Water Proofing • Waterproofing defined • Importance • Methods ( Conventional )• Methods ( Modern) • Waterproofing of Basements • Terraces • Bathrooms & W C • Chemicals used for waterproofing treatment • Role of Consultants

Background • The most widely and effectively used construction

material in world today is concrete, beside steel and wood.

• Making good concrete in the laboratory is not at all difficult.

• But at the site, it is possible to make concrete waterproof.

• Ideally, the concrete is supposed to be watertight, if it is done in a manner in which all the parameters are followed strictly.

• But, in practice, concrete is quite porous

Waterproofing Meaning

• “Any system or material (s), which helps in preventing ingress of water into structures can be broadly termed as waterproofing.

• Waterproofing is often misused and misunderstood term

• Waterproofing is defined as treatment of surface or structure to prevent the passage of water under the hydrostatic pressure

IMPORTANCE OF WATERPROOFING• If we refer back to the definition of waterproofing as an impervious barrier

designed to prevent water entering or escaping from building structures. Problems caused by water • Rotting of timber structures and finishes such as floor joints, beams, floors,

studs, skirting, architraves and frames.• Corrosion of metals such as steel reinforcement in concrete, steel beams,

lintels, metal door frames etc.• Swelling of plasterboards and the subsequent debonding of ceramic tiles.• Electrical hazards causing the possible short circuit of lighting and power

points.• The blistering of paint.• Unsightly deterioration of the building facade.• Health problems due to dampness, which may lead to respiratory

problems.• Rotting carpet.

Source & Causes of leakages Sources of leakages• Subsoil water rising by capillary action.• Cracks in external plaster• Vegetation growth• Separation gaps between partition wall and beams and the

columns.• From expansion joints

Causes of leakages • Defective structural design• Use of poor quality construction material• Porous structures• Improper methodology of construction• Improper slopes on top surfaces.

Review of Conventional Waterproofing Systems• Brick Bat Coba system or Lime Terracing• Bituminous Treatment/Systems • Metallic Sheet Wrapping• Poly-urethane based Water- proofing

treatment• Epoxy Based Waterproofing Treatment• Box Type Waterproofing System

Brick Bat Coba system or Lime Terracing

• This system was developed during the initial stages of flat roof construction with lime mortar & burnt clay brick aggregate

• This system involved laying of lightweight mortar on the roof and spreading it to give gentle slopes for draining away the rainwater immediately. The mortar consisted of lightweight brick pieces as aggregates and ground brick with lime as binding matrix

Brick Bat Coba system or Lime Terracing• Procedure • All existing treatment, coatings on roof slab top is to be removed

and surface cleaned by hard wire brush and washed with water. • The surface should be free from any oil, grease, dust etc. Remedial

measured by provided to all structural cracks. • Expansions joints should be treated as per standard practice• All non-structural cracks more than 0.5 mm wide and construction

joints if any, should be cut in “V” shape, cleaned with wire brush and washed, the cracks are then filled by polymer modified cement or mortar using acrylic polymer, with addition cement slurry mix is spread upon cleaned SSD roof surface. Over this 15 mm thick cement, sand mortar, 1:4 admixed, with water proofer is laid.

• On the above green mortar, a layer of brick bats, soaked over night in water, is laid, having an average thickness of about 110 mm, about 70 mm near rain water pipe and 150 mm at ridge.

Brick Bat Coba system or Lime Terracing

• Limitations :This system has following limitations• There is a possibility of improper compaction• Chances of crack development on the top

surface.• Brickbat coba is a source of water retention

and absorption.• If slab has cracks the retained water may leak.• The absorbed water may allow penetration to

the slab level.

Bituminous Systems • Bitumen is more commonly used in the form of felt or

flexible membrane formed by sandwiching jute fabric or fibre glass/polypropylene mats with chemically modified bitumen.

• These membranes are laid on the roofing system over a bitumen primer.

