4.11 QUALITY CONTROL OF TIMBER
Timber is widely used in construction for formwork, doors, windows, roofing, furniture, and structural elements. Quality control ensures strength, durability, resistance to pests, and dimensional stability.
4.11.1 Objectives of Timber Quality Control
- Ensure timber meets mechanical strength and durability requirements.
- Detect defects such as knots, splits, warping, and decay.
- Confirm compliance with BIS / ASTM standards for structural and non-structural use.
- Ensure proper seasoning, storage, and handling to maintain quality.
4.11.2 Types of Timber Used in Construction
| Type |
Description / Typical Use |
| Softwood (e.g., Pine, Deodar) |
Used in formwork, furniture, paneling, and temporary structures. |
| Hardwood (e.g., Teak, Sal, Mango) |
Used in doors, windows, flooring, and load-bearing structural members. |
| Engineered Timber (Plywood, Laminated Veneer Lumber, Glulam) |
Used in flooring, partitions, roof trusses, and decorative panels. |
| Treated Timber |
Timber treated with preservatives to resist decay and insect attack. |
4.11.3 Laboratory Quality Tests for Timber
| S. No. |
Test Name |
Description / Objective |
Typical Requirement / Acceptance Criteria |
Standard Reference |
| 1 |
Moisture Content Test |
Determines the water content in timber; affects shrinkage, warping, and strength |
Moisture content ≤ 12–15% for structural use |
IS 287, ASTM D4442 |
| 2 |
Density / Specific Gravity Test |
Determines strength and stiffness characteristics |
Density ≥ 500–800 kg/m³ (species-dependent) |
IS 1734, ASTM D2395 |
| 3 |
Visual Inspection |
Checks for knots, cracks, splits, warping, decay, insect attack |
Free from large defects; knots ≤ 1/10 of width |
IS 1659, ASTM D245 |
| 4 |
Bending / Modulus of Rupture (MOR) Test |
Measures flexural strength |
Meets grade-specific MOR values |
IS 1734, ASTM D198 |
| 5 |
Compression Test Parallel / Perpendicular to Grain |
Measures compressive strength along grain and across grain |
Parallel: ≥ 35–50 MPa; Perpendicular: ≥ 5–10 MPa |
IS 1734, ASTM D198 |
| 6 |
Shear Test |
Measures resistance to shearing along grain |
Shear strength ≥ 5–10 MPa (species-dependent) |
IS 1734, ASTM D143 |
| 7 |
Durability / Decay Resistance Test |
Assesses susceptibility to fungal or termite attack |
Resistant to decay and insect attack |
IS 401, ASTM D2017 |
| 8 |
Preservative Treatment Verification |
Confirms adequate penetration and retention of chemical preservatives |
Penetration ≥ 6–12 mm, retention per IS / ASTM |
IS 305, ASTM D4442 |
4.11.4 Field Quality Control Measures
- Proper Storage: Keep timber raised from ground, covered, and well-ventilated to prevent moisture absorption.
- Handling: Avoid dropping or dragging timber to prevent surface damage and internal cracks.
- Seasoning: Ensure timber is air-seasoned or kiln-dried to the required moisture content before use.
- Preservative Treatment: Check treated timber for uniform penetration and retention of chemicals.
- Inspection: Examine for visible defects such as warping, splitting, and termite attack before installation.
4.11.5 Acceptance Criteria for Timber
| Property |
Softwood |
Hardwood |
Engineered Timber |
| Moisture Content |
≤ 12–15% |
≤ 12–15% |
As per manufacturer |
| Density |
400–600 kg/m³ |
600–900 kg/m³ |
As per manufacturer |
| Bending Strength (MOR) |
≥ 40 MPa |
≥ 60 MPa |
As per design |
| Compression Strength |
30–40 MPa |
50–60 MPa |
As per design |
| Surface / Visual Quality |
Free from large knots, splits, cracks |
Free from decay, knots, cracks |
Smooth, defect-free |
| Durability |
Moderate |
High |
High (treated or laminated) |
4.11.6 Important BIS / ASTM Standards (Latest Revision)
| Standard No. |
Title / Description |
| IS 1734 |
Methods of Testing Small Clear Specimens of Timber |
| IS 287 |
Methods for Determination of Moisture Content of Timber |
| IS 1659 |
Code for Visually Graded Structural Timber |
| IS 401 |
Durability of Timber – Fungal and Insect Resistance |
| IS 305 |
Preservative Treatment of Timber – Penetration and Retention |
| ASTM D198 |
Test Methods for Static Tests of Lumber in Structural Sizes |
| ASTM D143 |
Test Methods for Small Clear Specimens of Timber |
| ASTM D4442 |
Test Method for Moisture Content of Wood |