METHODOLOGY / PROCEDURE OF TERRACE SLAB WATERPROOFING

WORK METHODOLOGY OF TERRACE  SLAB  WATERPROOFING

Option – 01:  Waterproofing with two part component Cementitious waterproofing

Option – 02: Waterproofing with Solvent Based Polyurethane ( PU ) membrane

Option – 01: Waterproofing with two part component Cementitious waterproofing

STEP-1: `SURFACE PREPARATION:

Ø  Concrete surfaces should be fully cured (minimum 28 days) prior to application.

Ø  The concrete surface shall be cleaned thoroughly of all contaminants like dust, traces of curing compound, oil and grease.

Ø  All surface imperfections, protrusions, structurally unsound and friable concrete must be removed and repaired with a suitable concrete repair mortar.

Ø  All surface cracks, undulations and voids shall be repaired appropriately before application.

Ø  All cracks above 5mm deep,  shall be cut opened, cleaned and shall be filled with shrink free crack filling material. i.e. GP2 or equivalent.

Ø  The entire surface to be coated must be in SSD condition prior to application of coating.

Ø  All the construction joints need to be opened and treated with polymer modified mortar (Cement: sand: SBR Latex) or ready to use modified mortar.

Ø  Injection grout shall be done at all construction joints. Nozzle shall be fixed @ 500mm centre to centre at all construction joints.

Ø  3 days ponding test has to be carried out, if the leakages are observed then repeat the above procedure till to achieved water tight toilet area

STEP- 02 : SEALING OF PIPE INLET / OUTLET DRAINAGE PIPES AND FILLING CUTOUT HOLES

Ø  The surface of the pipe shall be free from dust, laitance, oil and water.

Ø  The core cut shall be free from debris, dust or any foreign materials.

Ø  Bath seal tape need to be unrolled to required length and wrap around the pipe by removing release film from one side of the tape.

Ø  The length of the tape shall be taken in such a way that the overlap of tape maintains to be 150mm.

Ø  Pipe need to be inserted with Bathseal tape or equivalent wrapped into the core and support it with formwork from below the slab or support from the periphery of the wall so that the gap around the pipe and the core shall be uniform throughout.

Ø  The bore packing shall be done with Non-shrink free flow cementitious grout, , so that there is no air entrapment / voids creating

STEP- 3:  APPLICATION OF TWO PART COMPONENT ACRYLIC POLYMER BASED CEMENTITIOUS COATING

Ø  Top level of the waterproofing shall be marked.

Ø  The entire surface to be coated must be in SSD condition prior to application of coating acrylic polymer based cementitious coating as per approved brand.

Ø  Mixing: Using a slow speed mechanical mixer and a clean suitable mixing vessel, slowly add the powder component to the liquid polymer and stir until a smooth and homogenous slurry is achieved.

Ø  Allow the mixed slurry to stand for 5 – 10 minutes to remove air bobble created during mixing.

Ø  Do not dilute with water at any time of mixing.

Ø  Apply mixed cementitious slurry by brush or roller.

Ø  Allow the first coat to dry completely for 6 – 8 hours before applying the second coat.

Ø  Apply second coat at right angles to the first coat.

Ø  Coating to be applied as per recommendation of manufacturer regarding application tool.

Ø  Allow the coating to cure for 3 – 4 days before application of protection layer.

Ø  Cure the applied cementitious slurry for period of 7 to 10 days. Or minimum of 3 to 5days if further activities starts immediately.

STEP- 4 : PROTECTION OF COATED SURFACE

A.   Protection to waterproof coating (Horizontal Surface)

Ø  Cement sand mortar to be laid for protection to the coating laid to slope to the drainage point.

Ø  This mortar shall be minimum 30 to 40mm thick and shall admixed with integral waterproofing compound as per approved brand.

Ø  Cement mortar for base coat shall be used minimum ratio of 1:4

Ø  Curing shall be done at least for 7 to 10 days.

B.   Protection to waterproof coating (Vertical Surface)

Ø  After chemical coat, a rash coat shall be applied for better bonding with cementitious mortar bedding.

Ø  Protection Layer or base coat will be carried out.

Ø  This mortar shall be minimum 15 to 20mm thick and shall admixed with integral waterproofing compound as per approved brand.

Ø  Cement mortar for base coat shall be used ratio of 1:4 .

Ø  Top of base coat shall be trowel finish to receive the block / brick bat upto required level.

Ø  Curing shall be done at least for 7 to 10 days.

STEP- 4 : BRICK BAT COBA FOR FILLING OF SUNKEN AREA or TERRACE SLAB;

Ø  Level pad shall be prepared as per the required slop towards nahani trap as per drawing or specification.

Ø  Bricks selected for using as brick bat coba shall be either full brick or ¾ brick made out of one complete brick by breaking into required sizes using mallets.

Ø  Brick bat shall be soaked thoroughly for about 15 minutes prior to their placing.

Ø  A thin layer of cement slurry shall be laid on cleaned slab prior to laying of brick bats, cleaning to be ensured before laying the brick bat.

Ø  On applied cement surry, 10 to 20mm thick layer of cement sand mortar in the proportion 1:4 mixed with compatible waterproofing compound shall be laid.

Ø  Approved integral waterproofing admixture shall be mixed with cement mortar as per data sheet.

Ø  Mortar shall be mixed properly and same shall be used within 60 minutes from its mixing time.

Ø  Broken brick bats of required size shall be placed over the cement mortar bed by hand packing having minimum 15 to 20mm gap between broken bricks.

Ø  Pre-soaked brick bats shall be laid in radial by inserting brick bat s to a depth of about 10mm by light tamping.

Ø  Mortar shall be ratio of 1:4 shall be used for filling of gaps between broken bricks.