• There are two types of membranes one is cold applied and the other is hot applied which means one needs to heat the edges of the felt ,so that they melt and stick to the second layer in the overlap area.

• On the RCC flat roofs, the bitumen felts have not been successful because of the unacceptable black appearance and inaccessibility of the terrace for other social uses

Bituminous Systems • There are certain essential pre-requisites for any bitumen based water

proofing system to be successful. • The surface to be treated should be smooth, having proper slope. • There should be no depression or cracks • The surface should be dry. • Any structural defaults in the roof or the parapet wall should be

attended to before starting the treatment. • Detailed steps in laying of the bitumen based surface barrier systems

will i) Make surface smooth, even and dry, remove local depressions and loose dirt. ii) Paint the dried surface with bituminous primer and allow it to cure. iii) Apply foundation coat of bitumen. iv) Lay surface barrier membrane i.e. bitumen felt. v) Apply on coat of bitumen and finish with grit or coarse sand.

Bituminous Systems • Technically, it is not preferred because bitumen layer or felt on the

terrace not only makes it watertight but also airtight. Concrete has the breathing property.

• It takes water/moisture and breathes out water vapour.• Hindrance of this breathing property of concrete develops pore

pressure which causes blisters in the felt. • After a few seasons, the blisters multiply and eventually delaminate the

felt from the concrete surface.• Hindrance of breathing property of concrete, makes the concrete weak.• But on the asbestos cement sheets and zinc sheets in factory roofs, this

bitumen felt is the only dependable waterproofing system. Hence most of the factory roofs in India adopt this waterproofing system Bitumen is still the product of first choice where it is commonly recommended, in areas such as industrial roof waterproofing, basement water- proofing, and damp-proof course.

• Moreover, bitumen is the most economical product presently available for waterproofing

Polyurethane Based Waterproofing Treatment• Polyurethane consists of two liquid components one is called the

Base component and the other is called reactor or curing agent• Base is a polyol and the reactor is an isocyanide.• The combination of these two ingredients results in a formation

liquid applied rigid membrane or a foam depending upon the selection

• In waterproofing, this rigid liquid membrane was tried with fibre glass reinforcing mats. The systems failed because coefficients of thermal expansion of concrete and rigid PU membrane being different lateral movement or creep occurred with the passage on one working climatic cycle. When exposed to ultra violet rays or direct sunlight, most polyurethane rigid membranes became brittle and crumbled. Apart from this, the application of polyurethane coating needed very rigorous surface preparation.

• Surface Preparation : needed, neutralization , alkalinity.

Epoxy Based Water- proofing System• Like polyurethane epoxy is also a two-component system having

a base resin and a reactor or curing agent.• Base resin is obtained by dissolving Bis-phenol ‘A’ flakes in

epichlorohydrin. This base is available in various viscosity ranges to suit different application conditions.

• The curing agent is an amine/polyamine aliphatic or aromatic or an amine-adduct for general applications and polyamide or an amino-amide for coating purposes.

• After mixing base and reactor components, the resultant viscous liquid or paste if some fillers are added to it can be brush applied like a paint or trowel applied like a mortar.

Box Type Waterproofing• This type of waterproofing system is used only for basement

waterproofing or structures below the ground level from outside to prevent leakages of subsoil water into the basement. In this method, limestone slabs (Shahabad Stones) are first laid in the excavated pit over blinding concrete in a staggered joint fashion to avoid the continuity of the mortar joints.

• The joints are effectively filled with rich cement, sand mortar admixed with integral waterproofing compound and cured. Over this, the raft is laid and shear/brick walls constructed.

• The limestone slabs are erected around the walls in a similar fashion leaving a gap of one to two inches between the external surface of the wall and the inner face of the stone surface.

• The joints again effectively sealed with rich admixed mortar and the same mortar is filled in the gap between the wall and the stones. This stonework is continued up to ground level.

