Dictionary of islamic architecture

haud or hauz
A pool or tank, often in the centre of the courtyard
of a mosque.
Hausa
West African people living in northern Nigeria with a
long-established distinctive architectural tradition.
Modern Hausa society is a combination of two
groups of people, the Hausa themselves and the
Fulbe-speaking Fulani people. The Fulani first
moved into the area in the fifteenth century
although it was not until the nineteenth that large-
scale migrations took place. The Fulani constitute
a literate Muslim class attached to the ruling élite
in Hausa society. In addition to the Muslim urban
populations there is also a rural population of non-
Muslim Hausa known as Maguzawa. The Hausa
civilization is generally agreed to have formed in
about 1000 CE and comprised the cities of Daura,
Kano, Gobir, Katsina, Zaria, Biram and Rano. In the
nineteenth century a Fulani-led jihad established a
caliphate in Hausaland with the new city of Sokoto
as its capital. The main materials of Hausa
architecture are oval mud bricks (tubali) and palm
wood (deleb). Walls are built out of mud brick
whilst palm trunks split into beams (azarori) are
used for roofing. Unlike most other areas of West
Africa, Hausa architecture is in the hands of a
hereditary group of trained masons who are
organized into guilds. These trained masons have
been responsible for some of the most celebrated
architecture in West Africa.
The traditional layout of a Hausa city consists of
narrow winding streets set within a thick outer
enclosure wall. In the older cities the outer walls have
an irregular/organic shape but the walls of Sokoto,
established in the nineteenth century, are square as
an expression of Islamic conformity and bordered by
houses which consist of courtyard compounds. In the
past the street façades of the houses were left
unadorned although in recent times there has been a
tendency to decorate the outer façade of the entrance
vestibule with em-bossed designs. Circular rooms
with two entrances are traditionally used as entrance
vestibules and are known as 
zaure.
Square or
rectangular rooms, called 
sigifa,
are usually used for
internal reception rooms. In recent times circular
rooms have become less common and have been
replaced with rectangular rooms with the more
complex 
daurin guga
dome form.
The characteristic feature of Hausa architecture
is the domed room formed by a number of
intersecting arches projecting from the walls of the
building. The arches are made of lengths of palm
wood set into the wall and projecting at increasing
angles until they are horizontal at the apex of the
arch where they are joined to a similar construction
projecting from the opposite wall. The palm-wood
frame is then covered with mud to produce smooth
free-standing arches which support a ceiling made
of palm-wood panels and covered with rush mats
and then with a water-resistant layer of plaster, like
material made out of the residue of indigo dye pits.
Two main types of arch configuration are used
depending on the shape of the room to be covered.
The simplest form, known as the 
kafin laima
vault, is
used for a circular room and has all the arches or
ribs meeting at a central point which is often
decorated with an inset metal or ceramic bowl. The
more complex vault form, known as 
daurin guga,
is
used for rectangular or square rooms and consists
of two sets of parallel arches or ribs which intersect
at the centre to form square com-partments. The
soffits of the arches are often decorated with abstract
designs which may either be relief mouldings or
painted in bright, locally produced colours.