Guidelines for falsework for concrete structures

IS 14687 - Scope: Key Specifications & Tolerances

1. Scope Overview

• Covers design, construction, and inspection of formwork and falsework for concrete structures.
• Ensures proper positioning and dimensional accuracy of finished concrete.

2. Tolerance in Formwork (Clause 9.6)

3. Permissible Stresses (Clause 7.4)

• Shall not exceed values in relevant IS codes (e.g., IS 456 for concrete).
• Special care for reusable steel/timber components.

4. Inspection Checklist Highlights (Clause 9.9)

• Props undamaged, straight, and properly restrained.
• Sole plates seated correctly.
• No over-extension of adjustable props.
• Proper lateral restraints and bracing.
• Correct alignment and plumbness.
• Adequate bearing areas and no timber splitting.
• Proper tensioning of guy ropes/stays.
• Compliance with dimensional tolerances.

5. Referenced IS Codes (Annex A)

• IS 456: Plain & Reinforced Concrete
• IS 800: Steel Construction
• IS 875 (Parts 1-5): Design Loads
• IS 4990: Plywood for shuttering
• IS 883: Structural Timber
• IS 1161: Steel Tubes
• IS 2062: Steel for Structural Purposes

Summary Diagram: Tolerance Limits for Formwork

graph TD
    A[Formwork Dimensions] --> B[Cross-section: -6 to +12 mm]
    A --> C[Footings Plan: ±12 mm]
    A --> D[Eccentricity: 0.02 × width (max 50 mm)]
    A --> E[Thickness: ±0.05 × thickness (max 50 mm)]

Use this as a baseline for ensuring formwork accuracy and compliance with IS 14687.

IS 14687: General Requirements Summary

1. Permissible Stresses (Clause 7.4)

• Must comply with relevant IS codes for permanent structures.
• For reusable components (steel, timber), stresses must not exceed specified limits.

2. Formwork Pressure (Fig. 3)

• Maximum pressure on formwork depends on:
  • Concrete temperature (T)
  • Rate of placement (height in m/h)
• Pressure units: kN/m²

3. Material Specifications (Clause 6.1.3)

• Steel sheet plates: IS 2062 / IS 8500 / IS 1977
• Rolled sections & tubes: IS 2062 / IS 8500 / IS 1161
• Steel clamps & couplers: IS 2750

4. Proprietary Falsework Systems (Annex B, Clause 5.2)

• Manufacturer must supply technical info as per Annex B.
• Includes design data, material specs, and load capacities.

Typical Formwork Components (Fig. 4)

• Wire or tie backs
• Plywood beam sides
• Solid beam bottoms
• Double post shores

Example: Permissible Stress Limits (General Reference)

flowchart TD
    A[Fresh Concrete Placement] --> B[Pressure on Formwork]
    B --> C[Wire/Tie Back]
    B --> D[Plywood Beam Side]
    B --> E[Solid Beam Bottom]
    B --> F[Double Post Shore]
    C & D & E & F --> G[Formwork Stability]

Summary: Ensure stresses follow IS limits; use specified steel grades; obtain manufacturer data for proprietary systems; control formwork pressure based on concrete temperature and placement rate.

IS 14687: Materials for Falsework - Key Points

1. Permissible Materials (Clause 6.1.1)

• Timber (softwood, partially seasoned) — conforming to IS 883 for scaffolding, beams, columns, props, bracings.
• Plywood
• Steel
• Aluminium
• PVC and other plastics (e.g., reinforced plastics, HDPE, polypropylene)
• Ferro-cement
• Masonry, concrete, earthwork (in specific applications)
• Polythene sheets (for lining)

2. Timber Requirements

• Use softwood, partially seasoned to prevent swelling/warping.
• Must meet IS 883 for strength and durability.

3. Commercial Falsework Systems (Clause 5.2)

• Can be used if they comply with IS 14687.
• Supplier should provide detailed info per Annex B (design data, load capacities, etc.).

Typical Design Considerations for Falsework Materials:

Basic Formula for Timber Prop Load Capacity:

[ P = A \times f_c / FS ]

• (P) = allowable load
• (A) = cross-sectional area
• (f_c) = allowable compressive stress (from IS 883)
• (FS) = factor of safety (usually 3 to 5)

flowchart TD
    A[Falsework Materials] --> B[Timber (IS 883)]
    A --> C[Steel]
    A --> D[Aluminium]
    A --> E[Plastics (PVC, HDPE)]
    A --> F[Ferro-cement]
    A --> G[Masonry/Concrete/Earthwork]

Summary: Use IS 883 timber, steel or approved proprietary systems with

IS 14687: Functional Requirements - Key Points

1. Functional Requirements (Clause 4.4)

• Formwork must ensure finished concrete is accurately positioned relative to reference points.
• Must conform to dimensions and shapes as per design drawings.