Box Type Waterproofing• In this system, the raft and the sidewalls are protected from

direct exposure to sub soil water This system works on two principles of common sense.

• First the area exposed to subsoil water is only the area of the joint where as the whole stone is impervious to water, hence only a fraction of area, that is, that of the joint is exposed to subsoil water when the joint itself is filled with rich and quality mortar.

• Secondly, the path of water to reach the raft or the sidewall is elongated. This elongated path is through quality mortar. This system seeks to delay the occurrence of leakages in the basements. A lot of building structures are waterproofed using this system. A few notable successes are to its credit especially in five star hotels and of-course there are a few failures as well.

Box Type Waterproofing• For basements, Swimming Pools and under-ground ducts such

as lift-pits, the waterproofing has to withstand the water pressure in addition to it’s basic stress. Shahabad Box Type treatment method of waterproofing is very commonly used in India.

• A base-coat in cement mortar 1:4 mixed with waterproofing compound is laid over the Raft PCC and above this rough Shahabad tiles of size 2’-0” X 2’-0” or 2’-0” X 3’-0” are fixed with minimum thickness of joints.

• Joints are staggered. Thickness of the Shahabad tile should be between 32mm to 40mm (1.25”-1.5”). After fixing the tiles, the joints are sealed with C.M. 1:3 and 15mm metal is pressed in the joints for enhanced strength and less shrinkage.

• Over this, a joint less layer of C.M. 1:3 with waterproofing compound approx. 25mm thick is applied and cured for 7 days. This layer provides a smooth layer for the raft and also protects the Shahabad tiles from getting damaged by steel bars laying and labour movement.

Box Type Waterproofing• Over this plastered base, raft is cast and RCC retaining

walls are erected. Shahabad tiles are fixed to the vertical retaining walls from outside. Cement paste is applied on all four corners of a Shahabad tile and it is pressed firmly on the RCC wall in line and level. At a time only a height of 1m is fixed.

• Total height above the ground level is taken as 1’-6”. Joints are then sealed in C.M. 1:2 (Pointing). The Shahabad dado is then grouted using cement slurry with waterproofing compound and cured for 7 days.

• After curing, a jointless waterproofing plaster coat is applied and cured. Thickness of this treatment is around 65mm to 75mm.

• This entire process forms a box around the structure and does not allow any water to seep through or leak from the basement.

Box Type Waterproofing

Box Type Waterproofing ( Basement waterprofing) Limitations/Disadvantages • Use of Shahabad tiles, joints should be grouted properly or else the

leakage would be from the joints.• It is a labour intensive work for which it requires more time for

installation• Waterproofing membrane such as • Bituminous, polymer modified bituminous of APP (Atactic Poly

Propylene) • SBS (Styrene Butadine Styrene), PVC, HDPE can be used for basements• Since APP membrane is torch applied, it requires more skilled labour

and a protective screed to avoid any damages to the membrane.• SBS is cold applied by simply sticking with a paste. But it is not suitable

for high water table. It also requires a screed for protection• HDPE is the best material for waterproofing in high water table.

Modern Techniques in Waterproofing• Modern technique aims to understand the functional

behavior of the structure, understand the properties of the available materials to arrive at a system, which is best suited for the structure and incorporate the design stage itself.

• A single product or technique is not usually enough, involvement of various bodies and techniques in coordination is essential for making structures waterproof.

• For success of any system, the building structure should have sufficient and efficient control joints if the slabs dimensions are more than twenty meter in any direction.

• Crystalline Waterproofing System• Flexible membrane waterproofing system

Crystalline Waterproofing System• The method of treatment involves saturating with water the

surface to be treated. • Then mixing two and half volume of the powder with one

volume of water to form neat consistency hot slurry.• This slurry is brush applied on the saturated surface. The

active ingredients in the slurry pass through the water bearing capillaries and react with calcium oxide present in the concrete to form insoluble crystals, which effectively block the capillaries.

