - Agreed value: A settlement amount fixed at policy issue rather than calculated at loss. Common on higher value coaches and worth asking about before you need it. - Total loss threshold: The percentage of vehicle value at which a carrier settles instead of repairing. It varies by carrier and by state, and it is not always disclosed up front. - Appraisal clause: A policy provision allowing each side to hire an appraiser, with an umpire deciding between them, when a valuation is disputed. - Right to choose: State level consumer protection that lets an owner select the repair facility rather than accept an assignment. ## Terms Owners Most Often Mix Up A handful of these pairs cause the majority of counter conversations. They sound like synonyms and are not, and the distinction usually decides whether a job runs two weeks or ten. If you take nothing else from this page, take these. Each pair is already defined above and is restated here in the form owners most often get wrong at the counter. Marking the ones that apply to your estimate is a reasonable use of five minutes. The pattern behind all of them is the same. One term in each pair describes a surface, and the other describes what is behind the surface. Coaches are built so that the surface can look nearly untouched while the structure behind it has moved, absorbed water, or lost its bond. That is why an honest scope on this kind of work starts with disassembly rather than with a number, and why an estimate written from the parking lot is a starting position instead of an answer. - Delamination is not a bubble in the paint. Paint bubbles are a finish failure. Delamination is the wall coming apart behind the skin. - Gelcoat is not paint. Gelcoat is the molded surface of the part and is repaired with resin and reinforcement, not with primer and basecoat. - A supplement is not a price increase. It is scope that was physically not visible when the first estimate was written. - Actual cash value is not what you paid, and it is not what a replacement costs today. It is replacement cost with depreciation removed. - Structural damage is not the same as visible damage. A coach can drive straight and still have a bent outrigger and a separating rear wall. ## Frequently asked questions ### What is the difference between delamination and a bubble in my sidewall? A bubble in the finish is a coating problem. Something under the paint or gelcoat lost adhesion in a small area, and the repair is confined to that surface. Delamination is a construction failure. The outer skin has separated from the core of a laminated wall, so the panel no longer works as a bonded sandwich and has lost stiffness across whatever area is affected. The test most owners can run themselves is the knuckle test. Tap across the wall in a grid and listen. Bonded laminate returns a tight, solid sound. Delaminated laminate returns a hollow, drum like sound, and the boundary between the two sounds usually maps the damage more accurately than what you can see. If the hollow area is larger than a dinner plate, it is a repair worth scoping now rather than next season, because delamination spreads along the failed bond line. ### Is gelcoat the same thing as paint, and does it matter? It matters a great deal to the cost and method of your repair. Paint is a coating applied on top of a substrate: primer, basecoat, clearcoat, each a separate layer with its own cure. Gelcoat is the pigmented outer layer of the fiberglass part itself, sprayed into the mold before the reinforcement is laid in, so it is part of the structure rather than a layer on it. Repairing gelcoat means grinding out the damaged area, laying in matched resin and reinforcement, then sanding and polishing that new material to blend with the surrounding surface. Repairing paint means preparing, priming, and spraying color over a repaired substrate. Many coaches have both, gelcoat on molded caps and painted graphics over the sidewalls, and a repair crossing that boundary needs both methods executed so the transition is invisible. ### My estimate has a supplement on it. Am I being upsold? Usually not, and on coach work a job with no supplement is more suspicious than one with a supplement. The opening estimate is written from what an estimator can see with the vehicle assembled. Laminated walls, molded caps, and finished interiors hide the damage path completely, and an estimator who commits to a final number before teardown is guessing. A supplement is the document that adds scope once disassembly shows what actually happened. What you should expect is documentation. Every supplement line should come with photographs taken at the stage of disassembly where the damage became visible, and a plain explanation of why that operation is required. If you get a supplement with new dollars and no photographs, ask for the photographs before approving it. That single request resolves the vast majority of legitimate concerns owners have about supplements. ### What is the difference between actual cash value and agreed value? Actual cash value means the carrier pays replacement cost minus depreciation for age and wear. It is the default on many recreational vehicle policies, and it is the reason owners are sometimes shocked at a total loss offer on a coach they have maintained well. Depreciation is applied by formula, not by how nice your unit is. Agreed value means you and the carrier set a specific insured amount when the policy is written, often supported by an appraisal, and that figure is what gets paid on a total loss without a depreciation calculation at claim time. Agreed value typically costs more in premium and is more commonly available on higher value coaches. The time to find out which one you have is now, while nothing has happened, not during a claim. Check your declarations page and ask your agent directly. ### My EPDM roof is chalky. Does it need to be replaced? Chalking on its own is normal aging, not a failure. EPDM membrane sheds a fine white powder as the surface oxidizes under ultraviolet exposure, and in Southern California that happens faster than in milder climates. A chalky roof that is still continuous, still bonded to the decking, and still has intact sealant at every penetration is a roof that needs cleaning and sealant maintenance, not replacement. What does drive replacement is loss of substrate. Walk the roof and note any area that gives underfoot, any seam that has opened, any place the membrane has lifted from the decking, and any penetration where sealant has cracked through to daylight. Soft decking means water has been in the structure long enough to degrade it, and at that point the membrane is being replaced anyway to get at what is underneath. ### What is betterment, and can I dispute it? Betterment is a deduction a carrier applies when a repair leaves your vehicle measurably better than it was immediately before the loss. If a ten year old roof is replaced because of collision damage, the carrier's position is that you now have a new roof and some of that value is not attributable to the loss, so a portion is charged back to you. It is a legitimate concept and it is written into most policies. It is also frequently applied more aggressively than the facts support. Betterment should reflect the actual remaining service life of the specific component, not a generic schedule. If a component was recently serviced, recently replaced, or documented as being in strong condition, that documentation is the basis for pushing back. Maintenance records are what win betterment arguments. Photographs and dated invoices carry more weight than any description you can offer verbally. ### Why does my estimator keep saying structural when nothing looks bent? Because on a coach, the part that carries load and the part you can see are usually not the same part. The house structure sits on a chassis, and both can be damaged independently. An impact absorbed by the sidewall skin can transfer into an outrigger, a floor crossmember, or a slide opening header while the skin itself springs back and looks acceptable. The evidence shows up in alignment, not appearance: a slide that suddenly needs more effort, a door that stops latching cleanly, a gap that runs wider at one end than the other. Those are the symptoms that prompt an estimator to put the unit on a measuring system rather than write a panel repair. It is also why a structural call is verified with measurements before and after, so there is a record proving the corrected dimensions rather than an opinion that it looks straight. --- OCRV Center performs all work in shop at 23281 La Palma Ave, Yorba Linda, CA 92887. Serving Westminster and Orange County. Call (949) 799-3387 or email info@ocrvcenter.com. Posted labor rates are published at https://ocrv.online/prices/.