Brickbat Coba waterproofing is an effective way of providing waterproofing and insulation for thermal comfort for flat RCC roofs to prevent leakage of water.
It is one of the oldest procedures of waterproofing, which consists of laying brickbats on the flat RCC roof and grouting the same with waterproofing compound with a slope to drain the surface water.
In this article, we discuss the procedure and disadvantages of brickbat coba waterproofing.
Procedure of Brickbat Coba Waterproofing
1. Surface Preparation
In the case of existing treatment, the coating on the slab top shall be removed, and surface cleaned by hard wire brush and washed with water. In the case of a new slab to be cast, the surface of the concrete must be roughened by scraping. In case the slab has already been cast, and the surface is fairly finished, the same shall be cleaned neatly of all mortar droppings, loose materials, etc.
The main aim of the surface preparation is to make the surface of the slab free from any oil, grease, dust, etc. Proper measures shall be adopted for all structural cracks as per standard practice.
2. Application of Slurry and Base Coat
The slurry is prepared with cement and water to a required consistency. It shall be applied over the dampened surface with brushes very carefully, including the joints between the floor slab and the parapet wall, holes on the surfaces and joints of pipes in masonry or concrete.
The prescribed quantity of slurry application is 2.75 Kg of cement per Sqm. The pot life of the slurry shall be considered as 1/2 hour. The use of the slurry should continue up to a height of 300 mm over the parapet wall.
The laying of a 25mm thick base coat is carried out soon after the application of slurry when the application is still green. The cement plaster of 25 mm thick with a mix ratio of 1:4 is evenly applied over the concrete surface.
3. Placing of BrickBat
While the base coat is still green, brickbats of the size (65mm to 120mm) are placed with a gap of 15 and 20mm. The brickbats shall be wholly burnt and are well soaked overnight before laying.
Once after laying of brickbats, curing is carried out for a minimum of 24 hrs after which, the gaps between the brickbats are filled with the same mix mortar used for base coat.
4. Laying of Protective Coat
A waterproofing compound confirming to IS 2645 is blended with the cement water mixture as per the manufacture specification. However, not more than 3 % of the waterproofing compound shall be used per 50 Kg of grey cement.
A cement mortar of a 1:4 ratio is prepared with the waterproofing compound and applied over the surface, including the haunches/ gola and 300mm on the parapet wall.
The surface is neatly finished with the help of wooden / steel hand float. The finished surface shall be allowed to dry for a while till a string mark can easily be made on the surface when 300mm x 300mm square marks shall be made over the entire surface.
5. Curing
The entire surface thus treated shall be flooded with water by making bunds with low cement mortar. The curing shall be carried our for a minimum period of 2 weeks.
Disadvantages of Brickbat Waterproofing
Brickbat waterproofing is one of the oldest methods of waterproofing, and with new modern waterproofing products available in the market, brickbat waterproofing has become absolute these days. The significant disadvantages of brickbat waterproofing are detailed below-
1. Unnecessary Dead Load
The thickness of the brickbat is around 125mm to 150 mm, which adds the dead load of the building—hence making it uneconomical.
2. Maintenance
The maintenance of this waterproofing is very tedious work as the chances of water seeping in the waterproofing is very high. Once the waterproofing is infected with water, repairing, or doing patchwork hardly provides any solutions.
3. Cracks
Due to the rigidness in the brickbat waterproofing, the formation of the crack is very likely due to the climatic variations. Once cracks are formed, neither patchwork nor grouting can prevent the water from entering into it for a long time.
4. Skilled Workmanship
The brickbat waterproofing is easily influenced by the external factors such as climate variations and heavy rainfall. A poor workmanship will only add to cause.
A skilled manpower with prior experience in the brickbat waterproofing is required for the application to maintain the basic requirements such as leveling, grouting, etc.
Read More:
1. Waterproofing in Buildings – Methods and Types of Waterproofing
2. Concrete Waterproofing- Types, Steps, and Advantages
FAQs on Brick Bat Coba Waterproofing
Coba brick waterproofing is the oldest method, the procedure of which involves laying brickbats on the flat concrete roof and grouting the same with waterproofing compound with a slope to drain the surface water.
This waterproofing is used on a flat concrete roof to provide slope to drain the water and prevent the leakage of water into the roof.