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CSA A123.25-18: Standard Specification for Cold-Applied, Self-Adhering Polymer-Modified Bituminous Sheet Membranes for Waterproofing
Scope, Technical Requirements, and Compliance Guidelines for Below-Grade and Above-Grade Waterproofing Applications
Scope and Purpose
CSA A123.25-18 establishes material specifications, performance requirements, and testing methods for cold-applied, self-adhering polymer-modified bituminous sheet membranes intended for use in waterproofing of below-grade walls, foundation slabs, plaza decks, tunnels, and other horizontal or vertical building elements. The standard covers membranes that are fully adhered to the substrate without the use of torches, hot asphalt, or solvent-based adhesives.
The primary aim of this standard is to ensure that self-adhering waterproofing membranes deliver reliable, long-term protection against water ingress under a range of service conditions, including exposure to soil backfill, hydrostatic pressure, and moderate temperatures. Membranes conforming to CSA A123.25-18 are designed to bridge hairline cracks, accommodate minor structural movements, and maintain adhesion over a wide temperature range during installation and service life.
Technical Requirements
Material Composition
The membrane shall consist of a factory-manufactured, flexible sheet comprising a polymer-modified bituminous compound (e.g., SBS or APP modified) bonded to a carrier fabric (such as non-woven polyester or fiberglass scrim). The product must be pre-coated with a release liner that is easily removed at the time of installation. The standard requires that the bituminous compound be homogeneous, free of defects such as holes, tears, or foreign inclusions, and capable of forming a tacky, self-adhered bond when pressed onto prepared substrates.
Physical Properties and Performance Criteria
CSA A123.25-18 specifies the following minimum physical performance requirements, determined in accordance with referenced ASTM or CSA test methods:
| Property | Test Method | Requirement | Typical Unit |
|---|---|---|---|
| Tensile Strength (MD/CD) | ASTM D412 / ASTM D638 | ≥ 4.0 / ≤ 3.5 | kN/m (lbf/in) |
| Elongation at Break (MD) | ASTM D412 | ≥ 200 | % |
| Tear Resistance (MD) | ASTM D1004 | ≥ 20 | N (lbf) |
| Peel Adhesion (to concrete) | ASTM D903 | ≥ 1.75 | N/mm (lbf/in) |
| Water Absorption (24h) | ASTM D570 | ≤ 2.0 | % by mass |
| Low-Temperature Flexibility | ASTM D1970 / E96 | Pass at -18 °C (0 °F): no cracking | — |
| Heat Resistance | ASTM D5147 | No slippage at 100 °C (212 °F) | °C (°F) |
| Hydrostatic Resistance | EN 1928 | ≥ 60 m water column | kPa (psi) |
| Puncture Resistance | ASTM D4833 | ≥ 350 | N (lbf) |
Values for machine direction (MD) and cross direction (CD) are required to be within the defined ratio to ensure adequate in-service performance.
Implementation and Installation Considerations
Proper surface preparation is critical for achieving the adhesion and long-term performance required by the standard. The substrate must be clean, dry, free of protrusions, oil, grease, and curing compounds. Concrete surfaces should have a surface pH ≤ 10 and a moisture content ≤ 4% (by weight) at the time of membrane application. Ambient temperature should be within the manufacturer’s recommended range, typically between 4 °C (40 °F) and 35 °C (95 °F), to ensure adequate tack and adhesion.
Tip: For below-grade applications, ensure the membrane extends at least 300 mm above the final finished grade and is adequately protected by a drainage board or protection course prior to backfilling. Use pressure-sensitive primer on low-suction substrates to maximize bond strength.
The standard recommends lapping all side and end joints by at least 75 mm (3 in). End laps should be staggered to avoid continuous vertical joints. Immediately after positioning, the membrane must be firmly rolled with a weighted roller (minimum 70 kg) to develop full adhesion. All penetrations such as pipes and conduits must be sealed with compatible priming and patching compound after membrane application.
