Recommendations for use of polyethene film for water-proofing of roofs

IS 7290: Scope - Key Points & Specifications

Scope (Clause 2.0):
Defines terminology and applicability for testing water vapour transmission through sheets.

Key Specifications:

• Test Specimens (Clause 3):
  Specimens must be representative of the sample; templates may be used to define test area (Clause 2.6).

• Reproducibility (Clause 7.1):
  Results from different specimens of the same sample should not vary more than ±10% from their average.

• Test Report (Clause 6.1):
  Must include:

  • Material description
  • Sheet thickness
  • Test conditions (temperature, humidity)
  • Water vapour transmission values for all four specimens and their average

Summary Table: Reproducibility Limits

This ensures consistent, reliable testing and reporting of water vapour transmission properties.

IS 7290 - Key Definitions & Specifications Summary

• Clause 2.0 (Definitions): Establishes terminology for the standard.

• Clause 2.6 (Template):

  • A template is used to define the test area and apply the wax seal during testing.

• Clause 6.1 (Test Specimens Report Requirements):
  Reports must include:

  • Material description
  • Sheet thickness
  • Test conditions (temperature, humidity)
  • Water vapor transmission values for all four specimens and their average

• Clause 7.1 (Reproducibility):

  • Results from different specimens of the same sample should not differ by more than ±10% from their average.

Summary Table: Reproducibility Limits

Notes:

• Use templates to ensure consistent test area definition.
• Maintain controlled environmental conditions during testing.
• Report all individual and average measurements for transparency.

flowchart TD
    A[Prepare Specimen] --> B[Use Template to Define Test Area]
    B --> C[Apply Wax Seal]
    C --> D[Conduct Water Vapor Transmission Test]
    D --> E[Record Results for 4 Specimens]
    E --> F[Calculate Average & Check Reproducibility (±10%)]
    F --> G[Prepare Test Report]

This concise framework ensures standardized testing and reliable comparison of water vapor transmission properties per IS 7290.

Detailed content not available.

IS 7290 - Key Formulas, Tables & Specifications for Materials

1. Bonding Materials (Clause 4.2)

• Use straight-run bitumen conforming to IS 73-1961.
• Cold cutback bitumen (IS 73-1961) allowed over the film.
• Cutback bitumen temperature ≤ 50°C during application.

2. Material Test Report (Clause 6.1)

Report must include:

• Material description.
• Sheet thickness tested.
• Test conditions (temperature, humidity).
• Water vapour transmission values for 4 specimens + average.

3. Reproducibility (Clause 7.1)

• Variation between specimens from the same sample ≤ 10% of average.

Additional Notes:

• Use low-density polyethylene film as per relevant specifications.
• Bitumen grades and specifications are detailed in IS 73-1961 (Paving Bitumen).
• Testing ensures waterproofing/damp-proofing material quality and consistency.

Summary Table: Bitumen Application Temperature

flowchart LR
    A[Bitumen Material] --> B{Type}
    B -->|Straight-run| C[Use as per IS 73-1961]
    B -->|Cutback| D[Apply at ≤ 50°C]
    E[Film Material] --> F[Low-density polyethylene]
    G[Testing] --> H[Report: Description, Thickness, Conditions, Water Vapor Transmission]
    G --> I[Reproducibility ≤ 10% variation]

For detailed specifications, refer to IS 73-1961 and IS 7290 clauses.

IS 7290: Preparation of Roof Surface – Key Points

• Reference Standards:

  • Primer: Bitumen primer must conform to IS 3384-1965.
  • Surface preparation details refer to IS 3067-1966.

• Sequence of Operation (Clause 7.1):

  1. Clear roof surface of all foreign materials (dust, dirt, loose particles) as per IS 3067.
  2. Lay waterproofing treatment and flashings.
  3. Treat gutters and drain mouths.
  4. Finish surface.
  5. Clean and remove surplus materials.

• Surface Preparation Essentials:

  • Ensure roof is clean, dry, and free from loose particles.
  • Repair cracks and unevenness.
  • For bituminous treatment, apply bitumen primer uniformly.
  • Pre-sloped roofs should follow treatments in Clause 6.1 for drainage.

Typical Primer Application (from IS 3384-1965)

Summary Diagram: Roof Surface Preparation Workflow

flowchart TD
    A[Start] --> B[Clear Roof Surface]
    B --> C[Repair & Level Surface]
    C --> D[Apply Bitumen Primer]
    D --> E[Laying Waterproofing Treatment]
    E --> F[Treat Gutters & Drains]
    F --> G[Surface Finishing]
    G --> H[Clean & Remove Surplus]
    H --> I[End]

Note: For detailed specifications and design considerations, refer directly to IS 3067-1966 and IS 3384-1965.

