Functional Requirements of Walls in Building Construction
Madeh Izat Hamakareem
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The main purpose of walls in building construction is not only to protect buildings from damage but also to divide them for different rooms or spaces. There are various functional requirements of walls that should satisfy to perform its functions adequately.
Functional Requirements of Walls in Building Construction
Following are the functional requirements of walls in a building construction:
Weather and ground moisture resistance
Resistance to heat passage
1. Strength Requirements of Walls
Strength requirements of walls in building construction is governed by strength of material that is employed to build the wall and how materials are fitted together. The strength of materials is determined by its compressive and tensile strength which can be achieved from tests.
Material ultimate strengths at failure are obtained from testing samples and strength reduction factor is applied for the ultimate strength to compute allowable material strength. This factor is used to consider both material strength variations and their response under stresses.
Stone, brick, steel and concrete are examples of materials that could be used to construct walls.Generally, the entire compressive strength of bricks and stones are not employed in small building such as houses by functional stability of the building.
2. Stability Requirements of Walls
Stability of walls greatly depends on stability of its foundation, load eccentricity, temperature effects, lateral loads such as earthquake and wind loads, and changing in moisture.
Overturning tendency of the wall is due to loads that are not acting on the center of the wall like loads from roofs and floors and lateral loads. If both lateral loads and eccentric loads increases wall deformation is increasing and thus the wall will be unstable.
Building codes provide recommendation for wall height and width to prevent instability resulted from loads. Moreover, horizontal restrictions such as tie between walls and roofs and intersection between walls and piers prevent deformation due to lateral loads.
Furthermore, walls with irregular configurations as shown in Figure-1 are more stable than regular straight walls because buttress actions come into effect in the former.
Figure-1: Different irregular profile walls
3. Weather and Ground Moisture Resistance of Walls
Walls should have enough resistance against moistures (water vapor and liquid water) that might penetrate through foundation walls by absorbing water from ground or by falling of rain on the walls.
Damp-proof layer with a thickness of 150 mm can be employed above ground level for all foundation walls. This could prevent water absorption from the ground which could have a detrimental effect if it is not dealt with properly.
The water that might penetrate walls from the rainfall depends on many factors such as quality of materials and the way of assembling those materials together and prevailing winds.
There are several solutions for situations such as using greater thickness for walls, construction brick, stone, or block walls in two skins with 50 mm cavity between them, protecting wall outer face by cladding or plastering, and utilizing a glass sheet as a curtain wall.
Moreover, environmental features such as hills, trees, or other constructed buildings around should be taken into consideration in determining proper solutions, because these can change severity of exposure conditions to prevailing winds that direct rain on the walls
4. Durability Requirements of Walls
Durability of walls is determined by frequency and the amount of work that is required to make the wall meet the minimum requirements functionally and aesthetically acceptable. Functional requirements might include the wall capability to resist rain and thermal properties.
It is difficult to specify standard acceptable appearance of walls especially in cases where unusual materials such as glass and plastic sheets are used. This is because the minimum acceptable appearance can be varied from person to another. However, this not the case when familiar materials are employed such as high quality bricks or stones which are chosen with good judgments.
The wall that is constructed with bricks will be durable and need not be repairing over its lifespan if good burned bricks and high quality mortars is used, proper attentions is paid to wall openings, and exposure conditions is considered.
When lime mortar is used for brick wall construction is will be necessary to repoint the lime mortar to avoid moisture penetration and regain good appearance.
5. Fire Safety Requirements of Walls
The first and most important measure against fire is providing a convenient way to escape from it because at early stages of breaking out life of occupant will be in danger because of fumes and smokes.
Safety against spreading of fire is the second measures which include restricting lining, structural, external fire spread in addition to provide access for fire fighters. The restrictions are carried out by providing fire resistance for walls and specify level of flammability of materials used to cover inside walls and floors.
6. Resistance to Heat Passage
It is very important to contain heat and prevent its loss because it leads to obtain cost effective, desirable, and comfortable thermal conditions in buildings. Therefore, it is recommended to construct a wall that is thermally insulated to avoid too much loss of heat.
The loss of heat can be prevented by using light weight and low conductive materials. Moreover, dense high conductive materials have great capacity for thermal storing compare with lightweight materials with low conductivity.
If a building has a continuous source of heating it would be useful to apply low density materials for the outside face of the wall and high density material for inside face. In contrary, using light weight material is advantageous when the building is heated intermittently.
7. Sound Resistance of Walls
Impact and airborne are the two ways of transmitting sounds. The latter is induced as cyclical disturbances of air from a source such as radio while the former is generated because of an impact on solid surfaces for example footsteps that induce floor vibration and in return the air around is vibrated and heard as sound.
High density materials can be used to resist airborne sounds such as concrete walls, cavity wall, and solid wall. However, impact sounds are transmitted quickly through dense materials therefore, materials which can cushion or interrupt path of the impact sound should be employed.