Indian timbers for door and window shutters and frames- Classification

IS 12896 Scope Summary & Key Specifications

• Scope: Covers definitions (per IS 707:1976) and specifications for timber used in shutters and frames, focusing on durability, treatability, and seasoning refractoriness.

• Timber Groupings:

  • Super Group Timbers for Shutters (Annex A, Clause 4.1.1)
  • Group I Timbers for Frames (Annex E, Clause 4.2.1)
  • Group III Timbers for Frames (Annex G, Clause 4.2.3)

• Key Properties:

  • Durability Classes: I (most durable), II, III (less durable)
  • Treatability Codes: e (easy), c (moderate), b (difficult), - (not suitable)
  • Refractoriness to Seasoning: A (best), B, C (least)

Example Table Extract (Super Group Timbers for Shutters)

Notes:

• Use timbers with appropriate durability and treatability for specific applications.
• Seasoning refractoriness affects drying and processing.
• Refer to respective annexes for detailed species lists and properties.

flowchart LR
    A[Timber for Shutters & Frames] --> B[Super Group (Shutters)]
    A --> C[Group I (Frames)]
    A --> D[Group III (Frames)]
    B --> E[Durability I, II]
    C --> F[Durability I]
    D --> G[Durability II, III]
    E --> H[Treatability: e, c, -]
    F --> I[Treatability: e, c, b, -]
    G --> J[Treatability: c, d, e, -]

For detailed species and properties, consult IS 12896 Annexes A, E, and G.

IS 12896 - Definitions & Key Specifications Summary

1. Definitions (Clause 3.1)

   • Uses definitions from IS 707:1976 (Wood Terminology) plus additional definitions in IS 12896.

2. Durability & Preservative Treatment (Clauses 4.1.1 & 4.2.1)

   • Timbers are grouped by Durability, Treatability, and Refractoriness to Seasoning.
   • Durability groups: I (most durable), II, etc.
   • Treatability codes: e (easy), c (moderate), - (difficult).
   • Refractoriness to seasoning: A (non-refractory), B (moderately refractory), C (refractory).

3. Key Tables (Annex A & E):
   | SI No. | Species Name | Durability | Treatability | Refractoriness to Seasoning | |--------|------------------------------|------------|--------------|-----------------------------| | 1 | Albizia lebbeck (kokko) | I | e | B | | 4 | Dalbergia latifolia (rosewood)| I | - | B | | 8 | Cedrus deodara (deodar) | I | c | C | | 11 | Dysoxylum malabaricum | I | - | B | | 21 | Tectona grandis (teak) | I | e | B |

4. Usage:

• Select timber based on durability and treatability for frames and shutters.
• Refractoriness guides seasoning method and drying time.

Summary Diagram of Timber Selection Criteria

flowchart TD
    A[Timber Selection] --> B{Check Durability}
    B -->|Group I| C[Highly Durable]
    B -->|Group II| D[Moderately Durable]
    C --> E{Treatability}
    E -->|e| F[Easy to Treat]
    E -->|c| G[Moderate Treatability]
    E -->|-| H[Difficult to Treat]
    F --> I{Refractoriness}
    G --> I
    H --> I
    I -->|A

IS 12896 - Strength Coefficient: Key Points & Tables

1. Definition (Clause 3.2)

• Strength Coefficient is a comparative numerical value of timber species.
• It considers: weight, beam strength, post suitability, splitting, nail/screw holding, shape retention.
• Expressed relative to Teak = 100.

2. Selection Criteria by Groups

*Treatability classes refer to preservative treatment suitability (see Clause 7.2).