2. Manufacturer's Information (Annex B, Clauses 5.2 & 6.1.3)

• Proprietary falsework systems require detailed data from manufacturers including:
  • Load capacities
  • Material specifications
  • Assembly instructions
  • Safety factors

3. Tolerances in Formwork (Clause 9.6, Table 9.6)

Summary Formula for Eccentricity Tolerance:

[ \text{Eccentricity} \leq \min(0.02 \times \text{width}, 50 \text{ mm}) ]

flowchart TD
    A[Design Drawings] --> B[Formwork Fabrication]
    B --> C[Check Dimensions & Shape]
    C --> D{Tolerance Limits}
    D -->|Within Limits| E[Accept Formwork]
    D -->|Exceeds Limits| F[Modify/Rework]
    E --> G[Concrete Placement]
    F --> B

Note: Ensuring these tolerances is critical for structural integrity and aesthetics.

IS 14687: Falsework for Concrete Structures - Key Points on Types of Falsework

The standard outlines 5 types of falsework, each suited for specific structural and construction needs:

1. Shoring Falsework

   • Vertical supports (props, shores) to carry formwork loads temporarily.
   • Used for slabs, beams, and small spans.

2. Flying Falsework

   • Movable falsework that advances with construction (e.g., for bridges).
   • Designed for easy assembly/disassembly and reuse.

3. Truss Falsework

   • Uses truss members for longer spans and heavy loads.
   • Efficient load distribution, suitable for bridges and large slabs.

4. Cantilever Falsework

   • Supported at one end only, used where ground support is not possible.
   • Requires careful stability checks.

5. Suspended Falsework

   • Hanging falsework from overhead supports or existing structures.
   • Used in restricted ground access areas.

Key Design Considerations (Clause 4.4.5)

• Maximize reuse to reduce costs.
• Minimize material cutting and wastage.
• Plan assembly and member sizes early.

Typical Falsework Load Formula:

[ P = W_c + W_f + W_s ]

Where:

• (P) = total load on falsework
• (W_c) = weight of fresh concrete
• (W_f) = weight of formwork
• (W_s) = weight of construction loads (workers, equipment)

Simplified Falsework Load Table (Indicative):

graph

IS 14687: Key Points on Formwork Components and Accessories

1. Falsework Accessories (Clause 6.2)

• Use commercially available falsework systems complying with IS guidelines.
• Obtain detailed supplier information (see Annex B) when using proprietary systems.
• Accessories include wire ties, plywood beams, solid beams, double post shores, studs, wales, and bracings (see Fig. 4).

2. Permissible Stresses (Clause 7.4)

• Follow permissible stress limits as per relevant IS codes for permanent structures.
• For reusable steel/timber components, stresses must not exceed specified values.
• Fresh concrete pressure on formwork depends on concrete temperature and placement rate (Fig. 3):

(Approximate values; refer to Fig. 3 for exact curves)

3. Tolerance in Formwork (Clause 9.6)

Summary Diagram of Formwork Components

graph LR
A[Wire or Tie Back] --> B[Plywood Beam Side]
B --> C[Solid Beam Bottom]
C --> D[Double Post Shore]
D --> E[Stud and Wale with Bracing]

Use these guidelines to ensure structural integrity, safety, and dimensional accuracy of formwork systems per IS 14687.

IS 14687: Design of Falsework – Key Points & Formulas

Design Principles (Clause 7.1)

• Falsework must be designed per the loadings and safety criteria of the permanent structure.
• Consider material properties, site conditions, environment, and construction sequence (especially for cantilevers, domes).
• Ensure vertical members carry compressive forces only under combined vertical & horizontal loads.
• Check for:
  • Safety
  • Overturning
  • Overall stability
  • Progressive collapse

Materials (Clause 6)

• Use materials conforming to relevant IS codes (e.g., timber, steel).
• Material condition must reflect actual site usage.

Design Checks

• Axial load on verticals:
  [ P = \sum (Dead,Load + Live,Load + Construction,Load) ]

• Buckling check for vertical members:
  [ P_{cr} = \frac{\pi^2 E I}{(K L)^2} ] Where:

  • (E) = Modulus of elasticity of material
  • (I) = Moment of inertia
  • (K) = Effective length factor
  • (L) = Unsupported length

• Stability against overturning:
  Factor of safety against overturning ≥ 1.5

Use of Proprietary Systems (Clause 5.2)

• Commercial systems allowed if they comply with IS 14687.
• Obtain detailed supplier data (Annex B) for design validation.

