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D2626 – Standard Test Method Technical Guide
🛠️ Materials and Manufacture
ASTM D2626/D2626M covers asphalt-saturated and coated organic felt base sheet designed for built-up roofing systems. During manufacture, a single thickness of dry organic felt is saturated with hot asphalt, coated on both sides with a hot asphaltic material, and surfaced on the top side with protective mineral granules. The felt must be produced principally from organic fibers and exhibit a uniform, relatively smooth surface free of lumps and foreign substances. The coating may be compounded with a mineral stabilizer to enhance its performance. The reverse side of the base sheet may be covered with a suitable material to prevent sticking in the roll, ensuring efficient field application.
📐 Physical Properties and Dimensional Standards
The material must conform to strict physical requirements. Table 1 of the standard establishes the following key performance criteria for the base sheet.
| 🟦 Property | 🎯 Specification Requirement |
|---|---|
| Mass per unit area, min | 2900 g/m² [59 lb/100 ft²] |
| Ash, max, mass % | 30 % |
| Pliability (at 25 mm [1 in.] radius) | No cracking |
⚠️ Critical Handling Note: The finished product must not crack nor be so sticky as to cause tearing or damage upon being unrolled at temperatures between 10 and 60 °C [50 and 140 °F]. This ensures reliable workability across a wide range of ambient conditions.
Dimensional tolerances are equally critical. The base sheet must conform to the following standard roll dimensions as specified in Table 2 of the standard.
| 📏 Parameter | 📐 Specified Tolerance |
|---|---|
| Width | 914 mm [36 in.] (variation max: +3 mm, -0 mm) |
| Length per Roll | 31.1 m [102 ft] |
| Net Mass per Roll (Lot Average) | Min 31.2 kg [68.8 lb] / Max 34.5 kg [76.0 lb] |
🏗️ Application and Usage
Per the Scope (Section 1.1), the primary application for this sheet is as the first ply of a built-up roof assembly. When the sheet is manufactured without perforations, it is also suitable for use as a vapor retarder when applied with a solid mopping of asphaltic material under roof insulation or between multiple layers of insulation. Perforated base sheets must conform to the same requirements as the plain type but must also feature uniformly spaced perforations for venting. For sampling purposes, a lot shall consist of all material of the same type and size offered for delivery at one time.
💡 Technical Note: The values stated in either SI units or inch-pound units are to be regarded separately as standard. Combining values from the two systems may result in nonconformance with the standard.
❓ Frequently Asked Questions
🔍 What is the scope of ASTM D2626/D2626M?
This specification covers asphalt-saturated and coated organic felt base sheet with mineral surfacing on the top side. It is used as the first ply of a built-up roof and is suitable as a vapor retarder when unperforated.
💡 What are the temperature limits for handling the material?
The finished product must not crack or become excessively sticky when unrolled at temperatures between 10 and 60 °C [50 and 140 °F]. This ensures the material performs correctly during application.
📌 What test methods govern this specification?
The specification references ASTM D146/D146M (Sampling and Testing Bitumen-Saturated Felts) and ASTM D228/D228M (Testing Asphalt Roll Roofing) for evaluating compliance with physical requirements.
⚡ How is a lot defined for inspection purposes?
For the purpose of sampling, a lot shall consist of all material of the same type and size offered for delivery at one time. Individual rolls must conform to mass tolerances of ±1.8 kg [±4.0 lb] from the lot average.