What Is Cavity Wall? And Its Detail Of Constrution -lceted LCETED INSTITUTE FOR CIVIL ENGINEERS

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Sep 28, 2020

What Is Cavity Wall? And Its Detail Of Constrution

 What Is Cavity Wall?

A Cavity Wall is a type of wall that has a hollow centre. They can be described as consisting of two "skins" separated by a hollow space. The skins typically are masonries, such as bricks or blocks or gypsum board. Masonry is an absorbent material that can slowly draw rainwater or even humidity into the wall.

Cavity Wall

Details Of Cavity Wall Constructions

Details Of Cavity Wall Constructions

Is Both Side Skins Of Cavity Wall Should Equal?

Both side skins of cavity wall may be of equal thickness if it is a non-load-bearing wall or the inner skin wall may be thicker than the outer skin, to meet structural requirements.


How The Two Skins Of Cavity Wall Connected?

The two skins of the wall can be connected to each other by metal pins or a connecting brick at horizontal intervals of about 1000mm to 1200mm and vertical the interval of 300 to 450mm.


How Can Space Between Two Skins Of Cavity Wall Filled?

The cavity between the two skins should not less than 50 mm and not more than 75 mm. The space between the skins is either left as hallow or filled with Rock Wool, Glass Wool, Polystyrene Bead and Cavity Foam Insulation


What Are The Advantages & Disadvantages Of Cavity Walls


Advantages Of Cavity Walls

1.   Cavity walls have good fire-resistant

2.   Cavity wall can reduce the moisture condensation risk

3.   The wall can reduce the cost of cooling the building

4.   It has good protection against efflorescence.

5.   It gives good sound insulation property.


Disadvantages Of Cavity Walls

1.   Needs highly skilled labourers and mason

2.   Needs high supervision during the process

3.   Carpet area may decreases

4.   Main the problem of cavity walls is wall ties rusting. (life period of ties 10 to 15 years)

Special Points to be Observed in Cavity Wall Construction

(i) The cavity should extend to 15 cm below the damp-proof course level.

(ii) Below the ground level, the walls are built solid, or preferably the cavity should be filled up to 15 cm above the damp-proof course with fine concrete.


(iii) Under no circumstances, should the DPC be laid to span one leaf only. It should cover both leaves of the wall.


(iv) The upper part of the wall where it ends should also be built solid for two or three courses below the wall plate or roofline, to stiffen the head of the wall and distribute the load over both leaves.


(v) The wall ties must be kept free from mortar droppings by means of a timber batten suspended in the cavity and raised as the work proceeds during its construction. Some bricks may be temporarily left out at the ground floor level to form openings to permit the bottom of the cavity to be cleared of mortar droppings at the end of each day's work.


(vi) In exposed positions, it is desirable to leave a few vertical joints in the outer leaf open, at the bottom of the cavity to permit water to drain away.


(vii) A certain amount of ventilation to the cavity is desirable to prevent stagnation of air and excessive humidity. It can be provided by vents, say 150 x 75 mm (6" x 3") at intervals, near the base and top of the wall, by leaving a few joints open.


(viii) The cavity walls should not be built solid at the jambs [the sides of door and window openings (see Fig. 1.2)] unless a vertical "damp-proof course" is inserted to prevent water from driving to the inner face. Thus solid jambs without DPC are only permissible in fairly sheltered sites and where the wall surface is roughcast.


(ix) A lead, galvanised iron or other suitable material made to form a trough or gutter, may be placed in the cavity above all openings for exposed doors and windows to collect water which may drive through the outer leaf.


(x) The cavity wall should not be built solid below window sills also and a damp-proof course is desirable at this point also.


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