How many climatic zones are defined for timber moisture?

Four zones (Zone I to IV) based on the region's average annual relative humidity (Table 2).

IS 287

: 1993

Code of Practice for Design of Timber Structures

SupersededSpecializedGuidelinesMaterials Science · Timber and Wood

Superseded by IS 287:2022

This standard provides recommendations for the maximum permissible moisture content of timber based on its end-use (e.g., structural, joinery, furniture) and the climatic zone in India where it will be used. Engineers and architects use this to specify timber drying/seasoning requirements to prevent shrinkage, warping, and fungal decay.

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

Quick Reference Values

Zone I (Dry) Relative Humidity< 40%

Zone IV (Damp) Relative Humidity> 67%

Structural timber moisture limit (Zone I)12%

Structural timber moisture limit (Zone II)14%

Doors and windows moisture limit (Zone II)12%

Furniture moisture limit (Zone II)10%

Practical Notes

India is divided into four climatic zones (Zone I to Zone IV) based on average annual relative humidity. You must know your project's zone to specify the correct moisture content.

Moisture content should be checked at the time of fabrication or installation, not just at the time of delivery to the site.

Thicker sections of timber (>50mm) are generally permitted slightly higher moisture content than thin joinery sections.