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D6380 – Standard Test Method Technical Guide
🏗️ Scope and Classification of Roll Roofing
ASTM D6380/D6380M specifically covers asphalt roll roofing composed of an organic felt base saturated and coated with asphalt. The standard categorizes products into three distinct classes based on their surfacing and application, allowing specifiers to select the exact material required for the project.
- Class S (Smooth): Surfaced with powdered talc, mica, or other fine mineral matter to prevent sticking. Typically used when the surface will be concealed under a subsequent coating or layer.
- Class M (Mineral): Surfaced on the weather side with mineral granules for UV protection and aesthetics, except for any selvage edge.
- Class WS (Wide Selvage): Surfaced on the weather side for approximately half the width. The unsurfaced selvage provides a dedicated area for mechanical fastening or lap cement application.
Widths are agreed upon between the purchaser and the producer/supplier.
📊 Minimum Net Mass Requirements by Type
The core performance metric in this specification is the minimum net mass per unit area, which directly correlates to material thickness and durability. Each class is divided into Types (II, III, IV) that define these specific mass thresholds.
| 📐 Class | 🆎 Type | 📏 Mass (g/m²) | ⚡ Mass (lb/100 ft²) |
|---|---|---|---|
| Class S (Smooth) | Type III | 2495 | 51.1 |
| Class S (Smooth) | Type IV | 1943 | 39.8 |
| Class M (Mineral) | Type II | 3490 | 71.5 |
| Class WS (Wide Selvage) | Type III | 1733 | 35.5 |
| Class WS (Wide Selvage) | Type IV | 2090 | 42.8 |
⚠️ Critical Note on Units: Per Section 1.2 of the standard, values stated in SI units (g/m²) or inch-pound units (lb/100 ft²) are to be regarded separately as standard. They are not exact equivalents, and combining values from the two systems may result in non-conformance with the standard.
⚙️ Testing Compliance and Referenced Standards
Conformance to D6380 is verified strictly through methods defined in other ASTM standards. These referenced documents outline precise protocols for sampling, physical testing, and durability assessment:
- D146/D146M: Test Methods for Sampling and Testing Bitumen-Saturated Felts and Woven Fabrics.
- D228/D228M: Test Methods for Sampling, Testing, and Analysis of Asphalt Roll Roofing, Cap Sheets, and Shingles.
- D4977/D4977M: Test Method for Granule Adhesion to Mineral-Surfaced Roofing by Abrasion (essential for Class M and WS products).
- E96/E96M: Test Methods for Gravimetric Determination of Water Vapor Transmission Rate.
- D3019/D3019M: Specification for Lap Cement Used with Asphalt Roll Roofing.
📌 Terminology: Refer to Terminology D1079 (Relating to Roofing and Waterproofing) for the precise definitions of terms used in this specification. D6380 consolidates and replaces the withdrawn standards D224 (Smooth-Surfaced), D249 (Mineral Granule Surfaced), and D371 (Wide Selvage).
❓ Frequently Asked Questions
🔍 What distinguishes the “Type” classification in this standard?
The Type (e.g., Type III, Type IV) is strictly defined by the minimum net mass per unit area of the finished roofing sheet. It does not indicate granule size or base felt weight but the final composite mass. For example, Class S Type III mandates a minimum of 2495 g/m².
💡 Why does Class M Type II have the highest mass requirement?
Class M Type II requires 3490 g/m² (71.5 lb/100 ft²). This significantly higher mass is a direct result of the heavy mineral granule surfacing embedded into the coating on the weather side, which provides necessary UV resistance and durability for exposed applications.
⚡ Does this standard cover inorganic (fiberglass) based roll roofing?
No. This specification is strictly limited to organic felt based products. Fiberglass-based roll roofing, polymer-modified bitumen sheets, and fully self-adhering membranes are covered under other distinct ASTM specifications within Committee D08 jurisdiction.
📌 What safety practices are required by this standard?
Section 1.3 of the standard explicitly states that it does not purport to address all safety concerns. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to installation.