All about Waterproofing

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All about Waterproofing

• By B S Ranganath

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Introduction

• Waterproofing is a process enabling terraces,
  balconies, water closets, sunshades, sump tanks,
  overhead tanks etc. to be water-tight in
  buildings.
• Waterproofing could be carried out on surfaces of
  masonry, concrete, cement render, timber etc.
• This presentation imparts knowledge in brief
  about various types of waterproofing, to the
  aspirants .

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Picture 1 Latest application in progress
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Importance of Waterproofing

• Penetration of water into buildings because of
  porosity and cracks has proven to be one of the
  most destructive elements affecting stability and
  durability.
• Effective steps are taken at the pre and post
  construction stages to incorporate waterproofing
  and cut down maintenance costs, thereby providing
  comfort to the occupants of the building.

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Importance of Waterproofing

• Following damages caused due to seepage of
  water result in the building decay and
  deterioration.
• 1) Rotting of timber structures and finishes
  such as floors, skirting, architraves and frames.
  
• 2) Corrosion of materials such as mild steel
  round and deformed bars in concrete, metal door
  frames etc.
• 3) Swelling of the backing coat of plaster and
  the subsequent de-bonding of ceramic tiles.

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Importance of Waterproofing

• 4) Electrical hazards causing short circuit of
  lighting and power points.
• 5) The blistering of paint.
• The importance of waterproofing can not be
  overlooked. Damage caused to the building's
  structure, coupled with the high cost to be
  incurred on rectification warrants a careful
  design and application of waterproofing.

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Closely followed Applications

• Waterproofing has various approaches depending on
  usage of certain film, membrane, cementatious
  layer or stone layer. Some of the known
  applications are as follows.
• Tar felting for terraces
• Brickbat Coba for terraces
• Metal Coba for sunken slabs
• Box type waterproofing
• Cement Grouting and Chemical Coating
• Integral waterproofing

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Application of Tar Felt

• Tar felting is the oldest in practice. It has
  layers of tar held together with a variety of
  reinforcements. It prevents cracking to provide
  impermeable layer between water and the surface
  to be protected.
• It is categorized as three, five or seven layer
  treatment. Seven coat application is recommended
  for new jobs but seldom executed, since it costs
  as much as the other technically more advanced
  treatments.
• Though once universally used, it is found to be
  inadequate even for terrace waterproofing, for
  which it is primarily designed.

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Picture 2 Tar Felt Roll
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Brickbat Coba for Terraces

• This application consists spreading of brickbat
  in slope over roofs and then grouting with
  mortar, admixed with water proofing compounds.
• It will have IPS topping with 'tile pattern
  thread lining, to prevent cracks from appearing.
  This has the advantage of providing an excellent
  slope so that the water drains away.
• It even has the water retaining capacity, as
  water is absorbed by the brick when it rains and
  released when rain stops.

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Picture 3 Brickbat embedding
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Brickbat Coba for Terraces

• It is a 120mm average thick application over RCC
  roof slabs. To lay this, clear the RCC slab of
  loose particles and flood it with waterproofing
  compound mixed cement slurry. Over that, spread
  water proof cement mortar 15 to an average
  thickness of 20mm.
• On above screed while it is green, 100mm graded
  brickbats shall be embedded to a slope 1100.
  Joints between brickbats shall be filled with
  waterproof mortar 13. Over it shall be the final
  20mm thick waterproof screed 14, having a
  properly maintained slope to enable easy flow of
  water. Rounding off to a height of 300mm along
  parapet walls is a must.

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Metal Coba for Sunken Slabs

• It is a 50mm average thick application for toilet
  sunken slabs, water retaining structures etc. To
  lay this, Injection grout the surface by placing
  nozzles at 500mm intervals. Over that, spread
  water proof cement mortar 15 to an average
  thickness of 20mm.
• On the above screed while it is green, 20mm
  graded granite metal shall be embedded. Over it
  shall be the final 20mm thick waterproof screed
  14, having a properly maintained slope to enable
  easy flow of water. Rounding off the junctions
  of floor and walls is a must.

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Picture 4 Metal Coba in a Swimming Pool
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Box Type Waterproofing

• This is an external treatment to the structure
  that could be prone to water logging.
• It will provide watertight cover to the base of
  the structure remaining underground.
• It involves the process of applying neat cement
  slurry mixed with waterproofing compound evenly,
  to fill up undulations and cavities on the PCC
  layer below raft. Next step is to spread cement
  mortar 14 mixed with water proofing compound on
  the surface to an average thickness of 20mm.

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Picture 5 Shahabad Stone in Box type
Waterproofing
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Box Type Waterproofing

• While the screed is green, Shahabad or Cuddapah
  stone slabs (300mm x 300mm) 20mm to 25mm thick
  shall be embedded. Joints between Shahabad or
  Cuddapah stone slabs shall be filled with cement
  grout admixed with waterproofing compound. Over
  it shall be the final 20mm thick waterproof
  screed 14.
• This treatment has to continue vertically (by
  restricting the thickness of Shahabad or Cuddapah
  stone slabs to 15mm) all along retaining walls up
  to the ground level.

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Cement Grouting and Chemical Coating

• Mineral based coatings are most effective and act
  against water pressure. They have been in the
  market for more than twenty years now. These have
  a crystalline action and penetrate the
  capillaries and form insoluble hard crystal in
  them and make the concrete surfaces water tight.
• Cement grouting and Chemical Coating is fast
  replacing the other traditional practices.
• When you go for this, first of all you have to
  ensure that the entire surface is clean, free
  from dirt, grease, oil and other loose particles.

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Picture 6 Cement Grouting and Chemical Coating
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Cement Grouting and Chemical Coating

• Fill the visible cracks, joints and gaps with the
  cement grout. Allow it to cure for 24 hrs,
  Observe the filled area and if required fill the
  cracks once again to the level of the surface.
• Apply a coat of chemical on the prepared surface
  and allow it to dry for 4-6 hours. Apply second
  coat of the chemical. If subsequent coats are
  required, apply at an interval of 6 hours.
• Paint can be applied as a topcoat over the
  chemical coating directly. This process provides
  glossy finish and enhances the colour of the
  substrata.

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Integral waterproofing

• The latest trend in waterproofing is to use
  construction chemicals.
• There are a number chemicals and they have to be
  used in different combinations to get the desired
  result. Their use is tailor made for different
  categories of problems.
• Used as an admixture in the green concrete,
  construction chemicals would do wonders such as
  the roof slab becoming totally watertight,
  without requiring a measure like brickbat coba.

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Picture 7 Dr Fixit Range of Products
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Integral waterproofing

• Admixture of the construction chemical ensures
  the concrete to be denser leaving no room for
  honeycombs, capillaries, cracks etc.
• A dense and a strong concrete is more likely to
  be watertight over a longer period of time than a
  weak concrete that is covered with some barrier.
  
• However it should be borne in mind that the use
  of construction chemicals in only an aid to good
  civil engineering practice and not a substitute
  to the same.

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Picture 8 Cico Products