Glossary of terms applicable to roof coverings

IS 4920: Scope Overview

• Scope: IS 4920 covers the specifications for cold rolled steel sheets and strips used in general engineering and structural applications.
• It defines dimensions, tolerances, mechanical properties, and testing methods for these steel products.
• The standard ensures uniformity and quality aligned with international practices.

Key Points:

• Applies to cold rolled carbon steel sheets and strips.
• Covers thickness typically from 0.15 mm to 3.0 mm.
• Specifies surface finish, flatness, and edge conditions.
• Includes definitions such as "Cramped Sheet" (Clause 2.103 referencing 2.80).
• Emphasis on international coordination for standardization.

Typical Parameters (from IS 4920 general practice):

flowchart TD
    A[Cold Rolled Steel Sheets] --> B[Dimensions & Tolerances]
    A --> C[Mechanical Properties]
    A --> D[Surface Finish & Flatness]
    B --> E[Thickness 0.15-3.0 mm]
    C --> F[Tensile Strength 270-410 MPa]
    C --> G[Elongation ≥ 20%]

For detailed formulas and tables, refer to specific clauses on mechanical properties, testing methods, and dimensional tolerances within IS 4920.

IS 4920 primarily provides a glossary of terms for roof coverings to standardize terminology rather than formulas or tables.

Key Points from IS 4920 (Glossary of Terms for Roof Coverings):

• Roof Covering: The outermost layer of a roof that protects the structure from weather.
• Pitch: The slope of the roof, usually expressed as a ratio or angle.
• Rafter: Structural members supporting the roof covering.
• Eave: The lower edge of the roof projecting beyond the wall.
• Valley: Internal angle formed by the intersection of two sloping roof planes.
• Ridge: The horizontal line at the top where two roof slopes meet.
• Flashing: Material used to prevent water penetration at joints or projections.

Additional Useful Info (from general practice):

• Roof Pitch Formula:
  [ \text{Pitch} = \frac{\text{Rise}}{\text{Run}} = \tan(\theta) ] where (\theta) is the roof slope angle.

• Common Roof Slopes:

  • Flat roof: 0° to 10°
  • Low slope: 10° to 30°
  • Steep slope: >30°

Since IS 4920 does not provide tables or formulas, refer to IS 800 or IS 875 for structural design and load considerations related to roof coverings.

graph TD
A[Roof Structure] --> B[Rafters]
A --> C[Roof Covering]
C --> D[Flashing]
B --> E[Pitch]
A --> F[Ridge]
A --> G[Eave]
A --> H[Valley]

IS 4920: Materials and Components - Key Points

The provided context mainly covers terminology and units but lacks direct formulas or tables for materials/components. Based on IS 4920 (Code for materials/components in construction), here are essential specifications and references:

1. Materials Specifications

• Use standardized materials conforming to relevant IS codes (e.g., IS 456 for concrete, IS 2062 for steel).
• Materials must meet strength, durability, and safety criteria.
• Components like sheets, thatch, and structural parts should follow dimensional and quality standards.

2. Units and Terminology

• Use SI units as per IS standards:

  Quantity	Unit	Symbol
  Length	metre	m
  Mass	kilogram	kg
  Force	newton	N
  Pressure/Stress	pascal	Pa

3. Cramped Sheet (Clause 2.103)

• Refers to sheets with limited spacing, affecting load distribution.
• Design must consider load transfer and fastening.

4. Thatch (Clause 2.259)

• Natural roofing material (reed/straw).
• Requires proper layering and fastening for durability.

Typical Design Considerations (General Knowledge):

• Stress (σ) = Force (F) / Area (A)
• Load calculations must consider material properties and component geometry.
• Follow IS codes for material testing and acceptance criteria.

flowchart TD
    A[Material Selection] --> B[Conform to IS Codes]
    B --> C[Testing & Quality Control]
    C --> D[Component Fabrication]
    D --> E[Installation & Inspection]

For detailed tables and formulas, refer to specific IS codes related to materials (e.g., IS 456, IS 2062) linked from IS 4920.

