How to Waterproof Your Roof or Terrace During Construction

Terrace or Roof Waterproofing

The open terrace or the roof of your home is directly exposed to the heat of the sun and rains. The water entering inside the concrete of the slab reaches the reinforcement steel. The oxygen thus carried to the steel reacts to form oxides of iron that gives rust.

In this process, the reinforcement steel expands in volume and puts pressure in the surrounding concrete. This gives more room for cracks in the concrete.

As a result, more leakage and the cracks and leakages grow exponentially.

Once the leakage in the roof slab starts it becomes very difficult to repair. The problem becomes recurring and expenses of repairing become higher and higher.

Hence, it is most wise to go for a waterproofing treatment for your roof during the construction phase only. The cost of waterproofing at the construction stage is nominal. But ignoring this very important activity may be very expensive in future.

How to Waterproof Your Roof or Terrace During Construction

You may adopt a twofold step to waterproof your roof or terrace.

Integral Waterproofing

Membrane waterproofing

We will discuss the products Asian Paints Ltd offers here. We will find out what other companies offer in other blogs.

Integral Waterproofing - SmartCare Vitalia Neo from Asian Paints is a good option. 

This product may be used in a wet concrete mix.

The dosage of the red coloured liquid is mentioned in the pack. About 200 ml of the liquid chemical is to be added per 50 Kg bag of cement.

This is effective with M-sand (Manufactured sand) also.

Note that slight overdose of the chemical does not have any adverse effect.

For best result, you may follow the instructions of mixing mentioned on the pack.

The product comes in pack sizes of 200 ml, 1 ltr, 5 ltr, 10 ltr and 20 ltr.

While buying check that the pack is not older than 2 years from the date of manufacture.

SmartCare Vitalia Neo not only meets the requirement of IS 2645 for water permeability but is also compliant with IS 9103 for water reduction in concrete.

The product is lead-free and is water-based.

Some other benefits of SmartCare Vitalia Neo are

Imparts higher compressive strength 

Mixes easily with wet concrete/mortar

Resist corrosion of Reinforcement steel 

Now your slab concrete is in itself become a waterproof structure.

Membrane waterproofing - Smartcare Damp Proof from Asian Paints

Even after integral waterproofing, there might be certain points that may pose some chances of water seepage. To counter this and to have a long term benefit you should apply a membrane waterproofing.

Before applying you need to clean the surface thoroughly. This you can do by scrubbing the surface with a brush, grinder wheel, water jet. You should check that there is no loose particles and dust left.

Remember not to apply the coating in excessive heat or during rains. You need to ensure that the applied coating is not exposed to rain till 4 hours from the time of application.

You need to mix 3 parts of the liquid product with 1 part of clean water and stir well. The mixed liquid is to be applied on the cleaned surface with a roller or a brush in the same direction.

After the whole surface is covered in this manner with one coat let it dry for at least 4 hours.

After that, you can apply another coat of the liquid in the direction perpendicular to the previously applied direction. Let it dry for another 4 hours.

You can apply on the whole floor of the roof slab and extent till the top of the parapet. Ensure that no area is left out.

After the full application process, you will find a rubber-like soft layer been deposited. This is the waterproof membrane. This is an elastomeric resilient acrylic polymer and reinforced with polyester fibres for excellent elongation and tensile properties. Upon curing, it forms a thick, seamless, durable membrane.

Be careful that this membrane is not damaged by sharp objects. A protective coating of geotextiles, tile or simple cement mortar application may be applied so that the coating is not damaged.

Put your comments on how do you see waterproofing activity during the construction phase itself. Do you prefer to get it done during construction or you prefer to do it after some time has elapsed after construction.

Integral Waterproofing

Certain waterproofing chemicals are added to the concrete mix as an integral part of the concrete in minor quantity i.e. less than 3% by the weight of cement which reduces the permeability of the concrete and develops durability. This is known as integral waterproofing.

The manufacturers of such chemicals get the results authenticated by test procedures as described in IS 2645. A product certified by a competent authority of NABL approved testing laboratory may be relied upon.

While choosing an integral waterproofing compound you must check if the product passes IS 2645 test and guidelines and is certified.

These compounds may contain water-soluble Chlorides which is considered corrosive for concrete and reinforcement steel. Hence, you must check the contents of the product. 

The manufacturer is bound to mention chloride content which should be less than 2% by mass (Weight in common term) of the product.

