Waterproofing 001

8/2/2019 Waterproofing 001

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WATER-PROOFING / DAMP-PROOFING


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MEANING OF THE TERM DAMP-PROOFING

One of the basic requirements in case of all the buildings is that the structure should

remain dry as far as possible. If this condition is not satisfied , it is likely that the building

may become inhabitable and unsafe from structure point of view. Hence in order to

prevent the entry of dampness into a building , the course known as DAMP PROOF

COURSE is provided at various levels of entry of dampness into a building.

At present , practically all the buildings are given the treatment of Damp proofing. Thus ,

theprovision of Damp proofing courses prevents the entry of moisture through walls ,

floors and basements of a building.

The treatment given to the roofs of a building for the same purpose is known as WATERPROOFING.


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PROBLEM SOLUTION


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CAUSES OF DAMPNESS

The dampness in a building is a universal problem and the various causes which are

responsible for the entry of dampness in a structure are as follows:-

RISE OF MOISTURE FROM THE GROUND:-

The ground on which the building is constructed may be made of soils which easily allowthe water to pass. Usually the building materials used for the foundations, absorb

moisture by capillary action. Thus the dampness finds its way to the floors through the

substructure.

ACTION OF RAIN:-

If the faces of wall, exposed to heavy showers of rain, are not suitably protected, theybecome the sources of entry of dampness in a structure. Similarly the leaking roofs also

permit the rain water to enter a structure.

EXPOSED TOPS OF WALLS:-

The parapet walls and compound walls should be provided with a damp-proof course on

their exposed tops. Otherwise the dampness entering through these exposed tops ofsuch walls may lead to serious results.


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CAUSES OF DAMPNESS

CONDENSATION:-

The process of condensation takes place when warm humid air is cooled. This is due to

the fact that cool air can contain less invisible water vapour than warm air. The moisture

is deposited on the walls, floors and ceilings. This is the main source causing dampness in

badly designed kitchens.

MISCELLANEOUS:-

There are various miscellaneous causes of dampness as mentioned below:

(i) If the structure is located on a site which cannot be easily drained off, the

dampness will enter the structure.

(ii) The orientation of a building is also an important factor. The walls obtainingless sunshine and heavy showers of rain are liable to become damp.

(iii) The newly constructed walls remain damp for a short duration.

(iv) Very flat slope of a roof may also lead to the penetration of rain water

which is temporarily stored on the roof.

(v) The dampness is also caused due to bad workmanship in construction such

as defective rain water pipe connections, defective joints in the roofs, improper

connections of walls, etc.


7/52CAUSES OF DAMPNESS

Thus the important sources of dampness can be summarized as follows:

(1) defective junctions between roof slab and parapet wall;

(2) defective roof covering of the pitched roofs;

(3) faulty eaves and valley gutters;

(4) improper rain water pipe connections;

(5) inadequate roof slope;

(6) moisture from wet ground below foundation;

(7) splashing rain water;

(8) unprotected tops of walls, parapets and compound walls; etc.


8/52EFFECTS OF DAMPNESS

The building materials such as bricks, timber, concrete, etc., have a moisture content

which is not harmful under normal circumstances.

The rise in moisture content of these materials beyond a certain level from where it

becomes visible or when it causes deterioration leads to the real dampness.

In absolute terms, the moisture content of different materials may be the same. But the

acceptable limit differs from material to material.

For instance, the presence of 10 per cent by weight of water in timber is not harmful. But

the same level could saturate a brick or cause deterioration of plaster.



The structure is badly affected by dampness. The prominent effects of dampness are as

follows:

(1) A damp building gives rise to breeding of mosquitoes and creates unhealthy

conditions for those who occupy it.

(2) The metals used in the construction, of the building are corroded.

(3) The unsightly patches are formed on the wall surfaces and ceilings.

(4) The decay of timber takes place rapidly due to dry-rot in a damp atmosphere.

(5) The electrical fittings are deteriorated and it may lead to leakage of electricity and

consequent danger of short circuiting.

(6) The materials used as floor coverings are seriously damaged.

(7) It promotes and accelerates the growth of termites.

(8) It results in softening and crumbling of the plaster.

(9) The materials used for wall decoration are damaged and it leads to difficult and costly

repairs.


