Providing concrete proof

Is waterproofing an absolute necessityfor modern structures? Sukanta Mallikshows why it is important.

A renowned architect received acall from one of an infuriated client stating that water is dripping on thedinner table and his guests are about to reach his home. So, what should he doto stop the water from dripping? The architect replied: “Pull the dining tableto another part of your hall and enjoy the dinner.”

Waterproofing issues have botheredhumanity since the Neanderthals started living in caves and have been a majorissue for people living in contemporary structures. Throughout the early days,the fight to keep shelters safe from elements of nature like water haspersisted.

Despite centuries of material andconstruction technique advancements, these elements continue to pose achallenge to our buildings. We do not suffer due to a lack of effectivewaterproofing systems or products, but actually, it is due to the problemslisted below.

Increased complexity of construction

The inability to coordinateinterfacing between the multitude of construction systems involved in a singlebuilding and a blatant disregard for most of the waterproofing principles likecuring, joints and cracks treatment, surface preparation, etc., is one of themajor issues.

Most of the specifications do notmention the detailing of the transition from one component to another andtermination of the system into the structural components, etc., which areoverlooked during execution. But, the most important factor which isresponsible for the failures is the specified system’s inability to act as anintegrated system and act independently, not cohesively.

However, presently, the market isflooded with different versatile materials and specifications promoted bydifferent manufacturers. Also, most organizations are investing a considerableamount in R&D for better materials and systems. Without going into thedetails of each type of material, we will take a look into the basic principlesand techniques of waterproofing from where we can choose a proper material anddraw a proper specification.

For any successful waterproofingspecification, we need to design the ‘building envelope’ which is considered asthe most important defence system for any structure and includes three basicsteps:

1. Identifying the probable sourcesfrom where the water may penetrate. For this, we need to understand thestructural behaviour as well as the construction process through which thestructure will take the desired shape.

2. Identify the best-suitedmaterial and system which will be compatible with the particular type ofconstruction.

3. Designing the finalspecification with proper detailing of each component and different areas ofthe building envelope.

Water sources

The main sources of waterpenetration in a structure are the water that comes in contact with thepositive surface, such as rainwater for the roof chajjas, and other exposedareas and groundwater for the below-grade portion of the structure. The forceswhich push the water into the structure are generally:

1. Gravitational force.

2. Capillary force.

3. Hydrostatic pressure.

4. Surface tension.

5. Air/wind pressure.

Designing and framing specification

After the complete analysis andunderstanding of the structure, expected condition for the particulargeographical area, and the probable sources of the leakages, we can now startthe process of making the specification. A good specification should consist ofthree basic purposes:

1. Water barrier,

2. Drainage system, and

3. Diversion.

Water barrier: By its name, we canunderstand that this is the membrane system that will not allow the water totouch the main structure. This can be a liquid-applied membrane system or apre-formed membrane.  

Drainage system: This is a part of thebuilding envelope; this permits water absorption and infiltration through it toprovide a way of collecting water for diverting it to a natural source.

Diversion is the method that willredirect the collected water which may create a force on the membrane andprolonged pressure may damage the barrier.

Water Path

Besides the porous concrete surface,the other venerable areas from where the water ingress into the structure are:

Capillary pores: Generated duringhydration of cement.

Honeycomb: Due to poor mix ofproportion, wrong workability, and bad workmanship.

Cracks: Thermal cracks, settlementcracks, shrinkage cracks, etc.

Basic steps to be considered while making a specification ofWaterproofing

-         The concrete which will be usedfor the structure should be made dense and sound by using water reductionadmixture and using the integral waterproofing compound to reduce the capillarypaths and minimize shrinkage cracks.

-         Special care of constructionjoints is to be considered while making the specification as we know that theconstruction joints are the most vulnerable point through which the water isused to travel. To prevent leakages from the area, we need to use bondingagents and suitable water stoppers to make the construction joints leak proof.

-         Provide a water barrier at thepositive surface, which is known as a building envelope. This can be made byusing different type of materials which is largely classified as:

1. Liquid applied membrane, and

2.Preformed membrane.

Filling voids and cracks by injection grouting/crystallization processes: This system is generally used as post-construction waterproofing. Thereare different types of grouting materials ranging from cementitious to epoxy,PU, acrylic, etc. Grouting itself is a very big subject, which involves so muchdetailing and operations. In the future, this can be discussed in depth.

Design criteria for selecting Waterproofing Material

The following points are alsoneeded to keep in mind while choosing a material for a building envelope:

1 Should not be a biodegradablematerial and have a long life.

2 Easy to apply because, in the end,it will be applied by skilled or unskilled manpower at the site.

3. Reasonable price to make thesystem affordable and should not increase the project cost considerably.

4. Eco friendly: Presently, this isthe most important aspect.

A study says that poorwaterproofing has damaged far more structures than war and natural calamity. Toproduce a foolproof waterproofing system, we need not spend much but followsome basic rules such as:

1. The specification needs to befollowed religiously, and should not be compromised for time constraint.

2. For any type of waterproofing,surface preparation is very important. Even if the desired surface condition isnot achievable, the specification should be changed. However, while making thespecification, the same should be taken into account.

3. Care to be taken while doing theother activities like core cutting, groove cutting, etc., before executing thewaterproofing. The other work to be computed.

Waterproofing the Future

We always emphasize thewaterproofing material and technology for waterproofing which we are used to. Wegenerally need to pay more attention to the basic requirement of structurewhich will make the waterproofing successful. A minor modification and care,which really costs nothing to the owner, may reduce the cost of waterproofingdrastically.

Author’s credit:

Sukanta Mallik is a civil engineerwith 36 years of experience. He has worked 10 years in construction, and 26years in construction chemical industries with reputed industries in thisfield. He is presently working as an independent consultant and trainer for 
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