Domes

It was originated as a roofing method where the absence of suitable timber meant that it was impossible to make a flat timber roof. The earliest domes in the Middle East were associated with round buildings and were produced out of mud brick placed in layers which tilt slightly inwards.

When the Romans conquered the Middle East the dome was incorporated into Roman architecture and under the Byzantines it became the main method of roofing monumental buildings.

The chief advantage of domes is that large areas can be roofed without the interference of columns. At this time the wooden dome was developed which combined the space of dome building with the flexibility and lightness of wood. By the seventh century wooden domes were a normal method of roofing mosques and churches.

Wooden domes were usually covered with sheets of metal, either copper or lead, as protection against the weather. Most domes, however, continued to be built of less flexible materials such as stone, mud brick and baked brick. One of the main problems of dome construction was the transition from a square space or area into a circular domed area. Usually there was an intermediary octagonal area from which it is easier to convert to a circular area although there is still the problem of converting from square to octagon.

Two main methods were adopted, which are the squinch and the pendentive. The squinch is a mini-arch which is used to bridge a diagonal corner area whilst a pendentive is an inverted cone with its point set low down into the corner and its base at the top providing a platform for the dome. Squinches are the main method of transition in pre-Ottoman architecture whilst pendentives are more common after the sixteenth century. In India, arches where there was no tradition of before the advent of Islam, domes rest on flat corbels which bridge the corners.

Squinch:










Pendentive :

During the medieval period Islam developed a wide variety of dome types which reflect dynastic, religious and social distinctions as well as different construction techniques. One of the most extravagant dome forms is the Muckarnas or conical dome which appears as early as the eleventh century in Iraq at Imam Dur. A conical dome consists of multiple tiers of Muckarnas which blur the distinction between structure and decoration and between circular and square forms. Later on the idea of the double dome was introduced as it was recognized that there was a conflict between the external appearance of the dome and the aesthetics of the interior of the domed space. The result was tall external domes with shallower interior domes. Increasing emphasis on the exterior can be seen in Cairo and Egypt where masonry domes with intricately carved exteriors were developed. In Iran and Central Asia tall domes were covered in coloured (usually blue) glazed tiles, culminating in the huge bulbous fluted domes on a high circular drum which were characteristic of the Timurid period (fifteenth century). In pre-Mughal India the standard dome form was derived from Hindu architecture and consisted of a squat circular form with a lotus design around the apex and a characteristic bulbous finial. Ottoman architecture adopted the Byzantine dome form and developed it to produce vast domed areas such as that of the Selimiye in Edirne.

Muckarnas Dome:










Pictures from:

Squinch Dome:
http://www.arts.auckland.ac.nz/ahist/arthist111/ways_of_building/Images/squinch.gif
http://www.islamicarchitecture.org/art/images/techniques/squinch.gif

Pendentive Dome:
http://www.faculty.sbc.edu/wassell/ArchMath/Unit5/images/pendentive.jpg
http://www.brynmawr.edu/Acads/Cities/wld/00980/00980km.jpg

Mukarnas Dome:
http://www.mrfs.net/trips/2003/Spain/Nasrid_Palace/dome.jpg
http://www.sakkal.com/islamic_geometry/images/gaghard/geghard03.jpg