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(10) The continuous presence of moisture in the walls may cause efflorescence which

may result in disintegration of stones, bricks, tiles, etc. and the strength of wall is then

reduced,

(1 1) The floorings get loosened because of reduction in the adhesion when moistureenters through the floor.

(12) The dampness combined with warmth and darkness breeds germs of dangerous

diseases such as tuberculosis, rheumatism, etc., and the occupants may also become

asthmatic.


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REQUIREMENTS OF AN IDEAL MATERIAL

FOR DAMP PROOFING

Following are the requirements of an ideal material for the damp-proofing:

(1) The material should be durable. As a matter of fact, the damp-proof course

should remain effective during the useful life of the building.

(2) The material should be such that it remains steady and does not allow any

movement in itself.

(3) The material should be perfectly impervious.

(4) The material should be capable of resisting safely the loads coming on it.

(5) The material should be flexible so that it is capable of accommodating the

structural movements without any fracture.

(6) The material should be dimensionally stable.

(7) The material should be reasonably cheap.


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REQUIREMENTS OF AN IDEAL MATERIAL

FOR DAMP PROOFING

(8) The material should be such that it is possible to carry out leak-proof jointing work.

(9) The material should be free from deliquescent salts like sulphates. chlorides and

nitrates.


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MATERIALS USED FOR DAMP PROOFING

Following are the materials which are commonly used for damp-proofing:

(1) Hot bitumen: This is a flexible material and is placed on the bedding of concrete or

mortar. This material should be applied with a minimum thickness of 3 mm.

(2) Mastic asphalt: This is a semi-rigid material and it forms an excellent impervious layer

for damp-proofing. The good asphalt is a very durable and completely impervious

material. It can withstand only very slight distortion. It is liable to squeeze out in very hot

climates or under very heavy pressure. It should be laid by experienced men of the

specialist firms.

(3) Bituminous felts: This is a flexible material. It is easy to lay and is available in rolls of

normal wall width. It is laid on a layer of cement mortar. An overlap of 100 mm is

provided at the joints and full overlap is provided at all corners. The laps may be sealed

with bitumen, if necessary. The bitumen felt can accommodate slight movements. But it

is liable to squeeze out under heavy pressure and it offers little resistance to sliding. The

material is available in rolls and it should be carefully unrolled, especially in cold weather.


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(4) Metal sheets: The sheets of lead, copper and aluminium can be used as the

membranes of damp-proofing. The lead is a flexible material. The thickness of lead

sheets should be such that its weight is not less than 200 N/m2 .

The lead can be dressed to complex shapes without fracture and it possesses highresistance to sliding action. It is impervious to moisture and it does not squeeze out

under ordinary pressure. It resists ordinary atmospheric corrosion. The surfaces of lead

coming in contact with lime and cement are likely to be corroded and hence the metal

should be protected by a coating of bitumen or of bitumen paint of high consistency.

The copper is a flexible material. It possesses higher tensile strength than that of lead. Itis impervious to moisture and it does not squeeze out under ordinary pressure. It

possesses high resistance to sliding action. The external walls, especially of stones, are

likely to be stained when a damp-proof course of copper is adopted. The surfaces of

copper coming in contact with mortars are likely to be affected. But, for normal use, the

metal does not require any protective coating.

The aluminum sheets can also be used for damp-proofing. But they should be protected

with a layer of bitumen.

( ) C bi i f h d f l l d f il i d i h d b h l


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(5) Combination of sheets and felts: A lead foil is sandwiched between asphalt or

bituminous felt. This is known as the lead core and it is found to be economical, durable

and efficient.

(6) Stones: The two courses of sound and dense stones such as granites, slates, etc. laid

in cement mortar with vertical breaking joints can work as an effective damp-proofingcourse. The stones should extend for full width of the wall. Sometimes the stones can be

fixed, as in case of roof surfaces, on the exposed faces of the wall, etc.

(7) Bricks: The dense bricks, absorbing water less than 4.50 % of their weight, can be

used for damp-proofing at places where the damp is not excessive. The joints are kept

Open. Such bricks are widely used when a damp-proofing course is to be inserted in anexisting wall.

