How to Waterproof a Concrete Roof? Steps, and Tools

1. Clean the Concrete Roof Surface

You should clean the concrete rooftop before you start the waterproofing on the concrete roof. You should clean the concrete rooftop thoroughly using these 7 steps.

7 Steps for Concrete Roof Cleaning for Waterproofing

1. Remove furniture, plant pots, tools, and any other items that might be on the concrete rooftop.
2. Use a broom or a brush to sweep away loose debris such as leaves, dirt, and dust. Pay special attention to concrete roof corners and hidden areas where dirt accumulates.
3. Remove broken and loosening materials on the concrete rooftop.
4. Remove the plaster from the concrete roof if the roof is an old one.
5. Use a pressure washer to wash the solid surface.
6. After pressure washing the concrete rooftop, check for stain marks, oil marks, and molds on the rooftop. You can use a mixture of bleach to clean the surface. You should scrub the stained areas with a stiff brush until the stains are gone on the rooftop
7. Let the cement surface dry before applying any waterproofing membrane.

After the concrete rooftop cleaning process, you should check the surface for cracks and damage.

2. Check and Repair Cracks and Damages on the Concrete Rooftop

Mark and note the visible cracks, damages, potholes, deteriorated materials, and weakened materials for repairing, filling, and fixing.

How to Fix Cracks on the Concrete Roof?

You can fix and seal the cracks on the concrete roof using the following 3 steps

1. Grove along the crack lines if the crack width is more than 2mm. You can use a masonry cutting disc for the grooving. These groove lines help to increase the bonding area to close the crack’s width and increase the adhesive strength between the concrete.
2. Use cement compound sealant to seal the crack width if the crack width is more than 5 mm.
3. Remove all the loosening materials and fill the area with cement and plaster mixture on the concrete roof.

Hairline cracks (width is <2mm) will be sealed by the primer and waterproofing coating when the surface is sealed.

3. Seal Joints and Corners on the Concrete Roof

After roof cracks and damages are fixed, you should seal the structural joints and corners on the concrete roof.  You can use a fabric mesh on the joints and corners of the roof to further strengthen and seal them. You can use a paintbrush to apply the mesh with an appropriate sealer.

In particular, you should fillet the roof and wall connection edge using waterproof cement. Roof and wall edges have a higher probability of leaking water from the roof. Hence, you should waterproof all the joints, corners, and channels on the roof to prevent water from the roof.

4. Apply Primer on the Concrete Roof

Primer improves the adhesion between the waterproofing layer and substrate. Hence, it should be applied on the concrete surface under the recommended conditions. You can use a roller, paintbrush, or spray to apply the primer on the surface uniformly.

You should apply a recommended primer on the concrete roof after fixing and sealing all cracks and spaces. You can apply both liquid and sheet waterproofing membranes on the concrete roof. According to the waterproofing membrane, you should apply the primer on the concrete rooftop.

You should not expose the primed roof surface once you apply it. You should be allowed to dry the primer layer according to the weather conditions and the product instructions.

5. Apply the Waterproofing Layer on the Concrete Roof

After priming, you should apply the waterproofing layer on the roof. You can apply both liquid and sheet waterproofing methods for the roof waterproofing.

You can use cementitious waterproofing, polyurethane, and acrylic waterproofing as the liquid waterproofing membranes on the concrete roof waterproofing.

You can use EPDM, PVC, HDPE, TPU, and bituminous membranes (SNS) as sheet waterproofing membranes on the concrete roofs. When you apply a liquid waterproofing membrane on the concrete roof, you should apply it uniformly.

You should apply the first coat on the concrete roof in one way. The second coat should be applied perpendicular to the first coat. You can use a brush, roller, or spray to apply the liquid waterproofing membrane on the concrete roof.

When you apply the sheet membrane on the concrete roof, you should install it properly with proper joints and sealing lengths and overlapping lengths. These lengths prevent the water from leaking from the seams and joints of the sheet membrane.

You can use a gas torch for the modified bituminous waterproofing membranes. The temperature for the bituminous waterproofing membranes should be 54°C (130°F) – 65°C (150°F).

You can use a heat gun (550 C°) to install PVC waterproofing. Other sheet waterproofing should be installed on the roof, using a recommended glue or sealant.

