Waterproofing Works for RCC Flat, Sloped Roofs and Sunken slabs

Tools to be used for Waterproofing works
Mason’s brush, Chipping tools, Wire brushes, Soft brushes, Air compressor, wheel barrow, paint brushes, plumb bob, sponge, Tube level, Aluminium straight edge, hammer, water barrel, spirit level, scissors, cutters, Gas cylinder, bitumen roller,dumpy level, line thread, sprit level, wooden mallet.

waterproofing works

for floors & slabs

Surface preparation and screed concrete works for flat and sloped roof waterproofing works

Surface preparation :

  • Is the most important aspect before carrying out waterproofing works for any concrete surface
  • Using appropriate chipping tools and brush, the surface should thoroughly chipped and free from existing cement mortar, dead mortar, concrete deposits, dust and all kinds of loose material.

Water leakage test :

  • Water leakage Test is to be done by filling the concrete surface with standing water by making ponds, and if any leakage or dampness visible, to be clearly marked by using crayons in the respective ceiling below the terrace.
  • After this, depending on the depth of dampness, a 12 mm diameter GI nipples to be inserted on the ceiling locations.
  • The cement pressure grouting procedure, admixed with water proofing compound from top of the roof to be done, through these GI nipples until the grouting reaches the bottom surface.

V-Grooves : For all joints of brickwork, block work or concrete junctions, cracks appeared to be widened by making V grooves along the joints and filled with suitable sealant material.

Fiber reinforced mesh : All rain water pipe lines, plumbing pipe lines to be properly sealed by using a good quality fiber reinforced mesh with first coat plastering, cure it for two days, then go ahead with final coat of plaster as waterproofing works finishing.

Base coat : 

  • First, base coat or bonding coat is to be applied over concrete surface using cement and polymer additive .
  • Over this, apply two coats of Acrylic polymer waterproof coating system or equivalent as per manufacture’s specifications or as per tender document,continuing the application, including overlapping of parapet wall plastering by one foot height.
  • This monolithic action of floor with parapet wall serves the strong bonding purpose as well as easy flow of rain water through proper slopes.

Screed concrete :

  • After this, provision for slopes, ridges and valleys over the floor to be marked with reference pads as per drawings, with minimum and maximum thickness of 25 to 30 mm to carry out a protective layer of screed concrete.
  • Ensure the cement slurry brushing for concrete surface before screed concrete.
  • Smooth plastering finishing (mixer of cement and recommended waterproofing compound) to be given for this screed concrete exposed top surface in order to protect the coating from weather conditions.
  • Allow it for minimum 24 hours to 4 – 5 days for testing by ponding water at 50 – 100 mm depth, for the effectiveness of water proofing treatment.
  • Now the surface is finished by giving smooth finish of Indian patent stone (IPS floor) or with weathering tiles laying by maintain the same profile and slopes of Waterproofing works.

Cement based waterproofing works treatment using brickbat coba for terrace slab

Surface Preparation :

  • Clean the surface over the slab by removing all loose materials, dust etc. and wash with clean water
  • Over this cleaned surface, provide a layer of Cement mortar of 1:3 ratio including water proofing compound with an average thickness of 20 mm.

Brick bats Laying : 

  • Start laying brick bats of 115 mm thick in random pattern, braking monotony of joints with 10 mm thick joints between two bricks, and fill it uniformly.
  • Continue the brickbats in a systematic circular pattern, following the slope line, till the end of rainwater outlet provided.
  • Try to avoid as far as possible dry brick bats and over burnt brick bats while laying.
  • In case the brick bat coba is laid on the base coat instantly on initial set there will be no need of applying cement slurry over the base coat before laying the brick bat coba.
  • Conversely, if the brick bat coba is to be laid on the following day, cement slurry is to be applied over the top surface of the base coat and then only the brick bat coba to be laid.

Glass fiber mesh :

  • Laying Finishing Layer also called a Protective Coat, Immediately on applying the cement slurry over the surface of the brick bat coba and when the slurry applied is still green, the waterproofing glass fiber mesh of thin approved brand, flexible, chemically resistant borosilicate glass fibre, is to be spread uniformly on the surface without any bend, twist and pressed to see that no air gaps exist.
  • Create a haunch portion between the junction of roof and parapet wall using brickbat coba only and continue the fiber glass cloth for parapet walls and inserted in the groove at a height of 300 mm on wall.

Curing : 

  • Curing to be done for this layer for a minimum of 3 days before taking up the next layer.
  • Even if there is any delay for continue the final layer over this layer, curing should not be stopped and continued for a period of at least 10 days.

Final Finishing : 

  • The groove in the parapet wall over the haunches also to be filled neatly, packing the mortar firmly in the groove.
  • The surface of the final finishing layer or protective coat is to be neatly finished with cement slurry.
  • Then, finished surface shall be allowed to dry for a while and then using 8 mm thick line thread, a pattern of 300 mm x 300 mm groove, is pressed by gently tapping the line thread with wooden mallet, over the entire surface after waterproofing works.
  • The entire surface after waterproofing works is to be allowed for air curing for 4 hours and later the surface to be cured with clean water for 7 days.
  • On completion of curing, the grooves where the fibre glass cloth is inserted, is to be neatly closed with cement mortar admixed with water proofing compound and the repaired surface should be cured by clean water for 7 days

Sunken Slab waterproofing works for bathrooms and toilet floors

  • The procedure is similar for sunken areas of bathrooms and toilets also, and the treatment to be applied for the full depth of sunken portion including water testing, for at least 200 mm depth of standing water in sunken portions.
  • Caution: All Electrical chasing works and Plumbing chasing works, boreholes etc. to be completed and properly packed, sealed either by means of fiber mesh, or by water proofing compound including curing, before the commencement of waterproofing  treatment.
  • Avoid strictly the chasing works after completion of Waterproofing works.
  •  Cinder : After the treatment, this treated surface to be filled with cinder for full depth, nicely compacted and finished with 75 mm to 100 mm thick screed concrete of M 15 grade and cured for 4 -5 days.

Advice : Bathroom level difference

  • In order to maintain the level difference between main floor area and bathroom floor area by preventing toilet water entering into the main area, it is always recommended, to have bathroom floor level by one tile thickness or 20 mm below the main floor.
  • Hence unfinished floor or screed concrete level in bath room area is also to be 20 mm below the unfinished floor of main area.

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