Cavity Wall Construction Methods
Cavity Wall – It is formed with two parallel levels of masonry, detached by a continuous air space. Continuous space is known as a cavity. Cavity walls comprise of the following sections:
1. The exterior leaf i.e. the exterior portion of the wall
2. The cavity, the constant open-air space
3. The inner leaf i.e. the inside portion of the wall
Cavity Wall Advantages - The cavity walls provides the following benefits :
1. Damp Prevention: Due to cavity wall, the moisture can’t enter from exterior leaf to the inside leaf and as a result, there is not dampness in inside of the building. In cavity walls, proper ventilation is arranged for cavities, therefore, when moisture enters through the exterior leaf is vaporized by the air inside the cavity.
2. Thermal Insulation: The air in the cavity functions as a non-conductor of thermal heat and consequently the heat transmission from the exterior face of the interior leaf is reduced. In this way cavity walls facilitates maintaining the thermal insulation of the buildings significantly.
3. Sound Insulation: The air in the cavity wall functions as a barrier for sound absorption. With the adoption of cavity walls building becomes soundproof as significant external noise is consumed in the cavity.
4. Efflorescence: As dampness is resisted to enter by a cavity, the inside wall of the cavity that is always a load-bearing wall is retained free from efflorescence impact.
5. Economy: Cavity walls are casted about 20% less as compared to the construction of similar thickness solid wall.
Size And Position of Cavity Wall: The cavity among two leaves should not remain under 50 mm and not in excess of 75 mm. The ventilation of cavity is done with air brick in the exterior leaf adjacent to bottom and top of the cavity.
The cavity is commenced from the top of the foundation concrete block, but the cavity underneath damp proof course is not suitable. Therefore, up to 100 to 300 mm underneath D.P.C. at plinth level, brickwork in the foundation is normally built up solid and the cavity is provided only about 150 mm underneath the D.P.C. level.
This 150 mm depth under DPC allows in drawing any condensed moisture underneath the level of DPC. Damp proof course for the two leaves of the wall is settled on an individual basis bye at a corresponding level.
The cavity may proceed right up to the top of the parapet and transformed by copying and D.P.C. It may be stopped levels but D.P.C. should be placed over the cavity.
Cavity Wall Construction Methods: The cavity walls contain two leaves internal and external with hollows space among them. The width of the cavity is changed from 50 mm to 75 mm. The thickness of the external leaf of the wall that is normally non-load bearing wall is half-brick. Inside wall is always load-bearing and its thickness should not be under one brick. Wall ties or bonded bricks are used to tie the two parts of the wall.
Metal wall ties are arranged at horizontal gaps of about 0.90 mm and vertical interval of 450 mm. The wall tie is provided in a staggered fashion. The outside wall always remains in stretcher bond, but it can be built up in other bonds as well with brickbats.