City of Toronto’s Basement Flooding Protection Subsidy Program
January 19, 2017

Waterproofing: some Do’s and some Don’ts

Through the years, man has progressed from caves to the multi-storied structured of today’s industrial age. The construction industry plays a very important and responsible part in this rapid industrial development and expansion. Structures such as basements, tunnels, subways, reservoirs, laboratories, research, centres, commercial buildings,  godowns,  workshops silos etc are required to be constructed to keep pace with development along with large housing complexes and ancillary buildings like hospitals, schools, markets, welfare centres etc.

Needless to say that waterproofing is one of the most important items in the construction of these structures. In fact without waterproofing even the concrete structures would be rendered useless.
Waterproofing today has become the need of the day. It is not merely  avoiding the inconvenience of dripping ceilings, or the peeling of  paint on the walls, efflorescence, etc, for which Waterproofing is  recommended. Leakages cause damage to the structure itself, inhibiting  corrosion, leading to ultimate structure failure. Hence, Waterproofing  must not be taken lightly.

It is important to elaborate on the necessity of waterproofing and how leakages and dampness have adverse effect on the life of structures. They cause deterioration of the structure due to disintegration of material, corrosion in reinforcement, decay of wood. Leakage also causes short circuiting which in  turn may lead to fire. Besides damaging painting, furniture, false ceilings, etc, it also encourages the formation of fungus, inconvenience such as failure of lifts, cold storages and air-conditioning are only some of the many caused by leakage. Dampness is also a hazard to health as it provides an ideal breeding ground for germs and bacteria, when combined with warmth and darkness and diseases  like TB, Asthama etc, spread fast.

Sources of leakage

External walls through cracks and junctions of walls with RCC members like beams, columns etc.

  •     Canopy, chajjas and Balcony projections
  •     Terrace slab
  •     Sanitary blocks flooring and dado
  •     Underground seepage in basements, ducts, tunnels subways
  •     Expansion joints
  •     Overhead and underground tanks
  •     In life machine rooms and in life-pits
  •     Plumbing joints and concealed pipes

What causes leakage

The used of sub standard material is one of the major causes of leakage. Bad workmanship is another   Sometimes due attention is not paid to vital parts during construction, hence resulting in leakage. Defective planning and poor maintenance are also common causes.

Various methods of waterproofing

  •     Surface treatment
  •     Integral treatment

Interposing a layer or membranes of water–repellent material

Surface Treatment :  By this method, the small pores in the exposed surface are blinded by a coat or thin film of a water-repellent such as solution of silicate of soda or potash, coal tar, bitumen etc. However this only fills up small pores and unnoticeable hair cracks, thus providing only temporary relief. There are waterproofing paints, and solutions which are available in the market and used for such temporary treatments. Surface Treatments are normally done after the concreting and cementing  work is completed, or even after the completion of the building. The  object is to treat the surface subsequently, overcoming the defects,  and making the surface waterproof.

Surface treatments gain further importance because of the fact that  concrete has a tendency to develop cracks, due to the expansion and  contraction of the surface on account of temperature fluctuations  or due to shrinkage, or the concrete is not impermeable due to improper  workman ship or materials.

Whatever be the reasons, once the concrete or plaster is leaking only  surface treatments can make it waterproof, without breaking and redoing  the substrate. Surface treatments are also provided as precautionary  measure to overcome the likely problems in the concrete.

Surface Treatments can be broadly classified in the following categories  :

Tarfelts / Polymer Sheets : This type of treatment involves  laying of factory made sheets or felts, which are available in specific  width rolls. This is laid on the surface over a layer of molten tar,  or similar adhesive, and over lapped at joints. The entire surface  is thus covered with the sheets. Joints are a vulnerable part of this  treatment apart from the weak bond given by the bitumen. Water which  may enter from the joints / punctures, etc may subsequently cause  blistering and puncture of the felts. Use of surface is also restrictive.  Further, bitumen, which is a petroleum bi-product, is devoid of necessary  oils and plasticisers, reducing its effectiveness. Weathering, UV  radiation, temperature changes also cause deterioration and brittleness  of the tarfelt and causes cracking.

Capilliary Crystalisation :  This process involves the application  of liquid chemicals on the surface of the concrete. These chemicals  enter the pores of the concrete / plaster and thereafter crystalise,  thus reducing and sealing the pores. One major limitation is that  the concrete/ plaster is prone to further damage, cracks developing,  wear and tear and further leakage which may develop.

Protective Surface Coatings : Waterproofing by use of surface  coatings are the latest type of treatment gaining immense popularity,  due to its effectiveness and ease of application, apart from economy.  However, proper care in selecting the adequate treatment and proper  application would play an important part in effective Waterproofing.  Protective coatings are generally based on Epoxy, Bitumen,  Rubberised,  Silicons, Polyurethanes, etc.

