Water proofing is the process of making an object or structure waterproof or water resistant so that it remains relatively unaffected by water or resisting the ingress of water under specified conditions. “Water resistant and “water proof” often refer to penetration of water in its liquid state and possibly under pressure, whereas: “damp-proof” refers to resistance to humidity or dampness.
In Uganda, the standards guiding the Construction Industry in relation to water proofing is the British Standards Institution (BSI) BS.8102:2009 -“Protection of Below Ground Structures against water from the ground.” This has also greatly improved the standards for water proofing bathrooms in domestic construction over the years due to the general tightening of the building codes.
In construction, water proofing is used in reference to building structures such as: basements, decks, or wet areas. A building or structure is water proofed with the use of membranes and coatings to protect contents as well as protecting structural integrity. Water proofing is a fundamental aspect of creating a “building envelope” (physical separator between the conditioned and un conditioned environment of a building including the resistance to air, water, heat, light and noise transfer) which is a controlled environment.
Water and water vapour control;
The main strategies commonly employed are perfect barriers, drained screens and mass/storage systems. Moisture can enter basements through the walls or floor. Basement water proofing and drainage keep the walls dry and a moisture barrier is needed under the floor. The roof covering materials, siding (wall cladding), foundations, and all of the various penetrations through these surfaces need to be water-resistant and sometimes waterproof.
Roofing materials are generally designed to be water-resistant and shed water from a sloping roof, but in some conditions, such as: ice damming and on flat roofs, the roofing must be waterproof.
Many types of waterproof membrane systems are available, including
- APP (which stands for Atactic Polypropylene). This membrane is the most commonly used waterproofing material on concrete roofs, low-slope roofs, lean to roofs &/or hidden roofs with parapet walls
- Others include; felt paper or tar paper with asphalt or tar to make a built-up roof, other bituminous water proofing, EPDM rubber, hypalon, polyvinyl chloride, liquid roofing and many others. Walls aren’t subject to standing water, and the water-resistant membranes used as house wraps are designed to be breathable to let moisture escape.
But in concrete in foundations needs to be water proofed with a liquid coating, basement water proofing membrane (even under the concrete slab floor where polyethylene sheeting is commonly used) or an additive to the concrete.
As for the earth sheltered houses, the potential problem is too much humidity; so water proofing is critical in these houses. Water seepage can lead to mould growth causing significant damage and air quality issues. Properly water proofing foundation walls is required to prevent deterioration and seepage.
Another specified area of water proofing is roof top decks and balconies. Water proofing systems have become quite sophisticated and are a very specialized area. Failed waterproof decks and tile decks are one of the leading causes of water damage to building structures, as well as personal injury when they fail.
Where major problems occur in the construction industry is when improper products are used for the wrong application. While the term “waterproof” is used for many products, each of them has a very specific area of application and when manufacturer specs and installation procedures aren’t followed, the consequences can be severe.
Another factor is the impact of expansion and contraction on waterproofing system for decks. The penetrations through a building envelope need to be built in a way such that water doesn’t enter the building e.g. using flashings and special fittings for pipes, vents, wires etc. Some caulking is durable, but many aren’t a reliable method of water proofing.
There are 2 main types of integral water proofing systems namely;
1. Hydrophilic system. This system typically uses a crystallization technology that replaces the water in the concrete with insoluble crystals. It must be noted that various brands available in the market claim similar properties, but not all can react with a wide range of cement hydration by-products and thus require caution.
2. Hydrophobic system. This uses fatty acids to block pores within the concrete, preventing water passage.
Generally, new technology in waterproof membranes relies on polymer-based materials that are extremely adhesive to create a seamless barrier around the outside of a structure. Water proofing should not be confused with roofing since roofing cannot necessarily withstand hydrostatic head while water proofing can.
‘Hydrostatic head’ is used to denote the amount of pressure of water that is required in order to penetrate a given fabric.