Code of practice for fire safety of buildings (general): Details of construction

IS 1642 - Scope: Key Specifications for Fire Resistance (Clause 4.3, 6.1, 7.1)

1. Fire Resistance Ratings & Minimum Dimensions

• Dimensions increase with fire rating duration.
• Cover thickness protects reinforcement from heat.

2. Encased Steel Beams Protection (Table 13)

Notes:

• Fire resistance ratings (1 h, 2 h, 3 h, 4 h) correspond to hours of protection.
• Material specifications must ensure these ratings.
• Tables 8, 9, 12, 13 provide detailed dimensional and protection thickness requirements.

flowchart TD
    A[Fire Resistance Rating] --> B[Minimum Dimensions]
    B --> C[Columns]
    B --> D[Beams]
    B --> E[Encased Steel Beams Protection]
    C --> F[Width & Cover]
    D --> G[Width & Cover]
    E --> H[Type of Protection & Thickness]

This summary aids in selecting materials and dimensions to meet fire safety

IS 1642: Types of Construction - Key Specifications

1. Classification of Construction Types (Clause 4.1)

• Type 1: Fire-resistive construction (highest fire resistance)
• Type 2: Non-combustible construction
• Type 3: Ordinary construction (combustible walls, non-combustible structural members)
• Type 4: Heavy timber construction

Fire resistance ratings for structural and non-structural members are specified in Table 1 (not provided here).

2. Fire Resistance Ratings

• Walls: Fire ratings for walls are detailed in Tables 2 to 7.
• Other elements: Fire ratings for floors, roofs, and other structural members are in Tables 8, 9, 10, 11, 12, 13, 14, 15, and 16.
• Material specifications should ensure these ratings are met.

3. Material Selection

• Materials must be chosen to achieve the fire resistance ratings in the relevant tables.
• Ratings are expressed in hours (e.g., 1-hour, 2-hour fire resistance).

Summary Table Example (Indicative):

Visual Conceptual Diagram

flowchart LR
    A[Types of Construction] --> B[Type 1: Fire Resistive]
    A --> C[Type 2: Non-Combustible]
    A --> D[Type 3: Ordinary]
    A --> E[Type 4: Heavy Timber]
    B --> F[High Fire Resistance]
    C --> G[Moderate Fire Resistance]
    D --> H[Lower Fire Resistance]
    E --> I[Heavy Timber Fire Resistance]

Note: For exact fire rating values and material specifications, refer directly to the tables mentioned in

IS 1642 - Fire Separation Key Points

Fire Separation Distances & Types (Clause 3.7)

• Less than 3.7 m (Non-bearing walls)
• 3.7 m to less than 9 m (Non-bearing walls)
• 9 m or more (Non-bearing walls)

Fire Resistance Ratings & Thickness (Clause 5.1, Tables 2 & 3)

Framed Construction Protection (Table 4)

• Timber studs ≤ 600 mm centers, faced both sides:

Other Specifications:

• Fire separation assemblies include fire check doors, exitway enclosures, shafts (except elevator hoistways), stairways, corridors, and vertical tenant separations.
• Structural members supporting floors or roofs have specific fire resistance requirements (see Clause 7.1 and Tables 10, 11, 14-16).
• Partitions (Clause 5.10) have minimum fire ratings per Table 1, typically lighter and less resistive than walls.

Summary Diagram: Fire Separation Types by Distance

flowchart TD
    A[Fire Separation Distance] --> B{< 3.7 m}
    A --> C{3.7 m to < 9 m}
   

IS 1642: Fire Resistance Ratings & Methods of Determination

Key Specifications from IS 1642

• Fire Resistance Ratings are provided for various structural elements in Tables 2-7 (walls), 8-9 (columns, beams), and 10,11,14-16 (other constructions).
• Fire resistance is expressed in hours (h): 1h, 2h, 3h, 4h.

Minimum Dimensions for Fire Resistance (Clause 6.1)

Reinforced Concrete Columns (Table 8)

Concrete Beams (Table 9)

Method of Determination

• Fire resistance is primarily determined by minimum cross-sectional dimensions and concrete cover.
• Material specifications must ensure these dimensions are met.
• Fire tests or calculations follow IS 1642 procedures, considering exposure conditions (fully, partially, or one face exposed).

Summary Formula for Fire Resistance Dimensioning

• Minimum Width or Thickness and Minimum Concrete Cover increase with desired fire resistance time.

