1. UNIT:- VI
Dampness :-
Dampness indicates the entry of presence of moisture in building
due to several causes such as rainwater penetration, rise of
ground water, condensation in building, improper drainage &
orientation, used of defective materials or bad workmanship.
The treatment given to prevent leakage of water from roof is
called as water-proofing.
the treatment given to keep the walls, floors and basement dry is
called as damp-proofing.

2. Causes of Dampness :-
Dampness rising through the foundation walls. Moisture from wet ground may rise well above ground level on account of capillary
action.
Splashing rain water which rebounds after hitting the wall surface.
Penetration of rain-water through unprotected tops of walls, parapets, compound walls etc.
In case of sloped roofs, rain-water may percolate through defective
roof covering.
On condensation, the moisture present in the atmosphere gets deposited on the components of the building.
In case of flat roofs, inadequate roof slopes, improper rain-water
pipe connections and defective junction between roof slab and parapet.
Due to leakages in wet areas of a building which include kitchen,
bathroom, water closet etc.
The leakages could be on account of use of sub-standard plumbing
fittings and fixtures as well as faulty execution of work and bad
work­manship.

3. It may result in softening and crumbling of plaster.
Effect of Dampness :-
It causes efflorescence which may ultimately result in disintegration of bricks, stones, tiles etc.
It may result in softening and crumbling of plaster.
It may cause bleaching and flaking of paint with the formation of
coloured patches.
It may lead to the corrosion of metals.
It may damage electrical fittings.
It promotes growth of termites.
It breeds mosquitoes and creates unhealthy living conditions for
the occupants.

4. 1) Membrane damp-proofing 2) Integral damp-proofing
METHODS OF DAMP-PROOFING :-
1) Membrane damp-proofing
2) Integral damp-proofing
3) Surface treatment
4) Guniting
5) Cavity wall construction
Membrane Damp-proofing :-
This consists in providing layer or membrane of water repellent
material between the source of dampness and the part of the
structure adjacent to it.
This type of layer is commonly known as damp proof course
(D.P.C.)
It consist of materials like bituminous felts, mastic asphalt, silicon,
polymers, plastic or polythene sheets, cement concrete etc.

5. Membrane Damp-proofing

6. Depending upon the source of dampness, D.P.C. may be provided
horizontally or vertically in floors, walls etc.
Provision of D.P.C in basement is normally termed as 'tanking.’
2) Integral damp-proofing :-
Addition of certain water-proofing compounds with the concrete
mix to increase its impermeability.
Such compounds are available in market in powdered as well as
liquid form.
The compounds made from clay, sand or lime (chalk, fuller’s
earth etc.) help to fill the voids in concrete and make it water
proof.

7. 3) Surface treatment :-
Surface treatment consists in filling up the pores of the surfaces
subjected to dampness.
The use of water repellent metallic soaps such as calcium and
aluminium oleates and stearates is much effective in protecting
the building against the heavy rain.
Bituminous solution, cement coating, transparent coatings, paints
and varnishes fall are also used.
Other surface treatments given to walls is lime cement plaster.
The walls plastered with cement, lime and sand mixed in proportions of 1 : 1 : 6 is found to serve the purpose of preventing
dampness in wall due to rain effectively.

8. 4) Guniting :-
This consists in depositing an impervious layer of rich cement
mortar over the surface to be water-proofed.
The operation is carried out by use of a machine known as
cementgun.
The assembly broadly consists of a machine having arrangements
for mixing materials and a compressor for forcing the mixture
under pressure through a 50 mm dia flexible hose pipe.
The hose pipe has nozzle at its free end to which water is supplied
under pressure through a separate connection.
5) Cavity wall Construction :-
This consists in shielding the main wall of the building by an
outer skin wall leaving a cavity in between the two.
The cavity prevents the moisture from travelling from the outer to
the inner wall.

