Code of Practice for Laying and Fixing of Sloped Roof Covering, Part I: Slating

IS 5119 Part 1 (1968) — Scope Key Points & Specifications

Scope Summary (Clauses 2.0, 3.1)

• Applies to roofing with slates fixed on supporting elements.
• Requires detailed info on:
  • Surface area coverage
  • Supporting elements & arrangement restrictions
  • Junction treatment with walls
  • Slope and drainage provisions
  • Fixing methods for slates

Important Definitions

• Verge (2.16): Edge of roof at a gable.

Inspection & Quality Control (Clause 10.1 & Table 1)

Practical Notes

• Ensure joints in reepers align only on joists.
• Maintain slope for drainage to avoid water accumulation.
• Overlapping of slates must follow minimum overlap guidelines (usually 50-75 mm depending on slate size).

Diagram: Slate Fixing Concept

flowchart LR
    A[Supporting Joist] --> B[Reeper laid with joints only on Joists]
    B --> C[Slate fixed with proper overlap]
    C --> D[Slope for drainage]
    D --> E[Water flows off roof]

For detailed fixing dimensions and slope recommendations, refer to IS 5119 Part 1 tables and figures (not included here).

IS 5119 Part 1 - Key Definitions & Specifications

Definitions (Clause 2.0 & 2.16)

• Verge: The edge of a roof surface finished at a gable (see Fig. 1A).

Inspection & Defects (Clause 10.1, Table 1)

Necessary Design Information (Clause 3.1)

• Surface area to be covered
• Type and arrangement of supporting elements
• Treatment of junctions with walls
• Provision for slope and drainage
• Fixing provisions for slates

Summary Diagram of Verge & Roof Edge

graph LR
A[Roof Surface] --> B[Verge (Edge at Gable)]
B --> C[Tilting fillet at eaves]
C --> D[Joist supporting reeper]

Note: For detailed design and construction, ensure compliance with inspection criteria to avoid defects like sagging, cracking, and leakage.

IS 5119 Part 1 - Necessary Information Summary

Key Necessary Information for Roof Laying (Clause 3.1)

• Surface area to be covered.
• Type of supporting elements and any restrictions.
• Treatment of junctions with walls.
• Provision for slope and drainage.
• Provision for fixing slates.

Inspection Guidelines (Clause 10.1 & Table 1)

Additional Notes

• Detailed drawings and instructions must be provided to workers (Clause 3.1.1).
• Proper slope and drainage are critical to avoid water accumulation and damage.
• Overlapping slates prevent water ingress.

Visual Concept: Roof Verge & Slope

flowchart LR
    A[Roof Surface] --> B[Verge (Edge at Gable)]
    A --> C[Slope for Drainage]
    C --> D[Water Flow to Gutters]

Keep these details clear for efficient and defect-free roof construction.

IS 5119 Part 1 - Slate Material and Dimensions Summary

Slate Material Specifications (Clause 4.1)

• Shape & Size: Rectangular slates, uniform thickness.
• Common Sizes:
  • 60 x 30 cm
  • 50 x 25 cm
  • 40 x 20 cm
• Thickness: 5 to 10 mm.
• Thickness Variation: For any lot of 20 slates, thickness variation between lots ≤ 25%.

Physical Properties (Clause 4.1.4)

• Water Absorption: ≤ 2% by weight after 6 hours immersion.
• Edge Soaking: Water rise ≤ 12 mm after 6 hours immersion on edge; no swelling, splitting, or flaking.
• Soundness: Hard, brittle, gives ringing sound when struck, no breakage from 1.25 m drop.

Key Checks for Slate Quality (Clause 4.1.1)

• Uniform size, color, texture.
• Free from white patches.
• Brittle but not tough.

