Code of practice for roofing with Mangalore tiles

IS 2858: Scope & Key Specifications

Scope (Clause 3.1)

For efficient design and construction of Mangalore tiled roofs, consider:

• Surface area to be covered
• Type and arrangement of supporting elements
• Junction treatment with walls
• Slope and drainage provisions
• Fixing provisions for ridge tiles

Dead Loads for Strength & Stability (Clause 4.5)

Additional Notes:

• Values should be rounded as per IS 2:1960.
• Dead load values are crucial for calculating structural support requirements.

Typical Dead Load Calculation Formula:

[ W = A \times w_d ]

Where:

• ( W ) = total dead load (N)
• ( A ) = surface area (m²)
• ( w_d ) = dead mass per unit area (kg/m²) × 9.81 (m/s²)

flowchart LR
    A[Start: Design Requirement] --> B[Determine Surface Area]
    B --> C[Select Roof Type]
    C --> D[Refer Dead Load Table]
    D --> E[Calculate Dead Load W = A × w_d × g]
    E --> F[Design Support Structure]
    F --> G[Check Stability & Strength]
    G --> H[Construction]

This concise scope and load data guide design and construction of Mangalore tiled roofs per IS 2858.

IS 2858: Definitions & Key Specifications

• Clause 2.1 (Definitions): Establishes terms used in the standard for uniform understanding. Definitions cover materials, components, and testing methods relevant to roofing tiles and associated elements.

• Rounding Off (Clause 0.5): Test results must be rounded per IS 2:1960, matching the significant figures of the specified values.

• Sheet Metal for Valley Gutters (Clause 5.9):

  • Material: Galvanized metal
  • Minimum Thickness: 1.25 mm

• Related Material Specifications Referenced:

  • Ordinary and Low Heat Portland Cement (Third Revision)
  • Portland Pozzolana Cement (Second Revision)
  • Portland Slag Cement (Third Revision)
  • Building Limes (Second Revision)
  • Mild Steel Wire Nails (Second Revision)
  • Clay Roofing Tiles and Ventilating Tiles (Various revisions)

Summary Table: Sheet Metal for Valley Gutters

Rounding Off Rule (IS 2:1960)

• Final test values rounded to the same decimal places as specified values.
• Ensures consistency in reporting and compliance verification.

flowchart TD
    A[Test Result] --> B{Compare with Specified Value}
    B --> |Round off| C[Rounded Value]
    C --> D[Compliance Decision]

This ensures clarity and uniformity in interpreting test results under IS 2858.

IS 2858: Design Considerations & Preparatory Work for Mangalore Tiled Roofs

Key Points from Clauses:

• Clause 3.1: Essential info before design:

  • Surface area to cover
  • Supporting elements & restrictions
  • Junction treatment with walls
  • Slope and drainage provision
  • Fixing of ridge tiles

• Clause 3.3: Ensure proper communication between all involved parties.

• Clause 6.1: Roof framework must be complete with reepers nailed before roof covering.

Dead Loads for Strength & Stability (Clause 4.5)

Additional Notes:

• Use Code of Practice for Structural Timber for material, grading, and design.
• Follow Code of Practice for Preservation of Timber for durability.
• Use Specification for Mild Steel Wire for fixing elements.

Summary for Preparatory Work:

1. Complete roof framework with reepers.
2. Confirm surface area and slope.
3. Plan junction treatment & drainage.
4. Fix ridge tiles provision.
5. Account for dead loads as per table above.

flowchart TD
    A[Start: Preliminary Info] --> B{Surface Area, Supports, Junctions}
    B --> C[Design Roof Framework]
    C --> D[Nail Reepers in Position]
    D --> E[Fix Ridge Tile Provision]
    E --> F[Lay Roof Covering]
    F --> G[Ensure Drainage & Stability]

This ensures safe, durable Mangalore tiled roofing per IS 2858.

IS 2858 Key Points on Weather Resistance & Roof Drainage

Weather Resistance (Clause 4.1)

• Primary function: Drain rainwater effectively, preventing ingress.
• Tile interlocking & laying: Must ensure leak-proof joints.
• Roof drainage system: Use corrugation channels of Mangalore tiles + proper gutters and downpipes.
• Undercover provision: Adds insulation, waterproofing, and prevents debris/insects entry.