9. Guniting

10. 2) Semi-rigid materials :- Materials like mastic asphalt or
MATERIALS USED FOR DAME PROOFING :-
1) Flexible material :- bitumen felts, plastic sheeting (Polythene sheet) etc.
2) Semi-rigid materials :- Materials like mastic asphalt or
combination of materials or layers.
3) Rigid materials :- Materials like first class bricks, stones, slates,
cement concrete etc.
4) Grout consisting of cement slurry and acrylic based chemicals/
polymers
Requirement of ideal material for Damp proofing :-
1) It should be impervious.
2) It should be strong and durable.
3) It Should be capable of withstanding both dead as well as live
loads without damage.
4) It should be dimensionally stable.

11. It consist of two walls with a 5 cm to 8 cm cavity between them
Cavity walls :-
It consist of two walls with a 5 cm to 8 cm cavity between them
The outer wall also known as outer leaf & thickness is 10 cm
(half brick)
The inner wall is sufficiently thick & strong to carry the
imposed load safely
The minimum thickness of inner wall is 10 cm (half brick)
The provision of a continuous cavity in the wall efficiently
prevents the transmission of dampness to the inner wall
Purposes or advantages :-
There is no contact between the two leaves except at the wall ties
(impervious material), there is no possibility of moisture
travelling from the outer leaf to the inner
The layer of air in the cavity being non conductor of heat from
external face to the internal one
This wall have 25% greater insulating value than solid walls

13. They have good sound insulation property
They are economical
Sound proof construction :-
Sound absorbents :-
The material having hard, rigid and non-porous surface, provide
the least absorption, whereas those which are flexible, soil porous
and can vibrate, absorb more sound
The efficiency of the sound absorption, depends more upon the
porosity of the material used as sound absorbent
The term used to express the percentage of the incident sound
that can be absorbed by a material is known as absorption co-
efficient of the material
If the absorption co-efficient of a material is 0.75, mean that the
material is capable of absorbing 75 % of the incident sound

15. low density materials have higher absorption co-efficient
The absorption co-efficient differs with the frequency of the
incident sound
low density materials have higher absorption co-efficient
Classification of Absorbents :-
Porous absorbents
Resonant absorbents
Cavity resonators
Composite type of absorbents
Porous absorbents :-
When sound waves strike the surface of porous material, a part of the waves get reflected while a part enters the pores of the material and dissipated into heat energy
The efficiency of this type of absorbent increases with the increase in the resistance offered by the material

16. Porous absorbents

17. Resonant absorbents :-
It is used to absorb sound having high frequency
Resonant absorbents :-
The absorbent material is fixed on sound framing (timber) with an
air space between the framing and the wall at back.
Such arrangement works most efficient for absorbing sound waves
at low frequency
The principle of sound absorption is that sound waves of the
appropriate frequency cause sympathetic vibrations in the panel
which acts as a diaphragm
The absorption of sound takes place by virtue of the dampening of
the sympathetic vibration
Dampening effect of this system can be improved by placing a
porous material in the air space

18. Resonant absorbents

19. 3) Cavity resonators :-
It essentially consists of a chamber with a narrow opening
(entrance) in which absorption takes place by resonance of the air
in the chamber which gives loss of sound energy
Such an arrangement can act effectively over a single selected
frequency.
Application of cavity resonator is normally restricted to
absorption from individual machine or in similar cases
4) Composite type of absorbents :-
They consist of perforated panels mounted on battens so as to
leave a cavity between panels and wall at the back
The panels maybe of metal, wood (plywood) hard broad, plaster
board etc
The area of holes in the panel should vary between 10 to 20 % of
the total area of the panel

20. holes and get damped by the resonance of the air in the cavity.
When the sound strikes the panel, the sound waves pass through the
holes and get damped by the resonance of the air in the cavity.
The effectiveness of this system can be increased by placing a
porous material like mineral wood etc. in the cavity
This type of absorbent is commonly used, as it is easy to install,
economical and it can accommodate wide range of frequencies
Characteristics of audible sound :-
There are three characteristics of sound –
Intensity & loudness
Frequency & pitch
Intensity & loudness :-
Intensity of sound is defined as the amount or flow of wave energy crossing per unit time through a unit area taken perpendicular to the direction of propagation.

21. It is a measure of quantity of sound.
Loudness of sound is defined as degree of sensation.
Which is not wholly physical quantity but partly subjective & does not depends upon ear & listener.
2) Frequency & pitch :-
Frequency or pitch is defined as the number of cycles which a sounding body makes in each unit of time.
It is a measure of quantity of sound.