3. Usage

• Strength coefficient guides timber species selection for structural applications.
• Higher values imply better mechanical and durability performance relative to teak.

flowchart LR
    A[Timber Species] --> B[Evaluate Properties]
    B --> C[Weight]
    B --> D[Beam Strength]
    B --> E[Post Suitability]
    B --> F[Splitting Coefficient]
    B --> G[Nail/Screw Holding]
    B --> H[Shape Retention]
    C & D & E & F & G & H --> I[Calculate Strength Coefficient (Teak=100)]
    I --> J[Classify into Groups (Super, II, III)]

Summary:
Use strength coefficient ≥ 65 for structural timber. Refer to tables in Clauses 4.1.1, 4.1.3, 4.2.3 for group classification based on strength, weight, and durability.

Timber Species Classification — IS 12896 Key Points

1. Strength Coefficient (Clause 3.2)

• Evaluated considering:
  • Weight
  • Beam strength
  • Post suitability
  • Splitting coefficient
  • Nail & screw holding
  • Shape retention
• Expressed relative to teak = 100

2. Group I Species (Clause 4.1.2)

• Species listed in Annex B

3. Group II Species (Clause 4.2.2)

• Species listed in Annex F

4. Seasoning Classification (Clause 6.1)

Summary Table

This classification helps in selecting timber based on mechanical properties, durability, and seasoning behavior for structural use.

IS 12896 - General Requirements for Timber Selection

Key Criteria for Timber Groups (Clauses 4.1.1, 4.1.3, 4.2.3)

Notes:

• Strength Coefficient: Indicates relative strength; higher values mean stronger timber.
• Durability Classes: I (Very Durable), II (Durable), III (Moderately Durable).
• Treatability Classes (a, b, c): Refer to preservative treatment suitability (see Clause 7.2).
• Species for each group are detailed in respective annexes (A for Super Group, G for Group III).

Summary:

• Select timber based on strength coefficient, weight, durability, and treatability.
• Use Super Group species for premium applications requiring strength and appearance.
• Group II and III species are for general structural use with appropriate preservative treatments.

flowchart TD
    A[Timber Selection] --> B{Strength Coefficient}
    B -->|≥80| C[Super Group]
    B -->|≥70| D[Group II]
    B -->|≥65| E[Group III]
    C --> F[Durability I or II]
    D --> G[Durability I, II or III]
    E --> H[Durability I, II or III]
    F --> I[Weight 75-115]
    G --> J[Weight 70-125]
    H --> K[No weight

IS 12896: Seasoning and Moisture Content – Key Points

Moisture Content Requirements

• Timber must be seasoned to moisture content as per IS 287:1973 (Clauses 3.1 & 4.1).
• Moisture content is typically:
  • Below 12% for indoor structural use.
  • Varies with timber type and application (consult IS 287 for exact values).

Seasoning Process

• Follow IS 1141:1973 for seasoning methods (air seasoning, kiln drying).
• Seasoning aims to reduce moisture content to permissible limits without excessive surface or end cracking.
• Moderately refractory timbers require controlled drying to avoid cracks (surface cracks ≤2 mm for shutters, ≤3 mm for frames as per Clause 5.3).

Moisture Content Determination

• Use:
  • Oven dry method (standard for accuracy).
  • Electrical moisture meters as per IS 11215:1985.

Typical Moisture Content Limits (from IS 287)

Formula for Moisture Content (Oven Dry Method):

[ \text{Moisture Content (%)} = \frac{W_{wet} - W_{dry}}{W_{dry}} \times 100 ]

• (W_{wet}): Weight before drying
• (W_{dry}): Weight after oven drying

flowchart LR
    A[Green Timber] --> B[Seasoning Process (IS 1141)]
    B --> C{Moisture Content?}
    C -->|> Specified Limit| D[Use Timber]
    C -->|> Limit Exceeded| B

Summary: Season timber as per IS 1141, check moisture content by oven or meter (IS 11215), ensure moisture <12% for structural use, and limit surface cracks as per IS 12896 Clause 5.3.

