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IS 1708:2014 is the Indian Standard (BIS) for methods of testing small clear specimens of timber. This standard specifies the procedures for testing small clear specimens of timber to evaluate their physical and mechanical properties. It provides standardized methods for determining moisture content, specific gravity, static bending strength, compressive strength, and other critical parameters necessary for timber grading and design.
Specifies the procedures for conducting various tests on small, clear timber specimens to determine their physical and mechanical properties.
! Specimens must be strictly 'clear', meaning completely free from natural defects like knots, cracks, and decay, to accurately measure the fundamental properties of the wood matrix.
! Timber is highly anisotropic; always ensure the grain direction is properly aligned (parallel or perpendicular) with the loading axis as specified for each test.
! Strength properties are highly sensitive to moisture; results should always be adjusted to a standard 12% moisture content for fair comparison.
Standard Test Methods for Small Clear Specimens of Timber
Both provide comprehensive methods for determining mechanical and physical properties of wood using small, defect-free specimens.
ISO 13061 series (e.g., -1, -2, -3, -4)ISO (International Organization for Standardization), International
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Physical and mechanical properties of wood — Test methods for small clear wood specimens
This series collectively covers the same tests as IS 1708, but structures them into separate parts for each property.
BS 373:1957BSI (British Standards Institution), United Kingdom
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Methods of testing small clear specimens of timber
The historical basis for many current standards, it defined test methods for small clear specimens that are conceptually similar to IS 1708.
Key Differences
≠IS 1708 is structured in two parts (Part 1 for primary tests, Part 2 for secondary). ASTM D143 is a single comprehensive document. The ISO 13061 series is modular, with a separate standard for each specific property test (e.g., ISO 13061-3 for bending, ISO 13061-6 for compression perpendicular to grain).
≠While the primary specimen size of 50x50 mm is common, IS 1708 prominently includes a 20x20 mm cross-section as a secondary standard specimen, which is the primary specimen size in many ISO 13061 parts. ASTM D143 is more strongly focused on the imperial equivalent 2x2 inch (50x50 mm) specimen.
≠The specified rate of testing can differ. For static bending, IS 1708 specifies a rate of fiber strain (0.0015 mm/mm/min), whereas ASTM D143 specifies a rate of crosshead motion (e.g., 2.5 mm/min for a 50mm specimen), which are technically different control methods.
≠The empirical constants and formulas used for adjusting strength properties to the standard 12% moisture content can vary slightly between standards, reflecting different research bases and species groups.
Key Similarities
≈All standards are based on the fundamental principle of testing 'small clear specimens'—wood samples free from defects like knots, splits, and decay—to determine the intrinsic properties of the wood material itself.
≈The core set of mechanical tests performed is virtually identical, including static bending, compression parallel and perpendicular to the grain, hardness, shear, cleavage, and tension.
≈All standards mandate the conditioning of test specimens to a constant weight at a specified temperature and humidity, aiming for a target moisture content (typically 12%) to ensure test results are comparable.
≈The methodology for the Janka hardness test, including the use of an 11.28 mm (0.444 in) diameter steel ball penetrator, is consistent across IS 1708 and ASTM D143.
Parameter Comparison
Parameter
IS Value
International
Source
Static Bending Specimen (Primary)
50 x 50 x 750 mm
2 x 2 x 30 in (50 x 50 x 760 mm)
ASTM D143-21
Static Bending Span (Primary)
700 mm
28 in (710 mm)
ASTM D143-21
Static Bending Specimen (Secondary)
20 x 20 x 300 mm
20 x 20 x 360 mm
ISO 13061-3:2014
Compression Parallel to Grain Specimen
50 x 50 x 200 mm
2 x 2 x 8 in (50 x 50 x 200 mm)
ASTM D143-21
Janka Hardness Test Penetrator Diameter
11.28 mm
0.444 in (11.28 mm)
ASTM D143-21
Shear Parallel to Grain Specimen Overall Size
50 x 50 x 62.5 mm
2 x 2 x 2.5 in (50 x 50 x 63 mm)
ASTM D143-21
Standard Moisture Content for Reporting
12%
12%
ASTM D143-21 / ISO 13061-1
⚠ Verify details from original standards before use
Key Values5
Quick Reference Values
oven drying temperature103 ± 2°C
standard reference moisture content12%
static bending specimen size50 x 50 x 750 mm
compression parallel specimen size50 x 50 x 200 mm
static bending loading rate2.5 mm/min
Key Formulas
Moisture Content (%) = ((W1 - W0) / W0) x 100
Modulus of Rupture (Static Bending) = 3PL / (2bd²)
Compressive Strength = P / (b x d)
Tables & Referenced Sections
Key Tables
Table 1 - Minimum number of specimens for testing
Table 2 - Rate of continuous loading for various tests
Key Clauses
Part 1 - Determination of Moisture Content
Part 2 - Determination of Specific Gravity
Part 3 - Determination of Static Bending Strength
Part 4 - Determination of Compressive Strength Parallel to Grain
Part 5 - Determination of Compressive Strength Perpendicular to Grain