Classification of Commercial Timbers and Their Zonal Distribution

IS 399 Foreword - Key Highlights & Specifications

• Purpose: Provides strength coefficients and properties of Indian timbers for various engineering uses.
• Data Source: Strength values from Forest Research Institute, Dehra Dun, based on recognized timber evaluation studies (1954, 1959).
• Units: Metric system used throughout; weights also in imperial units (lb/ft³) for transition ease.
• Tables I-V: List timbers by zones, uses, and properties including:
  • Availability per zone
  • Average weight & range (kg/m³ and lb/ft³)
  • Durability classification
  • Amenability to antiseptic treatment
  • Refractoriness to air seasoning
  • Strength coefficients for design use

Sample Table Columns Summary (from IS 399):

This standard aligns with trade practices and references latest Indian Standards where applicable.

For detailed design, refer to strength coefficient tables and timber classification in IS 399 clauses 4 and 7.

IS 399 - Scope Summary

• Scope (Clause 1 & 4):
  IS 399 covers classification, properties, and utilization of Indian timbers. It provides detailed tables (I to V) listing commercially available timbers by zone, their uses, and physical/mechanical properties.

• Key Tables (I to V):
  Each table includes:

  Parameter	Description
  Availability	Presence of timber species in specific zones
  Average Weight	Weight of air-seasoned timber (kg/m³ and lb/ft³)
  Weight Range	Variation in timber weight
  Durability	Broad classification of timber durability
  Treatability	Amenability to antiseptic treatment under pressure
  Refractoriness	Resistance to air seasoning
  Strength Coefficient	Strength indices for various uses (from Forest Research Institute)

• Units:
  Metric system is primary; weights also given in imperial units for transition ease.

• Strength Coefficients:
  Derived from standardized evaluation methods (Symposium on Timber and Allied Products, 1959).

Example: Strength Coefficient Concept

[ \text{Strength Coefficient} = \frac{\text{Strength of Timber Species}}{\text{Reference Timber Strength}} ]

Used for comparing suitability of timber species in different applications.

flowchart LR
    A[Timber Species] --> B{Zone Availability}
    B --> C[Weight (kg/m³ & lb/ft³)]
    B --> D[Durability]
    B --> E[Treatability]
    B --> F[Refractoriness]
    B --> G[Strength Coefficient]
    G --> H[Suitability for Use]

This scope ensures comprehensive data for selection and use of Indian timbers per zone and application.

IS 399: Key Specifications on Uses of Timber

Uses Classification (Clause 2.1)

Timber uses are grouped into:

• a) Constructional purposes (posts, beams, bridges, sleepers, poles)
• b) Furniture & cabinet making
• c) Light packing cases
• d) Heavy packing cases (machinery)
• e) Agricultural implements & tool handles
• f) Turnery articles & toys
• g) Veneers & plywood

Tables Overview (Clauses 0.7 & 4.0)

Tables I to V provide:

• Zone-wise availability of timber species
• Average weight & weight range (Air-seasoned timber)
  • In kg/m³ and lb/ft³
• Durability classification
• Treatability (ease of antiseptic pressure treatment)
• Refractoriness (resistance to air seasoning)
• Strength coefficient

Example Table Columns (from Table II - East Zone)

Practical Use:

• Select timber species based on zone availability and intended use.
• Consider durability and treatability for long-term performance.
• Use strength coefficient for structural design calculations.

flowchart TD
    A[Timber Species] --> B{Zone Availability}
    B --> C[East Zone]
    B --> D[West Zone]
    B --> E[North Zone]
    C --> F[Use Classification]
    F --> G[Construction]
    F --> H[Furniture]
    F --> I[Packing]
    G --> J[Strength Coefficient]
    G --> K[Durability]
    G --> L[Treatability]

This structured approach ensures optimal timber selection per IS 399 for various applications.