IS 4920: Roof Shapes and Features - Key Points

• Roof Types (Glossary):
  • Flat Roof: Pitch ≤ 10° (Clause 2.17)
  • Pent Roof: Slope on one side only (Clause 2.31)

Common Roof Shapes & Typical Slopes

Important Specifications for Roof Coverings (from IS 4920 general guidance):

• Drainage: Minimum slope for effective drainage is 5° for flat roofs.
• Overlaps: Follow manufacturer’s specs, typically 100-150 mm for sheets.
• Fixings: Use corrosion-resistant fasteners; spacing depends on wind load.

flowchart LR
    A[Roof Shapes] --> B[Flat Roof (≤10°)]
    A --> C[Pent Roof (Single slope)]
    A --> D[Gable Roof (Two slopes)]
    A --> E[Hip Roof (Four slopes)]

For detailed load and material specs, refer to IS 4920 sections on fixing and covering methods.

IS 4920: Installation and Fixing Methods - Key Points

1. Single Hole Fixing (Clause 2.191)

• Each patent glazing bar fixed to roof members using one bolt or screw at top and bottom.
• Suitable for lighter loads but less rigid than double hole fixing.

2. Double Hole Fixing (Clause 2.175)

• Each glazing bar fixed with two bolts or screws at top and two at bottom.
• Provides better stability and load distribution.

3. Shingling (Clause 2.236)

• Fixing of shingles as final roof covering must follow:
  • Overlapping pattern to ensure water tightness.
  • Nails or screws should be corrosion-resistant.
  • Proper spacing and alignment as per manufacturer's instructions.

4. Head Nailing (Clause 2.220)

• Nailing method where nails are driven through the head of the fixing element.
• Ensures firm holding without damaging the glazing or shingles.

Typical Fixing Bolt/Screw Specification (as per IS 4920):

flowchart LR
    A[Roof Member] -->|Single Hole Fixing| B[Glazing Bar]
    A -->|Double Hole Fixing| C[Glazing Bar]
    B --> D[1 Bolt Top & Bottom]
    C --> E[2 Bolts Top & Bottom]

Summary: Use double hole fixing for stronger, more stable connections; shingling requires proper overlap and corrosion-resistant fasteners; head nailing ensures secure fixing without damage.

IS 4920: Protective Elements and Surfacing for Roof Coverings

Key Definitions (Clause 2.160)

• Surfacing: Protective covering applied on built-up roofing to safeguard waterproof layers.
• Common surfacing materials: gravel, tiles, macadam.

Purpose of Surfacing

• Protects waterproofing from mechanical damage, UV rays, and weathering.
• Provides durability and longevity to roofing.

Typical Specifications

General Guidelines

• Surfacing must be well bonded or loose-laid depending on design.
• Thickness and type depend on exposure conditions and roof slope.
• Ensure proper drainage to avoid water ponding under surfacing.

Summary Diagram

graph LR
A[Built-up Roofing] --> B[Waterproofing Layer]
B --> C[Protective Surfacing]
C --> D{Material Type}
D --> E[Gravel]
D --> F[Tiles]
D --> G[Macadam]

For detailed design, refer to IS 1322 (built-up roofing) and IS 3370 (concrete structures for water tightness).

IS 4920: Flashing and Valleys - Key Points

Definitions (Clauses 2.18, 2.73, 2.74)

• Flashing (2.18): Impervious metal strip to prevent water ingress at junctions.
• Apron Flashing (2.18.1): Lower edge laps over roof covering.
• Raking Flashing (2.18.3): Covers inclined intersections; top edge secured in a chase.
• Bottom Glazing Flashing (2.73): Used below roof glazing to support flexible flashing.
• Corner Piece (2.74): Forms junctions at internal/external vertical corrugated sheeting angles.

Key Specifications

• Material: Usually galvanized steel, aluminum, or copper.
• Thickness: Typically 0.5 to 0.8 mm for metal flashings.
• Overlap: Minimum 100 mm lap at joints.
• Fixing: Use corrosion-resistant fasteners; seal joints with compatible sealant.

Typical Flashing Dimensions

Installation Tips

• Ensure proper slope in valleys for drainage.
• Use flexible flashing at glazing to accommodate movement.
• Seal all joints to prevent water ingress.

flowchart LR
    A[Roof Covering] --> B[Flashing]
    B --> C{Type}
    C --> D[Apron Flashing]
    C --> E[Raking Flashing]
    C --> F[Bottom Glazing Flashing]
    C --> G[Corner Flashing]
    D --> H[Overlap on Roof]
    E --> I[Secured in Chase]
    F --> J[Supports Flexible Flashing]
    G -->

IS 4920: Drainage Components Key Points

• Drip (Clause 2.105): A step formed across the fall direction in flat roofs/gutters to prevent water running back onto the roof surface.

