Editing Chartres Cathedral (section)

===Plan and elevation – flying buttresses===
<gallery mode="packed" heights="200">
File:Plan.cathedrale.Chartres.png|Chartres floorplan (1856) by [[Eugène Viollet-le-Duc]] (1814–1879)
File:Triforium Chartres.jpg|The elevation of the nave, showing the gallery on the ground level; the narrow triforium; and, on top, the windows of the [[clerestory]]
File:Strebewerk.jpg|[[Flying buttress]] supporting the upper walls and counterbalancing the outward thrust of the vaulted ceiling, allowing thin walls and greater space for windows
File:Cathedrale nd chartres tour057.jpg|Flying buttresses seen from above
File:Chartres - Cathédrale (2012.01) 03.jpg|The [[rib vault|vaults]] of the roof, connected by stone ribs to the pillars below, combined with the flying buttresses outside make possible thinner walls, and the great height and large windows of the cathedral
</gallery>

The plan, like other [[Gothic cathedrals]], is in the form of a cross and was determined by the shape and size of the 11th-century Romanesque cathedral, whose crypt and vestiges are underneath it. A two-bay [[narthex]] at the western end opens into a seven bay [[nave]] leading to the crossing, from which wide [[transept]]s extend three bays each to north and south. East of the crossing are four rectangular bays terminating in a semicircular apse. The nave and transepts are flanked by single aisles, broadening to a double-aisled [[ambulatory]] around the choir and apse. From the ambulatory three deep semi-circular chapels radiate (overlying the deep chapels of [[Fulbert of Chartres|Fulbert]]'s 11th-century crypt).<ref name="Houvet 2019 p. 20">Houvet (2019) p. 20</ref>

While the floor plan was traditional, the elevation was bolder and more original, thanks to the use of the [[flying buttress]] to support the upper walls. This was the first known use in a Gothic cathedral.<ref name="Houvet 2019 p. 20"/> These heavy columns of stone were joined to the walls by double stone arches, and reinforced by columns, like the spokes of a wheel. Each of these columns is made from a single piece of stone. The arches press against the walls, counterbalancing the outward thrust from the [[rib vault]]s over the cathedral interior. These vaults were also innovative, having just four compartments, unlike the six-part vaults of earlier Gothic churches. They were lighter and could cross a greater distance. Since the flying buttresses were experimental, the architect prudently added additional buttresses concealed under roofs of the aisles.<ref name="Houvet 2019 p. 20"/>

The elevations of earlier Gothic cathedrals usually had four levels to give them solidity; an arcade of massive columns on the ground floor, supporting a wide arched tribune gallery or tribune, below a narrower arcade [[triforium]]; then, under the roof, the higher and thinner walls, or [[clerestory]], where the windows were. Thanks to the buttresses, the architects of Chartres could eliminate the gallery entirely, make the triforium very narrow, and have much more room for windows above. Chartres was not the first cathedral to use this innovation, but it used it much more consistently and effectively throughout. This buttressing plan was adopted by the other major 13th-century cathedrals, notably [[Amiens Cathedral]] and [[Reims Cathedral]].<ref name="Houvet 2019 p. 20"/>

Another architectural innovation at Chartres was the design of the massive [[Pier (architecture)|piers]] or pillars on the ground floor which receive the weight of the roof through the thin stone ribs of vaults above. The weight of the roof is carried by the thin stone ribs of the vaults outwards to the walls, where it is counterbalanced by the flying buttresses, and downwards, first through columns made of ribs joined together, then by alternating round and octagonal solid cored piers, each of which bundles together four half-columns. This pier design, known as ''[[pilier cantonné]]'', was strong, simple, and elegant, and permitted the large stained glass windows of the clerestory, or upper level.<ref name="Houvet 2019 p. 20"/>

Although the sculpture on the portals at Chartres is generally of a high standard, the various carved elements inside, such as the capitals and string courses, are relatively poorly finished (when compared for example with those at [[Reims Cathedral|Reims]] or [[Soissons Cathedral|Soissons]]) – the reason is simply that the portals were carved from the finest Parisian limestone, or ' 'calcaire' ', while the internal capitals were carved from the local "''[[Berchères-les-Pierres|Berchères]] stone''", that is hard to work and can be brittle.