Guide for storage and protection of logs and sawn timber
1979 Edition

The introduction of IS 9104 establishes the framework for specifications related to timber structures, covering scope, terminology, and general instructions without including direct formulas or tabulated data.

Highlights from IS 9104 Introduction:

• Encompasses materials, workmanship, and structural design principles for timber.
• Focuses on durability, strength, and functional performance of timber elements.
• Clarifies fundamental terms concerning timber characteristics and structural applications.

Design Considerations (General):

• Design stresses depend on species, grade, and moisture levels.
• Key parameters include allowable bending stress (Fb), shear stress (Fv), and compression stress (Fc).
• Modulus of elasticity (E) is used for deflection computations.

Common Formulas (Timber Design Practice):

• Bending stress:
  [ \sigma_b = \frac{M}{Z} ]
  where M is bending moment and Z is section modulus.

• Shear stress:
  [ \tau = \frac{V}{A} ]
  where V is shear force and A is shear area.

• Deflection:
  [ \delta = \frac{PL^3}{48EI} ]
  for a simply supported beam with point load P.

For detailed stress values and tables, refer to complementary standards IS 883 and IS 1905.

flowchart TD
    A[Timber Properties] --> B[Strength Characteristics]
    B --> C{Design Stresses}
    C --> D[Bending Stress (Fb)]
    C --> E[Shear Stress (Fv)]
    C --> F[Compression Stress (Fc)]
    B --> G[Modulus of Elasticity (E)]
    G --> H[Deflection Analysis]

Summary: The introduction section of IS 9104 lays down the foundational concepts; detailed formulas and tabulations are available in related codes such as IS 883.

IS 9104:1979 addresses the Code of Practice for the structural application of timber within India. It sets forth guidelines covering:

• Timber selection and grading criteria
• Structural design principles for timber frameworks
• Specifications for workmanship and durability requirements
• Methods for stress and load capacity calculations

Scope Highlights:

• Applicable to timber used in structural elements like buildings and bridges
• Covers seasoning, preservation, and grading procedures
• Defines allowable stresses for various timber species and conditions
• Includes instructions on joints, fasteners, and connections

Essential Formulas (Structural Timber Design):

• Bending Stress:
  [ \sigma_b = \frac{M}{Z} ]
  where M represents bending moment and Z is section modulus

• Shear Stress:
  [ \tau = \frac{V}{A} ]
  where V is shear force and A is cross-sectional area

Sample Stress Values (from IS 9104 and associated standards):

Note: For detailed grading and stress data, consult IS 883 and IS 1708.

flowchart TD
    A[Timber Structural Applications] --> B[Selection & Grading]
    A --> C[Design Principles]
    A --> D[Workmanship & Durability]
    C --> E[Stress Computations]
    E --> F[Bending Stress]
    E --> G[Shear Stress]

Refer to the complete IS 9104 document and related codes for comprehensive data.

IS 9104 offers recommendations for storing logs at depots and sawmill yards to prevent damage such as cracking, mould formation, decay, and insect infestation.

Key Storage Guidelines:

• Logs in depots typically have shorter storage durations compared to sawmill yards; however, all logs must be stored systematically to minimize losses.
• Protective measures include:
  • Preventing surface and end cracking through proper stacking and covering.
  • Avoiding biological deterioration by ensuring adequate ventilation and dryness.
• Stacking practices:
  • Incorporate supports or stickers between log layers to facilitate air circulation.
  • Elevate logs above ground level to prevent moisture absorption.
• Environmental controls:
  • Prefer shaded, well-drained storage locations.
  • Cover stacks with waterproof yet breathable materials.

Recommended Specifications:

flowchart LR
    A[Logs] --> B[Stack with Stickers]
    B --> C[Elevate from Ground]
    C --> D[Cover with Waterproof Sheet]
    D --> E[Maintain Ventilation]
    E --> F[Prevent Cracking and Decay]

Note: IS 9104 guidelines should be adapted considering local climatic conditions and timber species.

IS 9104: Guidelines on Log Protection

1. Storage and Protective Treatments (Clause 2.1.4)

• Preventive Treatment:

  • Debarked logs should be sprayed with preservatives following IS 401-1967.
  • Repeat applications every 3 to 6 months depending on the severity of biological threats including fungi, termites, and insects.

