All you need to know about waterproofing in Singapore

• Waterproofing is the combination of materials used to prevent water intrusion into the structural elements of a building or its finished spaces. Its main purpose is to resist hydrostatic pressure exerted by moisture in the liquid state.

• TO PROVIDE PROTECTION FROM ALL ELEMENTS INCLUDING WIND, COLD, HEAT, AND RAIN.

3 STEPS TO ENSURE WATERTIGHT AND ENVIRONMENTALLY SOUND INTERIOR

• 1. Understanding water sources likely to be encountered.
• 2. Designing systems to prevent leakage from these sources.
• 3. Finalizing the design by properly detailing each individual envelope component into adjacent components.

WATER SOURCES

Water likely to penetrate building envelopes is most commonly from rainwater on above-grade components and groundwater intrusion below-grade. Other sources also should be considered as appropriate, such as melting snow, overspray from cooling towers, land-scaping sprinklers, and redirected water from such sources as downspouts and gutters.

TYPES OF FORCES

• ● Natural gravity
• ● Surface tension
• ● Wind/air currents
• ● Capillary action
• ● Hydrostatic pressure

DESIGNING TO PREVENT LEAKAGE

• 1. Barrier
• 2. Drainage
• 3. Diversions

BARRIER SYSTEMS

• Barrier systems are, as their name implies, effective and complete barriers to water infiltration. They include actual waterproofing systems such as below-grade urethane membranes and other envelope components such as glass.

DRAINAGE SYSTEMS (RAIN SCREEN SYSTEM)

• Drainage systems are envelope components that might permit water absorption and some infiltration through the substrate but provide a means to collect this water and divert it back out to the exterior before it causes leakage.

DIVERSIONS

• Diversions actually redirect water being forced against envelope components and divert it elsewhere before it infiltrates or absorbs into the substrate.

COMPLETING THE ENVELOPE

• Once the sources of water have been identified, the types of systems to prevent leakage chosen, and the materials selected to provide necessary aesthetics to the finished product, the envelope design must be carefully constructed and reviewed to ensure successful performance of the completed product. 

BASIC ENVELOPE DESIGN

• Roofing
• Below-grade waterproofing
• Above-grade waterproofing
• Damp proofing
• Flashing
• Diversion
• Building envelope

Roofing

• That portion of a building prevents water intrusion (usually from gravitational forces) in horizontal or slightly inclined elevations. Although typically applied to the surface and exposed to the elements, roofing systems also can be internal, or sandwiched, between other building components.

Below-grade waterproofing

• Materials that prevent water under hydrostatic pressure from entering into a structure or its components. These systems are not exposed or subjected to weathering such as by ultraviolet rays.

Vulcanized rubbers

Vulcanized rubbers are available in butyl, ethylene propylene diene monomer (EPDM), and neoprene rubber. These materials are vulcanized by the addition of sulfur and heat to achieve better elasticity and durability properties. Membrane thickness for all rubber systems ranges from 30–60 mil. These materials are nonbreathable and will disband or blister if a negative vapor drive is present. As with thermoplastic materials, vulcanized rubbers are available in rolls of varying widths. Seam sealing is by a solvent-based adhesive, as heat welding is not applicable. A separate adhesive application to vertical areas is necessary before applying membranes. Vulcanized rubber systems incorporate loosely laid applications for horizontal installations.

Above-grade waterproofing

• A combination of materials or systems that prevents water intrusion into exposed structural elements. These materials can be subject to hydrostatic pressure from wind conditions and are exposed to weathering and pollutant attacks.

Damp proofing

• Materials are resistant to water vapor or minor amounts of moisture that act as backup systems to barrier systems or an integral part of drainage systems.

Flashing

• Materials or systems are installed to redirect water entering through the building skin back to the exterior. Flashings are installed as integral components of waterproofing, roofing, and damp proofing systems. They also can act as diversion systems.

