How are timber poles classified under IS 876?

They are classified into different strength classes based on their dimensions and ultimate breaking load capacity.

Can any type of wood be used for overhead lines?

No, only specific durable and treatable timber species listed in the code (e.g., Sal, Teak, specific pines) are permitted.

Is preservative treatment mandatory?

Yes, all wood poles must undergo preservative treatment as per IS 401 before deployment to ensure adequate service life.

IS 876

: 1992

Wood Poles for Overhead Power And Telecommunication Lines

CurrentSpecializedSpecificationStructural Engineering · Timber and Timber Stores

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This standard details the specifications, timber species, permissible defects, dimensions, and testing requirements for wood poles used in overhead electric power transmission and telecommunication lines. It emphasizes strength classification and mandatory preservative treatments for durability.

Wood Poles for Overhead Power And Telecommunication Lines

Quick Reference Values

Depth of plantingGenerally 1/6th of the pole length

Moisture content before treatmentMaximum 25%

Tolerance on length+50 mm, -25 mm

Maximum sweep limitMust not exceed 1 in 60 of length

Practical Notes

Timber poles must be properly treated with chemical preservatives (as per IS 401) to prevent premature failure from termite attack or fungal decay, especially at the ground-line.

Inspect incoming poles strictly for sweep, crook, and large knots, as excessive defects significantly reduce the buckling capacity of the pole.

Poles are categorized into strength classes based on their ultimate breaking load; the engineer must select the class based on the wind zone and span length.