How to Waterproof Mother Slab? Should I Waterproof Terrace Slab?

In this article, we will guide you in detail about waterproofing the Mother slab or Terrace slab of your house.

What is a Mother Slab or Terrace Slab?

The concrete roof slab facing the sun and rain which constitutes the topmost part of your home is called the Mother slab.

The roof of the house plays an important role in shielding your home from rain and sunlight. The more stronger and protected it is, comfortable the people living inside it.

The chemicals used in the Terrace Slab waterproofing are mainly a Latex repair liquid along with an Acrylic coating or a Polyurethane coating. Here is the detailed article on chemicals to use for Terrace Waterproofing.

Here are the 5 simple steps to waterproof your terrace Slab. Do read them patiently:

Step 1: Surface Preparation:

Image 1: Person cleaning the surface using water jets

Sweep your terrace from all the dust. After sweeping use a wire brush to thoroughly remove any weak deposits on the terrace.

Once done with the above two jobs, use the water hose to remove traces of dust.

Step 2: Repair Cracks:

Image 2: Here we are cleaning cracks using wire-brush.

Once you have cleaned your terrace, you will see a few cracks here and there. Open those cracks a tiny bit using a grinder. We are opening the cracks so that they can be sealed properly. Remove the dust using a blower.

Now make a mortar using a repair latex (E.g. Dr. Fixit URP) 1 kg cement, 150 gm repair latex, and water as per workability. Sprinkle water over the cracks and let it dry for 10-15 mins. Apply the mortar over the cracks and flatten them. Wait for 24 hours to let it dry.

Image 3: Here we have filled repair mortar in the cracks.

Step 3: Check the status of the Angle Fillets:

Angle Fillets are the transitional edge between the parapet wall and roof surface. It is made at an angle of 45 Degree, having dimensions of 100 mm X 100 mm. Check the image below for clarity.

Image 4: Here we have created fillet with mortar.

If there is no fillet on your terrace, construct one using mortar around all the parapet walls covering the perimeter of your roof. If there is an existing fillet, check for any damage and repair it with the repair mortar.

Step 4: Sealing of drainage pipes:

Areas near the sealing drain or outlet pipes are vulnerable to water leakages. Seal the periphery of the same using the repair mortar as an added precaution.

Step 5: Waterproofing coating application:

There are many options in the market for waterproof coating like Dr. Fixit Roofseal Classic, Asian Paints Dampproof, Nerolac's No-damp, etc. We recommend Dr. Fixit Roofseal Classic because of its superior material quality. The coatings can not be applied during rain.

Spray water on the terrace and let it dry for 20-25 mins. Now apply primer coat ( make primer from your coating chemical by it with 50% water. In 20 Liter bucket, add 10 Liter water) on the surface. Let it dry for 3-4 hours.

Image 5: Here two experts are applying coating on the roof.

Apply the first coat (no dilution) on the primed surface in one direction. No zig-zag painting. Apply unidirectionally over your roof. After the first coat, wait for 4-6 hours. Apply the second coat perpendicular to the direction of the first coat. Finish the job. Initial drying will take 4-6 hours. Complete drying takes 3 days, after which you can walk on the terrace.

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