Diversions

• Diversions redirect water being forced against envelope components and divert it elsewhere before it infiltrates or absorbs into the substrate. Examples include flashings, downspouts, sloped concrete decks, and drainage mats.

Building Envelope

• The combination of roofing, waterproofing, damp proofing, flashing, and diversion systems in combination with all exterior facade elements acting cohesively as a complete barrier to natural forces and elements, particularly water and weather intrusion. These systems envelop a building or structure from top to bottom, from below grade to the roof.

MOST IMPORTANT PRINCIPLE

• The 90% / 1% principle: 

90 percent of all water intrusion problems occur within 1 percent of the total building or structure exterior surface area.

SECOND MOST IMPORTANT

• The 99% principle: 

Approximately 99 percent of waterproofing leaks are attributable to causes other than material or system failures.

Surface water control

• Water present at below-grade surfaces is available from two sources—surface water and groundwater. Beyond selection and installation of proper waterproofing materials, all waterproof installations must include methods for control and drainage of both surface and groundwater.

Groundwater control

• Besides protection from normal groundwater levels, allowance is made for temporary rises in groundwater levels to protect interior areas. Groundwater levels rise due to rain accumulations and natural capillary action of soils. Waterproof materials must be applied in heights sufficient to prevent infiltration during temporarily raised groundwater levels.

Water Stops

• Whenever a construction joint occurs in a below-grade concrete structure, a water stop should be installed in the joint to prevent the transmission of water through the joint. Construction joints, also referred to as “cold-joints,” occur when one section of concrete placed and cured or partially cured before the adjacent concrete placement occurs.
• ● Polyvinyl chloride (PVC)
• ● Neoprene rubber
• ● Thermoplastic rubber
• ● Hydrophilic (modified chlorophene)
• ● Bentonite clay
• ● Asphalt plastic

Cementations system

• Cementations waterproofing systems contain a base of Portland cement, with or without sand, and an active waterproofing agent. There are four types of cementations systems: metallic, capillary system, chemical additive systems, and acrylic modified systems. Cementations systems are effective in both positive and negative applications, as well as in remedial applications. These systems are brushed or toweled to concrete or masonry surfaces and become an integral part of a substrate.

Cementation system

• Metallic System

  • Metallic materials contain a mixture of sand and cement with finely graded iron aggregate or filings. When mixed with water to form a slurry for application, the water acts as an agent permitting the iron filings to oxidize. These materials expand due to this oxidizing, which then effectively seals a substrate and prohibits further transmission of water through

• Capillary/crystalline systems are mixtures of cement and sand in combination with proprietary chemical derivatives in dry or liquid form. The systems are applied in trowel, brush, or spray applications. Unlike other cementations systems however, capillary have the additional advantage of an application using only the dry mix product that is broadcast directly over concrete that has not yet reached final set and cure. This is referred to as the “dry-shake” method, commonly used on slab components as a vapor barrier, as additional protection with below-grade slab waterproofing systems, or as a stand-alone waterproofing system.

• Chemical cementations systems are a mixture of sand, cement, and proprietary chemicals (inorganic or organic), which when applied to masonry or concrete substrates provide a watertight substrate by chemical action. Proprietary chemicals are unique to each manufacturer, but typically include silicate and siloxane derivatives in combination with other chemicals. While the chemicals do not penetrate the substrate like the other cementations systems, chemical systems also effectively become an integral part of the substrate after application.

• Acrylic modified cementations systems add acrylic emulsions to a basic cement-and-sand mixture. These acrylics add waterproofing characteristics and properties to in-place materials. Acrylic systems are applied in two trowel applications, with a reinforcing added into the first layer immediately upon application. This mesh adds some crack-bridging capabilities to acrylic installations. However, since the systems bond tenaciously to concrete or masonry substrates, movement capability is limited.