IS 12896: Durability & Preservative Treatment Key Points

1. Durability Classification (Clause 7.1)

2. Moisture Content & Seasoning (Clause 6.2)

• Timber must be seasoned to moisture content as per IS 287:1973 (Clauses 3.1 & 4.1).
• Seasoning methods per IS 1141:1973.
• Moisture content measured by oven dry or electrical moisture meters (IS 11215:1985).

3. Species Grouping & Properties (Annex E, Clause 4.2.1)

• Group I Timbers for Frames: Species like Albizia lebbeck, Cedrus deodara, Dalbergia latifolia, Tectona grandis.
• Properties include:
  • Durability: Mostly Class I (≥120 months).
  • Treatability: e (easy), c (moderate), b (difficult), or "-" (not specified).
  • Refractoriness to Seasoning: A (easy), B (moderate), C (difficult).

4. Example Table Extract (Group I Timbers)

Summary:

• Select Class I durable timbers for longevity.
• Season timber to specified moisture content for durability.
• Use treatability and seasoning refractoriness data to guide preservative treatment and processing.

flowchart LR
    A[Timber Species] --> B{Durability Class}
    B -->|

IS 12896: Annex A - Super Group Timbers for Shutters

Key Specifications:

• Durability Class: Mostly Class I or II (highly durable)
• Treatability: Varies (e.g., 'e' = easy, 'c' = moderate, '-' = not applicable)
• Refractoriness to Seasoning: Mostly Class B (moderate), some A or C

Super Group Timbers (Examples):

Treatment Requirements (Clause 7.3.1):

• Shutters from Super Group species with Durability Class II must be pressure/vacuum treated after fabrication using PCP/solvent system.

Notes on Treatment Depth:

• Minimum preservative penetration: 2 mm in finished products (for certain groups).

Summary Table Legend:

• Durability: I (Very durable), II (Durable), III (Moderately durable)
• Treatability: e (easy), c (moderate), a/b (difficult), - (not applicable)
• Refractoriness: A (easy), B (moderate), C (difficult) to seasoning

flowchart LR
    A[Super Group Timbers] --> B{Durability Class}
    B -->|I| C[Treatment: Optional]
    B -->|II| D[Treatment: Pressure/Vacuum PCP after fabrication]
    D --> E[Minimum 2 mm penetration]

Use this table and clauses to select timber species and decide on preservative treatment for durable, quality shutters per IS 12896.

IS 12896 Annex B: Group I Timbers for Shutters - Key Specifications

Notes:

• Durability Classes: I = Durable, II = Moderately Durable.
• Treatability Codes:
  • a = Easy
  • b = Moderate
  • c = Difficult
  • d = Very Difficult
  • e = Very Easy
• Refractoriness to Seasoning:
  • A, B, C indicate ease of seasoning (B = moderate).

Treatment Specification (Clause 7.3.1 & 7.3.2):

• Group I

IS 12896 Annex C: Group II & II(A) Timbers for Shutters - Key Points

1. Timber Groups & Species (Annex C, Clause 4.1.3)

2. Durability & Treatability Codes (Clause 4.1.1 - 4.1.3)

• Durability Classes: I (Highly durable), II, III (Moderately durable), etc.
• Treatability Codes: a, b, c, d, e (indicate ease of preservative penetration)
• Refractoriness to Seasoning: A, B, C (ease of seasoning)

3. Preservation Treatment (Clauses 7.3.1 & 7.3.2)

• Shutters from Group II and II(A) timbers must be pressure/vacuum treated after fabrication with PCP/solvent system.
• Minimum preservative penetration: 2 mm in finished products.
• Treatment ensures durability especially for species with durability/treatability III(d), III(e), or unspecified.

