How is the volume of a coniferous log calculated according to this standard?

Volume (V) is calculated using the quarter-girth formula: V = L × (G/4)², where L is length and G is the mid-girth under bark (Clause 7.3).

What are the main grades for coniferous logs?

Logs are graded into Class I, Class II, and Class III based on the extent of permissible defects like knots, splits, and decay (Clause 5 and Table 2).

What is the minimum length of a log covered by this standard?

The minimum length specified for logs is 3.0 meters (Clause 7.1.1).

Which common Indian timber species are covered?

The standard includes species like Deodar (Cedrus deodara), Kail/Blue Pine (Pinus wallichiana), Chir Pine (Pinus roxburghii), and Fir (Abies pindrow/spectabilis) (Clause 4).

IS 5246

: 2000

Coniferous logs

CurrentSpecializedSpecificationMaterials Science · Timber and Timber Stores

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This standard lays down the specifications for coniferous logs intended for conversion into sawn timber, veneers, and other wood products. It covers species, grading based on defects, dimensional requirements, and the method for measuring volume.

Coniferous logs

Quick Reference Values

Minimum log length3.0 m

Minimum girth for Class I & II logs90 cm

Minimum girth for Class III logs60 cm

Free trimming allowance over nominal length10 cm

Maximum permissible individual sound knot diameter (Class I)1/6th of log diameter at the point of occurrence

Maximum permissible heartwood rot or hollow (Class I)Not permitted

Key Formulas

V = L × (G/4)² — Formula for calculating log volume (Quarter-girth or Hoppus's formula)

Practical Notes

The Quarter-girth formula (Hoppus's formula) is the standard method for volume calculation, using the girth measured at the mid-point of the log's length.

Grading is critical for valuation. Class I logs have the fewest defects and yield the highest quality timber, while Class III logs are suitable for less demanding applications.

Always measure girth under bark for accurate volume calculations, unless specified otherwise.