Orangi Housing Primer

1.4 Openings

The doors and windows of “pucca” houses are made of steel, which are available at the local “lohras” (manufacturers of metal construction goods). Reinforced concrete lintels are used on top of the openings to support the concrete blocks. (See photograph 37). These lintels are available in standard sizes, at the “thallawalas”. In some cases cement “jallis” (concrete lattice work) obtained from “thallas” are also used for windows. The use of steel doors and windows is the cheapest solution whereas treated, seasoned timber is more expensive (see photograph 38).

1.5 Flooring

Floors of “pucca” houses are usually cemented and at times mud plastered. To construct a cemented floor a bed of crushed stone is first compacted and concrete poured over it. It is allowed to cure for 2 – 4 days.

2. Economic And Social Conditions Of The Owners Of Pucca Houses

Owners of the pucca houses fall in two categories. First category is of the owners of RCC structures who belong to the middle and high income bracket of Orangi residents having an income of Rs 2,000 and above. RCC houses have the facilities of water, electricity and usually sewerage. Such houses are built by contractors, who employ their own labour.

Second category of the pucca house owners belongs to the lower middle income group of Orangi, earning a salary of Rs l,200 and above. Houses of such owners are characterised by load bearing concrete block walls, block/stone foundations and asbestos/G.I. sheet roofs. Absence of reinforcement is an indication of the economic constraints of the owners. Construction of such houses is carried out by hiring masons and labour under the guidance of the owner himself. The owner saves money by eliminating the role of the contractor. Presence of electricity and water is dependent upon the location of the house and economic condition of the owner. Absence of sewerage is a problem in most of these cases except in localities which have organized to solve their problems.

3. Construction Relations

Houses which are supervised by the owners and constructed by hired masons and labour, comprise 55 – 60% of the total houses in Orangi. These houses are characterised by non-RCC construction, load bearing concrete block walls and stone or concrete block foundations. Cost of these houses is about Rs 35,000 – Rs 40,000 and they can be constructed in approximately 20 days. These houses usually have 2 – 3 rooms depending on the economic condition of the owner and are built over a period of time as cash flows in. Material for construction is obtained from the “thallawalas” by the owners. In cases where these houses are built on labour rates by contractors, the costs can go up-to Rs 50,000 to Rs 55,000 each. Problems with the construction process start from the time of procurement of material from the “thallas”. The ‘thallawalas” sell substandard material due to 2 reasons, (a) to maintain their margin of profit (b) substandard manufacture is produced due to use of bad quality aggregate, poor mixing and insufficient curing. Due to the owners’ lack of knowledge and the mason’s attempts to cheat the owner, quality of construction and workmanship suffer greatly. This results in problems with the house later on. These problems are discussed in section 3.1.1. of this paper.

Four to 5% of the houses in Orangi have RCC structures and are constructed by contractors. No supervision is conducted by the owners. Cost of these houses is between Rs 70,000 to Rs 75,000. If the economic conditions of the owner permits, blocks for construction are manufactured on site, otherwise they are obtained from the “thalla”. The quality of construction is usually poor due to attempts of the contractor to make excessive profits by using poor quality material. Technical problems of the RCC structure are discussed in section 3.1.1.

4. Construction Problems

4.1 Technical Problems

4.1.1. Foundations

The use of stone for foundation, in the absence of mortar, causes uneven settlement of the stones which results in cracks in the walls (see photograph 39). The concrete block foundation and RCC foundation are subject to sulphur attack and seepage of water. This takes place due to bad quality of aggregate used, absence of water proofing, and insufficient curing of blocks. These defects are caused due to technical ignorance of the owner and the contractor and at times due to the “delinquency of the latter” (see photograph 40 & 41).

4.1.2 Walls

The concrete blocks used in walls that are obtained from the “thallas” are of poor cement aggregate ratio, bad aggregate and are not sufficient cured. This is done to maximize profits by the “thallawala” and at the same time make the manufacture affordable for the residents. These un-plastered walls absorb water during rains and become weaker. In RCC construction as well damp proofing of walls is non-existent and concrete is not sufficiently cured.

In addition to the problems mentioned above the walls suffer from the following problems as well:

• In the construction of load bearing concrete block walls the corners of the intersecting walls are usually not tied together. This results in weakening of the structure making it susceptible to the forces of nature (see photograph 42).
• The periodic dust storm in Karachi have illustrated the inappropriate slenderness ratio employed in the construction of concrete block walls. The ratio of the thickness to the height of the walls, is inappropriate which results in buckling and overturning when faced with axial and lateral loads (see photograph 43).
• The mortar used for joining the blocks is usually of a poor mix and not sufficiently cured. This again makes the wall susceptible to strong wind pressure.

4.1.3 Roofs

Problems with asbestos/G.I. sheet roofing are similar to the ones discussed above in semi-pucca houses. The water leaking from the roofs seeps into the un-plastered walls and renders them weak. Supports to the roofs sag over time and due to absence of ties between the sheets and girders, roofs fly off under strong winds.

RCC roofs usually develop cracks and leaks over time. This is due to insufficient curing, poor workmanship and poor quality aggregate.

4.1.4 Flooring

The cemented floors in “pucca houses in Orangi seldom make use of expansion joints. This results in the development of cracks in the floors. Due to poor aggregate and cement ratios the cemented floors also erode with time.

5. Social Problems

Problems with construction process start with the procurement of material, as mentioned above. The “thallawalas” to maximize their profits, use poor quality material and workmanship. The owners of the houses, in spite of knowing this can do little to rectify the situation. Dependence of the residents of Orangi on the “thallawalas” is complete since there is no other parallel system of construction to replace the “thallas” This complete monopoly of the “thallas” gives them free reign to continue their malpractices.
During the second stage of the construction process relationship between the owner and the builder usually gets strained. This is due to the delinquent behaviour of the builders and masons who try to cheat the owner by using bad quality materials and poor workmanship. The owner is seldom in a position to improve the situation, having no technical skills and construction knowledge. This further strains the relationship between the builder and the owner. The owner is usually left with a product that has severe construction problems which need maintenance for the entire life span of the building.