Quality Control and Verification
Installed membranes must be visually inspected for voids, fishmouths, and inadequate adhesion. CSA A123.25-18 encourages performance verification through pull-off adhesion testing on representative areas, with a minimum bond strength of 1.0 N/mm (5.7 lbf/in) considered acceptable for most substrates. For critical applications, including those exposed to heavy hydrostatic pressure, a second layer of membrane may be required with staggered overlaps.
Warning: Self-adhering membranes must not be applied to damp or frozen surfaces. Moisture trapped between the membrane and the substrate can lead to blistering, debonding, and premature failure. Always verify concrete moisture conditions before starting installation.
Compliance and Certification Notes
Manufacturers claiming compliance with CSA A123.25-18 must provide certified test reports from an accredited laboratory demonstrating that their product meets all the physical criteria listed in the standard. Periodic audits by a recognized certification body (e.g., CCMC or CSA Group) are recommended to maintain listing. Product packaging must bear the manufacturer name, product name/type, lot number, date of manufacture, and the statement “Conforms to CSA A123.25-18”.
Compliance Tips:
- Verify that the membrane’s minimum temperature for installation is indicated on the packaging, and always follow the manufacturer’s storage instructions.
- Keep a daily log of substrate temperature, ambient temperature, and relative humidity during installation.
- Use only accessories (primer, sealants, flashings) that are tested and listed to complement the membrane.
It is also important to note that the standard does not cover membranes intended for hot-applied application, solvent-based adhesives, or liquid-applied membranes. Contractors and specifiers should clearly distinguish CSA A123.25-18 membranes from other bituminous sheets (e.g., Type IV SBS modified bitumen roofing membranes) that fall under different CSA standards.
Important: Substitution of non-conforming membranes or dilution of the self-adhering compound can void the warranty and compliance. Field modifications (e.g., cutting, splicing) must follow the manufacturer’s written instructions to avoid compromising the waterproofing integrity.
FAQs
Q: What is the primary application for CSA A123.25-18 membranes?
A: They are used for below-grade waterproofing of foundations, basements, tunnels, and plaza decks, as well as for certain above-grade applications such as balcony decks and planters where a self-adhered sheet membrane is suitable.
A: They are used for below-grade waterproofing of foundations, basements, tunnels, and plaza decks, as well as for certain above-grade applications such as balcony decks and planters where a self-adhered sheet membrane is suitable.
Q: Are CSA A123.25-18 membranes compatible with all concrete substrates?
A: They are designed for clean, dry concrete, masonry, and cement board. For low-suction surfaces or smooth trowel finishes, a compatible primer is recommended to ensure bond. The membrane is not intended for direct application to polystyrene or other thermoplastic insulation without a suitable separation layer.
A: They are designed for clean, dry concrete, masonry, and cement board. For low-suction surfaces or smooth trowel finishes, a compatible primer is recommended to ensure bond. The membrane is not intended for direct application to polystyrene or other thermoplastic insulation without a suitable separation layer.
Q: Can the membrane be installed in cold weather?
A: Yes, but only if the ambient and substrate temperature are above the minimum specified by the manufacturer (typically -10 °C to +5 °C depending on product). The membrane should be stored in a warm environment for 24 hours before installation, and a pressure-sensitive primer may be required to activate the adhesive in colder temperatures.
A: Yes, but only if the ambient and substrate temperature are above the minimum specified by the manufacturer (typically -10 °C to +5 °C depending on product). The membrane should be stored in a warm environment for 24 hours before installation, and a pressure-sensitive primer may be required to activate the adhesive in colder temperatures.
Q: Is a protection course always required?
A: In most below-grade applications, yes – the membrane must be protected from punctures during backfilling by a layer of protection board, rigid insulation, or a drainage composite. For vertical walls, a mechanical attachment of the protection course may be needed to prevent pull-down forces during backfill compaction.
A: In most below-grade applications, yes – the membrane must be protected from punctures during backfilling by a layer of protection board, rigid insulation, or a drainage composite. For vertical walls, a mechanical attachment of the protection course may be needed to prevent pull-down forces during backfill compaction.
This article is prepared for informational and training purposes only. Always consult the latest edition of CSA A123.25-18 and manufacturer instructions for complete requirements.
— Published 2026