(8) Mortar: The mortar to be used for bedding layers can be prepared by mixing 1 part of

cement and 3 parts of sand by volume. A small quantity of lime is added to increase the

workability. For plastering work, the water-proof mortar can be prepared. It is prepared

by mixing 1 part of cement, 2 parts of sand and pulverized alum at the rate of 120 N perm3 of sand. In the water to be used, 0.75 N of soft soap is dissolved per litre of water and

this soap water is then added to the dry mix. The mortar thus prepared is used to plaster

the surfaces. Alternatively some patented water-proofing material such as Pudlo, Cido,

Dempro, etc. may be added to the cement mortar.


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(9) Cement concrete: A cement concrete layer in the proportion 1 :2:4 is generally

provided at the plinth level to work as a damp proofing course. The depth of cement

concrete layer varies from 40 mm to 150 mm. It stops the rise of water by capillary action

and it is found to be effective at places where the damp is not excessive.

(10) Plastic sheets: The material is made of black polythene having thickness of about

0.50 mm to 1 mm with usual width of wall and it is available in roll lengths of 30 m. This

treatment is relatively cheap but it is not permanent.


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GENERAL PRINCIPLES OF DAMP PROOFING

It should be remembered that when a damp-proof course is found to be ineffective, the

fault usually lies in its position or location rather than the defects in the material: The

general principles to be observed in case of all the damp-proofing methods are as

follows:

(1) The' damp-proofing course may be horizontal or vertical.

(2) The horizontal damp-proofing course should cover the full thickness of the wall

excluding rendering.

(3) At junctions and corners of a wall, the horizontal damp proofing course should be laidcontinuous.

(4) The mortar bed which is prepared to receive the horizontal damp-proofing course

should be even and levelled and free from projections so that the damp-proofing course

is not damaged. .

(5) The damp-proofing courses should be laid so as to make a continuous protection.


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GENERAL PRINCIPLES OF DAMP PROOFING

(6) The damp-proofing course should not be kept exposed on the wall surface. Otherwise

it is likely to be damaged by carpenters tile layers, etc. during the finishing work.

(7) When a horizontal damp-proofing course i.e. that of a floor is continued to a vertical

face, a cement concrete fillet of about 75 mm radius should be provided at the junction.


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METHODS OF DAMP PROOFING

There are various methods of damp-proofing and depending upon the nature of surface,

situation of the structure and amount of dampness, the proper method is selected.

Following are the methods or measures adopted to prevent entry of dampness:


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( 1) It the level of the ground floor is in level with the ground surface or just above it,

the damp-proofing course is provided as shown in fig. 6-1. The material should be

flexible and it should be stepped vertically through the wall to meet the damp-proofing

course of the solid floor.


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(2) If two ground floors at different levels are connected by an internal wall, the damp-

proofing course may be provided as shown in fig. 6-2. It should be noted that the damp-

proofing course on the internal wall is in level with the lower floor level.


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(3) In order to prevent the rising of moisture from the adjacent ground, the air drains

may be provided as shown in Fig. 6-3. An air drain is a narrow hollow space which is

constructed parallel to the external wall. The width of air drain is about 200 mm to 300

mm. The openings with gratings are provided at regular Intervals for the passage of air.

The wall forming the air drain rests on the foundation concrete of the main wall and is

carried about 150 mm above the ground level. The top of air drain is covered either by

an R.C.C Slab or a stone and necessary arrangements are provided for the inspection of

the air drain. The vertical and horizontal damp-proofing course are provided as shown in

fig. 6-3.


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(4) In case of basements, the damp-proofing course should be properly provided.

Otherwise the basements' become useless except for the storage of materials unaffected

by dampness. The usual practice is to provide asphalt tanking as shown in fig. 6-4.


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The important facts to be observed in case of asphalt tanking are as follows:

(i) The layer of asphalt should be continuous.

(ii) The vertical end of asphalt layer may end in a horizontal damp-proofing course, ifnecessary.

(iii) The vertical damp-proofing course should be taken above ground level for a

minimum distance of 150 mm.

(iv) The sequence of construction should be: inner wall, asphalt layer and protectivewall. The reverse sequence may also be adopted but with less success.

(v) The thickness of horizontal asphalt layer at basement floor level is 30 mm and it is

laid in three coats. The thickness of vertical asphalt layer is 20 mm and ,it is laid in three

coats.