Epoxy : Coatings have very good bonding properties with the  substrate, and form into an impermeable membrane over the entire surface.  Though it has good abrasion resistance properties, and also resistance  to mild acids and chemicals, Epoxies being rigid in nature, cannot  withstand the expansion and contraction of the surface and develop  cracks. Also due to its weak resistance to UV radiation, Epoxies are  not recommended for external applications.

Bitumen : based coatings are normally modified with polymers,  oilds and plastisizers, and can be considered as an economical but  very temporary method of Waterproofing. The additives only give limited  resistance to heat, UV etc. and the treatment tends to become brittle  and cracks in time.

Rubberised : compounds have good elasticity and bond with the  surface and can easily expand and contract without cracking. However  these compounds deteriorate fast with the effects of UV and ozone,  causing loss of the very properties, thus rendering the system ineffective.

Silicon : based emulsion and coatings are colourless coatings  which do not change the appearance of the surface, while making the  surface water repellent. Its biggest drawback is its lack of crack  bridging capacity. Silicons are thus not suitable for flat terraces  or horizontal surfaces. At the most it may be used on vertical walls  for repellancy.

Polyurethane : Coatings are supposed to be fat most effective  surface coatings available. It has good adhesion to the substrate,  forms into a monolithic membrane, totally impervious to water and  elastic to withstand the expansion and contraction of the surface.  UV resistance, resistance to mild acids, salts etc. help Polyurethane  coatings to withstand for long periods.

Importance of Proper Application

For effective Waterproofing treatment by Surface Coatings,  it is essential  that the application is done with proper care. The substrate should  be clean and dry. All adage formations, loose particulates, dust etc  should be wire brushed and removed before the treatment is applied.  Cracks and joints need to be properly detailed as per the specifications  to avoid their reopening. Application plays as important a part in  the success of any Waterproofing treatment, as the material itself.

Choice of Waterproofing treatment should be need based, and properties  of the product to be selected should be studied in conjunction with  the individual requirements.

Integral Treatment

In treatment an inert material like chalk, talc or other waterproofing compound is mixed with concrete to fill up the pores. This method is also not completely effective and hence cannot be depended upon.
In the third type of treatment, a layer is put on the floor roof and walls. Tarfelt and asphalt are common examples although they are not permanent solutions. Cement based water-proofings fits into this third category and provides permanent relief, and thus scores over all other methods.

Cement based waterproofing treatment :  Cement based waterproofing has special advantages over all other conventional methods. These treatment are not mere pore fillers. They integrate the materials without the use of any extenders and end the occurrence of pores and capillary channels in the structure and make it impermeable permanently.

Cement based waterproofing materials are able to stand expansion and contraction of the structure under any pressure of weather condition without cracking. They are based on cement and natural mineral waterproofing compound.

These treatments are temperate and cool and act as heat insulation. They are smooth and jointless. They withstand normal wear and tear and disintegration. While providing effective waterproofing cement based treatment protect the structure from cracks and add to its strength the enhancing the life of the structure. There is no maintenance cost involved which results in ultimate economy. These treatments are also guaranteed for a very long period much longer than any other methods, on account of their long life span.

Permanent cement based waterproofing treatment is best administered while the construction is in progress to obtain the optimum results. In the case of existing structures, the existing treatment has to be removed to expose the  bare surface, before carrying out cement based waterproofing treatment.

A brief description of the specifications will impart a better understanding as to how these treatments are carried out.

Terraces, Chajjas, Canopies, Parapets

The waterproof brickbat coba (grey cement plaster) is directly  laid over the RCC slab, providing necessary gradient for easy flow-away of rain water. This is covered with waterproof plaster finished smooth. This treatment is carried along the inner side of parapet and /or other adjoining walls upto a height of one foot in the shape of a round vata. The average thickness of this treatment is about 100mm with a minimum thickness at water outlets being 75mm. The treated surface is hard and tough and suitable for all normal domestic activities.

Basements, Water-tanks and other underground structures

In the case of existing structures, the treatment is given from inside. Injections of approved waterproofing compound and cement solution are given into the structure. Thereafter a water proof layer, finished smooth in cement, is laid on the floor and continued on the side and partition walls. The average thickness of this treatment is about 65mm on the floor and 25mm on the walls.
In case of new basements and other underground structures, the Box Type treatment is given, It starts over the levelling course of plain cement concrete (RCC) of adequate thickness and waterproof layer is provided over the PCC. After the surface is superimposed with RCC raft slab and after the side walls are complete, the waterproof layer is continued along the outer surface of walls upto 300 mm above the ground level. The average thickness of this treatment is about 75 mm on the floor and 32 mm on the walls.

By this method, the entire structure is encased by the treatment and becomes like a seal-tight box.

