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7 most popular waterproofing systems and their procedures

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Roof Waterproofing methods

The wide variety of terrace waterproofing methods often makes it difficult to select a right waterproofing system. Some of the deciding factors are insulation requirements; availability of proper slope; available contractors preference; condition of a structure. Here are some popular waterproof methods and their procedures.

1. Integral waterproofing

Unlike methods that can be applied after concrete pour, Integral waterproofing makes the concrete impervious by adding chemical admixtures during the concrete making. There are three types of integral waterproofing systems based on the process by which the admixture achieves waterproofing.

  • Hydrophobic admixture based: Cement contains calcium ions. The water-repellent or Hydrophobic admixtures like Sika 1+ reacts with the calcium ions to form a water-repellent within the pores and blocks the pores. This process makes the concrete less absorbent of water and prevents water ingress.
  • Densifying admixture based: Concrete can be produced with a low water-cement ratio by using a densifying admixture making a less permeable and low absorption concrete. This process makes the concrete waterproof.
  • Crystalline admixture based: The crystalline admixtures forms crystalline composites and blocks the capillary pores. This process makes the concrete waterproof.

The decision to go with the integral waterproofing system and choosing the admixtures, procurement of the products etc. need to be finalized before actual pouring of concrete. Many a time this may indeed knock off few months from the project completion.

Procedure

  • Design the concrete mix with the proposed integral waterproofing admixture to determine optimum dosage.
  • Add the admixture with the water by means of a calibrated dispenser to the concrete ingredients.
  • Lay the concrete and cure well similar to any other concrete.

Advantages

  • Damage to the surface will not alter waterproofing properties. Whereas, in all other kinds of waterproof coatings, utmost care is required not to damage the protective coating.
  • Does not require a separate schedule for waterproofing activity resulting in savings to project completion time.

2.   Brickbat Coba waterproofing

The brickbat coba is used for waterproofing of RCC flat roofs. It consists of putting brickbats on roofs maintaining a proper slope and then grouting the same with mortar mixed with waterproofing compounds. This method is now out of favor and many choose superior alternative methods and better products from leading providers.

Procedure

  • Surface preparation:  Thoroughly clean the surface free of loose materials and dust
  • Slurry or mortar preparation:  Blend the cement with waterproofing compound (if in powder form) or water mixed with waterproofing compound (if in liquid form) and prepare the mortar. In the entire Brickbat Coba procedure, wherever slurry or mortar is used, it shall be used mixed with waterproofing compound only
  • First layer (sub-base):  Dampen the surface and apply slurry with brush including in all joints
  • Second layer (base):  Apply 25 mm thick cement mortar in 1 cement : 4 sand ratio while the first coat is still green.
  • Third layer (brickbat):  Place with hand 40 to 75 mm thick brickbats with 15 mm thick mortar packed below the brickbat over the second layer. Leave suitable gaps between brickbats. Cure the surface for 24 hours. After 24 hours curing, apply slurry and fill the gaps between brickbats with 1 cement : 4 mortar.
  • Fourth layer (Protective layer):  Apply 20 mm thick cement mortar in 1 cement : 4 sand ratio while the third layer is still green. Finish the surface smooth with cement slurry.
  • Test the treated surface by making bunds with cement mortar and flooding the water. Keep the water for a minimum of two weeks. Observe for any leaks.

Advantages

  • Maintaining slope is easy
  • Workforce easily available particularly in the interior areas
  • Provides heat insulation
  • High wear and tear resistance
  • Cracks will not occur easily because of temperature variations. This will, in turn, prevents leakages. Putting china chips on top can further prevent cracks formation due to thermal variation.

3.   Cementitious coating waterproofing

Cementitious waterproofing system is cement based modified with acrylic polymers. While the cementitious materials provide the tensile strength, polymers improve elastic and adhesion properties. This makes the coating elastic and prevents water ingress to make it suitable for a waterproofing system. Cementitious coatings are popular due to their ease of application and easy availability at any building product stores. In addition to waterproofing, these coatings can also enhance the durability of an existing surface.

Procedure

  • Clean the surface thoroughly free of loose particles, dirt, and oil traces.
  • Mix the materials well as per manufacturer specification. The product comes in two components and requires site mixing making it a thin liquid.
  • Wet the surface to a saturated surface dry condition.
  • Apply the mix over the surface with brush or roller maintaining uniform thickness as specified.

Check out this video of cementitious waterproofing by BASF

 

Advantages

  • Good bonding with the existing surface
  • Easy application
  • Availability of materials at most of the building material stores
  • High wear and tear resistance

4.  Polymer modified Bitumen membrane waterproofing

Modified bitumen membranes are made of bitumen blended with polymers and reinforced with polyester. These are also known as APP (Atactic-Polypropylene) modified bitumen membrane. The resultant membrane offers flexibility and heat resistance in addition to preventing water ingress. These properties of modified bitumen membrane make it suitable as a waterproof coating. They are available in a roll form and can be easily applied by the torch-on method.