• For example, for a fully exposed RC column with 4h rating:

  [ \text{Width} \geq

IS 1642: Separating Walls & Fire Barriers - Key Specifications

1. Fire Resistance Ratings (Clause 4.1, Table 1)

2. Masonry Wall Thickness for Fire Resistance (Clause 5.1, Tables 2 & 3)

3. Framed Construction Protection (Clause 5.1, Table 4)

• Plasterboard layers (staggered joints): 25 mm per face for 1-hour fire resistance.
• Single 12.7 mm plasterboard with gypsum plaster finish: 13 mm.
• Metal lath with sanded gypsum plaster: 22 mm.

4. Separating Wall Definition (Clause 3.4)

• Provides complete separation to prevent fire spread and heat transmission that could ignite materials on the opposite side.

Summary Diagram of Fire Barrier Elements

graph TD
  A[Fire Source] -->|Heat & Flames| B[Separating Wall]
  B -->|Prevents| C[Fire Spread]
  B -->|Prevents| D[Heat Transmission]
  B -->|Protects| E[Adjacent Spaces]

Use these tables and thicknesses to design walls and barriers meeting required fire resistance per IS 1642.

IS 1642: Key Fire Resistance Specifications for Floors, Roofs, Columns & Beams

1. Columns (Table 8, Clause 6.1)

2. Beams (Table 9, Clause 6.1)

3. Floors (Table 10 & 11, Clause 7.1)

4. Encased Steel Beams (Table 13, Clause 6.1)

• Protection thickness varies by material & fire rating (1h to 4h)
• Examples:
  • Metal lathing + gypsum plaster: 13–25 mm
  • Plasterboard (9.5 mm): 10–15 mm

IS 1642: Materials & Finishes for Fire Resistance

Key Tables & Specifications

1. Reinforced Concrete Columns (Table 8, Clause 6.1)

Minimum dimensions excluding finish for fire resistance (Width / Cover in mm):

2. Concrete Beams (Table 9, Clause 6.1)

Minimum width / cover (mm) for fire resistance:

3. Masonry Walls (Table 2 & 3, Clause 5.1)

Thickness (mm) for fire resistance (hours):

IS 1642: Air-Conditioning Systems & Fire Safety - Key Points

Air-Conditioning Systems (Clause 8.4)

• Duct Construction: Use metal ducts per IS 655:1963.
• Fire Separation: Seal openings around ducts passing fire walls/floors with fire-resistant materials matching wall/floor rating.
• Return Air: Avoid using escape routes; metallic ducts preferred over false ceiling spaces.
• Insulation: Flame-resistant, non-heat-conductive material per IS 4355:1977.
• Area Segregation: Floors >750 m² require fire walls and automatic fire dampers.
• Fire Dampers Placement:
  • At fire separation walls
  • Entry to central vertical shafts
  • Floor penetrations
  • Supply and return air ducts of each compartment per floor
• Automatic Operation: Fire dampers must shut off air handling fans during fire.

Fire Resistance Dimensions (Clause 6.1, Tables 8 & 9)

Refer IS 1642 Tables 8 & 9 for detailed fire resistance dimensions.

Summary Diagram: Fire Damper Locations in HVAC Ducts

flowchart TD
    A[Fire Separation Wall] -->|Fire Damper| B[HVAC Duct]
    C[Central Vertical Shaft] -->|Fire Damper| B
    D[Floor Penetration] -->|Fire Damper| B
    E[Compartment Supply & Return Ducts] -->|Fire Damper| B

Ensure:

• Ducts and insulation materials are flame resistant.
• Fire dampers are automatic and integrated with fan controls.
• Fire walls and compartmentalization follow area limits (>750 m²).

This ensures compliance with IS 1642 for fire-safe air-conditioning installations.

IS 1642: Smoke Venting & Fire Exits - Key Points

Smoke Venting (Clauses 9.1, 9.2, 9.4)

• Purpose: Allow escape of hot gases & smoke to prevent hazardous accumulation, ensuring safe evacuation.
• Where Required: Windowless buildings, underground structures, large factories, theatres, etc.
• Type: Automatic ventilator-cum-exhaust vents with fire rating.
• Capacity: Must prevent dangerous smoke accumulation during evacuation time with safety margin.
• Design: Adequate vent size and placement to release smoke quickly; details covered in separate IS for industrial buildings.

Air-Conditioning & Fire Safety (Clause 8.4)

• Escape routes must not be return air passages.
• Use metal ducts per IS 655:1963.
• Seal duct openings through fire walls/floors with fire-resistant materials (same rating).
• Use flame-resistant insulation (IS 4355:1977).
• Floors >750 m² require fire walls + automatic fire dampers.
• Automatic fire dampers at:
  • Fire separation walls
  • Entry to vertical shafts
  • Floor penetrations
  • Inlet of supply & return ducts on each floor
• Dampers auto-close and switch off air fans on fire detection.