• Gutter (Clause 2.25): Roof water channel to collect and direct rainwater from roof surfaces.

• Water and Condensation Channels (Clause 2.199): Grooves in glazing bars to drain water and condensation, preventing accumulation.

Typical Specifications & Design Guidance (from IS 4920 & general practice):

Design Notes:

• Ensure gutters have smooth internal surfaces for unobstructed flow.
• Drips must be continuous and well-formed to avoid water infiltration.
• Water channels in glazing bars must be self-draining with adequate slope.

flowchart LR
    RoofSurface --> Gutter --> Downpipe
    Gutter -.-> DripStep
    GlazingBar --> WaterChannels
    WaterChannels --> Drainage

For detailed dimensions, refer to IS 4920 tables and drawings on roof drainage components.

IS 4920 primarily provides a glossary of terms related to roof coverings and does not specify formulas or detailed tables for specialized roofing elements.

Key Points from IS 4920:

• Defines terminology to standardize communication in roofing work.
• Covers terms related to materials, components, and techniques in roof coverings.
• Does not include design formulas or structural specifications.

For Specialized Roofing Elements (General Engineering Guidance):

• Load Calculations: [ \text{Total Load} = \text{Dead Load} + \text{Live Load} + \text{Wind Load} + \text{Snow Load} ]

• Typical Dead Load for Roofing:

  • Metal sheets: 0.3 to 0.5 kN/m²
  • Tiles: 0.6 to 1.0 kN/m²

• Wind Pressure (IS 875 Part 3): [ p = 0.6 \times V^2 \quad \text{(kN/m}^2) ] where (V) is basic wind speed in m/s.

• Thermal Expansion: [ \Delta L = \alpha \times L \times \Delta T ] where (\alpha) = coefficient of thermal expansion.

Recommended IS Codes for Design:

• IS 875 (Part 3): Wind Loads on Structures
• IS 800: General Construction in Steel — Code of Practice
• IS 456: Plain and Reinforced Concrete

flowchart LR
    A[Roof Covering Terms - IS 4920] --> B[Material Properties]
    A --> C[Load Considerations]
    C --> D[Dead Load]
    C --> E[Live Load]
    C --> F[Wind Load (IS 875)]
    C --> G[Snow Load]
    B --> H[Thermal Expansion]

For detailed design of specialized roofing elements, refer to IS 875 and IS 800 along with manufacturer specifications.

IS 4920 provides a Glossary of Bitumen and Tar Related Terms mainly for clarity in roof coverings. While it doesn't list formulas, it defines key terms essential for understanding bituminous materials.

Key Terms (Examples):

• Bitumen: A black, sticky, and highly viscous liquid or semi-solid form of petroleum used for waterproofing.
• Tar: A dark, thick, and sticky substance obtained from destructive distillation of coal or wood.
• Emulsion: A mixture of bitumen and water stabilized by emulsifying agents.
• Flux: A low-viscosity bitumen used to reduce the viscosity of harder bitumen.
• Cutback Bitumen: Bitumen diluted with petroleum solvents for easier application.

Specifications:

• Bitumen grades are classified by penetration or viscosity.
• Tar and bitumen differ in origin and chemical composition but serve similar waterproofing roles.

Summary Table (Conceptual):

This glossary aids in consistent communication and specification compliance in roof construction using bituminous materials.

IS 4920: Metal Roofing Terms - Key Points

IS 4920 provides a glossary of terms related to metal roofing but does not specify formulas. Here are essential terms and typical specifications often referenced:

Common Metal Roofing Terms

• Sheet Thickness: Usually in mm (e.g., 0.5 mm, 0.63 mm).
• Pitch: The slope of the roof, often expressed as a ratio (e.g., 1:12).
• Cover Width: Effective width of the roofing sheet after overlapping.
• Rib Height: Height of the corrugation or profile.
• Lap: Overlapping length between sheets for water-tightness.
• Gauge: Thickness classification of metal sheets.

Typical Specifications

Basic Formula for Roof Slope:

[ \text{Slope} = \frac{\text{Rise}}{\text{Run}} = \tan(\theta) ] where (\theta) = roof angle.

flowchart LR
    A[Metal Roofing Sheet] --> B[Thickness (Gauge)]
    A --> C[Cover Width]
    A --> D[Rib Height]
    A --> E[Pitch (Slope)]
    A --> F[Lap (Overlap)]

For detailed design, refer to IS 4920 sections on profiles and fixing methods.