Summary Table: Falsework Design Checks

flowchart TD
    A[Load Application] --> B[Falsework Vertical Members]
    B --> C{Check Compressive Force}
    C -- Yes --> D[Buckling Check]
    C -- No --> E[Redesign]
    D --> F{

IS 14687: Falsework for Concrete Structures - Key Points for Specific Structural Elements

Scope (Clause 1.1)

• Applicable to general buildings & ordinary civil engineering structures (up to 4 storeys or 15 m height).
• Dead load of formwork + concrete ≤ 20 kN/m².
• Excludes bridges and special structures.

Key Design Considerations

• Falsework must safely support dead loads (formwork + fresh concrete) and construction loads.
• Stability against buckling and lateral forces is essential.
• Use standard safety factors (usually 1.5 for load, 1.15 for material strength).

Typical Load Calculation Formula:

[ P = q \times A ] Where:

• (P) = Load on falsework member (kN)
• (q) = Load intensity (kN/m²)
• (A) = Tributary area supported (m²)

Material Specifications (Clause 6.2)

• Use steel or timber accessories with adequate strength.
• Ensure proper connections and bracing to prevent displacement.

Suggested Falsework Design Table (Example):

flowchart TD
    A[Load on Falsework] --> B{Calculate Load}
    B --> C[Dead Load (Formwork + Concrete)]
    B --> D[Live Load (Construction)]
    C & D --> E[Apply Safety Factors]
    E --> F[Design Falsework Members]
    F --> G[Check Stability & Deflection]

For detailed design, refer to IS 14687 clauses on materials, load combinations, and construction practices.

IS 14687: Key Points on Erection, Inspection & Maintenance of Falsework

1. Erection Tolerances & Forces (Clause 7.7)

• Horizontal reaction force = 1% of applied vertical load, due to erection tolerance.
• Max permissible eccentricity: 25 mm from vertical centroid.
• Applies to tubes, props, steel sections, proprietary supports.

2. Inspection Checklist (Clause 9.9)

• Adjustable steel props: undamaged, pins in place, lateral restraints, beam centralizers.
• Sole plates: properly seated.
• Screw adjustments not over-extended.
• Horizontal load members aligned (no eccentricity).
• Adequate restraints against tilting, overturning, and horizontal loads.
• Tightened bracing and securing devices.
• Use standard proprietary components.
• Proper bearing areas under washers, steel on timber.
• No timber splitting; stagger bolts where needed.
• Props plumb within tolerance; aligned vertically in multistage falsework.
• Bearing plates flat and undistorted.
• Guy ropes/stays tensioned.
• Falsework dimensions within tolerance.
• Provision for vibrators and plant movement.
• Camber as per drawings for long spans/cantilevers.

3. Safety Precautions (Clause 9.1)

• Barricades and safety signs.
• Experienced form watchers during concrete placement.
• Adequate illumination.
• Lifting points in formwork design.
• Scaffoldings, guardrails integrated.
• Field safety inspection program.
• Stripping only after full restraining forces mobilized for cantilevers/beams.

4. Material Specifications (Clause 6.1.3)

• Steel plates: IS 2062 / IS 8500 / IS 1977.
• Rolled sections & tubes: IS 2062 / IS 8500 / IS 1161.
• Clamps & couplers: IS 2750.
• Proprietary system data per Annex B.

Summary Table: Typical Checks for Falsework Components

IS 14687: Key Points on Stripping and Releasing of Falsework

1. Design & Construction (Clauses 4.4.1 & 7)

• Falsework must allow partial removal in sequence without damaging concrete or destabilizing other parts.
• Connections should be easily detachable for safe stripping.

2. Stripping Procedure (Clause 9.5 & 9.5.2)

• Sequence knowledge: Workers must know the exact order of form and prop removal.
• Material handling: Falsework components must be stacked properly; no dropping from height.
• Form removal: Forms should be eased off gently to avoid damage.
• Adherence to sequence: Follow planned dismantling steps strictly for safety.

3. Release Agent (Clause 6.3.2)

• Choose release agents based on:
  • Surface type
  • Concrete type and finish quality
  • Application conditions
• Avoid waste oil; prefer agents containing fatty acids for better release.

Summary Table: Falsework Stripping Checklist

flowchart TD
    A[Start Stripping] --> B[Check worker knowledge]
    B --> C[Inspect falsework condition]
    C --> D{Is sequence laid down?}
    D -->|Yes| E[Follow sequence]
    D -->|No| F[Plan safe sequence]
    E --> G[Remove forms gently]
    F --> G
    G --> H[Remove props carefully]
    H --> I[Stack materials properly]
    I --> J[Complete stripping safely]

This ensures safety, concrete integrity, and efficient falsework reuse.

IS 14687: Design Information & Load Considerations

1. Design Information (Clause 7.2)

• Obtain site investigation report (soil, groundwater, etc.).
• Define loading scheme: how loads transfer during construction.
• Detail sequence of erection & releasing of formwork.
• Specify concreting procedure and time frames for curing & formwork removal.