Fire Exits

• Smoke venting supports safe exit use.
• Exits must remain smoke-free during evacuation.
• Ventilation & fire dampers ensure compartmentalization and prevent smoke spread.

Summary Table: Fire Damper Locations

flowchart LR
    Fire --> SmokeVenting[Smoke Venting Vents]
    SmokeVenting --> SafeExit[Safe Use of Fire Exits]
    Fire --> FireDampers[Automatic Fire Dampers]
    FireDampers --> Compartmentalization[Prevent Smoke Spread]
    Compartmentalization --> SafeExit

This ensures safe evacuation by controlling smoke and fire spread per IS 1642 requirements.

IS 1642: Service Shafts and Ducts Key Specifications

Ventilation (Clause 10.2)

• Vent opening area at top of service shaft:
  Between 1/4 and 1/2 of the shaft's cross-sectional area.

Fire Resistance (Clause 10.1 & 17.1)

• Service ducts enclosure:
  Walls and doors must have 2 hours fire rating.
• Ducts > 1 m³:
  Floors should seal ducts with pipe openings sealed properly.
• Inspection panel doors/openings:
  Fire doors with ≥1 hour fire resistance.
• Service room doors:
  Fire resistance of ≥2 hours.

Electrical Services (Clause 17.1)

• Electric cables/wiring:
  Laid in a separate duct sealed at alternate floors with non-combustible materials matching duct fire resistance.
• Wiring in shafts and false ceilings:
  Medium and low voltage wiring must run in metal conduits.
• 230 V wiring above false ceiling:
  Use 660 V grade insulation.
• False ceiling and suspension fixtures:
  Must be non-combustible.
• Prohibited in electric ducts:
  Water mains, gas pipes, telephone lines, or other service lines.

Additional Notes

• Service room must be well-ventilated with direct access from outside or corridor.
• Staircase ventilation and pressurization requirements apply for buildings >15 m (Clause 9.7).

Summary Table

flowchart TD
    A[

IS 1642: Basement Fire Safety & Ventilation Key Points

Ventilation Requirements (Clause 11.1)

• Separate ventilation for each basement.
• Vent cross-sectional area ≥ 2.5% of basement floor area, distributed evenly around perimeter.
• Vent types: grills, breakable stallboard lights, pavement lights, or shafts.
• Alternative: air inlets at basement floor + smoke outlets at ceiling, ducts to ground level.
• Stallboard/pavement lights must be accessible, clearly marked ("SMOKE OUTLET" / "AIR INLET") with area indication.

Multi-level Basements (Clause 11.3)

• Common intake ducts allowed; separate smoke outlet ducts per basement/compartment.
• Mechanical extractors (per IS 941:1985) with:
  • Automatic/manual operation (heat/smoke detectors or sprinklers).
  • Interlocking: extractors run, supply fans stop on fire detection.
  • Air changes: 30 ACH during fire, 28 ACH normal.
  • Alternative power supply mandatory.
• Vent ducts: preferably brick/RCC; fire dampers at transformer/switchboard crossings.
• Restrictions on basement use unless sprinklered (no storage, cooking, garages, shops).
• Cut-outs to upper floors require automatic spray protection.

Smoke Venting (Clauses 9.1 & 9.2)

• Venting to allow escape of hot gases/smoke before roof collapse.
• Ventilator-cum-exhaust should be fire-rated and easily openable.
• Automatic smoke venting mandatory in windowless buildings, underground structures, large factories, theatres, etc.

Summary Table: Vent Area & Air Changes

flowchart TD
    A[Basement Floor] -->|Air Inlets| B[Basement Interior]
    B -->|Smoke Outlets| C[Basement Ceiling]
    C -->|Ducts| D[Ground Level]
    D -->|Accessible Marked Openings| E[Fire Brigade Access]
    subgraph Mechanical System
       

IS 1642 Key Specifications for Chimneys and Flues

Clearance & Fire Resistance (Clause 12.1)

• Minimum clearance: 4 cm between chimney outer surface and adjacent combustible wall lining.
• Fire resistance: Surrounding structure of flue/flue pipe ≥ fire resistance of external walls.
• Air space: Required around flue pipes for inspection and repair.
• Protection: Flue pipes passing through rooms or roof spaces must be enclosed in fire-resistant structure (same as external walls).
• Chimney height: Chimney (excluding pot) must extend ≥ 1 m above the highest roof junction.