• Further the chemical ingredients of the product remain in concrete to reactivate the process of crystallisation and when a new capillary is developed.

• This system of waterproofing, the water retaining structures is practiced in most of the developed countries

Crystalline Waterproofing System• The waterproofing effect is based on two simple reactions, one chemical

and one physical. Concrete is chemical in nature. When a cement particle hydrates, the reaction between water and the cement causes the concrete to become a hard, solid mass.

• The reaction also generates chemical by-products such as calcium hydroxide, sulfates and carbonates of sodium potassium and calcium as well as un-hydrated or partially hydrated cement particles all of which reside in the capillary tracts of the concrete.

• Crystalline waterproofing introduces another set of chemicals to the concrete. When these two chemical groups, the by-products of cement hydration and the crystalline chemicals, are brought together in the presence of moisture, a chemical reaction occurs. The end product of this reaction is a non-soluble crystalline formation.

• This crystalline formation can only occur where moisture is present, thus it will only form in the pores, capillary tracts, and shrinkage cracks of the concrete. Wherever water goes, crystalline waterproofing will form filling the pores, voids and cracks.

Crystalline Waterproofing System• Cracks if any should be cut into ‘V’ shaped grooves one inch wide and

proper size width & depth Cut honey combed areas back to sound concrete.

• Repair these areas first by priming with crystalline waterproofing slurry and then by filling them with crystalline modified mortar produced by mixing crystalline waterproofing powder OPC and zone II sand in the proportion of 1:1:4 and water enough to produce a stiff consistence paste. Allow the repair mortar to dry.

• Thoroughly sprinkle water on the area to be treated till the surface becomes saturated. Some recommend overnight ponding for effective results

• Prepare crystalline waterproofing slurry by mixing the powder and water in the proportion of two and half volume of powder to one volume of water to form a hot slurry. Brush apply this slurry on the water saturated surface in two coats.

• When the second coat is still wet plaster the surface with 1 : 4 cement sand mortar admixed with an integral waterproofing compound and cure properly.

Flexible Membrane Waterproofing System• The main product used in this system, comprises two

components one liquid and the other is a powder packed roughly in the proportion of 1:4 by weight. The liquid component is an acrylic emulsion and the powder component is a polymer-modified cement with film forming chemicals and fillers

• When these two ingredients namely the pre-weighed powder and the liquid are mixed together an uniform slurry results.

• This slurry is brush applied on the roof surface, which upon drying forms a flexible film. Since there is cement in this product, its compatibility with concrete is excellent.

• The film further allows the breathing of the concrete without any hindrance hence there is no problem of its de-lamination from the concrete surface.

• This film being flexible takes care of the deflections in the slab and the movements caused because of primary or secondary settlements, movements due to wind loads and temperature stresses developed in the concrete

Flexible Membrane Waterproofing System• Cracks if any should be cut into ‘V’ shaped grooves of

a proper size in depth. Cut honey combed areas back to sound concrete.

• Repair these areas with a stiff paste of fibre reinforced polymer repair mortar generally sold in the name of crack fill.

• Mix the powder and the liquid components of the product to form an uniform slurry and brush apply this slurry on the surface to be waterproofed.

• When the waterproofing coating is still tacky apply 1 : 4 cement sand screed and cure normally

Membrane Selection

When selecting a membrane it is essential to consider a number of relevant factors including:

• Whether the membrane will be exposed to weather or protected by subsequently applied floor finishes

• The type of floor finishes and adhesives that will be applied• The exposure conditions of the membrane (e.g. coastal or other aggressive

environments)• Anticipated substrate movement • Ambient weather conditions (some membranes must be applied within

specific temperature and humidity ranges)• The durability of the membrane• Ongoing maintenance requirements• Availability of specialist contractors to apply certain systems• Ease of application• Re -coating time and time before subsequent finishes can be applied• The moisture content of the substrate.