22. - General planning principles & factors which are important for
General principles & factors in acoustical design of
Auditorium hall :-
- General planning principles & factors which are important for
good acoustical condition in Hall :-
Site selection & planning
Dimensions
Shape
Seat & seating arrangement
Treatment of interior surfaces
Reverberation & sound absorption
1) Site selection & planning :-
Problem of noise is an important consideration in design.
Noise survey of area should be made.
The site selected should be depends upon surroundings.
Sound insulation like plantation should be provided.

23. Proper orientation, site selection in cases where no air conditioning is provided.
2) Dimension :-
The site should be fixed in relation to number of audience required
to be seated .
Also in proportion to intensity of sound to be generated.
For music halls, the volume should be large so that enough spaces
available for the music to spread in the hall.
For lecture halls, small volumes are useful.
3) Shape :-
Shape of hall or auditorium is an important factors.
The shape of hall is geometrically arranged in the view of better
audibility.
A fan shape floor plan is preferred.

24. The side walls should be arranged to have an angle not more
than 100 degree with curtain line.
The distance of farthest seat from the curtain line should not
normally exceed 23 m.
4) Seat & Seating arrangement :-
The seat should be arranged in concentric arcs of circles
The angle subtended with horizontal at the front most observer
by the highest object should not exceed 30⁰
For drama, distance of the first row is about 3.6m.
For cinema, it is 4.5m.
The width of seat should be 45cm to 56 cm.
For balcony, its projection into the hall should not be more than
twice the free height of opening of balcony.

25. 5) Treatment of interior surfaces :-
Ceilings, side walls, rear walls play an important role in acoustical
design.
Ceiling & wall should provide favorable reflection.
The auditorium rear walls should be either flat or convex in shape.
6) Reverberation & sound absorption :-
A certain amount of reverberation is desirable, specially for giving
richness to music.
But too much reverberation is undesirable.
The optimum time for reverberation for a hall depends upon the
purpose for which it is to be used, audience factor.

26. Fire Proof Construction :-
Fire resisting properties of materials :-
The fire resisting properties of the different materials commonly
used for construction purposes are as below :-

27. Brick :-
First-class bricks molded from good clay can stand exposure to
fire for a considerable length of time.
Fire resistant properties of bricks depends on the method of construction of bricks and the component of fire-resistive material in bricks i.e. clay etc.
It has been well established that brick masonry construction is
most suitable for safeguarding the structure against fire hazards.
Stone :-
The usage of stone in a fire resistive construction should be strictly restricted to the minimum
Hot stone when subjected to sudden cooling develops cracks and
can lead to failure of structure.
Granite & Lime stone is least recommended.

28. Where as compact sand-stone having fine grains may be used as it
can stand the exposure to moderate fire without serious cracks
Steel :-
Steel although incombustible has a very low fire resistance value.
With the increase in temperature, the co-efficient of elasticity of
the metal falls, rendering the structural members soft and free to
expand.
When the members in this state come in contact with water, they
tend to contract, twist or distort and thus the stability of the entire
structure is endangered .
Concrete :-
The influence of fire on concrete varies with the nature of its
coarse aggregate and its density.
It has been found that aggregates obtained from igneous rocks
containing higher calcerous content, tend to crack when subjected
to fire.

29. Coarse aggregates like foamed slag, cinder and brick are best suited
for a concrete which has to be fire resistive .
It has been noticed that in an average fire, the concrete surface gets
disintegrated for a depth of about 25 mm.
Hence in a reinforced concrete fire resistant construction, the
thickness of clear cover should be more.
Glass :-
Because of its low thermal conductivity, the change in volume on
account of expansion or contraction is very small.
So it may be considered to be a good fire resisting material.
However when subjected to sudden and extreme variation of
temperatures, it fractures or cracks.
By the use of glass reinforced with steel wire netting, such cracks
can be minimised

30. Asbestos :-
Asbestos is a fibrous mineral which is combined with Portland
cement to form a material having great fire resistive value.
Asbestos cement products are largely used for the construction of
fire- resistive partitions, roof etc
Plaster or Mortar :-
Plaster or mortar is incombustible and by suitable choice of the
type of mortar, the walls or ceiling of a building can be made more
fire resistant
Cement mortar is preferred to lime mortar.
Timber :-
Timber has unique property of self-insulation and slow burning.
Additional fire resistance is achieved through impregnation of timber with large quantities of fire-retarding chemicals.