IS 399 - Timber Zones Summary

India (including Sikkim & Bhutan) is divided into 5 Timber Zones based on timber availability and consumption:

Key Specifications from Tables I-V (per Zone)

• Timber species availability (general presence in zone)
• Average density (air-seasoned timber): kg/m³ and lb/ft³
• Durability classification (e.g., durable, moderately durable)
• Treatability (amenability to antiseptic pressure treatment)
• Refractoriness (resistance to air seasoning)
• Strength coefficients for design calculations

Usage Notes

• Timber from one zone may be available in others due to trade routes.
• Zones help select timber species based on regional supply and properties.
• Refer to Tables I-V for detailed species-wise data per zone.

graph LR
A[India + Sikkim & Bhutan] -->|Zone I| B(North Zone)
A -->|Zone II| C(East Zone)
A -->|Zone III| D(Centre Zone)
A -->|Zone IV| E(West Zone)
A -->|Zone V| F(South Zone)

For detailed species data and design values, consult Tables I to V in IS 399.

IS 399 - Classification of Timbers (Clause 4)

IS 399 classifies timber durability based on average life in exposed or ground-contact conditions:

Key Points:

• Classification is comparative, reflecting timber life under normal atmospheric and soil conditions.
• Life expectancy varies with local climate and soil.
• A strength coefficient (relative to teak = 100) is provided for each timber species to aid design.
• Seasoning effects (cracking/splitting) are considered in classification.

Usage:

• Use this classification to select timber species for durability-critical applications.
• Combine with strength coefficients for structural design.

flowchart TD
    A[Timber Species] --> B{Average Life?}
    B -->|≥120 months| C[High Durability]
    B -->|60-120 months| D[Moderate Durability]
    B -->|<60 months| E[Low Durability]

This classification helps engineers choose timber with appropriate durability and strength for specific environmental exposure.

IS 399 - Availability of Timbers: Key Points & Tables

Availability Classes (Clause 4.1)

• Availability data includes forest and non-forest sources (fields, roadside, tea gardens).
• Actual commercial availability may be less due to extraction difficulties.

Durability Classification (Clause 4.3)

• Durability is relative and depends on local soil/climate.

Summary of Tables (Clause 4.0 & 0.7)

• Tables I-V list timber species by zone with:
  • Availability class (X, Y, Z)
  • Average weight (kg/m³ and lb/ft³)
  • Durability class
  • Treatability for antiseptic pressure treatment
  • Refractoriness to air seasoning
  • Strength coefficient

Example Table Extract (Simplified):

This classification aids selection based on availability, durability, and treatment suitability for structural use.

IS 399: Weight per Cubic Metre of Timber

• The average weight and range of weights per cubic metre (kg/m³) at 12% moisture content are provided for various timber species.
• These values are based on extensive sampling by the Forest Research Institute, Dehra Dun.
• Weight varies due to climatic, soil conditions, and position within the tree.
• Tables I to V in IS 399 list:
  • Timber species per zone
  • Availability
  • Average weight (kg/m³) and range (in parentheses)
  • Durability class
  • Treatability (ease of antiseptic treatment)
  • Refractoriness to air seasoning
  • Strength coefficients

Typical Data Format from IS 399 Tables

Note: Values are indicative; refer to IS 399 tables for exact species data.

Formula to estimate weight of timber volume:

[ \text{Weight} = \text{Density} \times \text{Volume} ]

Where:

• Density = Average weight per cubic metre (kg/m³)
• Volume = Timber volume in cubic metres (m³)

flowchart LR
    A[Timber Species] --> B[Average Weight (kg/m³)]
    A --> C[Weight Range]
    A --> D[Durability]
    A --> E[Treatability]
    A --> F[Refractoriness]
    A --> G[Strength Coefficient]

Summary: Use IS 399 tables for species-specific average weight and range at 12% moisture content; multiply density by volume for weight estimation.

IS 399: Durability of Timber - Key Points

Durability Classification (Clause 4.3)

• Durability is comparative and depends on local soil and climate.
• Useful for exposed situations and ground contact.

Important Tables (Clause 4.0)

• Tables I-V classify timbers by zones and uses.
• Each timber species lists:
  • Availability in zones
  • Average weight (kg/m³) & range
  • Durability class (High, Moderate, Low)
  • Amenability to antiseptic treatment
  • Refractoriness to air seasoning
  • Strength coefficient (Teak = 100 baseline)

Practical Notes

• Durability guides selection for structural use.
• Strength coefficient aids in design calculations.
• Antiseptic treatability indicates preservation potential.

