What Is Bituminous Waterproofing?
Bituminous waterproofing is the dominant category of below-grade waterproofing product sold in North America today. Bituminous products are based on bitumen—a viscous, petroleum-derived hydrocarbon that is the primary component of asphalt and is also produced as a byproduct of coal tar processing. In waterproofing applications, bitumen is modified with rubber compounds or polymer additives to improve flexibility and workability, producing the rubberized asphalt and SBS-modified asphalt membranes sold under hundreds of brand names as peel-and-stick sheets, torched-applied rolls, and trowel-applied coatings.
Bituminous waterproofing has been the industry standard for decades, and it works—on smooth concrete substrates, in the absence of UV exposure, within certain temperature ranges, and when lap seam quality is consistently maintained. But modern construction uses substrates and building methods that expose the fundamental limitations of bituminous chemistry. Hulk Systems Evolved Composite Waterproofing was developed to address those limitations with an acrylic-based system. Learn more about our acrylic waterproofing membrane technology.
Why Bituminous Products Degrade in Sun Exposure
Bituminous waterproofing membranes are inherently vulnerable to ultraviolet radiation. Bitumen contains aromatic hydrocarbon chains that absorb UV energy and undergo photo-oxidation—a chemical breakdown process that progressively hardens and embrittles the material. On a construction site where a foundation is excavated, waterproofed, and waiting for backfill, the membrane may be exposed to sun for days, weeks, or even months. During this window, UV degradation is actively reducing the membrane’s flexibility, elongation, and overall performance.
The practical consequence is well-documented: bituminous membranes installed in spring may begin cracking before fall backfilling occurs. Manufacturers typically specify maximum exposure times for their bituminous products—commonly 30 to 60 days—after which performance cannot be guaranteed. On large projects with extended construction timelines, staying within these exposure windows is operationally difficult. Acrylic-based waterproofing products like Hulk Systems composite waterproofing do not contain bituminous compounds and do not share this UV degradation vulnerability.
Fire Rating Comparison: Acrylic vs Bituminous
As discussed in our post on Class A fire-rated waterproofing, bituminous products are combustible hydrocarbons that cannot achieve Class A fire ratings. Regardless of brand, formulation, or additives, no bituminous waterproofing membrane achieves a Class A flame spread classification under ASTM E84. These products typically test at Class C—the lowest classification—or are unrated.
Hulk Systems acrylic composite waterproofing has been tested to ASTM E84 and carries a Class A fire rating. For projects in jurisdictions with fire-rated assembly requirements, or for applications where a non-combustible waterproofing product is specified or preferred, Hulk Systems composite waterproofing is the clear choice. Explore the complete range of Hulk Systems waterproofing solutions to find the right system for your project.
Flexibility in Freeze-Thaw Cycles
Below-grade waterproofing membranes in cold climate regions must withstand repeated freeze-thaw cycles without cracking or delaminating. This is where bituminous products—particularly aged, UV-degraded bituminous products—frequently fail. As bitumen hardens with age and UV exposure, its elongation and flexibility properties deteriorate. A membrane that was flexible at installation may be brittle by its second or third winter, cracking under the strain of frost heave and thermal movement that a flexible membrane would accommodate without damage.
Acrylic polymer membranes maintain their flexibility across a wide temperature range. Hulk Systems composite waterproofing retains meaningful elongation at temperatures well below freezing, accommodating substrate movement during freeze-thaw events without membrane failure. This freeze-thaw flexibility advantage is one of the primary reasons that contractors in northern climates—Alberta, Saskatchewan, Manitoba, the northern plains, and the upper Midwest—are switching from bituminous to acrylic composite waterproofing systems.
Environmental Considerations
Bituminous waterproofing products, particularly those based on coal tar, have raised environmental and health concerns related to polycyclic aromatic hydrocarbons (PAHs), which are known carcinogens. Coal tar-based products are increasingly restricted or banned in many jurisdictions. Asphalt-based products have lower PAH content but remain petroleum-derived with associated environmental considerations. Acrylic-based waterproofing systems have a more favorable environmental profile and do not carry coal tar or PAH concerns.
The Modern Alternative: Acrylic Composite Waterproofing
The case for switching from bituminous to acrylic composite waterproofing is compelling across multiple dimensions: superior UV stability, Class A fire rating, better freeze-thaw flexibility, compatibility with modern substrates like ICF and SIP, faster spray application, seamless monolithic coverage, and a more favorable environmental profile. Hulk Systems has built the Evolved Composite Waterproofing system to deliver all of these advantages in a single, integrated product that outperforms bituminous alternatives in every meaningful performance category.
Find a Hulk Systems Dealer Near You
If you are ready to make the switch from bituminous to acrylic composite waterproofing—or if you want to understand the difference before your next project specification—Hulk Systems certified dealers are available to discuss your project requirements and provide a system recommendation.
Find a dealer at hulksystem.com/supplier-locator or call 1-833-485-5797. Hulk Systems · hulksystem.com · 1-833-485-5797 · Evolved Composite Waterproofing