**4. Building materials and construction technology**

Historic buildings of Jeddah are mostly built with the same materials, technology and principles. Structure relies on a wall bearing system that transfers loads across its section. The walls are built of coral blocks "*Al-kashur*" or "*Al-Mangabi*" stones, then covered by plaster "*nourah*" for insulation and esthetic purposes. *Al-mangabi* stones are cut from coral fossils or from the sea, *Al-arba<sup>c</sup> een* lake or *Al-Mangabi* lagoon, just north of Jeddah. Then, it is shaped in blocks form and used in constructing the walls. *Nourah* is a type of calcareous stone treated by fire and then dismantled, drained and mixed with water. It is used alone in the case of external polishing, while mixed with stone fragments for repairs. The silt, precipitated after rain, is utilized as mortar to cement blocks to each other. Notably, these are natural, renewable and recyclable materials.

*Al-Mangabi* stones proved efficiency as an insulation and resistance median. Empirical studies indicate that *Al-Mangabi* stone wall of 70 cm thickness gives high thermal mass to the building, which reduces and delays heat gain inside. A difference of 2.7°C (from 35°C to 32.3°C) between outer and inner surfaces of external wall is measured [16]. Also, the thermal properties of the stone were examined in comparison to contemporary building materials. The results confirmed that the change in the temperature of the internal surface of the stone was almost like double-brick wall section with insulation (**Figure 14**). Hence, it was recommended for use in contemporary buildings; the cost of insulation and the energy required for air conditioning can be lowered [17]. Results could be more enhanced with the white color of plaster which reflects the direct solar radiation and reduces the heat gained in the building's mass.

Wood is the other major construction material which was used in structure and decoration. Structurally, Mangrove is widely used in roofing for the length of its poles which reach about 2.8 m and accordingly dictate room widths. While, Teak "*sajj*" and sandalwood "*sandal*" were used to make windows, *rawasheen*, doors and different forms of lattice work. These woods were imported from India, Java or East Africa. Local woods available in the region, such as palm trees and leaves, acacia and juniper were also used. Sustainability of wood has been heavily documented. Though, being imported is a shortage.

However, the construction process starts with a shallow foundation trench to the depth of one or two courses of *Al-Mangabi* blocks. At every six rows (120 cm), a bonding course of round wood beams "*takaleel*" is inserted and locked with short pieces at the ends to ensure homogenous load distribution. They support the building to resist the settlement stresses (**Figure 15**). Also, they enable maintaining the wall by supporting the wooden beams from the external and internal side and changing damaged stones underneath (**Figure 16**).

At ground level, the walls thickness is about 80 cm. The higher the building go, the thickness would be reduced by about 15 cm with each floor. This reduction is taken from the internal side of the wall to create a ledge with sufficient space to place the ceiling beams side by side. Spaces assigned for *rawasheen*, windows and doors would be left according to width. Wooden lintels or arches as well as wooden fixtures of *rawasheen* are then utilized in position. The internal walls are provided with niches "*taqat*" which are used as cupboards. Both openings area and niches served to alleviate the weight of the structure, not ignoring reduction of the walls thickness and areas taken out in balustrades. In many cases, voids covered by *rawasheen* are found to reach around 50% of the wall surfaces [18] (**Figure 17**).

For the roofing of each floor, wooden beams are placed resting on ledges of two parallel walls and firmly impeded inside the wall. Several layers are then implemented above the wooden beams including palm leaves or light weight wood planks, sackcloth, wet soil, crushed gravel, lime and finally clay mortar, which are natural materials are used too (**Figure 18**).

**Figure 15.** *External views of* Al-Mangabi *blocks and wood beams.*

**Figure 16.** *Supporting traditional wall for maintenance.*

*Sustainability Features of Jeddah Traditional Housing DOI: http://dx.doi.org/10.5772/intechopen.98735*

**Figure 17.** *Solid and void percentage of selected facades.*

From structure view, staircase, is the backbone of the building. Being rectangular stone walls with central column "*fahl el-daraj*" running vertically across the building height, it is considered as a main pillar. Whereas walls of staircase and external walls mutually support each other through the wooden beams.
