CSA A123.3-05 (2015): Asphalt Saturated Organic Roofing Felt — Technical Specifications and Compliance Guide

Scope and Purpose

CSA A123.3-05 (R2015) — Asphalt Saturated Organic Roofing Felt — is a normative standard developed by the Canadian Standards Association (CSA) that defines the material requirements, performance criteria, and testing procedures for organic-based felts impregnated with asphalt. These felts are primarily used as underlayments in roofing assemblies to provide a temporary or permanent secondary moisture barrier beneath the primary roof covering (e.g., asphalt shingles, clay tiles, or metal panels). The standard was originally published in 2005 and reaffirmed in 2015 without technical changes, confirming its continued relevance within the Canadian construction industry.

The standard covers organic felt manufactured from a base of cellulose fibers (e.g., rags, wood pulp, or recycled paper) that are saturated with a specific grade of asphalt. It excludes coated felts, fiberglass-based felts, and polymer-modified bitumen sheets, which are addressed by other CSA A123 series standards (e.g., CSA A123.4 for glass felt and CSA A123.21 for modified bitumen). The scope also explicitly addresses two product types that correspond to traditional #15 and #30 felt weights, designated as Type I and Type II, respectively.

The primary purpose of CSA A123.3-05 (2015) is to ensure that organic felt underlayments deliver adequate tensile strength, punctur resistance, dimensional stability, and moisture management during the service life of the roof system. By establishing minimum physical property thresholds, the standard helps specifiers and installers select products that can withstand handling, temporary exposure, and the long-term loads imposed by the roofing assembly.

Technical Requirements and Performance Characteristics

2.1 Material and Workmanship

The felt shall be manufactured from a uniform blend of organic fibers, uniformly saturated with asphalt. The asphalt saturation must be sufficient to fill the interstices of the felt without leaving uncoated voids that could compromise water resistance. The finished product shall be free of visible defects such as tears, holes, lumps, or uneven saturation. Rolls must be tightly wound and properly wrapped to prevent damage during transportation and storage.

2.2 Physical Properties

CSA A123.3-05 (2015) establishes minimum performance values for key physical parameters. These requirements are differentiated by type, as summarized in the following table.

The mass and asphalt content values ensure that each product type provides an adequate thickness of bituminous material to resist moisture penetration during a roofing assembly’s service life. Tensile and tear requirements guard against rupture during installation, walking loads, and wind uplift. The low moisture content limit prevents premature decay and dimensional distortion, while the dimensional stability parameter (tested at an elevated temperature for 24 hours) confirms that the felt will not shrink excessively when exposed to moderate heat during installation or service.

2.3 Roll Dimensions and Tolerances

The standard also covers roll sizes. Type I rolls are typically 914 mm (36 in) wide by 36.6 m (120 ft) long, and Type II rolls are normally 914 mm (36 in) wide by 18.3 m (60 ft) long. Tolerances of ±3 mm on width and ±1% on length are allowed. The mass per roll shall be calculated from the required mass per unit area and the roll dimensions; each roll must meet the minimum mass after accounting for the end lap (typically 150 mm) that is excluded from the net area.

Implementation Considerations in Roofing Assemblies

When specifying or installing CSA A123.3-05 (2015) organic felts, several practical factors must be considered to ensure the product performs as intended.

Installation Practices

Organic felt is laid dry with minimum 150 mm top lap and 50 mm side lap. For steep-slope applications (roof slope ≥ 1:3), fastening frequency is typically 300 mm along laps and 600 mm in the field. On low-slope roofs (1:10 to 1:3), the felt should be applied fully adhered or mechanically fastened according to the manufacturer’s specifications. Type II felt is generally specified for high-traffic or exposed conditions because of its greater strength.

Compatibility with Roofing Systems

Asphalt-saturated organic felt is compatible with hot asphalt, cold-applied adhesives, and mechanical fasteners commonly used in conventional built-up roofing (BUR), modified bitumen, and shingle systems. However, it should not be used directly under EPDM or TPO membranes unless a slip sheet is installed, as some polymers may migrate into the felt and cause adhesion problems. The felt also functions adequately as a vapor retarder under limited conditions (see FAQ), but dedicated vapor retarder standards (e.g., CAN/ULC S705.2) are preferred for assemblies with high moisture loads.

Storage and Handling

Rolls must be stored upright in a dry, ventilated area away from excessive heat sources. Exposure to temperatures above 50°C can cause the asphalt to soften and stick adjacent layers. If rolls are stored on a roof deck before application, they should be covered with a waterproof tarp and weighed against wind uplift. CSA A123.3-05 (2015) does not specify a shelf life, but industry practice recommends using the felt within 12–24 months of purchase if stored properly.

Compliance and Quality Assurance

Certification and Marking

Products claiming compliance with CSA A123.3-05 (2015) should bear the CSA mark or be accompanied by a manufacturer’s certificate indicating conformance. Third-party testing by an accredited laboratory (e.g., CSA Group, UL, or Intertek) is required for full certification. The standard requires that each roll be labeled with the manufacturer’s name, product type (Type I or Type II), roll dimensions, and net mass. Caution should be taken to verify that the label also references the standard number (CSA A123.3-05) and the year of reaffirmation (2015), as some older rolls may carry outdated designations.

Quality Control at Factory

The manufacturer must implement a quality management program that monitors mass per unit area, asphalt content, and tensile strength at a minimum frequency of once per production shift. If any lot fails to meet the specified limits, the entire lot is rejected unless re-testing of representative samples demonstrates compliance. In addition, dimensional stability and moisture content must be verified at least quarterly.

Relationship with Other Standards

CSA A123.3-05 (2015) is comparable to ASTM D226-09 (2015) but includes additional provisions for dimensional stability and a different tear test method. For projects that must meet both Canadian and U.S. codes, designers should verify which standard is referenced by the contract documents and the local building authority. In Canada, CSA A123.3 is the primary reference for organic felt underlayments, while asphalt-coated sheets are covered under CSA A123.5.

FAQs

Year of publication: 2026