• Storage Conditions:

  • Store logs in shaded areas to reduce exposure to sunlight and rainfall.
  • Place logs on timber supports treated with preservatives to prevent ground contact and termite damage.

• End Protection:

  • Apply protective coatings (paint or spray) on log ends to minimize end-cracking.

2. Specifications Overview

Process Flow

flowchart TD
    A[Debarked Logs] --> B[Preservative Treatment (IS 401)]
    B --> C[Storage in Shade]
    C --> D[Placement on Treated Timber Supports]
    D --> E[End Coating Application]
    E --> F[Periodic Reapplication Every 3-6 Months]

Refer to IS 401-1967 for detailed types of preservatives and application techniques.

IS 9104 emphasizes correct inspection and handling methods for logs to avoid damage such as cracking, mould, decay, and insect attack.

Inspection Requirements:

• Examine logs for surface and end cracks.
• Detect signs of mould, decay, or insect infestation.
• Segregate and treat or discard logs showing defects.

Handling Instructions:

• Utilize appropriate lifting devices to prevent mechanical injury.
• Avoid dropping or dragging logs over abrasive surfaces.
• Handle logs carefully to prevent bruising.

Storage Recommendations:

• Store logs on raised, well-drained platforms to reduce moisture exposure.
• Stack logs uniformly spaced to allow air circulation.
• Cover stacks with breathable waterproof sheets.
• Keep logs off the soil to prevent decay.

Typical Stack Dimensions:

Protection Measures:

• Apply fungicides or insecticides upon detecting infestation.
• Rotate stock regularly to avoid extended storage.

flowchart LR
    A[Log Inspection] --> B{Any Defects?}
    B -- Yes --> C[Treatment or Segregation]
    B -- No --> D[Proper Handling]
    D --> E[Storage on Elevated Platform]
    E --> F[Cover and Ventilate]
    F --> G[Ongoing Monitoring]

This ensures logs remain in optimal condition for conversion to quality timber.

IS 9104 highlights the importance of proper storage for both logs and converted timber to avoid damage such as cracking, mould, decay, and insect attack.

Key Points:

• Storage durations for logs in depots are shorter than in sawmill yards but require diligent handling.
• Protective measures include scientific stacking to prevent surface and end cracks.
• Apply preservatives effectively to insect-affected regions.
• Segregate timber deemed unusable following treatment.
• Maintain good ventilation and moisture control to limit biological deterioration.

Practical Recommendations:

Additional Note:

• Follow IS 2-1960 for rounding off test data during compliance assessments.

flowchart LR
    A[Incoming Logs] --> B[Damage Inspection]
    B -->|No Damage| C[Stacking with Adequate Airflow]
    B -->|Damage Detected| D[Apply Preservatives]
    D --> E[Segregate Damaged Timber]
    C --> F[Regular Monitoring]
    F --> G[Dispatch or Processing]

These practices help preserve timber quality throughout storage after conversion.

IS 9104: Measures to Avoid Cracking During Air Seasoning

Key Guidelines (Clause 6.1):

• Timber species susceptible to cracking (such as sal, laurel, irul) require specialized treatment during air seasoning.
• Employ hygroscopic and anti-shrinkage chemicals, including:
  • Polyethylene glycol (PEG-1000) – the most effective option
  • Urea
  • Common salt
• Treatment involves spraying or soaking timber in a 50% aqueous PEG-1000 solution combined with 1-2% sodium pentachlorophenate for protection against insects and fungi.
• Treatment temperature ranges from 45 to 506C, extendable up to 606C for enhanced penetration.
• Duration depends on timber species’ resistance and cross-sectional thickness.
• Post-treatment, timber should be briefly close-packed, followed by air drying under shade or sheds as per IS 1141-1973.

Additional Recommendations:

• Apply end coatings before stacking to reduce end splitting.
• Air seasoning sheds must be suitable for the local climate, timber species, and thickness.
• Prophylactic treatments are critical in humid environments.

Protection Method Summary

flowchart TD
    A[Green Timber] --> B[Treatment with PEG-1000 Solution]
    B --> C[Close Packing]
    C --> D[Air Drying in Shed or Shade]
    D --> E[Reduction in Cracks and Splits]

These steps help minimize cracking during air seasoning, especially for difficult-to-treat species.