How does IS 287 classify climatic zones?

It divides India into four zones (Zone I, II, III, IV) based on the annual average relative humidity of the region.

What is the acceptable moisture content for structural timber in highly humid areas (Zone IV)?

The maximum permissible moisture content is 16%.

Which code should be used for the actual structural design of timber members?

IS 883 covers the design of structural timber in buildings, while IS 287 primarily provides the permissible moisture content requirements prior to use.

IS 287

: 2022

Code of Practice for Design of Timber Structures

CurrentSpecializedGuidelinesMaterials Science · Timber and Wood

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IS 287 provides recommendations for the maximum permissible moisture content of timber based on its end-use. It divides India into four climatic zones based on relative humidity and specifies moisture limits to minimize shrinkage, warping, and fungal decay. Note: While the title in some databases may confuse it with timber structural design, actual structural design criteria are covered in IS 883.

Lays down guidelines for the structural design of timber members in buildings, including allowable stresses and design considerations.

Quick Reference Values

Structural timber max moisture content (Zone I)12%

Structural timber max moisture content (Zone II & III)14%

Structural timber max moisture content (Zone IV)16%

Doors and windows > 50mm thick max moisture content (Zone I)10%

Doors and windows > 50mm thick max moisture content (Zone IV)16%

Practical Notes

Always identify the climatic zone (Zone I to IV) of the final project location before specifying timber moisture limits.

Do not use green (unseasoned) timber for structural applications; ensure it is properly kiln or air-seasoned to the limits in Table 1.

Electrical moisture meters are excellent for quick field checks, but oven-dry methods should be used for precise lab verification.