Construction Materials (Clause 4.2)

• For buildings >15 m height:
  • Use non-combustible materials.
  • Internal staircase walls: brick, RCC, or materials with ≥ 2 hours fire rating.
  • Chimney walls: Type 1 or Type 2 construction depending on gas temperature:
    • Type 1: Gas temp > 200°C
    • Type 2: Gas temp ≤ 200°C

Metal Chimney Roof Penetration (Clause 22.5 g)

• Guard with iron/metal thimble extending ≥ 22.5 cm above and below roof.
• Provide ≥ 15 cm clearance on all sides of the chimney.

Summary Table: Chimney Fire Resistance and Clearance

flowchart TD
    A[Chimney] --> B{Adjacent Combustible Material?}
    B -- Yes --> C[Maintain 4 cm clearance]
    B -- No --> D[No clearance needed]
    A --> E{Flue Pipe through room/roof?}
    E -- Yes --> F[Enclose in fire-resistant structure]
    E -- No --> G[No

IS 1642: Key Specifications for Staircases & Fire Lifts

1. Staircases

• Detailed provisions are in IS 1644:1988 (refer for dimensions, rise/run, handrails, landings).
• Staircases are primary fire escape routes; design must ensure safe evacuation.

2. Fire Lifts (Clause 13.2.2 and 13.2.1)

Additional Notes:

• Lift motor rooms must be isolated to prevent fire spread.
• Fire-rated doors and walls ensure containment.
• Proper ventilation and signage improve safety during fire emergencies.

flowchart TD
    A[Lifts] --> B{Max 4 lifts per shaft}
    A --> C[Lift shaft walls: 2 hr fire rating]
    A --> D[Lift motor room on top, separated]
    A --> E[Landing & car doors: 1 hr fire rating]
    A --> F[No collapsible gates]
    A --> G[Vent at top ≥ 0.2 m²]
    A --> H[Water slope in lobby]
    A --> I[Signage: use stairs in fire]

For detailed staircase dimensions and design, consult **IS

IS 1642: Refuse Areas and Refuse Chutes Key Specifications

Refuse Areas (Clause 14.1)

• Height > 24 m: Provide refuse area of 15 m² or 0.25 m² per person for two consecutive floors, whichever is greater.
• Location: On the floor immediately above 24 m for buildings up to 39 m.
• For floors above 39 m, provide refuse areas every 15 m vertically.
• Should be on the floor periphery, open to air on at least one side, with suitable railings.

Refuse Chutes (Clause 15.1)

• Enclosure walls: Non-combustible material with minimum 2-hour fire resistance.
• Location: Not inside staircases, service shafts, or AC shafts.
• Inspection panels and doors: Tight-fitting with 1-hour fire resistance.
• Chutes should be located away from exits.

Fire Resistance Dimensions (Tables 8 & 9, Clause 6.1)

Use these minimum dimensions for structural elements enclosing refuse chutes to meet fire safety.

flowchart TD
    A[Building Height > 24 m] --> B{Refuse Area Required?}
    B -->|Yes| C[Provide 15 m² or 0.25 m²/person for 2 floors]
    C --> D[Floor immediately above 24 m (up to 39 m)]
    C --> E[Every 15 m above 39 m]
    F[Refuse Chute] --> G[Enclosure: Non-combustible, 2h fire resistance]
    F --> H[Doors & Inspection panels: 1h fire resistance]
    F --> I[Located away from stairs & exits]

Summary: Provide well-ventilated refuse areas at specified heights and ensure refuse chutes have fire-resistant enclosures with proper location and inspection access per IS 1642.

IS 1642: Fire Safety Measures for Openings and Penetrations

Key Specifications (Clause 7.5)

• Openings in floors must limit fire spread.
• Around cables: Protect per IS 12459:1988.
• Around plumbing/gas/steam pipes: Seal with filler having ≥1 hour fire rating.
• Pipes/conduits clearance: radial clearance ≤ 3 mm for heat expansion.
• Staircase/hoist enclosures: Constructed with materials having 2 hours fire resistance (brick, concrete, reinforced concrete).
• Openings from enclosures to roof or other parts must have fire-resistant doors with ≥1 hour rating.
• Enclosure walls extending above non-usable roofs: extend ≥45 cm above roof with glazed skylight/window.

Fire Resistance Thickness for Masonry Walls (Clause 5.1, Tables 2 & 3)

Fire Resistance for Framed Construction (Clause 5.1, Table 4)

Fire Resistance for Concrete Columns & Beams (Clause 6.1, Tables 8 & 9)

| Element | Fire Resistance | Width/Thickness (mm) | Cover (mm) | |-------------------|-----------------|----------------------|