Compressive Strength, initial and final setting times of the concrete should be within limits as mentioned in IS 2645. Note if there is any special caution mentioned by the manufacturer regarding these points.

How does Integral waterproofing compound work

The strength and permeability of the concrete, mortar plaster depend upon the Water – Cement ratio in the concrete during mixing and placing of concrete.

What the integral waterproofing compound does is, it helps to reduce the water requirement in the concrete mix this reducing the water-cement ratio.

When this compound is added it keeps the concrete flowable and workable even with less usage of water.

With less water, the concrete becomes less permeable to water and develops waterproofing quality.

The compound prevents surface cracks (which are developed due to drying shrinkage)

3 Top Integral Waterproofing solutions

There are many integral waterproofing compounds in the market now. One of the main reason for this is that consumers like you and me have understood the importance of waterproofing. We have become aware of the necessity of using an integral waterproofing compound more than ever before.

This is the most effective method since this is a type of preventive method. All other surface applications of water may fail if the subgrade (the concrete, mortar or plaster) is not of good quality.

The 3 most prominent integral waterproofing solutions are mentioned below with their brand names and manufacturers.

SmartCare Vitalia from Asian Paints

Conplast P211 from Fosroc

Sika CIM from Sika

I will discuss one by one to find out which one is most suitable for you.

SmartCare Vitalia Neo from Asian Paints

This product may be used in concrete, cement mortar in brickwork, internal and external cement plaster and even external putty.

You can make use of this compound in water retaining structures, bathrooms, drains, basements and any type of masonry surfaces.

This is effective with M-sand (Manufactured sand) also.

When used with external putty it improves the life of the paint in addition to giving a waterproof surface.

The dosage of the red coloured liquid is mentioned in the pack. About 200 ml of the liquid chemical is to be added per 50 Kg bag of cement.

Note that slight overdose of the chemical does not have any adverse effect.

For best result, you may follow the instructions of mixing on the pack.

The product comes in pack sizes of 200 ml, 1 ltr, 5 ltr, 10 ltr and 20 ltr.

While buying check that the pack is not older than 2 years from the date of manufacture.

SmartCare Vitalia Neo not only meets of the requirement of IS 2645 for water permeability but is also compliant with IS 9103 for water reduction in concrete.

The product is lead-free and is water-based.

It has some other benefits as 

Imparts higher compressive strength.

Mixes easily with wet concrete/mortar.

Resist corrosion of Reinforcement steel.

Conplast P211 from Fosroc

Conplast P211 may be used in concrete and mortar.

This may be used in the concrete and mortar for any place where water tightness is necessary. 

It is also very effective for inner and outer plaster of structures and in renovation works.

While buying check that the date of manufacturing is not more than a year.

The product dosage is not specified and needs a trial and error method at given site condition. The range of usage is 200 to 500 ml per 100 Kg of cement. The dosage may be arrived at while doing the mix design of the concrete.

This is a brown coloured liquid that easily disperses in water and is compatible with other Fosroc concrete chemicals. 

Conplast P211 comes in the pack sizes of 5 ltr, 10 ltr and 20 ltr.

It meets the requirement of IS 2645 for water permeability and is water-based.

Sika CIM from Sika

Sika CIM is a brown coloured fluid admixture which works with concrete and mortar.

In addition to preventing water permeability, it also provides good workability and helps to improve compressive strength.

It is suitable for concrete and mortar for rooftop slabs, damp proof course, Beams, Columns, Water tanks, Culverts, Tunnels, Sewerage works and any structure where watertight cement is required.

It is also effective for inner and outer plastering of structures and renovation works. 

It helps reduce plastering mortar due to rebound.

The chemical also helps in reducing post concrete shrinkage, hence preventing surface cracks.

It meets the requirement of IS 2645 for water permeability and is water-based.

It is available in pack sizes of 200g, 1kg, 5kg, 10kg, 20kg, 230kg.

While buying check the date of manufacturing. It should not be more than 1 year old.

The dosage is only 100g per 50 Kg of cement.

Remember to cure the concrete or plaster with water as per good construction practice. Curing is a must for the efficiency of both the concrete and the compound.

How to choose the one product for your use

By now you must have understood that each of the products is good and are from reputed brands which are leading the markets for decades now.

So how do you choose one. Just follow the simple steps below.

Find out which product is most easily available in your local market through 'locate a dealer' page.

With the cost-calculator find out who has the least cost for the total usage quantity for your project.