Summary Table: Treatment Requirement for Group II & II(A) Timbers

Visual Summary (Mermaid.js)

flowchart TD
    A[Group II & II(A) Timbers] --> B{Durability Class}
    B -->|I or II| C[Pressure/Vacuum Treatment]
    B -->|III or Unspecified| C
    C

IS 12896 Annex D: Group III Timbers for Shutters – Key Specifications

1. Group III Timber Species (Durability Class III, Treatability d or e):

• Examples:
  • Abies pindrow (fir) - Durability III, Treatability d, Refractoriness C
  • Dipterocarpus macrocarpus (hollong) - Durability III, Treatability a, Refractoriness B
  • Grevillea robusta (silver oak) - Durability III, Treatability -, Refractoriness B
  • Picea smithiana (spruce) - Durability III, Treatability d, Refractoriness C
  • Vateria indica (vellapine) - Durability III, Treatability e, Refractoriness C

2. Treatment Requirements (Clause 7.3.2):

• Shutters from Group III timbers must be pressure/vacuum treated with PCP/solvent system after fabrication.
• Minimum penetration of 2 mm preservative in finished product is mandatory.
• Treatment ensures durability and protection as these timbers have moderate durability and treatability.

3. Durability and Treatability Classes (Summary):

4. Refractoriness to Seasoning:

• Indicates difficulty in seasoning (drying) the timber. Classes:
  • A: Easy
  • B: Moderate
  • C: Difficult

Summary Table: Selected Group III Timbers for Shutters

IS 12896 - Annex E: Super Group Timbers for Frames

Key Criteria (Clause 4.2.1)

• Strength Coefficient: ≥ 80
• Durability: Class I (Highly durable)
• Species: Listed in Annex E (Group I Timbers)

Annex E: Group I Timbers for Frames

IS 12896 - Annex F: Group II Timbers for Frames

Key Specifications (Clause 4.2.2)

• Strength Coefficient: ≥ 70
• Durability: Class I, II (with treatability a, b, or c) or Class III (with treatability a or b)
• Species: Listed in Annex F (not fully provided here, refer to IS 12896 Annex F for species list)

General Criteria for Timber Groups (for context)

Durability & Treatability (from Clause 4.2.1 Table 7)

• Durability Classes:
  • I: Highly durable
  • II: Moderately durable
  • III: Less durable
• Treatability Classes:
  • (a), (b), (c) indicate ease of preservative treatment
• Refractoriness to Seasoning:
  • A: Easy to season
  • B: Moderate
  • C: Difficult

Example Timber Properties (Group I from Annex E for reference)

Summary for Group II Timbers

• Select species with strength coefficient ≥ 70.
• Ensure durability class and treatability as per Clause 4.2.2.
• Refer to Annex F for approved species.
• Check preservative treatment compatibility and seasoning characteristics before use.

flowchart TD

IS 12896 - Annex G: Group III Timbers for Frames

Key Specifications for Group III Timbers (Clause 4.2.3)

• Strength Coefficient: ≥ 65
• Durability / Treatability Class:
  • Class I, II (any treatability)
  • Class III with treatability (a), (b), or (c)
• Use: Suitable for frames where moderate strength and durability are required.
• Species: Listed in Annex G (refer to the code for specific species names).

Treatment Requirements (Clause 7.3.3)

• For Group III species with durability/treatability Class III (c) in Annex F, pressure treatment to refusal is mandatory when ground contact preservative retention (per IS 401:1982) is not achievable.

Summary Table for Timber Groups (Simplified)

Notes:

• Strength Coefficient: Indicates relative strength compared to reference timber.
• Treatability Classes (a), (b), (c): Refer to preservative penetration and retention standards.
• Refer to IS 401:1982 for preservative treatment details.

flowchart LR
    A[Timber Selection] --> B{Strength Coefficient}
    B -->|≥ 80| C[Group I]
    B -->|≥ 70| D[Group II]
    B -->|≥ 65| E[Group III]
    E --> F{Durability Class}
    F -->|I, II, III| G[Treatability (a),(b),(c)]
    G --> H[Suitable for Frames]
    H --> I[Treatment as per IS 401:1982 if Class III(c)]

For exact species list and detailed parameters,