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The treatment of asphalt tanking is adopted when the subsoil water table is not very

high. It is possible that the vertical D.P.C., if not properly protected, is likely to get

punctured by roots of trees or damaged by salts or acids in the soil. The outer one-half

rick protective wall is constructed to grant protection from such damage to the D.P.C. A

protective flooring of flat bricks is provided on the foundation concrete to protect theD.P.C. from damage during the construction of floor slab.

(5) The rain water gutters, in case of pitched roofs. may be constructed in cement

concrete and standard rain water fittings may be used. Further the gutters may be,

lined with bituminous materials or burnt clay products.

(6) The cement paints, when applied suitably, act as effective vertical damp-proofing

courses.

(7) For cheaply constructed buildings, the damp-proofing course may be provided in the

form of a layer of well burnt bricks which are dipped in hot tar and pitch.

(8) In case of a sloping ground, the damp-proofing course should be stepped such that it

remains at a minimum vertical distance of 150 mm above ground as shown in fig. 6-5.

The damp-proofing course may be of any suitable flexible material such as bituminous

felt, etc.


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(9) The construction of cavity walls considerably prevents the entry of damp inside the

building. Suitable damp-proofing courses may be provided on these walls.

(10) The provision of coping on a wall prevents considerably the entry of damp from the

top surface of the wall.

( 1 1) The good workmanship and use of materials of better quality on face of the walls

immensely help in preventing the entry of dampness inside the building.

(12) For providing damp-proof course in an existing wall, the following procedure is

adopted: (i) The level at which the damp-proof course is to be provided is carefully

decided after considering the ground level and the floor level. It is usually kept

about 150 mm above the ground level or floor level, whichever is higher.

(ii) A special saw made of steel blades is used to make a cut at the corner of the

wall.(iii) The loose bricks from the course just above the cut are carefully removed.

(iv) The damp-proof membrane, usually bituminous felt, is inserted immediately

after the cut is made.


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(v) The cycle of cutting the slot and inserting the damp proof membrane is repeated till

the entire length of wall is completed.

(vi) The removed bricks are re-laid and the surface is finished with plaster or pointing.

The above method of providing damp-proof course in an existing wall proves to be

speedy, easy and economical. After the layer is laid, the height of exposed wall between

the damp-proof layer and floor or ground level should be treated with suitable paint.


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WATER LEAKAGE

MEANING OF THE TERM

The term water leakage in the buildings means the coming out of water from

components like walls and floors of the buildings.

It is observed that in the building industry that 99% of water leakage problems areconcentrated on the terrace roofs and in the toilets. The water leakage in the buildings is

the most common problem particularly in all types of buildings such as residential flats ,

hospitals , offices , school buildings , etc.,


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REASONS AND PREVENTIVE MEASURES FOR

WATER LEAKAGE

It is necessary to prevent water leakage in the buildings so as to provide healthy and

happy environment. It will also avoid damages to household articles, costly painting and

short circuiting of electrical Wiring. The defects which cause water leakages in the

buildings can be grouped in the following three categories:

( 1) Defects due to poor maintenance

(2) Defects in construction

(3) Defects in design.


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WATER LEAKAGE

(1) DEFECTS DUE TO POOR MAINTENANCE: The neglected maintenance along with

weathering and aging leads to the water leakage in the existing buildings. The flowing

water is dynamic and rushes through valves, traps, washers, taps and cocks situated at

several places in the building. These things are subjected to constant wear and tear.

They therefore require periodical maintenance. As such, non-repairing attitude proves

detrimental to the safety of the structure. Following are the measures to be taken to

minimize water leakage due to poor maintenance:

(i) Filling of joints: The joints in the drainage system should be filled with rich cement

mortar. Due to aging, the strength of cement mortar deteriorates resulting in leakages

through the cracked joints. The remedy lies in filling such joints, initially with epoxymortar or at least at a later stage while repairing the same.

(ii) Improper use of toilets: It is necessary to educate the public for properly using the

toilet system. For instance, in the drainage system of public hospitals, it is observed that

the patients and their near relatives misuse the toilet systems by throwing bandages,

cottonwaste, injection bottles, etc. It ultimately leads to the choking of the drainage system.


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WATER LEAKAGE

(iii) Joints in floor of toilets: The joints in tiles of bath and water closet are filled with

white cement. These joints get loose after continuous use and require periodical

maintenance and sealing with white cement.