Roof Drainage (Clause 4.6)

• No cross-roof discharge: Gutters/downpipes shouldn’t drain from one roof to another unless from small areas (e.g., dormers).
• Valley gutters:
  • Sheet metal extends ≥ 300 mm under roof on both sides.
  • Near walls, sheet metal extends ≥ 75 mm into the wall, fixed with cement mortar.
• Sheet metal thickness for valley gutters: Minimum 1.25 mm galvanized metal (Clause 5.9).

Additional Design Considerations (Clause 3.1)

• Calculate surface area.
• Consider support types and restrictions.
• Plan junctions with walls.
• Ensure adequate slope for drainage.
• Provision for fixing ridge tiles.

Typical Slope & Drainage Formula (General engineering knowledge)

• Minimum roof slope for effective drainage: 1:12 to 1:6 (approx. 4.8° to 9.5°)
• Rainwater flow rate ( Q = A \times I )
  • ( A ) = Roof area (m²)
  • ( I ) = Rainfall intensity (m/hr)

Summary Table: Valley Gutter Sheet Metal

flowchart TD
    A[Rainfall on Roof] --> B[Tile Corrugations]
    B --> C[Gutters]
    C --> D[Downpipes]
    D --> E[Discharge to Ground or Drain]
    subgraph Valley Gutter
        F[Galvanized Sheet Metal]
        F -->|Extends 300mm under roof| B
        F -->|

IS 2858: Materials and Components – Key Specifications & Tables

1. Sheet Metal for Valley Gutters (Clause 5.9)

• Material: Galvanized metal
• Minimum thickness: 1.25 mm

2. Roof Dead Loads (Clause 4.5, Table 4)

3. Inspection Points (Clause 12.1, Table 12)

Additional Material Standards Referenced

• Ordinary & Low Heat Portland Cement (3rd Rev.)
• Portland Pozzolana Cement (2nd Rev.)
• Portland Slag Cement (3rd Rev.)
• Building Limes (2nd Rev.)
• Mild Steel Wire Nails (2nd Rev.)
• Clay Roofing Tiles (Mangalore Pattern, 2nd Rev.)
• Clay Ridge & Ceiling Tiles (1st Rev.)

Summary Diagram: Roof Load Consideration

graph TD
    A[Roof Type] -->|Embedded in mortar| B[Dead Load = 110 kg/m²]
    A -->|Without mortar| C[Dead Load = 80 kg/m²]
    A -->|Tiles alone| D[Dead Load = 90 kg/m²]

Use these specifications to ensure compliance in materials selection, load calculations, and quality inspection for tiled roofing systems as per IS 2858.

IS 2858 – Programming the Work: Key Points & Specifications

1. Programming the Work (Clause 6.1)

• Pre-requisite: Complete roof framework before roof covering.
• Preparation: Nail reepers (battens) in position to support roof tiles.
• Wire for tying tiles: Use galvanized wire conforming to IS 280:1978 (mild steel wire for general purposes).

2. Design Considerations (Clause 4)

• Collect detailed info on:
  • Surface area to cover.
  • Type & arrangement of supporting elements.
  • Junctions with walls.
  • Slope/drainage requirements.
  • Fixing provisions for ridge tiles.

3. Wire Specification (IS 280:1978)

• Use galvanized mild steel wire.
• Typical wire diameter for tying: 0.9 mm to 1.2 mm.
• Ensure corrosion resistance and adequate tensile strength.

Summary Table: Work Programming Checklist

flowchart TD
    A[Complete Roof Framework] --> B[Nail Reepers]
    B --> C[Fix Roof Tiles]
    C --> D[Tie Tiles with Galvanized Wire (IS 280)]
    D --> E[Check Drainage & Ridge Fixing]

This ensures smooth coordination and quality roof covering installation per IS 2858.