2. Load Considerations

Dead Loads (Clause 7.3.1)

• Include self-weight of structure and permanent fixtures.
• Formwork load: Actual load to be used if available.
• Default formwork load:
  [ q_{formwork} = 500 , \text{N/m}^2 ] (used for initial design if actual data unavailable)

Imposed Loads (Clause 7.3.2)

• Loads due to construction activities, equipment, and temporary storage.
• Must be evaluated based on site conditions and construction methods.

Summary Table: Formwork Load for Initial Design

flowchart LR
    A[Start Design] --> B[Collect Design Info]
    B --> C[Site Investigation Report]
    B --> D[Loading Scheme & Sequence]
    B --> E[Concreting Procedure & Time Frame]
    C & D & E --> F[Evaluate Loads]
    F --> G[Dead Loads + Formwork Load]
    F --> H[Imposed Loads]
    G & H --> I[Structural Design]

Key: Always verify actual formwork loads for safety and economy. Use 500 N/m² as conservative estimate initially.

IS 14687 - Key Information to be Supplied by Manufacturers of Proprietary Falsework Systems

As per Clause 5.2 & Annex B (Clause 5.2 and 6.1.3):

• Detailed Technical Data:
  Manufacturers must provide comprehensive details to avoid misuse or unsafe assumptions by users. This includes:

  • Material specifications
  • Load capacities
  • Assembly and erection instructions
  • Limitations and unusual conditions handling

• Material Specifications:

  • Steel sheet plates: conform to IS 2062, IS 8500, or IS 1977
  • Rolled sections and tubes: conform to IS 2062, IS 8500, or IS 1161
  • Steel clamps and couplers: conform to IS 2750

• Information to be obtained before use:

  • Structural capacity and permissible loads
  • Connection details and bracing requirements
  • Safety factors and design assumptions
  • Compatibility with other construction materials/systems

Summary Table of Relevant IS Codes for Materials

Recommended Manufacturer Data Checklist

• Material grade & mechanical properties
• Load capacity charts (axial, bending, shear)
• Assembly diagrams & stepwise erection procedure
• Safety and maintenance guidelines
• Compatibility notes with other falsework elements

flowchart TD
    A[Manufacturer] --> B[Provide Detailed Info]
    B --> C[Material Specs (IS Codes)]
    B --> D[Load Capacities]
    B --> E[Assembly Instructions]
    B --> F[Safety & Limitations]
    F --> G[User/Designer]
    G --> H[Safe & Correct Use]

Note: Always verify proprietary system data against IS 14687 guidelines before design or use.

Typical Watchers Report Format (IS 14687 - Clause 9.9 & Annex C)

Key Points to Include in Watchers Report:

• Identification: Date, location, project, and watcher’s name.
• Falsework Inspection Checklist (from Clause 9.9):
  • Condition of adjustable steel props (undamaged, pins in place, lateral restraints, beam centralization).
  • Proper seating of sole plates.
  • Screw adjustments not over-extended.
  • Alignment of horizontal and vertical members.
  • Adequate restraints against tilting, overturning, and horizontal loads.
  • Tightening of securing devices and bracing.
  • Use of standard proprietary components.
  • Protection against accidental impacts.
  • Adequate bearing areas under bolts and steel parts on timber.
  • Timber integrity (no splitting, adequate nails/bolts).
  • Plumbness of supports within tolerance.
  • Props alignment in multistage falsework.
  • Flat, undistorted bearing plates.
  • Tension in guy ropes or stays.
  • Compliance with dimensional tolerances.
  • Provision for movement of vibrators and construction plant.
  • Presence of camber as per drawings.

Tolerance Limits on Formwork (Clause 9.6):

Summary Table for Falsework Inspection Checklist (Clause 9.9)

IS 14687: Committee Composition & Key Specifications

Committee Composition (Annex D)

• The Cement and Concrete Sectional Committee, CED 2 is responsible for formulating the standard.
• Includes experts from:
  • Cement companies (e.g., Orissa Cement Ltd, The India Cements Ltd)
  • Engineering research institutes (CSIR labs, Structural Engineering Research Centre)
  • Government departments (CPWD, Central Water Commission)
  • Construction firms (B. G. Shirke & Co, Gannon Dunkerley & Co)
• Chairperson: Dr. H. C. Visvesvarya

Manufacturer's Information Requirements (Clause 1.2, Table B-1)

Manufacturers must provide detailed data on falsework systems:

Summary Table: Strength Details to be Supplied

Typical Watchers Report Format (Annex C)

• Includes job location, placement details, equipment used, and detailed checklist for formwork and shoring conditions.
• Ensures safe and quality concrete placement.

flowchart TD
    A[Technical Committee: CED 2