A coachbuilder is a manufacturer of bodies for passenger-carrying vehicles.Construction has always been a skilled trade requiring a relatively lightweight product with sufficient strength. The manufacture of necessarily fragile, but satisfactory wheels by a separate trade, a wheelwright, held together by iron or steel tire#History, was always most critical.
The word ''coachbuilder'' is recorded as early as 1794. From about AD 1000, rougher work was carried out by a ''wainwright'', a wagon-builder. Later names are ''cartwright'', a carpenter who makes carts, also (from 1587);''coachwright''; (starting in 1599) ''coachmaker''. Subtrades include ''wheelwright'', ''coachjoiner'', etc. ''Oxford English Dictionary'' 2011 By extension, "coach" also may be used for a passenger car (rail) or railway carriage.
''Custom'' or ''bespoke'' bodies require a rolling chassis to avoid the vast expense of designing and building a suitable Vehicle frame#Unibody or monocoque structure. While the enormous cost of suitable machinery to make steel structures may be avoided by moulding synthetic materials for one-off bodies the high costs of structural design and development remain prohibitively expensive.
As well as true custom or bespoke bodies, coachbuilders also made short runs of more-or-less identical bodies to the order of dealers or the manufacturer of a chassis. The same body design might then be adjusted to suit different brands of chassis. Examples include Tickford' ''Tickford'' bodies with a patent device to raise or lower a convertible's roof, used on their 19th century carriages, or ''Wingham'' convertible bodies by Martin Walter of Folkestone.
''Custom body'' is the standard term in North American English. Coachbuilders are: ''carrossiers'' in French language, ''carrozzeria'' in Italian language, ''Karosseriebauer'' in German language and ''carroceros'' in Spanish language.
''Coach-built'' implies that a body's frame is wooden, but it may not be so. Coachbuilt also describes a recreational vehicle or motorhome that has been purpose-built. A whole new body has been made for a bare chassis, as opposed to a ''conversion'' built inside an existing vehicle body.
This "chassis" would be delivered by the manufacturer to the coachbuilder of the buyer's choice. It would be a rolling chassis, which included the chassis, drivetrain (engine, gearbox, differential, axles, wheels), brakes, suspension, complete steering system, including the wheel, radiator, Bulkhead (partition) and dashboard. The manufacturer delivered the chassis with lighting system, spare wheel(s), but probably without tyres, front and rear mudguards and (later) bumpers. The very easily damaged Radiator (engine cooling)#Radiator construction, later enclosed and protected by a shell, became the main visual element identifying the chassis' brand. The manufacturer retained an element of control over bodies. Bodies not approved by the chassis manufacturer would lose the chassis manufacturer's chassis warranties.
Until World War II it would not have been unusual to order the most popular cars as only a chassis and have a local coachbuilder put a body (passenger or commercial) on it. the Austin 7s of the 1920s and 1930s were favourite subjects.
For mass production, because the long-established and refined skills and tools (such as the English wheel) used to build the wooden and metal bodies of vehicles were so specialized, most automobile manufacturers in the United States contracted with existing coachbuilders to produce bodies. For example, Fisher Body built all of Cadillac (automobile)'s closed bodies in the 1910s and eventually all General Motors mass-produced products.
When popular automobile manufacturers brought body building skills in-house, the practice of bespoke or custom coachbuilding remained in favour among the wealthy, who continued the habit of centuries past. Commonly, larger dealers or distributors of ultra-luxury cars would pre-order stock chassis and the bodies they thought most likely to sell, and stock them in suitable quantities for sale off their showroom floor.
All ultra-luxury vehicles of automobiling's Golden Era before World War II sold as chassis only. For instance, when Duesenberg introduced their Model J, it was offered as chassis only, for $8,500. Other examples include the Bugatti Type 57, Cadillac V-16, Ferrari 250, Isotta Fraschini Tipo 8, and all Rolls-Royce Limiteds produced before World War II. Delahaye had no in-house coachworks, so all its chassis were bodied by independents, who created some of their most attractive designs on the Type 135. Most of the Delahayes were bodied by Chapron, Labourdette, Franay, Saoutchik, Figoni & Falaschi, Pennock (coachbuilder), and many more carrossiers.
The practice remained in limited force after World War II, with both luxury chassis and high-performance sports cars and gran turismos, waning dramatically by the late 1960s. Even Rolls-Royce acquiesced, debuting its first unibody model, the Rolls-Royce Silver Shadow, in 1965, before taking all R-R and Bentley bodying in-house.
The advent of Vehicle frame#Unibody construction, where the car body is unified with, and structurally integral to the chassis, made custom coachbuilding uneconomic. Many coachbuilders closed down, were bought by manufacturers or changed their core business to other activities:
Transforming into dedicated design or styling houses, subcontracting to automotive brands (e.g. Zagato, Pietro Frua, Gruppo Bertone, Pininfarina)
Transforming into general coachwork series manufacturers, subcontracting to automotive brands (e.g. Karmann, Gruppo Bertone, Vignale, Pininfarina)
Manufacturing runs of special coachworks for trucks, delivery vans, touringcars, ambulances, fire engines, public transport vehicles, etc. (e.g. Pennock, Van Hool, Plaxton, Heuliez)
Becoming technical partner for development of e.g. roof constructions (e.g. Karmann, Heuliez) or producer of various (aftermarket) automotive parts (e.g. Giannini Automobili)
Independent coachbuilders survived for a time after the mid-20th century, making bodies for the chassis produced by low-production companies such as Rolls-Royce (car), Ferrari, and Bentley."Steel Bodies: In an Eggshell", in Ward, Ian, executive editor. ''World of Automobiles'' (London: Orbis Publishing, 1974), p. 2178. Producing body die (manufacturing)s is extremely expensive (a single door die can run to United States dollar40,000), which is usually only considered practical when large numbers are involved—though that was the path taken by Rolls-Royce and Bentley after 1945 for their own in-house production. Because dies for pressing metal panels are so costly, from the mid 20th century, many vehicles, most notably the Chevrolet Corvette, were clothed with large panels of fiberglass reinforced resin, which only require inexpensive molds. Glass has since been replaced by more sophisticated materials, if necessary hand-formed. Generally these replace metal only where weight is of paramount importance.