In the course of interaction with the dealers, you will come to know who is providing a better service.

For small usages, Asian PAints is the best option.

If you want to use it for large scale projects you may go for Sika or Fosroc.

Hope this gives you a clear idea on the integral waterproofing, the 3 Top Integral Waterproofing Solutions providers and how you can easily select a product for your use.

Please put in your feedback on the article.

Also, write if you have personally used any of the products. If you are going to any of these write about your experience.

Your notes will be very helpful for many other people and guide them.

You may check out my other article on surface waterproofing treatment.

How do you waterproof a concrete water tank

Getting your concrete underground water tank waterproofed is wise rather than doing a layman job and suffering.

The concrete underground tank may develop a structural crack and lead to leakages both from outside and inside of the tank.

The development of structural Cracks may be due to different reasons

• Insufficient design of the RCC (Reinforced Cement Concrete) tank. Cracks develop due to the external pressure developed by the earth around the underground tank or groundwater pressure, especially during the rainy season.
• Once a crack is developed, underground water percolates into the tank along with soluble salts and cause further damage to the RCC structure – both the reinforcement steel and the concrete.

As the design of the RCC underground water tank is important for the success and durability, the waterproofing of the tank is also very necessary.

The waterproofing helps to negate the effect of negative water pressure and positive water pressure.

Negative water pressure is created by the groundwater on the external surface of the tank.

Positive water pressure is created by the stored water on the internal surface of the tank.

If we consider the financial implications and the ease of maintenance waterproofing becomes all the more important. Because the cost of repairing an underground water tank is far more than the cost of waterproofing during the construction stage itself.

Waterproofing both inside and outside the concrete underground tank surfaces

Here, I will give you the step by step waterproofing solution for your concrete underground water tank.

Note: The solution holds good provided the concrete structure is designed properly.

1. The concrete tank should be cured with water for 28 days after de-shuttering.

1. The surface of the tank should be cleaned of dust and free particulate matter and any loose concrete material with a water jet.
2. If any crack or honeycomb are observed on the concrete surface those should be filled with repair mortar. (The mortar may be Cement: Sand = 1:1 with the addition of non-shrink expansive chemical).
3. Check the volume of the tank should be greater than 4 times the surface of waterproofing.
4.  The inner surface should be damp with water but surface dry.
5.  Apply the waterproof paste in 2 coats. The 1st coat should be applied in a single direction – top to bottom or left to right. The 2nd coat should be applied perpendicular to the 1st coat.
6. Similarly, The outer surface should be damp with water but surface dry.
7. Apply the waterproof paste in 2 coats. The 1st coat should be applied in a single direction – top to bottom or left to right. The 2nd coat should be applied perpendicular to the 1st coat.

The waterproof chemical to be used may be in the powder form or in the liquid form depending on the manufacturer.

Different manufacturers have different products with respective brand names.

For this type of surface application for both positive and negative waterproofing, I will suggest

weberdry tex from Saint Gobain

This is a pre-mixed cementitious waterproof for underground concrete water tanks

The product is available in pack sizes of 5Kg and 20 Kg

When you buy to make sure the pack is not more than 1 year from the date of manufacture.

The paste is to be prepared by mixing weberdry tex: water = 3:1 with a slow speed mixer till consistency and lump-free.

2 coats are to be applied with each coat of 1 mm.

The product provides coverage of 5 Sqm/ 20 Kg bag.

Pros 

• Provide resistance to hard water and chlorinated water.
• Ease of application with a brush or trowel.
• Most suitable for water reservoirs.
• It is effective till 50m of depth.
• Resist water pressure both from inside and outside.
• Lower in VOC.
• Non-Toxic.

Cons

• Not suitable for application on porous surface, brickwork, light-weight concrete.
• Cannot be applied to structures subjected to movements or cracked structures.
• Not suitable for structures exposed to the acidic environment.
• The product is not flexible and tends to crack if there is structural movement.

Hope this gives you a fair idea of How to waterproof a concrete water tank with surface treatment.

Please put your comments if you have already used this technique and having a leakage-free tank.

If you have any success story using some other method please share in comments.

If you are facing any similar problem and do not know what is to be done, post the problem in the comments.

How to get a Waterproof Underground Concrete Water Tank

In every building be it residential, office, institute, hospital and so on we need to construct an underground concrete tank as a water reservoir.

Many times it happens that within a short period of time you face the problem of a leaking underground concrete water tank.