Procedure

  • Surface Preparation: Clean the surface thoroughly free from loose materials, dust, and oil. Surface cleaning plays a vital role in all membrane based waterproofing coating systems to ensure proper adhesion of the membrane with the base surface receiving waterproofing coating.
  • Primary coat: Apply a primary coat to prime the surface as per manufacturer’s specification. Solvent-based or water-based primers are suitable for bitumen membranes.
  • Unroll the membrane sheets. Check for the correct alignment and adjust the sheets wherever required.
  • Heat with a torch the burn-off film present at the underside face of the membrane. Now the membrane is ready for bonding with the underlying concrete surface.
  • Press the membrane firmly ensuring proper bonding with the concrete surface. Additional care should be taken for overlaps, edges and at angles to ensure proper bonding.

Advantages

  • High resistance to heat and temperature changes.
  • Highly elastic. Prevents crack forming
  • Very low water absorption
  • Durable: Long lasting material

5. Polyurethane liquid membrane waterproofing

Polyurethane (popularly known as PU) coating is highly elastic with excellent heat resistance in addition to preventing water ingress. These properties of polyurethane make it suitable as a waterproof coating. The application of the coating is relatively easy. They are available as a single component and can be easily applied with brush or roller.

Procedure

  • Surface Preparation: Clean the surface thoroughly free from loose materials, dust, and oil. Sprinkle some water on the surface and observe for any presence of oil contamination. If require using suitable solvents to removed oil traces. Other materials can be removed by grinding and other by other mechanical means. Surface cleaning plays a vital role in all membrane based waterproofing coating systems to ensure proper adhesion of the membrane with the base surface receiving waterproofing coating.
  • Crack filling: Clean all cracks and joints. Fill the cracks with a sealant approved by the polyurethane system manufacturer to ensure compatibility.
  • Primary coat: Apply a primary coat to prime the surface as per manufacturer’s specification.
  • First coat (Basecoat): Stir the liquid polyurethane compound slowly and thoroughly for around 2 minutes. Apply evenly with a brush or roller.
  • Sand: Sprinkle quartz sand on top of base coat.
  • Topcoat: Apply one more coat of polyurethane similar to the base coat.

 

Check out this video of a liquid membrane by Sika

 

Advantages

  • High resistance to heat and temperature changes.
  • Highly elastic. Prevents crack forming
  • UV resistant

6.  PVC membrane waterproofing

PVC (polyvinyl chloride) membrane is a plasticized membrane reinforced with polyester mesh or glass fiber. The resultant membrane is highly flexible with good tear resistance and impermeable qualities.

Procedure

  • Surface Preparation: Clean the surface thoroughly free from loose materials, dust, and oil.
  • Crack filling: Clean all cracks and joints. Fill the cracks with a sealant approved by the PVC membrane manufacturer. Apply reinforcing tape to joints and cracks.
  • Primary coat: Apply a primary coat to prime the surface as per manufacturer’s specification.
  • Unroll the membrane sheets without stretch. Check for the correct alignment and adjust the sheets wherever required.
  • Heat with a torch the underside face of the membrane to softening point. Now the membrane is ready for bonding with the underlying concrete surface.
  • Press the membrane firmly ensuring proper bonding with the concrete surface. Additional care should be taken for overlaps, edges and at angles to ensure proper bonding.
  • Finish the surface with Aluminium paint (for non-foot traffic area) and with protective screed (for the foot-traffic area).

Check out this video of PVC waterproofing membrane laying by TexsaTV

 

 

Advantages

  • Insensitive to thermal variations
  • High durability and long life
  • Widely used and proven system

7. EPDM membrane or Synthetic rubber waterproofing

Ethylene, propylene, diene terpolymer (EPDM) is an elastomeric compound or synthetic rubber compound and is one of the most effective waterproofing systems. The membrane is highly durable. EPDM system is suitable for a wide variety of waterproofing applications like roofs, pond lining etc.

Procedure

  • Surface Preparation: Clean the surface smooth thoroughly free from loose materials, dust, and oil. Make the surface dry by removing any water present. Get rid of any rough surfaces and unevenness to avoid any damage to EPDM.
  • Crack filling: Clean all cracks and joints. Fill the cracks and any voids with an approved material by the EPDM membrane manufacturer.
  • Unroll the membrane sheets without stretch. Check for the correct alignment and adjust the sheets wherever required.
  • Fold back the membrane and apply adhesive to both EPDM underside and on the concrete surface with roller or sprayer.
  • Roll back the membrane onto the adhesive coated roof surface.
  • Press the membrane firmly ensuring proper bonding with the concrete surface. Additional care should be taken for overlaps, edges, flashings, and roof drains to ensure proper bonding.

 

Check out this video of EPDM laying by Firestone

 

Advantages

  • UV resistance
  • Can withstand thermal variations
  • Extremely flexible.
  • Durability
  • Impact and tear resistant
  • Widely used and proven system

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