Quick Reference Table: Slate Sizes and Thickness

Additional Design Considerations (Clause 3.1)

• Surface area coverage.
• Support type & layout.
• Junction treatment with walls.
• Slope for drainage.
• Fixing provisions.

flowchart TD
    A[Slate Selection] --> B[Check Size & Thickness]
    B --> C{Thickness Variation ≤ 25%?}
    C -- Yes --> D[Check Water Absorption ≤ 2%]
    C -- No --> E[Reject Lot]
    D --> F[Check Edge Soaking ≤ 12 mm]
    F --> G[Check Soundness & Visual Quality]
    G --> H[Slate Approved]
    E --> I[Slate Rejected]

This ensures uniform, durable, and weather-resistant roofing slates per IS 5119 Part 1.

IS 5119 Part 1: Roof Design Key Points

Roof Slope and Slate Size (Clause 5.1)

• Preferred roof type: Hipped roof.
• Slope range: 22° to 30° for efficient drainage and slate fixing.

Design Considerations (Clause 3.1)

• Surface area to be covered.
• Supporting elements type and arrangement.
• Treatment of junctions with walls.
• Provision for slope and drainage.
• Provision for fixing slates.

Structural Elements

• Valley Rafter (2.11.4): Member at intersection of two roof surfaces forming a valley.

General Formula for Roof Slope

[ \text{Slope} = \tan^{-1}\left(\frac{\text{Rise}}{\text{Run}}\right) ]

flowchart TD
    A[Start: Roof Design] --> B[Determine Surface Area]
    B --> C[Select Roof Type (Hipped preferred)]
    C --> D[Choose Slope (22°-30°)]
    D --> E[Select Slate Size based on slope]
    E --> F[Design Supporting Elements]
    F --> G[Detail Junctions with Walls]
    G --> H[Provide Drainage & Fixing Provisions]
    H --> I[Prepare Drawings & Instructions]

This ensures proper drainage, structural stability, and slate fixing per IS 5119 Part 1.

Key Specifications & Formulas for Laying of Slates (IS 5119 Part 1):

Slate Dimensions & Thickness (Clause 4.1)

• Typical sizes:
  • 60 x 30 cm
  • 50 x 25 cm
  • 40 x 20 cm
• Thickness: 5 to 10 mm
• Uniform thickness control: difference in thickness of any 20 slates in a lot ≤ 25%.

Laying on Reepers (Clause 6.2.1)

• Slates must be laid on reepers (battens) as per Fig. 4 or engineer's direction.

Lap Requirements (Clause 6.1.6)

• Minimum vertical lap over the bottom course: 7.5 cm
• Minimum side lap: 5 cm

Valleys (Clause 5.3)

• Use lead or galvanized steel sheet gutters fixed on valley boarding.
• Gutter extends 20 cm on each side of valley line with beaded edges.
• Slates cut and fixed with 7.5 cm lap over gutter.
• Edges chisel dressed for true fit.

Summary Table: Slate Laying Dimensions

flowchart LR
    A[Slate on Reeper] --> B[Bottom Course]
    B --> C[Next Course with 7.5 cm vertical lap]
    C --> D[Side lap 5 cm]
    D --> E[Valley Gutter (Lead/Steel)]
    E --> F[Slates cut & lapped 7.5 cm over gutter]

This ensures water tightness and structural stability in slate roofing as per IS 5119 Part 1.

IS 5119 Part 1 - Finishing Edges Around Chimney Stacks: Key Points

1. Protection Against Leakage (Clause 7.1)

• At the junction of chimney stack and slate roofing:
  • Use galvanized steel sheet flashing.
  • Provide a double layer of bitumen felt underneath for waterproofing.

2. Junction Treatment with Walls (Clause 8.1)

• Slates should be let into the wall by minimum 5 cm depth.
• Provide a drip moulding at approx. 10 cm above roof surface.
• Joints must be grouted with waterproof mortar or equivalent.
• When no gutters/flashings exist, this ensures water tightness.

3. Typical Details (Fig. 4 & Fig. 5)

• Double slating and drip moulding are essential to prevent water ingress.
• Fig. 5 illustrates junction with wall where slates act as drainage.

