What is Cavity Wall?
A cavity wall is brick masonry having two walls, called “skins” or “leaves” of masonry separated by an air space and joined together by metal ties at suitable intervals. These walls are generally exterior walls, although sometimes used as interior walls due to good sound. A cavity wall consists of two walls having an air gap between them about 5cm to 8cm. The Exposed outside wall consists of a 200 mm thick wall and the inner wall is sufficiently thick and strong to carry the imposed loads safely and inner wall thickness restricted to 100mm.
Why use Cavity Wall
When there is a normal external wall is provided in house, as rain flash on its wall catch moisture in it and that transfer toward the inner face of wall which becomes a cause for many defects in the wall. The figure shows the movement of moisture in the house.
Cavity Walls restrict the entry of moisture into your home by mean of air space or cavity provided between the walls.
Advantages of cavity wall construction
1- Damp Prevention: cavity wall checks the prevention of dampness from outside to the inside of the building in a better way than a solid brick wall of the same thickness.
2- Heat Insulation: since air is a bad conductor of heat, a cavity wall decreases the heat transmission considerably hence it is easier to maintain the uniform temperature inside the building.
3- Sound Insulation: sound waves can travel faster in solid media than air, the cavity wall constructions considerably dampens the external noise and inside the building, external disturbances have little effect.
4- Economical: The construction cost of a cavity wall is about 20% less than the construction cost of a solid wall having the same thickness.
Able to withstand a driving rain in all situations from penetrating to the inner wall.
The disadvantage of cavity walls
1- Wall-ties used in a wall may face corrosion problems; cavity insulation makes the outer brick leaf colder, and therefore wetter, which can accelerate rusting of the wall ties. And if the ties hen has to be replaced, there is no satisfactory way of refilling the holes in the insulation, whatever the material.
2- Thermal bridging problems.
3- The width of the cavity restricts the thickness of the insulation material.
4- There are significant numbers of buildings with mortar droppings on ties within the cavity which result in penetrating dampness.
5- The cold bridging problem in cavity wall due to the Settlement and saturation of cavity-fill.