Ø  Cement mortar shall be filled up to 2/3rd height of the broken bricks.

Ø  Laying of brick bats should proceed from one corner and shall be laid in radial pattern to drain off any water which has seeped through.

Ø  Thiyyas / Level Pad for the same shall be given by operation engineer, Brick bat shall be laid accordingly.

Ø  Brick bat each layer will be cured for minimum 3 days

Ø  Post Curing, remaining 1/3rd height filling of brick bat and 20mm thick cement mortar screed / cement mortar plaster shall be provided in a single layer.

Ø  Sand mortar in the proportion 1:4 with waterproofing compound (as per mix ratio)

Ø  Top coat shall be of neat cement slurry of adequate consistency and shall be monolithic with brick bat.

Ø  Waterproofing plaster shall be extended upto 500 mm (from RCC slab Top) on vertical surface/ parapet wall.

Ø  Average thickness of brick bat coba shall be maintained as per project specification.

Ø  Top level shall be maintained as per drawing & slope.

Ø  Pond Curing shall be done for 7days and leakage shall be checked.

Option – 02: Waterproofing with PU membrane

STEP-1: `SURFACE PREPARATION:

Ø   

Ø  The surface needs to be clean, dry and sound, free of any contamination, which may harmfully affect the adhesion of the membrane.

Ø  Maximum moisture content should not exceed 5%. Substrate compressive strength should be at least 25 MPa, cohesive bond strength at least 1.5 MPa.

Ø  New concrete structures need to dry for at least 28 days. Old, loose coatings, dirt, fats, oils, organic substances and dust need to be removed by a grinding machine. Possible surface irregularities need to be smoothened.

Ø  Any loose surface pieces and grinding dust need to be thoroughly removed.

Ø  WARNING: Do not wash surface with water.

Ø  All surface cracks, undulations and voids must be repaired before application using a suitable repairing material.

Ø  Substrates must be surface dry prior to application.

Ø  During surface preparation all fittings of drain outlets work must be completed.

STEP-2 : PRIMING OF RCC SURFACE

Ø  Prime absorbent surfaces like concrete, cement screed with PU Primer and allow the primer to air cure according manufacturer’s technical instruction.

Ø  Allow the primer to cure for 6 – 8 Hrs to tacky condition

STEP-3 : APPLICATION OF PU MEMBRANE

Ø  Stir well before using of PU solvent.

Ø  Apply the PU solvent onto the primed surface and lay it out by roller or brush, until all surface is covered.

Ø  Airless spraying method can be allowed a considerable saving of manpower.

Ø  After 12-18 hours (not later than 48 hours) apply another layer of the PU solvent.

Ø  For best results, the temperature during application and cure should be between 5ºC and 35ºC.

Ø  Low temperatures retard cure while high temperature speed up curing. High humidity may affect the final finish.

Ø  The coverage shall be maintained at 1.8 Kg/sqm to achieve Dry Film Thickness of    1.5mm.

Ø  The membrane (both the coats) shall be applied over the angle fillet and shall be extended over the vertical wall (i.e. Parapet wall ) upto height such that it is terminated at 300mm above Finish Floor Level or Soil Filling Level.

Ø  Allow the membrane to air cure for minimum 3 – 4 days before any activity over it.

Ø  Allow the coating to cure for 2 – 3 days.

STEP- 4 : PONDING TEST OF APPLIED PU MEMBRANE (If required)

Ø  Make bund wall and fill water to pond the area as per the site requirement and allow the water for 72Hrs.

Ø  Remove water after 72 Hrs after inspection. Allow to dry for 24 Hrs.

STEP- 5: PROTECTION OF PU MEMBRANE (HORIZONTAL SURFACE)

Ø  Provide  200 GSM geotextile membrane over the waterproofing membrane to create a separation layer as well as protection layer from screeding.

Ø  The geotextile layer shall have 100 mm overlap and spot bonded and shall be extended at the wall up to 100mm above the slab floor.

Ø  Lay Concrete screed of minimum M20 grade concrete (RMC) over the geotextile membrane. 12mm poly-propylene fibers at 0.9Kg/cum may be added to avoid shrinkage cracks of concrete.

Ø  Provide slope of 1:1000 or as recommended by client.

Ø  The slope shall be provided in such a way that there is 40mm minimum thickness at the point of drain outlet.

Ø  The screed shall be finished rough with broom and in shape of watta / rounding at the wall and floor junctions.

Ø  The screed shall be cured with water for minimum 07 to 10 days.

Ø  After the screed is cured remove all the water, cut joints in screed with grinder of 10mm wide and 25 mm deep to form panels of 4M X 4M.

Ø  Clean the joints with compressed air to make it dust free and leave it for 1 or 2 days to remove the moisture from the joints.

Ø  Pack in backer rod of round cross-section inside the joint upto 10 mm depth left at top.

Ø  This joint shall be applied with PU primer. Allow to dry for minimum 2 – 3 Hrs to tacky condition. Then fill the joints with PU sealant.

Ø   Allow the sealant to air cure for 2 – 3 days before covering or laying of further tiles / pavers if applicable.

STEP- 6: PROTECTION OF PU MEMBRANE (FOR VERTICAL SURFACE SURFACE)

Ø  Over the waterproofing membrane apply 2 coats of Epoxy Bonding Agent conforming to Shear Bond strength as per ASTM C 881.

Ø  Sprinkle sand over the primed surface at 2 – 3Kg/sqm when the bonding agent is wet.

Ø  Allow it to dry to form firm key for the plaster.

Ø  Lay 15 to 20mm thick plaster in two coats over the prepared surface of cement sand mortar mixed with integral waterproof compound conforming to IS 2645-2003.