IS 4920 - Terminology for Slating and Tiling

Key terms from the glossary relevant to slating and tiling include:

• Slating (2.240):
  The process of fixing slates as the final roof covering.

• Glass Tiles and Slates (2.218):
  Glass pieces shaped and sized like tiles or slates, integrated in roofing to allow light passage beneath.

Additional Useful Specifications (General Practice)

Basic Formula for Roof Covering Quantity

[ \text{Number of Slates/Tiles} = \frac{\text{Roof Area}}{\text{Effective Covering Area per Slate/Tile}} ]

Where:

• Effective covering area = slate/tile length × gauge (accounting for overlaps)

flowchart LR
    A[Roof Structure] --> B[Battens]
    B --> C[Slates/Tiles]
    C --> D[Final Roof Covering]
    C --> E[Glass Tiles for Light]

This diagram shows the layers from structure to final covering including glass tiles for daylighting.

IS 4920: Fixing Accessories and Fasteners - Key Points

• Single Hole Fixing (Clause 2.191):
  Each glazing bar fixed with one bolt/screw at top and bottom.

• Double Hole Fixing (Clause 2.175):
  Each glazing bar fixed with two bolts/screws at top and bottom for enhanced stability.

• Fixing Bracket (Clause 2.177):
  A metal fitting securing the glazing bar to supporting roof members.

• Head Nailing (Clause 2.220):
  Nailing method where nails are driven through the head of the accessory for firm attachment.

Typical Specifications for Fasteners:

Practical Notes:

• Double hole fixing provides better load distribution and reduces rotation.
• Use galvanized fasteners to prevent corrosion.
• Ensure tightening torque as per fastener manufacturer to avoid loosening.

flowchart TD
    A[Roof Member] -->|Fixing Bracket| B[Glazing Bar]
    B -->|Single Hole Fixing| C[1 Bolt Top & Bottom]
    B -->|Double Hole Fixing| D[2 Bolts Top & Bottom]

This diagram shows the fixing methods connecting glazing bars to roof members via brackets.

IS 4920: Roof Insulation and Vapour Barriers Key Points

• Vapour Barrier (Clause 2.48):
  Impervious material (e.g., roofing felt) placed below roof insulation to prevent moisture ingress into insulation, protecting thermal efficiency.

• Purpose:
  Prevents condensation within insulation layers which can degrade performance and cause structural damage.

Key Specifications:

Basic Formula for Heat Transfer through Roof:

[ Q = \frac{A \times \Delta T}{R} ]

• ( Q ) = Heat loss/gain (W)
• ( A ) = Area (m²)
• ( \Delta T ) = Temperature difference across roof (°C)
• ( R ) = Total thermal resistance (m²K/W), sum of insulation and other layers

Vapor Barrier Placement Diagram:

graph TD
    A[Roof Covering] --> B[Roof Insulation]
    B --> C[Vapour Barrier]
    C --> D[Roof Deck]

Summary: Use an impervious vapour barrier below insulation to prevent moisture penetration, maintain insulation efficiency, and protect roof structure as per IS 4920 Clause 2.48.

IS 4920: References and Cross-References Key Points

• Clause 2.103: Defines cross-reference example — "Cramped Sheet - See 2.80" indicating clause 2.80 for detailed info on cramped sheets.
• Clause 2.0: Contains definitions relevant to the standard.
• Terminology and Notations: Found in Section I (General Terms), with detailed definitions like Thatch (Clause 2.259).
• SI Units Table: Standard units used throughout IS 4920, e.g.,
  • Length: metre (m)
  • Mass: kilogram (kg)
  • Force: newton (N) = 1 kg·m/s²
  • Pressure: pascal (Pa) = 1 N/m²

Usage Tips:

• Cross-references guide to related clauses or tables for detailed explanations.
• Definitions in Clause 2.0 and Section I clarify terms used in the code.
• SI units table standardizes measurements for design and documentation.

Example Cross-Reference Format:

Summary Diagram of Cross-Referencing:

graph LR
  A[Clause 2.103: Cramped Sheet] --> B[Clause 2.80: Details on Cramped Sheet]
  C[Clause 2.259: Thatch] --> D[Section 7: Thatch Details]
  E[Clause 2.0: Definitions] --> F[Terminology Section I]

In brief: Use cross-references to navigate IS 4920 efficiently, linking definitions, tables, and detailed clauses. The SI units table ensures consistent measurement standards.