Water infiltration facilitates mold growth, rots wood and cracks concrete, adversely affecting occupants’ health and causing structural issues. Waterproofing buildings during construction is vital for maximizing building longevity. If industry professionals move beyond the fundamentals, they can master weatherproofing. What essential strategies must they learn?
1. Mimicking Natural Drainage Systems
A green roof comprises a waterproof roof membrane, growing medium and vegetation. Each layer helps prevent water intrusion. Ground cover intercepts and stores rainwater, while the soil holds a considerable amount of runoff. The moisture barrier is the final line of defense, preventing ceiling leaks despite excess moisture.
This modern system can collect and disperse water, even in extreme rainfall. Research shows that a green roof with a 10-centimeter substrate can retain between 81 and 87 percent of stormwater on average, delaying runoff by up to 3.5 hours. It may not be suitable for every project since it has unique maintenance requirements, but architects and engineers should keep it in mind.
Researchers also identified that plant species selection significantly affects water retention capacity, with certain species providing optimal performance while requiring minimal maintenance.
2. Waterproofing Cement Before Pouring
Typically, waterproofing cement involves cementitious coatings or waterproof membranes. Instead, builders can incorporate a water-repellent additive into the mix at the batching plant or after filling the concrete mixer truck. It blocks cement mortar pores, preventing moisture transmission through the slab.
Unlike sealers, this waterproofing process does not require separate application, streamlining the construction process. It also does not adversely affect compression strength. Depending on its type, it may even increase flexural strength and freeze-thaw durability. A broad range of formulations exists for virtually any mix design, so careful selection is necessary.
Recent research on concrete waterproofing admixtures has identified four main categories based on their waterproofing mechanisms: densifiers, water repellents, pore blockers and crystalline admixtures. According to industry experts, crystalline waterproofing technology has shown the most promising results for long-term durability. These admixtures react with water and cement particles to form insoluble crystals that block pores and capillaries, creating a permanent waterproofing solution throughout the entire concrete structure rather than just surface protection.
3. Implementing Roof-Hardening Strategies
When selecting a waterproof membrane for the roof, professionals must consider the slope, climate and maintenance requirements.
Thermoplastic polyolefin and polyvinyl chloride can withstand freeze-thaw cycles and snow load pressure. They can also help prevent ice dams, stopping water from backing up and leaking into the building, making them ideal for colder climates. That said, no one-size-fits-all solution exists. Decision-makers should use their best judgment when selecting roof-hardening strategies.
Recent developments in TPO (thermoplastic polyolefin) roofing membranes have focused on improved durability and installation techniques. According to patent information, manufacturers have developed enhanced TPO membranes with improved stretchability, ranging between 5 lbf to 30 lbf (for 30-mil thickness samples). Additionally, innovations in TPO corner patching have addressed one of the most challenging aspects of installation. New corner patches formed from circular pieces of TPO membrane material use vacuum-formed flute designs that better conform to outside corners, creating more reliable watertight seals at these critical juncture points.
4. Diverting Water Away from the Foundation
The role of waterproofing in foundation health cannot be overstated. Long-term submersion of a below-grade membrane creates excessive pressure. The resulting concrete cracks allow for seepage, creating a hidden structural issue. The homeowners may not realize the building envelope is compromised until they wake up after a heavy storm to a flooded basement.
Drainage redirects water away from the foundation and keeps it from reabsorbing into the surrounding substrate. Perforated drains in gravel-fill trenches can prevent soil erosion and divert rainwater. They maintain the yard’s optimal grading, mitigating flooding. As a bonus, French drains and bioswales may contribute to property values.
The American Society of Civil Engineers (ASCE) Policy Statement 360 on Climate Change identifies the critical need for revising engineering design standards to address climate resilience in infrastructure systems, including foundations. The policy emphasizes that “Changes in ocean levels will require adaptation of infrastructure design in coastal areas… as well as residential and industrial areas.” ASCE specifically calls for engineers to “incorporate resilience to future climate changes into project design criteria” and notes that current practices “do not adequately address concerns associated with climate change.” The organization highlights that civil engineers must revise practices for infrastructure with long service lives (50-100 years) to ensure systems remain “functional, durable, and safe” despite increasing climate-related stresses, including changes in groundwater patterns and extreme precipitation events that directly impact foundation systems.
