Cavity walls are constructed with an empty space between two walls for insulation and damp prevention, consisting of an external and internal leaf interconnected by metal ties. They provide excellent insulation from heat and sound, and are cheaper to construct than solid walls, but require skilled labor and supervision. Key construction points include maintaining proper damp proof courses and ensuring ventilation to avoid stagnation.

1. CAVITY WALLS
NAME: Raghvani Dhvani P.
Subject: Building Construction-4
Div.: B, Roll No.: 6, Sem.: 4
L.J.school of Architecture
L.J. University

2. What is Cavity Wall????
 Cavity walls are those which are constructed in that way
that an empty space or cavity is left between the single
wall.
 Also known as hollow wall
 A little space is lifted between these two walls for
insulation purposes.
 These two walls having little space between them for
insulation purpose are known as leaves of the cavity
walls.
 Out wall is called external leaf,
 Internal wall is called internal leaf,
 The empty space or cavity size should be in between 4 to
10 cm.
 External and internal leaves should have 10 cm thickness.
 These two leaves of cavity wall are interconnected by
links or metal ties for strong bond.

3. Cavity Wall Construction:
• Normal 275 mm (11 inches) cavity wall is suitable for buildings
nor exceeding two stories in height, consists of two half brick
(4-1/2 inch walls with 2 inches cavity.
• Cavity prevents the dampness from the outer leaf percolating
into the inner leaf.
• They provide excellent insulation from heat and sound.
• When used in tropical countries: sufficient precautions must
be taken to see that they do not become breeding places for
lizards and insects.
• Inner leaf is found to take a greater portion of the imposed
load transmitted by floor and roof.
• Two leaves of the wall are bounded together with ties usually
placed 900 mm apart vertically and 450 mm horizontally in
every 6th course staggered.
• This gives more than 2 ties/ sq.m.

4. Cavity Wall Construction:
• These wall ties are made from mild steel wires of
3 to 4 mm diameter or MS bars fabricated to
shapes.
• They are dipped in hot tar and sanded or made
from galvanized steel to prevent rusting, copper
may be used.
• Wire ties are placed with their twisted end down
to allow water, that may seep inside, to drip down
in the cavity.
• The bond to be used for both the leaves, when the
thickness is half brick, is the stretcher bond.
• Inner leaves are made thicker for carrying heavy
loads, English bond can be used.

5. Special points to be observed:
1. Should extent to 15 cm below damp proof course level.
2. cavity should filled up to 15 cm below the damp proof course with fine concrete.
3. Under no circumstances, should the DPC be laid to the span of 1 leaf only.
4. Upper part of the wall where it ends should also be built solid for 2-3 course below the wall plate or roof line.
5. Wall ties must kept free from mortar droppings.
6. In exposed positions, it is desirable to leave a few vertical joints in the outer leaf open, to permit water to drain.
7. Certain amount of ventilation to the cavity is desirable to prevent stagnation of air
8. should not built solid at the jambs unless a vertical DPC is inserted to prevent water driving to the inner face.
9. Galvanized 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 window to collect water
10. Should not built solid below window sills also, and a DPC is desirable at this point also.

6. Advantages of Cavity
Walls:
1. Best for damp prevention than solid
building walls.
2. They work best as heat insulators, it
can decrease hear transmission from
the outside.
3. Sound waves travel faster in solid
walls as compared to hollow walls.
4. Construction cost of the cavity wall is
about 20% less than the construction
of solid walls.
Disadvantages of Cavity
Walls:
1. Highly skilled labor and masons are
required for cavity wall construction.
2. Require standard supervision during
its construction.
3. A vertical DPC is also necessary for it.