IS 7290: Key Formulas, Tables & Specifications for Types of Waterproofing Treatment

1. Types of Waterproofing Treatment (Clause 6)

• Single Layer Film Treatment over Thermal Insulation (Fig. 1):
  • Layers (bottom to top):
    • Thermal Insulation
    • Polyethylene Film
    • Kraft Paper laminated & bitumen coated
    • Tiles / Cement Concrete / Patent Stone

2. Film Treatment Steps (Clause 6.1.1.1a)

3. Typical Details for Roof Projections (Clause 7.2.6, Fig. 4)

• Use composite polyethylene-bitumen tapes for joints.
• Groove filled with cold cutback bitumen.
• Separating layer below polyethylene film.
• Cover fillet & chase filled with cement mortar (1:4).
• Cold cutback bitumen with filler or kraft paper finishing.

4. Preparation

• Roof surface must be smooth (IS:3067-1966 Clause 6.2).
• Primer application ensures adhesion and impregnation.

Diagram: Layering in Single Layer Film Treatment

graph TD
    A[Tiles / Cement Concrete / Patent Stone] --> B[Kraft Paper laminated & Bitumen coated]
    B --> C[Polyethylene Film]
    C --> D[Thermal Insulation]
    D --> E[Roof Surface (prepared)]

Summary:

• Primer → Hot bitumen → Polyethylene film → Cold cutback bitumen → Blinding material.
• Use proper layering and joint sealing for durability.

IS 7290 - Method of Laying Polyethylene Film (Clause 7.2.4.2 & related)

Key Specifications for Laying:

• Flat Roofs

  • Lay film at right angles to water flow direction.
  • Overlaps must face downwards to prevent water ingress.
  • (Refer Fig. 3A)

• Sloping Roofs

  • Lay successive layers along the slope.
  • Avoid laying film across the slope to prevent water accumulation under overlaps.
  • (Refer Fig. 3B)

• Curved Shell Roofs

  • Lay film across the slope to minimize excessive laps in troughs.
  • (Refer Fig. 3C)

Additional Guidelines:

• Avoid puncturing the film during installation (Clause 7.1.1).
• For protection under lime terracing or mud PHIUSKA, use protective layers (Clause 6.2.1), e.g., burnt clay tiles or lime terracing.

Summary Table: Laying Direction vs Roof Type

Illustration (Simplified):

flowchart LR
    A[Water Flow Direction] --> B[Flat Roof: Film ⟂ Flow, Overlap Down]
    A --> C[Sloping Roof: Film Along Slope]
    A --> D[Curved Shell Roof: Film Across Slope]

Reference: IS 7290 Clause 7.2.4.2 & Clause 6.2.1 for protective treatments.

IS 7290: Inspection and Maintenance - Key Points

Clause 7.2.6.1 (Related to parapets and downtake pipes):

• Provide an extra piece of polyethylene film around downtake water pipe openings.
• Cover film edges with cement plaster 1:6 to ensure waterproofing and durability.

Inspection & Maintenance Guidelines (General Best Practice)

• Regular inspection of rainwater drainage points, parapets, and waterproofing layers is essential.
• Check for cracks, blockages, or damage in downtake pipes and parapet coverings.
• Maintain the integrity of polyethylene film and cement plaster to prevent water ingress.
• Repair any damaged plaster or film immediately to avoid structural deterioration.

Reproducibility (Clause 7.1, Table A-7)

• Test results on different specimens from the same sample should not differ by more than 10% from their average, ensuring consistent quality.

Summary Table: Protective Measures at Downtake Pipes

flowchart TD
    A[Parapet] --> B[Opening for Downtake Pipe]
    B --> C[Polyethylene Film]
    C --> D[Cement Plaster (1:6)]
    D --> E[Waterproof Seal]
    E --> F[Drainage]

For detailed procedures, refer to IS 7290 and perform maintenance as per site conditions.

IS 7290: Method of Test for Water Vapour Transmission of Polyethylene Film

Key Specifications (Appendix A):

• Test Scope: Measures water vapour transmission rate (WVTR) through polyethylene film.
• Specimens: Four samples tested; report average WVTR.
• Test Conditions: Temperature, humidity, and film thickness must be recorded.
• Limit: WVTR ≤ 5.53 g/24 h/m² (Clause 5.53b).

Essential Test Report Includes (Clause A-6.1):

• Material description
• Film thickness (mm)
• Test conditions (temperature °C, relative humidity %)
• WVTR values for all specimens and average (g/24 h/m²)

Typical Formula for WVTR:

[ \text{WVTR} = \frac{\Delta m}{A \times t} ]

Where:

• (\Delta m) = mass of water vapour transmitted (g)
• (A) = area of film exposed (m²)
• (t) = time interval (24 hours)

Summary Diagram:

flowchart LR
    A[Prepare 4 film specimens] --> B[Condition specimens at set T & RH]
    B --> C[Measure water vapour transmitted]
    C --> D[Calculate WVTR for each specimen]
    D --> E[Report average WVTR ≤ 5.53 g/24h/m²]

Note: Ensure strict control of test environment and specimen thickness for reproducible results.