31. Fire resisting construction :-
Point to be kept in mind while designing fire resistance structure :-
In a fire resistant construction, the maximum use of non-combustible
materials should be encouraged.
The load-bearing walls or columns of masonry should be thicker, so that they may successfully act as fire barrier for a considerable time
As far as possible fire resisting material should be used in the construction of flooring.
Flooring made from materials like concrete, brick, ceramic tiles etc., is considered to be most suitable for fire-resistant construction.
Reinforced concrete framed structures should be preferred to steel structures, as steel is liable to twist under heavy fire.
The partition walls should be made up of fire-resistant material.

32. The load-bearing walls as well as non-load bearing walls, should be plastered with fire-resistive mortar
The doors, windows or exposed sides should be glazed and fitted with reinforced glass panels.
As far as possible, flat roof should be encouraged.
Fire protection requirements for multi-storeyed buildings :-
1) Structure :- The structural framework can be in R.C.C.
2) Internal walls and partitions :- Internal walls could be in brick,
hollow concrete blocks or tiles.
3) Staircase :- The enclosing walls of the main staircase should
have a fire resistance .
Access to the staircase should be through doors.
The doors should be of swing type opening in the direction of the escape.

33. 4) Basements :- The basement should be properly ventilated. The
main staircase of the building should terminate at ground floor and as far as possible the access to basement should be through a separate staircase.
5) Water-storage tank :- All multistoried buildings should be a provision of an underground water storage tank of one to two lakhs liters capacity provided for fire fighting purposes. The tank should have arrangement of replenishment of the water either by the municipal mains or by tube well.
6) Fire detection and Extinguishing System :- All multistoried
buildings should have adequate provisions for fire detection and fire extinguishing.

34. Joints :-
Provision / necessity of joints in large building :-
all building materials expand or contract due to change in temperature and variation in moisture content.
The magnitude of such expansion or contraction depends upon the type of material used in construction and the extent of variation in the temperature and moisture content.
Components of a structure are not allowed free movements therefore internal stresses will be set up which may result in formation of cracks.
To control or isolate thermal and other movements to avoid danger to a structure.
To break the continuity of a structure.
Joints sub-divide the building into smaller units and also permit free
movement of each unit.

36. The recommended spacing of expansion joints for different
types of works as per I.S :-
1) Walls : c/c spacing of joints
For load bearing walls with cross-walls at
intervals. Traditional type of one-brick thick or more m
b) Walls of warehouse type construction
(without cross walls.) m
2) Chajja’s, balconies and parapets to 12 m
3) (a) Ordinary roof slabs of R.C.C to 30 m intervals and at
protected by layers of mud changes in direction as in
phuska or other insulating media in L,T,H &U shaped struct.
un-framed construction.
(b) The unprotected slabs m

37. 4) Frames At 30 m intervals and
at corners of L, T, H and U
shaped structures.
5) Copings Corresponding to joints
in the roof slabs.
Location of Construction Joints for Different Members :-
The recommended position for construction joints in different structural components is as under.
i) For slabs:-
In case of slabs supported on two sides, the construction joints should be vertical at support.
It can also be provided at the middle of span at right angles to main reinforcement

38. In case of beams, the construction joint should be located at the
In case of two way slabs, the joint can be provided near the middle
of the either span
ii) For Beams :-
In case of beams, the construction joint should be located at the
middle or within the middle third of span and it should be vertical
iii) For columns :-
In case of columns, the construction joint should be formed
horizontally by stopping the concrete in column about 75 mm
below its junction with lowest soffit of the beam
The operation of concreting above the construction joint should be
taken up after a gap of at least 4 hours

39. iv) For walls :-
The horizontal construction joint in walls should be located at the
top of plinth, top or bottom of window opening or at any other
convenient height.