The problem of leakage may arise in a newly constructed water tank or an old water tank.

As you know prevention is better than cure. Hence, you must ensure to make the underground water tank waterproof during construction itself so that there is least possibility of the tank to leak after construction and also after many years of usage.

Waterproofing not only makes the water tank leakage-free but also gives strength to the structure.

Here are a few points that you must take care of during the construction phase

• The RCC water tank must be designed by a competent engineer - Reinforcements and Grade of concrete.
• Concrete mixing at site should be as per quality standards and as per the design mix. Weigh batching, Volume batching with concrete mixer is helpful.
• Line, level & dimension of each member of the tank should be maintained as per design.
• Placement of concrete with proper vibration techniques to release entrapped air and voids.
• Prevention of concrete-slurry loss during pouring and vibration with the use of cotton or foam plugs.
• Curing of the concrete structure after 24 hours for at least 7 days & up to 28 days. This is very important.

In addition to the above points, certain chemicals which have been developed as waterproofing chemicals are used at different stages of construction depending on the product to either make the concrete watertight and durable or to give a waterproof film layer blanketing the water retaining surfaces.

The theory states that concrete is watertight and truly so. This can be proved in a laboratory environment.

But all Civil engineers who are working in the construction field know the challenges they face while working at the site. 

The concreting conditions are most of the time not ideal and engineers need to meet the timelines.

Waterproofing is one field where much research has happened and many good products have been launched by various companies. 

What these chemicals do is help make the concrete impervious to water.

What will happen if Waterproofing is not done?

You will not face much problem in the structure in the first one year if there has been even an average quality of construction i.e. the construction been left to non-qualified supervisors and workers alone.

After the first year problems become visible. The root cause of most common problems is found out to be leakages, seepages, bulging and cracking of the concrete, plasters, pealing off the paints and dampness in the walls, formation of salty deposits.

Note that these problems might not appear in the whole of the structure. These are only at very small areas. 

Even these small problem areas will take away the peace of your mind and make you unhappy about your hard-earned investments. 

These problems do not stay at that, they grow in size very fast and exponentially. 

Many Technologies have been introduced by different companies in addressing the leakage problems in underground water tanks faced by engineers and owners in the country over the years.

You may ask, Will waterproofing not add to the cost of construction? Yes, waterproofing is costly. But it is worth the money spent. 

Believe me, I have seen from experience that the expenditure is worth having and will save much more in the long run. More importantly, it will buy you peace of mind.

For basic principles of concreting read waterproof underground concrete water tank 

Apart from adopting good practices during construction, we need to take care of the following

• The construction joints must be leak-proof.
• Treat the construction joints or cold joints using special methods.
• After construction and before usage, test the concrete tank by filling it with water and monitoring the water level inside, to identify any leakages.
• Pressure grout with 1:1 (Water: Cement) grout with the addition of waterproofing chemicals with the help of a manual pump if leakages are found at some points.

Use of waterproofing chemicals in concrete during construction 

Waterproofing chemical comes in liquid or powder form in different pack sizes.

For example, Dr Fixit Pidiproof LW+ from Pidilite Industries Ltd comes as a liquid in pack sizes of – 200ml, 1Ltr, 5Ltr, 10 Ltr, 20Ltr, 50 Ltr.

• The chemical is to be mixed with the concrete.
• The dosage of chemical is 200ml for 1 Bag (50Kg) of cement.
• The total concrete (Volume in Cum) to be used in the water tank can be easily calculated. You can follow my article on How to calculate the quantity of concrete in any structure. And the mix design will give the Bags of Cement / Cum of concrete. Read through the article on How to find cement bags quantity from mix design.
• Total chemical required will be 200ml x Total No. of Cement Bags
• Cost of 1 Ltr is about INR 155/-

Apart from waterproofing property, the chemical has some other benefits like

• Improvement in workability of concrete.

• Surface Cracking of Concrete is prevented.

• It protects the concrete from corrosion.

The chemical is easily available in the market. You may locate a dealer here (https://www.drfixit.co.in/locate/find-dealer)

Similarly, there are other chemicals too by Companies like Fosroc, Sika etc. 

I will bring you with similar other options with the comparative advantages and disadvantages.

Please let know how you look at this solution to waterproofing of underground concrete water tank. 

Write about your experiences and how you came out with an innovative idea. Let know what problems you are facing. 

We may find a solution together that will be helpful for all.