Toilet Blocks:  The treatment starts directly over the RCC slab with laying over the water proof brickbat coba to provide the necessary gradient for the easy flowaway of water. The walls are covered with waterproof plaster upto a height of one meter with surface finished suitably  to receive tiles.
Cement based waterproofing treatments should be carried out by  specialized agencies. It is also necessary that the work be given to a reputed firm to ensure quality and proper service. Although this involves a higher cost initially, it works out to be economical in the long run.

Epoxies and Resins

Waterproofing as a term is synonymous with the civil and building industry. Perhaps it is a misnomer as it is virtually impossible to exclude all moisture or water from ingressing into the structure . At least it is an operation to exclude the maximum amount of water from concrete surfaces and structures.

Concrete itself has good resistance against moisture penetration provided good engineering practices from design, workmanship and cure schedules are adopted. Nevertheless concrete requires further protection against water

  •     Alternate wetting and drying results in expansion and contraction of concrete, inducing stresses leading to cracks and seepage of water
  •     Different coefficients of thermal expansion of various constituents in RCC inducing stresses which again leads to cracks and seepage of water
  •     Corrosive conditions attack the concrete and reinforcements gradually causing fissures in the structure leading ingress of water
  •     Abuse of concrete surface through excessive wear and tear or sudden impacts that weaken those areas leading to soft spots which become susceptible areas to water seepage
  •     Inadequate knowledge of site conditions that have not been accommodated for during design or execution which lead to faults in the structures

These are a few of the possible causes that renders buildings and structures prone to water seepage and endless consequent problems. Epoxy resins are amongst the foremost building materials available, judicious use of which can often eliminate despair. To be completely successful in water proofing a structure, the root cause for the problems have to be identified, In building maintenance and repair user of epoxy resins are forewarned that this sophisticated building material can be used to overcome the manifestations of the problems such as cracks or potholes. TI eliminate the problems from recurring, designers will have to search for those causes that developed the fault.

Epoxy resins can be used not only for building maintenance but also in the construction of structures. Epoxy resins and Systems are characterized by the following outstanding properties;

  •     Mechanical properties are comparable to and often exceeds that of concrete
  •     Very short curing times, It takes just about 8 hours to achieve close to fully cured strength
  •     Low shrinkage during curing.
  •     Is exceedingly tough and resistant to abrasion against prolonged exposure to wear and tear
  •     It can be handled by conventional building techniques
  •     They are so versatile that epoxy resins can be injected as a liquid into cracks poured floor surfaces painted with a brush as a surface coat, or used as a mortar with coarse aggregates. Whatever the process they finally set into a hard infusible mass
  •     Outstanding bonding abilities to almost any substrate with exceptionally high strength. Today it is even possible to use epoxy resins for building or for maintenance in underwater conditions with excellent results compared to any other presently known technique

Epoxy resins are used with at least one other component called hardeners. As such epoxy resins are two component systems or sometimes more. The surface for treatment has to be prepared as per the instructions. Depending on the nature of the application, epoxy resins and Systems should be mixed in the recommended ratios and applied within a specified period after mixing.

After applying the epoxy system, the treated area should be simply exposed to the ambient conditions. Users will gradually become familiar with Surface preparation, method of application and ratios to be used  after initial guidance from manufacturers of epoxy resins. Some of the typical water proofing applications that designers and architects will encounter are;

  •     For protecting overhead water tanks and underground storage tanks from leaks and against corrosion
  •     Prevention of water seepage from swimming pools, fountains, ponds etc where large bodies of water are contained in reservoirs
  •     Flooring and ceiling leaks in bathroom and toilets
  •     For jointing of weather proofing tiles commonly used in the terraces of buildings through which rain water seeps
  •     As a putty for joining tiles in bathrooms, kitchens, hospitals wards and operating theatres preventing grooves which become the breeding grounds for harmful bacteria. Moisture does not get trapped in these crevices as they  otherwise normally do creating conducive conditions for their propogation. In fact epoxy resins should be used wherever sterile conditions are required both on the walls and floors
  •     Underground basement and storage bins which are to be protected from water seepage
  •     Foundations and underground structures that are to be rapidly cured and be fully protected against corrosion. This is especially required for precision grouting and foundations of machinery or in bridges, dams etc.
  •     Floors can be topped with epoxy resins to be resistant against chemical attack such as in factories, excessive wear and tear as in ware houses, against frequent use as in airports and public utility buildings.

Epoxy resins is not a recent phenomenon. It is already recognized for its uniqueness as a building tool internationally, but has been introduced in our country only recently. The permutations and applications of Epoxies are perhaps endless.

Remember, a dry home or office  is a healthy home or office, so protect your property investment and your health. Call us today for service you can trust, at a price you can afford. Call Master Waterproofing today for a free estimate at direct number: 416.518.4094, or simply contact us

Master Waterproofing 416.518.4094
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