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IS 287 (1993): Permissible Moisture Content For Timber Used
For Different Purposes - Recommendations [CED 9: Timber and
Timber Stores]
I8 287 : 1893
( R&affirmed 1998 )
Indian Standard
PERMISSIBLEMOISTURECONTENTFOR
TIMBERUSEDFORDIFFERBNTPURPOSES-
RECOMMENDATIONS
( Third Revision )
FirstReprintAPRIL 1999 j
UDC 674.03 : 545,812 ( 621.753~1 )
0 BJS 1993
BUREAU OF INDIAN STANDARDS
MANAK BHAVAN, 9 BAHADUR SHAH ZAPAR MARC
NEW DELHI 110002
June 1993 (^) Price Group 2
Timber Sectional Committee, CED 9
FOREWORD
This Indian Standard ( Third Revision ) was adopted by the Bureau of Indian Standards, after the draft finalized by the Timber Sectional Committee had been -approved by the Civil Engineering Division council.
This standard was first published in 1951. It was subsequently revised in 1960 to include a modified demarcation of climatic zones on the basis of meteorological data on relative humidity and then revised in 1973 to incorporate the latest data in regard to permissible moisture content for various purposes besides prescribing in greater detail the methods of testing moisture content. In this third revision the table on ‘Species Correction for Some Makes of Electric Resistance Type Moisture Meters for Common Commercial Timbers’ has been omitted. The methods for determination of moisture content of timber is deleted and reference has been made to IS 11215 : 1991 ‘Methods for determination of moisture content of timber and timber products (first revision )‘. Amendments No. 1 and 2 issued to second revision of this standard have also been incorporated.
The moisture content of a fully seasoned piece of wood depends mainly upon the atmospheric conditions prevailing in the locality in which it is seasoned, although the species of wood and cross- section of the piece also have an important bearing. The moisture content of seasoned wood changes from season to season depending chiefly upon the fluctuations in atmospheric humidity, though here again the nature of the species and the cross-sectional area of the piece as well as the surface treatment applied to it play an important part. For instance, a piece of teak is susceptible to lesser changes in ,’ moisture content than a piece of semul of the same size and exposed to the same atmospheric changes. Again, a piece of timber 100 mm x 100 mm in cross-section suffers lesser changes than a piece of the same timber loo-mm x 25 mm in the cross-section. The application of a paint or varnish to the surface of timber reduces changes in moisture content with changes in humt4i‘rlZty of the surrounding air. Dipping or pressure treatment with oil or creosote-oil mixture also has a similar effect.
India is a vast country with a variety of clitic conditions. For^ the^ purpose^ of^ this^ standard,^ the country has been broadly divided into four zones, from^ the^ very hot^ and^ dry^ climate^ to the^ coastal climate of South India where it is almost always hot and moist ( see 3 and Map of India ). Seasonal changes in the moisture content of wood occur mostly in zones II and III, where a hot, dry summer is abruptly followed by a wet rainy season.
It may be mentioned that with the data available to the committee, it was not possible to demarcate the zones in a clear-cut manner. Observations were carried out by the then Forest Research Institute and Colleges, Dehradun, at 19 localities, out of which only 12 now fall within the boundaries of India. Based on this information, and on the published meteorological data, an attempt has been made to divide the country roughly into four moisture content zones. Even within^ a zone,^ climatic^ conditions vary at different localities due to physical features, such as altitude and vicinity of mountains acting as barrier to moist or dry winds. The information given in this standard has, therefore, to be applied in a very general manner, taking into consideration the existing local conditions.
Timber shrinks on drying, and the shrinkage in fabricated stores leads to unsightly gaps between planks and loosening of joints besides deformation, cracks, etc. The shrinkage along the grain is very small and negligible for practical purposes, except^ when the^ timber^ contains^ compression^ and^ tension^ wood and wood from around the branches. There is appreciable shrinkage across the grain. The timber used in the manufacture of timber stores should, therefore, be properly seasoned before use, though for some types of stores a little more tolerance in moisture content is permissible than for others in the interest of -expediency and resultant economy. In a packing case, unlike a table top for instance, a gap of about 3 mm between adjacent planks, caused by shrinkage of wood subsequent to fabrication, is of no importance.
It is essential that timber used for the manufacture of wooden stores should have attained a moisture content as near as possible to the value that will be attained in equilibrium with the average atmos- pheric conditions in service. Full discussion^ of this subject^ is to^ be found^ in^ ‘A^ survey^ of^ seasonal variation of the moisture content of Indian woods’, Indian Forest Records, Utilization ( New Series ), Vol 2, No. 10. Strictly speaking, for different timber stores there is an optimum moisture content, depending upon the nature of use and the climatic conditions, at which timber should be seasoned and manufactured for best performance in service. ( Continued on third corer )
1s 287 : 1993
Table 1 Permissible Moisture Content of Timber for Different Uses
( Clauses-4 and 5 )
Sl No. Use (^) Moisture Content, Percent, MUX ----------- h-_-------,
9 ii) iii) iv) v>
vi) vii) viii) ix) x) xi)
xii) xiii) xiv) xv) xvi) xvii) xviii)
xix) xx) xxi) xxii)
xxiii)
xxiv)
xxv)
Aircraft
i-7)
Agricultural implements Ammunition boxes Artificial limbs Automobile bodies: a) 50 mm and above in thickness b) Thinner than 50 mm Beams and rafters Boot lasts Box shooks Carts and vehicles ( not motor driven ) Cooperage Doors and windows: a) 50 mm and above in thickness b) Thinner than 50 mm Electrical industry Flooring strips for general purposes Flooring strips for the tea gardens Furniture and cabinet making Handles Patternmaking Railway carriage building: a) 50 mm and above in thickness b) Thinner than 50 mm Rifle parts and gun stocks Shuttles and bobbins Sports goods, umbrellas and walking sticks Ship and boat building: Deck Frame Planking Sleepers
Timber meant for further conversion, post and poles
‘10)s. turnery, carving, clocks, brushes, pit- ture frames, brooms. cigar boxes, pens, pencils,~mathematical and musical instruments and household goods
. Zone Zone Zone (^) Zone I II III (^) IV i3) (^) (4) (5) (^) tG) (^10 12 14 ) (^12 14 16 ) (^10 12 14 ) (^8 10) I2 12
10 8 12 10 12 10 10
10 8 10 8 12 IO 12 8
10 8 8 8 IO
12 10 14 12 14 12 12
12 10 12 10 12 12 12 10
12 10 10 10 12
12 14 14
14 16 12 14 17 20 14 16 (^16 ) 14 16 !2 (^14)
14 1G 12 14 (^14 ) 10 12 14 16 14 I 14 15 12 14
14 14 12 12 12 12 12 12 I4 16
10 12 12
12 1-l 16 18 14 16 20 percent in all zones, moisture content being determined nithin a depth of 20 mm from the surface and excluding 300 mm from each end 20 percent in all zones, moisture content being determined within a depth of 12 mm from the surface and excluding 300 mm fiorn each end 8 10 12 12
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This Indian Standard has been developed from Dot : No. CED 9 ( 4858 ).
Amendments Issued Since Publication
Amend No. Date of Issue Text Affected
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