Preparation of Tiles Before Laying (IS 2858)

Key Specifications & Procedures:

• Flat Tiles (Clause 7.1):

  • Immerse in water for 2 hours.
  • Air-dry before laying.
  • Optionally, dip underside in whitewash (creamy consistency) and dry.

• Mangalore Tiles (Clause 7.2 & 9.1.2):

  • Soak in water for at least 2 hours before laying.
  • When laid over flat tiles with mortar:
    • Flat tiles prepared as above.
    • Mortar layer thickness: ≥ 25 mm.
    • Mangalore tiles fully embedded in mortar.
    • For roof pitch > 30°, fix fillets at ~1 m centers on reepers to retain flat tiles.

Additional Design Considerations (Clause 3.1):

• Surface area to cover.
• Supporting element types and layout.
• Junction treatment with walls.
• Slope and drainage provisions.
• Fixing methods for ridge tiles.

Summary Table:

flowchart TD
    A[Start: Tile Preparation] --> B{Tile Type?}
    B -->|Flat Tile| C[Soak 2 hrs in water]
    C --> D[Air dry]
    D --> E{Whitewash specified?}
    E -->|Yes| F[Dip underside in whitewash & dry]
    E -->|No| G[Ready for laying]
    B -->|Mangalore Tile| H[Soak ≥ 2 hrs in water]
    H --> I{Laying over flat tile?}
    I -->|Yes| J[Prepare flat tile as above]
    J --> K[Spread mortar ≥ 25 mm]
    K --> L[Embed Mangalore tile fully]
    L --> M{Roof pitch > 30°?

IS 2858: Fixing of Reepers – Key Points & Specifications

1. Fixing Details (Clause 8.1)

• Positioning: Reepers fixed over rafters at specified spacing.
• Nailing: Nails must penetrate at least 2 cm into rafters.
• Length: Reepers must extend over 3 spans between rafters.
• Nails: Use plain headed galvanized nails (Clause 5.8).
• Joints: Butt joints only, occurring over rafters; joints in adjacent rows must not align on the same rafter.
• Eaves: Use a tilting fillet if necessary (see Fig. 1 in IS 2858).

2. Material & Size (Clause 5.10)

• Timber species as per IS 883-1970.
• Minimum size as per Clause 4.3 (refer IS 2858 for exact dimensions).
• Timber must be treated against decay and termites as per IS 401-1982.

3. Nails Specifications (Clause 5.8)

Summary Diagram: Fixing of Reepers

graph LR
A[Rafters] -->|Nail penetration ≥ 2 cm| B[Reepers]
B -->|Extend over 3 spans| C[Continuous length]
B -->|Butt joints only over rafters| D[Joints staggered in adjacent rows]
A -->|Supports| B
E[Eaves] -->|Tilting fillet if necessary| B

Note: Always verify specific sizes and spacing from design drawings or IS 2858 Clause 4.3 and related tables.

Key Specifications & Formulas for Laying Mangalore Tiles (IS 2858):

1. Tile Preparation

• Flat tiles: Soak in water for 2 hours → dry → underside dipped in whitewash (creamy consistency) → dry.
• Mangalore tiles: Soak in water for 2 hours before laying.

2. Mortar Bedding

• Mortar layer thickness: ≥ 25 mm over flat tiles.
• Tiles embedded fully in mortar.
• For roof pitch > 30°, fix fillets at ~1 m centers on reepers to retain flat tiles.

3. Pitch & Lap

• Roof pitch: 24° ≤ pitch ≤ 45°.
• For heavy rainfall/elevated sites, increase pitch > 24° and tie/screw tiles.
• Minimum head lap (if not fixed by tile design): ≥ 75 mm.
• Side lap as per tile design.

4. Underlayer Options

• Tiles can be laid:
  • Directly on flat tiles with mortar.
  • Over flat tiles without mortar (if specified).
  • Over ceiling tiles with galvanized MS flat for tying.