Example: Strength Coefficient Use

[ \text{Design Strength} = \text{Base Strength} \times \frac{\text{Strength Coefficient}}{100} ]

flowchart TD
    A[Timber Species] --> B[Zone Availability]
    A --> C[Weight (kg/m³)]
    A --> D[Durability Class]
    A --> E[Treatability]
    A --> F[Refractoriness]
    A --> G[Strength Coefficient]
    G --> H[Design Strength Adjustment]

This summary helps select timber based on durability and design properties as per IS 399.

Treatability of Timber (IS 399: Clause 4.4)

Definition:
Treatability refers to the ease with which the heartwood of timber species can be penetrated by preservatives under a pressure of 10.5 kg/cm².

Classification of Treatability:

Treatment Conditions:

• Creosote-Crude Oil Mixture: Heated to 80°–90°C during pressure treatment.
• Water-Soluble Preservatives: Treated cold to avoid chemical precipitation.
• Treatment pressure: 10.5 kg/cm² (approx. 1 MPa).

Additional Notes from Tables I-V (Zone-wise Timber Data):

• Columns include:
  • Availability by zone
  • Average weight (kg/m³ and lb/ft³)
  • Durability class
  • Treatability grade (as above)
  • Refractoriness to air seasoning
  • Strength coefficient

Summary Diagram of Treatability Grades:

graph LR
  A[Heartwood] --> B[a: Easily Treatable]
  A --> C[b: Treatable, Partial Penetration]
  A --> D[c: Partially Treatable]
  A --> E[d: Refractory]
  A --> F[e: Very Refractory]

Reference: IS 399 & IS 401-1961 (Code of Practice for Preservation of Timber) for detailed preservative treatment methods.

IS 399 - Refractoriness to Air Seasoning

Key Points from Clause 4.5 & Tables I-V:

• Refractoriness to Air Seasoning classifies timbers into:

  • High refractoriness: Timber resists cracking/splitting well.
  • Moderate refractoriness: Timber shows moderate cracking/splitting.
  • Low refractoriness: Timber is prone to cracking/splitting during air seasoning.

• This classification is based on normal air seasoning practices suitable for each species.

• Tables I to V (zone-wise) provide:

  • Timber species availability.
  • Average & range of air-seasoned timber density (kg/m³ and lb/ft³).
  • Durability classification.
  • Treatability for antiseptic treatment.
  • Refractoriness to air seasoning (High, Moderate, Low).
  • Strength coefficient (relative to teak = 100).

Usage:

• Use the refractoriness classification to select species suitable for air seasoning with minimal defects.
• Refer to zone-specific tables for species data and seasoning behavior.

Example Table Extract Format (simplified):

Note: The standard does not provide explicit formulas but relies on empirical classification and tabulated data for practical decision-making.

flowchart LR
    A[Timber Species] --> B{Air Seasoning}
    B -->|High Refractoriness| C[Minimal Cracking/Splitting]
    B -->|Moderate Refractoriness| D[Moderate Cracking/Splitting]
    B -->|Low Refractoriness| E[Severe Cracking/Splitting]

Use these classifications to optimize seasoning schedules and reduce defects.

IS 399 - Comparative Strength Coefficient Summary

• Definition (Clause 4.6):
  Comparative Strength Coefficient (CSC) is a composite index reflecting the relative mechanical properties of timber species for specific uses (construction, furniture, packing cases, tool handles). It is expressed as a percentage relative to teak (CSC of teak = 100).

• Purpose:

  • Guides selection of timber species based on strength suitability.
  • Not a design parameter for sizing or dimensioning.

• Determination:

  • Weighted grouping of mechanical properties (strength, stiffness, etc.) considering green and dry conditions.
  • Data sourced from Forest Research Institute, Dehra Dun, and relevant timber research publications.

• Key Points:

  • Higher CSC → more suitable timber for the intended use.
  • Includes seasoning behavior (cracking/splitting) and durability.
  • Values tabulated in IS 399 Tables I to V (Column 11 gives CSC).
  • Lack of data indicated by dashes.

Typical Use of CSC in Selection

*Refer IS 399 Tables for exact species values.

Notes:

• CSC is a relative guide, not a design value.
• Always verify timber properties per latest IS standards and local availability.

flowchart LR
    A[Mechanical Properties] --> B[Weighted Grouping]
    B --> C[Comparative Strength Coefficient]
    C --> D[Relative to Teak (100)]
    D --> E[Use in Timber Selection]
    E --> F[Construction, Furniture, etc.]