Summary Table: Edge Finishing Specifications

flowchart TD
    A[Chimney Stack] --> B[Galvanized Steel Flashing]
    B --> C[Double Layer Bitumen Felt]
    C --> D[Slate Roofing]
    D --> E[Slates embedded 5 cm in Wall]
    E --> F[Drip Moulding 10 cm above Roof]
    F --> G[Waterproof Mortar Grouting]

This ensures a durable, waterproof edge around chimney stacks per IS 5119 Part 1.

IS 5119 Part 1: Treatment of Junctions with Walls

Key Specifications (Clause 8.1)

• Waterproofing at roof-wall junctions is essential.
• If no gutters/flashings are used:
  • Slates must be let into the wall at least 5 cm deep.
  • Provide a drip moulding about 10 cm above roof surface.
  • Joints between roof and wall must be grouted with waterproof mortar or equivalent.

Typical Detail (Fig. 5)

• Slates act as roof drainage.
• Drip moulding prevents water running back onto the wall.
• Cement mortar seals joints to avoid leakage.

Summary Table

Practical Notes

• Use galvanized steel sheet and double bitumen felt at chimney-roof junctions (Clause 7.1).
• Ensure slope and drainage provisions are compatible (Clause 3.1d).
• Proper fixing of slates and surface area considerations are essential for durability.

flowchart TD
    Roof -->|Slates embedded 5cm| Wall
    Wall -->|Drip moulding 10cm above roof| DripMoulding
    Roof -->|Joints grouted with waterproof mortar| Joint
    DripMoulding -->|Prevents water seepage| Wall
    Joint -->|Seals junction| Wall

This ensures effective waterproofing and durability at roof-wall junctions per IS 5119 Part 1.

IS 5119 Part 1 - Key Points on Measurements (Clause 9.1):

• Measurements are to be taken only for the finished work.
• Laps between slates are excluded from measurement.
• This ensures accurate quantification of actual material used and work done.

Inspection & Defects (Clause 10.1, Table 1)

Additional Specifications (Clause 8.1):

• At roof-wall junctions:
  • Slates must be let into the wall at least 5 cm.
  • Provide drip moulding ~10 cm above roof surface.
  • Joints grouted with waterproof mortar for watertightness.

Summary Diagram: Measurement Exclusion of Slate Laps

flowchart LR
    A[Finished Roof Work] --> B[Measure Total Area]
    B --> C[Exclude Laps Between Slates]
    C --> D[Final Measurement for Payment]

For detailed inspection and quality control, refer to Table 1 in Clause 10.1 to avoid defects like sagging, cracking, and water leakage.

IS 5119 Part 1 - Inspection: Key Points & Table Summary

Clause 10.1:
Inspection is critical to avoid defects due to unsatisfactory construction. Table 1 lists common defects linked to poor workmanship.

Table 1: Defects Due to Unsatisfactory Construction

Additional Specifications (Clause 5.2 - Ridges and Hips)

• Use galvanized steel sheet ridge and hip pieces (thickness 0.63 or 0.80 mm).
• Fix with roofing screws, limpet, and washers dipped in anticorrosive bituminous paint (IS:158-1965).
• Overlap ridge/hip pieces over slates by 7.5 cm.
• Make corresponding holes in slates for screws.

Summary for Effective Inspection

• Check joints in reepers strictly over joists.
• Verify tilting fillet height at eaves.
• Ensure slate overlaps meet minimum requirements.
• Confirm ridge/hip fixing and overlap as per specs.

flowchart TD
    A[Start Inspection] --> B{Stage}
    B --> C[Laying of Reeper]
    C --> D[Check joints only on joists]
    C --> E[Verify tilting fillet height]
    B --> F[Laying of Slates]
    F --> G[Ensure proper overlapping]
    B --> H[Ridges and Hips]
    H --> I[Check GS sheet thickness]
    H --> J[Check screw fixing and overlap]
    D & E & G & I & J --> K[Pass Inspection]

For detailed procedures, refer to IS 5119 (Part 1) - 1968.