Urethane

• Urethane systems are available in one- or two-component materials. Black coloring is added only to make those people who believe waterproofing is still “black mastic” comfortable with the product. Urethanes are solvent-based, requiring substrates to be completely dry to avoid membrane blistering. These systems have the highest elastomeric capabilities of fluid-applied membranes,  averaging 500–750 percent by standardized testing. Urethanes have good resistance to all chemicals likely to be encountered in below-grade conditions, as well as resistance against alkaline conditions of masonry substrates.Rubberized asphalts

Rubberized asphalt sheet systems originally evolved for use in pipeline protection applications. Sheet goods of rubberized asphalt are available in self-adhering rolls with a polyethylene film attached. Self-adhering membranes adhere to themselves, eliminating the need for a seam adhesive. Sheets are manufactured in varying widths of 3–4 ft and typically 50-ft lengths.

Fluid System

Fluid-applied waterproof materials are solvent-based mixtures containing a base of urethanes, rubbers, plastics, vinyls, polymeric asphalts, or combinations thereof. Fluid membranes are applied as a liquid and cure to form a seamless sheet.

• Rubber derivatives

Rubber derivative systems are compounds of butyls, neoprenes, or hypalons in a solvent base. Solvents make these materials flammable and toxic. They have the excellent elastomeric capability, but less than that of urethane membranes. Rubber systems are resistant to environmental chemicals likely to be encountered below grade. As with most fluid membranes, toxicity requires the safety training of mechanics in their use and disposal.

• Polymeric asphalt

A chemical polymerization of asphalts improves the generic asphalt material qualities sufficiently to allow their use as a below-grade waterproofing material. Asphalt compounds not require drying and curing of a masonry substrate, and some manufacturers allow installation of their asphalt membranes over uncured concrete. However, asphalt materials are not resistant to chemical attack as are other fluid systems. These membranes have limited life-cycling and are used less frequently than other available systems.

• Polyvinyl chloride

Solvent-based PVC or plastics are not extensively used in liquid-applied waterproofing. These derivatives are more often used as sheet membranes for roofing. Their elastomeric capabilities are less than other fluid systems and have higher material costs. They do offer high resistance to chemical attacks for below-grade applications.

• Coal tar and asphalt-modified urethane systems lessen the cost of the material while still performing effectively. Extenders of asphalt or coal tar limit the elastomeric capabilities and chemical resistance of these membranes. Coal tar derivatives are especially toxic, and present difficulties in installing in confined spaces such as small planters. Coal tar can cause burns and irritations to exposed skin areas. Field mechanics should take necessary precautions to protect themselves from the material’s hazards.

• Thermoplastics

Thermoplastic sheet-good systems are available in three compositions: PVC, chlorinated polyurethane (CPE), and chlorosulfonated polyethylene (CSPE), which is referred to as Hypalon. Materials are manufactured in rolls of varying widths, but difficulty with vertical applications makes smaller widths more manageable.

• Vulcanized rubbers

Vulcanized rubbers are available in butyl, ethylene propylene diene monomer (EPDM), and neoprene rubber. These materials are vulcanized by the addition of sulfur and heat to achieve better elasticity and durability properties. Membrane thickness for all rubber systems ranges from 30–60 mil. These materials are non-breathable and will disband or blister if a negative vapor drive is present. As with thermoplastic materials, vulcanized rubbers are available in rolls of varying widths. Seam sealing is by a solvent-based adhesive, as heat welding is not applicable. A separate adhesive application to vertical areas is necessary before applying membranes. Vulcanized rubber systems incorporate loosely laid applications for horizontal installations.

• Bentonite clay 

  • is an excellent waterproofing material, but it must be hydrated properly for successful applications. Clay hydration must occur just after installation and backfilling, since the material must be fully hydrated and swelled to become watertight. This hydration and swelling must occur within a confined area after backfill for the waterproofing properties to be effective. Precaution must be taken to ensure the confined space is adequate for clay to swell. If insufficient, materials can raise floor slabs or cause concrete cracking due to the swelling action.