Summary Table:

flowchart TD
    A[Prepare Flat Tiles] --> B[Soak 2 hrs & Dry]
    B --> C[Whitewash underside & Dry]
    C --> D[Lay Flat Tiles on Reeper]
    D --> E[Spread Mortar ≥ 25 mm]
    E --> F[Soak Mangalore Tiles 2 hrs]
    F --> G[Embed Tiles in Mortar]
    G --> H{Pitch > 30°?}
    H -- Yes --> I[Fix Fillets @ ~1m centers]
    H -- No --> J[No Fillets Needed]

This ensures a leak-proof, durable tiled roof with easy maintenance.

IS 2858: Finishing Edges Around Chimneys and Skylights (Clause 10.1)

• Full tiles must be used around chimney stacks and similar roof projections, integrated into the masonry.
• Flashing (metal or bitumen) is essential to cover the intersection between the top edge of tiling and the projection.
• Flashing should be:
  • Turned against the projection,
  • Dressed down over the tiles,
  • Well tucked into masonry joints or concrete grooves,
  • Wedged and pointed to ensure water tightness.

Key Specifications:

Important Notes:

• Flashing prevents water ingress at roof penetrations.
• Proper wedging and pointing ensure durability and leak-proof joints.
• Full tiles around projections maintain structural integrity and aesthetics.

flowchart TD
    A[Chimney/Skylight Projection] --> B[Full Tiles Around Projection]
    B --> C[Metal/Bitumen Flashing]
    C --> D[Tucked into Masonry/Concrete]
    D --> E[Flashing Turned Against Projection]
    E --> F[Flashing Dressed Over Tiles]
    F --> G[Wedged and Pointed for Seal]

This ensures a watertight, durable finish around chimneys and skylights as per IS 2858.

IS 2858 - Junctions of Roof with Walls: Key Specifications

• Waterproofing: Follow relevant IS waterproofing standards at roof-wall junctions (Clause 11.1).
• Tile Embedment: Tiles must be embedded into the wall to a minimum depth of 50 mm.
• Drip Moulding: Provide a drip moulding at about 100 mm above the roof surface to prevent water ingress.
• Joint Treatment: Grout joints between roof and wall with waterproof mortar or equivalent material.
• Roof Gutters & Flashings: Where no gutters/flashings exist, embed tiles and provide drip moulding as above (see Fig. 7).
• Hip & Ridge Junctions (Clause 9.3): Grout joints leak-proof; use metal saddle with minimum area 45 cm² under junctions.
• Chimney & Projections (Clause 10.1): Use full tiles around projections; apply metal/bitumen flashing turned against the projection and tucked into masonry/concrete joints.

Summary Table for Roof-Wall Junction Treatment

flowchart TD
    A[Roof Tiles] --> B{Embed into Wall}
    B -- Yes --> C[Depth ≥ 50 mm]
    C --> D[Provide Drip Moulding @ 100 mm]
    D --> E[Grout Joints with Waterproof Mortar]
    B -- No --> F[Use Roof Gutters/Flashings]
    E --> G[Waterproof Roof-Wall Junction]

This ensures durable, leak-proof junctions per IS 2858.

IS 2858: Maintenance and Repair - Key Points

1. Inspection (Clause 12.1)

• Laying of Reepers:

  • No joints except over joists.
  • Tilting fillet at eaves fixed at correct height.
  • Failure: Sagging or cracking if improper.

• Laying of Tiles:

  • Mangalore tiles over flat tiles: joints should avoid alignment with flat tile joints.
  • Ensure interlocking when laid over reepers or ceiling tiles.
  • Failure: Displacement or leakage.

2. Design Considerations for Roof Dead Loads (Clause 4.5)

3. Material Specification

• Valley gutters: galvanized sheet metal, thickness ≥ 1.25 mm (Clause 5.9).

Maintenance Tips:

• Regularly inspect joints and tilting fillets.
• Replace cracked or sagging tiles promptly.
• Maintain proper interlocking to prevent water ingress.

flowchart TD
    A[Inspection] --> B{Reepers}
    B -->|No joints except on joist| C[Correct tilting fillet height]
    C --> D[Prevents sagging/cracking]
    A --> E{Tiles}
    E -->|Avoid joint alignment| F[Ensure interlocking]
    F --> G[Prevents displacement/leakage]

This concise guidance ensures durability and stability of Mangalore tiled roofs per IS 2858.