Awarded as the best online publication by CIDC

Roof Waterproofing By Brick Bat Coba

Roof Waterproofing By Brick Bat Coba

Er. Kaushal Kishore ,
Materials Engineer, Roorkee

Waterproofing is a treatment of a surface or structure to prevent the passage of water under hydrostatic pressure. Waterproofing barrier system may be placed on the positive or negative side. Damp proofing is a treatment of a surface or structure to resit the passage of water in the absence of hydrostatic pressure. A damp proofing barrier system is used to perform the same functions as a waterproofing system but cannot be used to protect against water pressure. Water may be forced through building members by hydrostatic pressure, water vapour gradient, capillary action, wind-driven rain, or any combination of these. This movement is aggravated by porous concrete, cracks or structural defects, or joints that are improperly designed or installed. Leakage of water into structure may cause structural damage, and invariably cause damage to the contents of the structure.

New roofs RB or RCC slabs must be constructed specified by the designer. Roof waterproofing is a widely misunderstood subject. Often inadequate attention given during the construction of RB or RCC roof slab, wrong products used for waterproofing and generally insufficient treatment given, lead to leakage. Movement because of structural deflection, settlement, etc. and steep temperature variation being exposed, cause development of cracks in the roof slab and water start leaking from these cracks.

While constructing RCC roof slab, it should be borne in mind that the practice of using concrete which is not watertight and placing too much reliance on the waterproofing measures is not desirable. Concrete should be made watertight in itself and the waterproofing method should be looked upon as additional safety devices.

The grade of roof slab concrete shall be strictly as specified by the designer. The concrete materials should be properly proportioned, maintaining the specified maximum water, cement ratio, minimum cement content and required workability. The concrete should be admixed with a Superplasticiser.


Roof slabs constructed either by RC or RCC needs insulation for thermal comfort and waterproofing treatment to prevent leakage of water. Both these requirements are effectively full fill by brick bat coba treatment, the details of which are being below:

All existing treatment, coatings on roof slab top is to be removed and surface cleaned by hard wire brush and washed with water. The surface should be free from any oil, grease, dust etc. Remedial measured by provided to all structural cracks. Expansions joints should be treated as per standard practice.

All non-structural cracks more than 0.5 mm wide and construction joints if any, should be cut in “V” shape, cleaned with wire brush and washed, the cracks are then filled by polymer modified cement or mortar using acrylic polymer, with addition cement slurry mix is spread upon cleaned SSD roof surface. Over this 15 mm thick cement, sand mortar, 1:4 admixed, with water proofer is laid.

On the above green mortar, a layer of brick bats, soaked over night in water, is laid, having an average thickness of about 110 mm, about 70 mm near rain water pipe and 150 mm at ridge.

The gaps between the brick bats are generally kept between 15 and 20 mm. These gaps are filled with cement sand mortar, 1:4, admixed with waterproofer. In hot and dry weather, the surface should be covered with wet gunny bags immediately after finishing. Curing should start next day and continued for 7 days.

The top surface is then finished smooth with 20 mm thick cement sand mortar, 1:4, admixed with a waterproofer. All liquid admixtures should be mixed with the mixing water. The surface when green is marked with 300 mm false squares. Curing is to be done by ponding.


1. Kishore Kaushal, “Polymer Modified Mortars for Concrete Repair”. Civil Engineering & Construction Review, Nov. 1994, pp. 31-37.
2. Kishore Kaushal, “Polymer Adhesives Application in Concrete”, NBM & CW Dec. 98, pp. 21-26.
3. Kishore Kaushal, “Waterproofing of Buildings”, NBM & CR, Apr., 2000, pp. 50-55.
4. Kishore Kaushal, “Repair of cracks in Concrete Structures”, NBM & CW, Jul. 2000, pp. 65-68.
5. Kishore Kaushal, “Terrace & Roof Top Gardens”, NBM & CW Mar. 2001, pp. 68-72.
6. Kishore Kaushal, “Waterproofing of Old heritage Building with Ferrocement & Construction Chemicals”, NBM & CW May. 2001, pp. 54-57.
7. Kishore Kaushal, “Polymer Modified Mortars and Concrete Mix Design”, ICI Journal, Apr-Jun. 2001, pp. 39-42.
8. Kishore Kaushal, Dr. Krishan Kumar, “Waterproofing of Basements & Corrective Measures”, Proceeding of Seminar
on Structural Rehabilitation and Waterproofing. The Institution
of Engineers (India). All India Seminar 13-14 Oct. 2003,
pp. 19.1 – 19.5.
9. Kishore Kaushal, “Waterproofing of Basement”, CE % CR Dec. 2003, pp. 34-38.

We are thankful to Er. Kaushal Kishore for submitting this very useful research paper to us.

Share this post

Kanwarjot Singh

Kanwarjot Singh is the founder of Civil Engineering Portal, a leading civil engineering website which has been awarded as the best online publication by CIDC. He did his BE civil from Thapar University, Patiala and has been working on this website with his team of Civil Engineers.

44 comments on "Roof Waterproofing By Brick Bat Coba"

sharad soni says:

kindly let me know the cost of Brckbat coba in the old concrete roof for 100% waterproofing of my residential building.

Anil Verma says:

This civil work of Brick bat coba in sunken portion is of great importance and helpful to the civil engineers students and masons I appreciate this commandable research work of Er Kaushal Kishore paid as homeage to our nation

sachin raut says:

Please tell me how much quantity required of cement+sand + brick bat required for terrace waterproofing

chintukumar chokshi says:

how to measure length and width of toilet sunken slab having depth of 450 mm with vatas on four sides?


Why brick bat coba fails in Nasik maharashtra
the parapet wall displacement is observed on brick bat coba treatment in 5 to 6 years


we are planing to repair our factory buildings terrace with brick bat coba work. so if you possible to sent your engineer at our factory .

sohel raja says:

sir, what’s the best process of water proofing on an old construction… glass fibre net procedure benefitial over brick bat coba ????

Anil kumar singh says:

sir after doing brick bat coba how reduce on top surface cracks&funges,&after brick bat coba the tempreture fell down of Roof.

Vikram Patel says:

Sir What is the remedial solution for continously Damp walls in rainy season????

r k singh says:

Please tell me,can i use over burnt bricks whose water absorption is less then 10% in bricks bat coba water Proofing treatment

atul says:

1. What are the benefits of bricks coba treatment for a resident on top floor?
2. After this treatment by the builder what precautions should be taken by the resident on top floor?
3. Considering the heat in Delhi, is it advisable to purchase a top floor in a multi-story building?

Santosh bankar says:

Brikbat coba chemical proportion.

rohit gupta says:

May i ask how much quantity used of brick bats and cement and waterproofing compaund in one meter square in brick koba treatment a

Amol Patil says:

Why 300 mm false squares required and what is the use of fiber cloth in Brick Bat Coba treatment?

Mahesh Bhavsar says:

Mode of measurement for Brick bat Coba water proofing. Area upto which limit has not to be deducted from water proofing.

Ashish Pandey says:

How to calculate the material quantity for brick bat coba water proof ing in sunken


Expansion joint treatment and process

Leave a Reply

Your email address will not be published. Required fields are marked *