The Latest Trends in Waterproofing

The following methods can be used to achieve this:1. Use of Water tight concrete2. Liquid Applied Membranes

Use of Watertight ConcreteBlocking pores/capillaries in the concrete can be done using

the following methods:1. Using high performance PCE polymers2. Use of materials like Silica-fume or Aluminosilicate slurries

in concrete3. Use of highly specialized latest generation Integral

waterproofing compounds that work on process of Dynamic SynCrystallization® (DySC) technology

• Using high performance PCE( Polycarboxylate Ether ) polymers

The Latest Trends in Waterproofing

• It is well known that using PCE polymers, give excellent water reduction as compared to normal plasticizers.

• This helps to reduce the w/c ratios and cement contents, even in normal concretes. Lower the w/c ratio, lower are the number of capillaries in concrete.

• PCE based admixtures do not have the side effects of retardation often seen with normal retarding super-plasticizers. This is beneficial as workability time of concrete can be controlled but the hydration and setting of concrete will proceed unhindered.

• This ensures that any subsequent vibration to concrete after initial set will not open up capillaries, as is the case if concrete is retarded for a very long period of time, thereby rendering concrete relatively waterproof

The Latest Trends in Waterproofing

• Use of materials like Silica-fume or Aluminosilicate slurries in concrete

• Condensed Silica Fume or Aluminosilicates are extremely fine materials that function both as microfillers as well as pozzolanic materials that hydrate in the presence of the Calcium Hydroxide in Concrete.

• The combined effect of these materials as microfillers and hydrating materials help close capillaries in concrete, thereby rendering it waterproof

The Latest Trends in Waterproofing

Role of Waterproofing • The membrane must be impermeable to prevent the

passage of water.• Flexibility - membranes need to accommodate any

normal movement that may occur in building structures.

• The membrane must be durable, it must be able to retain it's integrity over a long period of time.

• The membrane must lend itself to design details in a building. It must be suitable for each specific application. The membrane is useless if it cannot be applied where needed because of structural details.

• The membrane must be able to breathe permitting the escape of moisture vapours from building interior and substrates.

Role of Waterproofing • The membrane must be compatible with adhesives to

ensure long term adhesion where tiles are directly fixed over the membrane.

• User friendly, the membrane must be easy to apply, relatively lightweight, non hazardous, and environmentally safe.

• In exposed areas such as rooftops, the membrane should require little maintenance, and in the event of damage must be easily repairable.

• It should provide a continuous film, without areas of weakness such as overlaps, which could prove to be a potential source of water entry.

• The membrane must be suitable to withstand environmental and climatic conditions.

Precautions to be taken by the Client and Consultant• Selection of an effective waterproofing system for a

structure taking all the performance criteria of the structure into account and also taking into the consideration, the performance of the materials in the system is of prime importance for any success of the waterproofing job.

• Waterproofing jobs awarded to waterproofing contractors purely on economical price considerations often fail.

• It is always advisable to involve the architect or the structural engineer in selection of a system and requisite performance guarantees should be taken from the contractors.

Precautions to be taken by the Client and Consultant

• It is better to avoid bargaining for the job value out of contractor’s margins. This could result in stretching the product beyond the coverage specified by the manufacturer or substitution of cheaper material in the system to cover the cost.

• Always supervise the job and the incoming materials for the intact tamperproof seals and quantities.

• Use the services of an engineer or architect in selection of materials. That too only procured from well know manufacturing firm.

Failure of Waterproofing Systems• Application of a waterproofing product in non-

specified areas, such as using a crystalline waterproofing system in waterproofing the terrace or using a flexible membrane system in the water tank results in failures even though the products themselves may be genuine.

• Stretching the coverage of the products beyond the specified limits by the manufacturer results in inefficiency of the product and hence a failure.

LIST OF SOME RELEVANT INDIAN STANDARD