Basement Waterproofing Basics

What is waterproofing and why do we need to waterproof? 

In any structure, water has played a major role in the rapid aging and destruction of some parts of it.  From the corrosion of metal members in a structural unit to the peeling of paint and the breaking of other interior finishes in your structure.  Water is a destructive element and should be controlled.

What do you mean by waterproofing something?  It's making someway of preventing or resisting water or any type of liquid from getting through a certain material.  Structurally speaking, waterproofing basically means coming up with a system or a combination of materials that you infuse to your structure to prevent water intrusion into the interior spaces of your building.

The "Building Envelope" or what we call the outer layer or skin of the structure is what we basically want to carefully waterproof.  A successful waterproofing solution is the combination of the right waterproofing systems that work together to fully secure the building envelope.  This means that it's not just one system that should be working but multiple systems that overlap and perfectly transitions from one system to the other.  These systems are the roofing systems, waterproofing of the wall structure, basement waterproofing or below grade structures, design details that compliments the waterproofing systems and other miscellaneous systems that help control water and prevent it from intrusion.

Below are the basic steps and design considerations when you're working on making a waterproofing solution for any structure:

1. Studying the water sources that may likely enter or would try to go through your structure.  Examples of these are rainwater, melting snow, water sprinklers, ground water or water table, water tanks, downspouts and gutters, etc.
2. From your initial investigation and review of the water sources, you now come up with applicable waterproofing systems that would control each sources and prevent them from leaking inside your building. 
3. Lastly is properly detailing of each individual system that will not only work as a system for a specific water source or problem but would also perfectly blend well and transition well with the other systems in your design.
   

Any design flaw in any of the individual systems would break the whole waterproofing system, so make sure that all individual systems should be working properly as designed.

In designing for a particular system for a particular water problem, we should first know how water gets through a structure.  Basically, three conditions must all be available for water to get through the structure, breaking any of these three conditions would then prevent water from entering.  These are:

1. A water source should be present.
2. Some kind of force should move the water.
3. A breach or hole should be present in the structure for the water to get in.

With all these conditions present, water will successfully get through.

The structure can be divided into two major parts for waterproofing.  The "Above Grade" structure or the part of the structure that is visible above the ground and exposed to air and sky, and the "Below Grade" structure or the part of the structure much lower than the ground and usually not exposed to air and the other exterior elements.

Both parts experience different forces - forces that can move water.  So different design solutions and systems are used for both.  Forces that act on the "above grade" are gravity, wind, and surface tension.  While forces that act on the "below grade" are capillary action and hydrostatic pressure.  These forces have been discussed on my past post so I would not discuss it anymore in detail here.  Here's the link to my past post - Waterproofing Through Design Solutions.

Basically, we can divide the major waterproofing systems into three:

• Barrier type - completely blocks of water under all expected conditions.
  
• Drainage type - would permit the absorption of water but then collects it and diverts it back to the exterior before it leaks into the structure.
  
• Diversion type - redirects the water to somewhere else before it is absorbed into the structure.  Example of this is the roof or sloping decks.

Just like what I've said before, these systems should work together, if one fails then everything fails.

Now that I've discussed the principle idea on waterproofing, let's move in more to details.

Let's start with the basics of the below grade or basement waterproofing system.

Basement Waterproofing Basics

Basement Waterproofing or below grade waterproofing systems are all barrier systems but diversion types are usually included with their design.

Let's run through the list of possible basement waterproofing systems that is used for basements:

Waterstops

These are used for construction joints to prevent water from transmitting through the joint. It usually is used with other basement waterproofing systems for a much foolproof design.  It is available in a variety of materials which are:

• Polyvinyl chloride or PVC
• Neoprene rubber
• Thermoplastic rubber
• Hydrophilic
• Bentonite clay
• Asphalt plastic

Cementitious Systems

These systems basically are cement types of basement waterproofing which contain a base of Portland cement, sand - although some do not require them, and a waterproofing agent.

Four types are available for cementitious waterproofing systems:

• Metallic
• Capillary
• Chemical Additive
• Acrylic Modified

Fluid-Applied Systems

These are solvent-based mixtures that are sprayed or brushed onto a surface.

Types of these are:

• Urethane
• Rubber Derivatives
• Polymeric Asphalt
• coal Tar
• Polyvinyl Chloride
• Hot-Applied

Sheet Membrane System

These are thermoplastics, vulcanized rubber and rubberized asphalts basement waterproofing in sheets.

Hot Applied Sheet System

These are like any other sheet membrane system but it uses materials that needs to be applied hot.

Clay Systems

Also known as bentonite, these are composed primarily of motmorillonite clay which swells up when wet.

Vapor Barriers

Typically used for slabs on grade, this system is not a total waterproofing system and may not replace any of the more suitable basement waterproofing systems above.  As its name implies, it blocks of transmission of water vapor that may be present in the soil.  Its use is usually for select areas where actual water transmission does not happen.

As you can see, there are a lot of possible basement waterproofing systems you can use to protect your basement and any below-grade structures.  Water conditions are far worse in below-grade structures than above-grade structure that is why a good basement waterproofing system should be applied on these areas.

I've explained just a basic idea of what you need to understand about basement waterproofing but I'll go through the details one at a time in future posts.