After the waterproofing coat is applied, you should not expose the layer to water until it is completely dried in the recommended period.

6. Let the Roof Waterproofing Dry and Check for Leaks

After the waterproofing is done on the top, you should let the layer dry. Do not expose the layer to water until it is completely dry. You should follow the manufacturer’s guidelines for applying and drying.

After drying the waterproofing membrane, you can check it by ponding 2-3 days before using it.

What are the Waterproof Membranes for Concrete Roofs?

Best Roof Waterproofing Cements for Concrete Roofs

Waterproofing cement is one of the best solutions for concrete roofs. Using waterproofing cements helps to prevent water penetrations, reduces cracks and leaks, improves durability, increases structural strength, and is a cost-effective solution.

Aqviz experts use these cementitious waterproofing membranes on the concrete roofs.

1. Dr. Fixit LW+
2. SikaTop Seal-107
3. Fosroc Brushbond
4. Mapei Planiseal 88
5. BASF MasterSeal 540
6. Asian Paints SmartCare Damp Proof

Best Sheet Waterproof Membrane Products for Concrete Roofs

Sheet waterproofing membranes are another successful method to seal the concrete roof. It helps to fully cover the concrete roof using a constant thickness layer. So these are the best sheet membranes and products for the concrete roofs.

Best Liquid Waterproof Membrane Products for Concrete Roofs

Liquid waterproofing membranes are easy to install on concrete roofs and produce a seamless layer on the roof. These membranes are flexible, waterproof, and UV-proof. These are the recommended liquid membranes and products from the Aqviz experts.

What are the Essential Tools for Concrete Roof Waterproofing?

These are the tools you should use for a concrete roof waterproofing. We have categorized them into the main 6 categories as follows.

1. Safety tools and gear: Nitrile gloves, PVC-coated gloves, safety goggles, respirator, hard hat, safety harness, rubber boots, coveralls
2. Surface preparation tools: Wire brush, angle grinder, cold chisel, hammer, pressure washer (1500-3000 PSI), scraper, putty knife
3. Crack and joint treatment tools: Caulking gun, trowel, injection grouting pump, V-notched trowel
4. Membrane and coating application tools: Brush (4-6 inch), roller (9-12 inch, long-nap), squeegee, airless spray machine (3000 PSI), torch gun
5. Finishing and protection tools: Concrete float, screed, measuring tape, chalk line, fabric scissors, utility knife
6. Testing and inspection tools: Moisture meter, infrared thermometer, water ponding test setup

How Does a Waterproof Concrete Roof Get Damaged?

A concrete roof waterproofing layer can be damaged due to these environmental effects and human activities.

1. Poor waterproof installation on the concrete roof
2. Bad weather conditions affected the concrete roof
3. Lack of concrete roof maintenance
4. Water ponding on the concrete roof
5. Concrete roof subjected to heavy loads
6. Rooftop open to chemical exposure

How Long Does a Concrete Roof Waterproofing Last?

A roof’s concrete waterproofing can last between 10 – 25 years if the concrete roof is regularly maintained and repaired. The durability of concrete waterproofing depends on the quality of the material, environmental impact, installation expertise, and human activities.

Can You Waterproof a Concrete Roof DIY?

Yes, you can do concrete roof waterproofing DIY. Before you start the DIY project, you should know all about roof waterproofing in order to conduct the project cost-effectively and time-effectively. When you reach Aqvize, one of our experts will help you to conduct your project more efficiently.

Should You Seal a Tiled Concrete Roof?

Yes, you should seal a tiled concrete roof using a waterproof coating or sealant like epoxy because tile and tile grouts are not waterproof materials. Tiles have a lower porosity, while tile grout has a higher porosity than tile. When these are saturated, water can seep over time. As well as there can also be small cracks and application errors in the grout line. This also increases the water leak to the concrete roof over time.

Should You Waterproof a Metal Roof?

Yes, you should waterproof the metal roof to prevent water leaking from the non-sealed screws, joints, and seams and stop the corrosion from the water. You should know how to waterproof a metal roof before you start doing it DIY. Metal roof waterproofing is easier than concrete waterproofing. But you should follow the proper metal roof waterproofing steps from the beginning.