References:

• IS 399 Clause 4.6, 7.1
• Forest Research Institute publications (1954, 1959)

IS 399: Classification Tables by Zone - Key Points

IS 399 classifies commercially available timbers into five climatic zones with tables listing:

• Zones: North, Centre, South, etc. (Clause 3)
• Tables: I to V correspond to zones, detailing timber properties (Clause 4.0)

Each table includes:

Example: Parameters in Table I (North Zone)

Usage:

• Select timber species suited for your zone.
• Use strength coefficient to adjust design values.
• Consider durability and treatability for service life.

flowchart LR
    Zone[Zone (North, Centre, South, etc.)] --> Table[Classification Table (I to V)]
    Table --> Species[Timb. Species]
    Table --> AvWeight[Avg. Weight (kg/m³)]
    Table --> Durability
    Table --> Treatability
    Table --> Refractoriness
    Table --> StrengthCoeff[Strength Coefficient]

Summary: Use IS 399 tables I-V for timber selection by zone, referencing weight, durability, and strength coefficients for design and treatment decisions.

IS 399: Standard Trade Names & Abbreviations for Timber

IS 399 provides standardized trade names, abbreviated symbols, local names, and timber properties in Tables I to V. Key points:

Key Columns in Tables (e.g., Table III, Centre Zone)

Example Extract (Centre Zone)

Usage Notes

• Abbreviated symbols help in bulk timber identification.
• Durability and treatability guide timber selection for various applications.
• Weight

IS 399: Veneers and Plywood - Key Specifications & Tables

IS 399 primarily provides timber properties relevant to veneers and plywood through comprehensive tables (I to V) covering:

• Timber Species Availability by zones
• Average Weight (Air-seasoned timber) in kg/m³ and lb/ft³
• Durability Classification
• Treatability (ease of antiseptic treatment under pressure)
• Refractoriness (resistance to air seasoning)
• Strength Coefficients for various uses

Important Notes:

• Strength coefficients are based on research by Forest Research Institute, Dehra Dun.
• Metric units are standard; imperial units also provided.
• Timber classification is zone-wise and use-specific.

Typical Table Columns (Example):

Application:

• Use these tables to select timber species for plywood and veneers based on durability, weight, and strength.
• Strength coefficients help in structural design calculations.

flowchart TD
    A[Timber Species] --> B[Zone Availability]
    A --> C[Weight & Density]
    A --> D[Durability & Treatability]
    A --> E[Strength Coefficient]
    B & C & D & E --> F[Selection for Veneer/Plywood]

For detailed tables and values, refer to IS 399 latest edition.

IS 399: Packing Cases and Tool Handles – Key Points

Timber Selection & Properties (Clauses 2.1, 4.0, 4.6)

• Timber species are classified by use:
  • Light packing cases (c)
  • Heavy packing cases (d)
  • Tool handles (e)
• Tables I to V list species by zone, with:
  • Availability
  • Average weight (kg/m³ and lb/ft³)
  • Durability
  • Treatability (ease of antiseptic treatment)
  • Refractoriness (air seasoning resistance)
  • Comparative Strength Coefficient (relative to teak = 100%)

Comparative Strength Coefficient

• Used to select timber species based on mechanical suitability.
• Higher coefficient → better suitability for packing cases or tool handles.
• Not a design formula but a guide for species selection.

Typical Strength Coefficient Ranges (Indicative)

Design Notes

• Use strength coefficients only for timber selection.
• Design dimensions must be based on structural calculations per IS codes or engineering judgment.
• Consider timber weight and durability for packing cases (lighter for light cases, durable & strong for heavy cases).
• Tool handles require high toughness and shock resistance.

flowchart TD
    A[Select Timber Species] --> B{Use Category}
    B --> C[Light Packing Cases]
    B --> D[Heavy Packing Cases]
    B --> E[Tool Handles]
    C --> F[Check Strength Coefficient]
    D --> F
    E --> F
    F --> G[Check Durability & Weight]
    G --> H[Select Suitable Species]

For detailed species data and exact coefficients, refer to Tables I–V in IS 399.