5. Applying Positive-Side Waterproofing
In addition to installing a waterproof membrane for the roof, builders should implement below-grade waterproofing. Water is a natural thermal conductor, catalyzing heat transfer in already-cold basements and crawlspaces. The foundation should have a water-impermeable coating to block moisture infiltration.
A prefabricated elastomeric sheet or liquid-applied membrane is necessary. Positive-side foundation waterproofing is generally superior to its blind-side and negative-side counterparts because it stops water intrusion at the source instead of after it has entered the substrate. However, it is not practical for high-rise structures or underground spaces in dense urban areas.
Waterproofing chemicals like rubberized asphalt provide a seamless, heavy-duty protective barrier for commercial or industrial use. This liquid-applied coating cures quickly, resists wear and is flexible. It adheres well to various substrates and resists cracking related to temperature changes or structural movement, making it ideal for below-grade applications.
6. Improving Building Envelope Tightness
Air sealing without contributing to moisture issues requires careful planning. Windows, doors and sheathing are key focus areas. Sealing the building envelope before adding the drywall will help prevent air gaps, preventing water from infiltrating or accumulating in concealed places.
Waterproofing chemicals are ideal because they quickly create durable protective barriers for long-lasting leak protection. Professionals can use epoxy injections to seal concrete cracks or a polyurethane membrane to waterproof flat roofs. They help extend structural longevity and can inadvertently improve indoor air quality by mitigating mold growth.
7. Positioning Adequate Roof Ventilation
Adequate ventilation allows cold air to circulate in the attic, preventing warm spots from contributing to ice dam formation. If melted snow cannot properly drain, the trapped water seeps under the shingles. Once water gets in, it can refreeze. Its volume will expand by 9 percent, causing structural damage. Ridge and gable vents can help regulate the indoor air temperature.
8. Installing Suitable Insulation Throughout
Insulation helps maintain a consistent roof temperature, preventing uneven snowmelt. Double or triple window glazing is ideal for reducing heat transfer. Added benefits include improved energy efficiency and quieter indoor environments, which may help convince clients to invest in more expensive solutions.
While foam, cellulose and fiberglass are common insulation materials, modern alternatives like mineral wool and polyurethane may be better. For instance, aerogel has a 10 R-value per inch, making it one of the best building insulators. However, decision-makers must consider material costs — superior solutions often have premium prices.
9. Inspecting and Maintaining Waterproofing
Roof age plays a role in ensuring a building is adequately waterproofed. In typical use cases, metal roofs last about 50 to 80 years, asphalt roofs last about 20 years and the lifespan of other materials lifespan also plays a factor:
- Slate: 60 to 100 years
- Copper: 60 to 70 years
- EPDM Rubber: 12 to 25 years
- TPO: 10 to 20 years
- Wood: 25 to 30 years
It is vital to consider the average roof’s longevity and the need for ongoing maintenance to seal and protect envelopes. Building occupants can easily miss leaks if they believe they are protected. They may notice water pooling in their basement after heavy rainfall, but seepage in concealed spaces like the attic is easy to overlook. Missing shingles, clogged gutters, and cracked vent boots compromise waterproofing strategies.
Regular inspections and maintenance ensure the integrity and longevity of sealants, insulation and membranes. Water spray tests and infrared monitoring can help professionals identify the point of entry and address the root cause of the problem. Architects should design with maintenance in mind to simplify this process.
The Importance of Waterproofing in Building Construction
Preventing water intrusion is vital for preserving building occupants’ well-being and preventing inconspicuous structural damage. Whether builders install a waterproof membrane for the roof or apply rubberized asphalt to the foundation, they lengthen the structure’s lifespan. Mastering these techniques will improve build quality and durability.