(iv) Replacement of taps: The leaking water taps lead to colossal waste of filtered water

and avoidable water leakages in the building. It is therefore necessary to provide good

quality bibcocks initially and go on replacing washers periodically, whether required or

not, as a preventive maintenance measure.


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WATER LEAKAGE

(2) DEFECTS IN CONSTRUCTION: The defects at the construction stage include

honeycombing in concrete, use of defective materials, bad workmanship, etc. The remedial

measures to avoid water leakage due to such defects are as follows:

(i) Defective concrete: The provision of well designed compacted dense concrete with

proper curing can solve number of leakage problems in a building.

(ii) Door frame joint near toilet: The joint between door frame and flooring of bath and

water closet should be made leak proof :y applying epoxy mortar or cement slurry.

(iii) Plumbing: The joints in the plumbing of w.c. seats and nahni traps should be filled with

rich cement mortar and cured for seven days. If curing is not properly done, the rich

cement mortar gets cracked and leads to leakage. If possible, one piece P trap should be

used to reduce one joint in the drainage system and it should be fixed before water-

proofing of the w.c. block is started.

(iv) Push cocks: The concussive or violently shaking type push cocks fitted for the flushingof w.c. pans lead to vibration and consequently the joints in the drainage system get

dislodged and lose watertightness. It is therefore desirable to provide wheel valves or other

suitable valves which do not cause vibrations.


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WATER LEAKAGE

(v) Rain water spouts: The improper fixing of the rain water spouts in the roof slabs leads

to leakage. For instance, if the rain water spout is fixed at higher level, the water stagnates'

and the leakage starts.

(vi) Sill to terrace door: If the terrace door is not provided with, sill, the water will find

entry in the staircase through the door.

(vii) Water-proofing of terrace: To prevent leakage from the roof, the terrace should be

given proper water-proofing treatment. The joint between terrace slab and parapet wall

should be properly finished to avoid leakages.


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WATER LEAKAGE

(3) DEFECTS IN DESIGN: The defects in planning and design can be avoided in the pre-

construction stage by entrusting the work to experienced and well trained architect and

engineer. Some of the measures to avoid water leakage due to faulty planning are as

follows:

(i) Design of floor slab: It should be seen that the design of floor slab and centering

should be such that the local stagnation of water does not occur.

(ii) Design of rain water spouts: The rain water spouts of less; than 100 mm diameter

should not be used. It is also desirable to provide one spout for every 40 m2 area of

terrace.

(iii) Fixing of nahni traps: The nahni traps are required for toilets, kitchen sinks,

washbasins, etc. The niche or pocket of clear size about 300 mm x 300 mm x 150 mm

should be provided to accommodate the nahni traps and their locations should be

clearly shown in the plan.


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WATER LEAKAGE

(iv) Location of sanitary block: For public buildings like schools, hospitals, hostels,

colleges, commercial centres, theatres, etc., it is desirable to detach the sanitary block

in the planning stage only. Such a criteria will help in keeping the building usable even if

the sanitary block suffers from leakage. It will also avoid the spreading of dampness in

the rest of the building. The entire sanitary block should be sunk to a sufficient depth to

accommodate the items of sanitation. As a matter of fact, the engineer should supply a

detailed plumbing drawing of the sanitary block showing the slope of pipes, slope of

gutters carrying urinal effluent, washbasin effluent, general slope of the toilet flooring,

etc.

(v) Relief valves: It is necessary to provide break pressure relief valves at suitable

vertical distance in multistoried buildings to prevent seepage of water through the

plumbing system.

(vi) Slope of terrace slab: The minimum slope of 1 in 100 to 1 in 60 should be clearly

shown on the terrace plan. It will help in adjusting the slope in centering with uniform

thickness of roof slab. The suitable provision of terrace slope would result in smoothdisposal of rainwater.


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WATER LEAKAGE

(vii) Water tanks: For overhead R.C.C. water storage tanks, it should be seen that the

permissible limits of stresses relating to resistance to cracking are not exceeded. The

detailed bar bending schedule should be supplied by the designer. The bottom slab of

overhead water tank should be placed one metre above the roof slab. It will facilitate

proper centering during construction and also for locating and repairing the leakages

after construction.


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Waterproofing 001

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