The IS 287:1993 standard specifies the allowable moisture content levels for timber intended for various uses throughout India's climatic regions. It assists engineers, designers, and manufacturers in maintaining timber quality by accounting for factors like regional humidity, timber species, and seasoning methods to ensure durability and optimal performance.
Overview
The IS 287:1993 standard specifies the allowable moisture content levels for timber intended for various uses throughout India's climatic regions. It assists engineers, designers, and manufacturers in maintaining timber quality by accounting for factors like regional humidity, timber species, and seasoning methods to ensure durability and optimal performance.
Audience
Contents
Structure
Frequently Asked
The standard divides India into four distinct zones based on average annual relative humidity: Zone I (<40%), Zone II (40-50%), Zone III (50-67%), and Zone IV (>67%). Timber should be dried to a moisture content that lies midway between the maximum and minimum equilibrium moisture contents specific to each zone. Typical tolerances include ±2% for average samples and ±3% for individual pieces, with certain uses allowing wider tolerances. Factors like timber species, cross-section, and surface finish influence these values. Moisture measurement should follow IS 11215:1991. Refer to Table 1 of IS 287 for detailed limits.
Different wood species absorb and release moisture at varying rates; for instance, teak experiences less moisture fluctuation than semul under identical conditions. Larger cross-sectional dimensions reduce moisture variation because moisture penetrates and equilibrates more slowly compared to thinner sections. Additionally, surface treatments such as paint or oil coatings help minimize moisture exchange. Seasonal climate changes further influence moisture variation, especially in zones with pronounced wet and dry periods.
For timber components like doors and windows with thickness equal to or exceeding 50 mm, moisture content should be close to the equilibrium moisture content of the service environment. The permitted tolerance is typically ±2% for the average moisture content of a batch and ±3% for individual samples to ensure dimensional stability and durability. Testing procedures should comply with IS 11215:1991.
Timber must be seasoned to reach a moisture level near the equilibrium moisture content relevant to its climatic zone. This can be achieved through air seasoning—exposing timber to local atmospheric conditions until moisture stabilizes—or kiln drying for faster results. The target moisture content is generally midway between the maximum and minimum EMC values for the intended zone. Variations due to species, cross-sectional size, and surface treatments must be considered. Moisture content determination should be done following IS 11215:1991.
IS 287 refers to IS 11215:1991 for moisture content measurement methods. Recommended procedures include the oven-dry method, which involves weighing the timber before and after drying in an oven to constant weight, as well as using calibrated electrical resistance moisture meters and other standardized techniques. Accurate determination of moisture content is essential for ensuring compliance with the permissible limits defined in IS 287.
Ask AI about any clause, requirement, or provision in IS 287. Get instant, clause-cited responses powered by our indexed library.
Free tier includes 150 queries (50 AI + 100 Reference) · No credit card required