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IS 6791 : 1973Method of testing natural durability of timber and efficacy of the wood preservatives against marine borers

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EN 275 · ASTM D2481-12(2018) · AWPA E5
CurrentSpecializedTesting MethodMaterials Science · Timber and Timber Stores
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Link points to Internet Archive / others. Not hosted by InfraLens. Details
OverviewValues5InternationalTablesFAQ4Related

IS 6791:1973 is the Indian Standard (BIS) for method of testing natural durability of timber and efficacy of the wood preservatives against marine borers. This standard specifies the method for conducting field tests in sea harbours to determine the natural durability of timber and the efficacy of wood preservatives against attack by marine borers. It details the size of test specimens, the apparatus for immersion, and the procedure for inspection and evaluation of borer damage over time.

Method of testing natural durability of timber and efficacy of the wood preservatives against marine borers

Overview

Status
Current
Usage level
Specialized
Domain
Materials Science — Timber and Timber Stores
Type
Testing Method
International equivalents
EN 275:2018 · CEN (European Committee for Standardization), EuropeASTM D2481-12(2018) · ASTM International, USAAWPA E5-19 · American Wood Protection Association (AWPA), USA
Typically used with
IS 401IS 1708
Also on InfraLens for IS 6791
5Key values2Tables4FAQs
Practical Notes
! This is a long-term exposure test; meaningful results often take several years. The test location must have known, significant marine borer activity.
! The standard has been reaffirmed multiple times (e.g., 2003, 2018), indicating its continued validity without major technical revisions.
! Proper identification of both the timber specimens and the marine borers causing the damage is crucial for accurate reporting.
Frequently referenced clauses
Cl. 3Test SpecimensCl. 4ApparatusCl. 5Location and Installation of Test SpecimensCl. 7Examination of Specimens and Evaluation of Results
Pulled from IS 6791:1973. Browse the full clause & table index below in Tables & Referenced Sections.
timberwoodwood preservatives

International Equivalents

Similar International Standards
EN 275:2018CEN (European Committee for Standardization), Europe
HighCurrent
Wood preservatives - Determination of the protective effectiveness against marine borers
Specifies a method for determining the effectiveness of wood preservatives against marine borers by exposing treated wood to the sea.
ASTM D2481-12(2018)ASTM International, USA
HighCurrent
Standard Test Method for Accelerated Evaluation of Wood Preservatives for Marine Services by Means of Small Size Specimens
Provides an accelerated method using small specimens to evaluate preservative efficacy against marine borers.
AWPA E5-19American Wood Protection Association (AWPA), USA
HighCurrent
Standard Test Method for Determining the Resistance of Treated Wood to Marine Borers
Details a procedure for evaluating the relative resistance of treated wood specimens in a marine environment.
Key Differences
≠IS 6791 specifies a large test specimen size (300x100x25 mm), which is significantly larger than the small, accelerated test specimens in ASTM D2481 (e.g., 19x19x76 mm) and different from EN 275 (250x80x20 mm).
≠The damage rating system in IS 6791 is qualitative and descriptive (Nil, Light, Moderate, Heavy, Destroyed), whereas international standards like AWPA E5 use a quantitative numerical scale (10 to 0) for more precise comparison.
≠International standards such as AWPA E5 mandate the inclusion of specimens treated with a reference preservative (e.g., CCA, creosote) for comparative performance, a requirement not explicitly stated in IS 6791.
≠IS 6791 suggests specific test harbor locations within India (e.g., Mumbai, Cochin), while international standards provide general environmental criteria for site selection (e.g., known borer activity, salinity, temperature).
Key Similarities
≈All standards are based on the fundamental principle of in-situ testing by submerging treated and untreated wood specimens in a natural marine environment.
≈The primary method of exposure is consistent, involving mounting specimens on racks or 'ladders' and placing them in the sea, typically below the mean low tide level.
≈All methodologies require the use of untreated control specimens from a susceptible wood species to confirm that the test site has sufficient and active marine borer populations.
≈The target organisms for evaluation are the same, focusing on attack by shipworms (Teredinidae) and gribble (Limnoriidae), which are the most destructive marine borers globally.
Parameter Comparison
ParameterIS ValueInternationalSource
Primary Test Specimen Size (mm)300 x 100 x 25250 x 80 x 20EN 275
Accelerated Test Specimen Size (mm)Not specified19 x 19 x 76ASTM D2481
Damage Rating SystemQualitative (Nil, Light, Heavy, etc.)Numerical scale from 10 (Sound) to 0 (Failure)AWPA E5
Damage Rating Scale (European)Qualitative (Nil, Light, Heavy, etc.)Numerical scale from 0 (No attack) to 4 (Severe attack)EN 275
Minimum Replicates per Treatment65EN 275
Inspection IntervalEvery 6 monthsAt least annuallyEN 275
Reference Preservative ControlNot requiredRequired (e.g., CCA, creosote)AWPA E5
⚠ Verify details from original standards before use

Key Values5

Quick Reference Values
Natural durability test specimen size300 x 38 x 38 mm
Preservative efficacy test specimen size150 x 38 x 38 mm
Minimum specimens per timber species/preservative5
Maximum inspection interval6 months
Destruction rating scale0 (Sound) to 100 (Completely destroyed)

Tables & Referenced Sections

Key Tables
Table 1 - Rating for Destruction of Test Specimens by Marine Borers
Table 2 - Classification of Timbers According to their Natural Durability
Key Clauses
Clause 3 - Test Specimens
Clause 4 - Apparatus
Clause 5 - Location and Installation of Test Specimens
Clause 7 - Examination of Specimens and Evaluation of Results

Related Resources on InfraLens

Cross-Referenced Codes
IS 401:2001Code of Practice for Preservation of Timber
→
IS 1708:2014Methods of Testing Small Clear Specimens of T...
→

Frequently Asked Questions4

What is the standard size of a test specimen for natural durability testing?+
300 mm long with a cross-section of 38 x 38 mm (Clause 3.1.1).
How often should the submerged test specimens be inspected?+
At intervals not exceeding six months (Clause 7.1).
How is the extent of damage by borers evaluated?+
Specimens are visually examined and given a destruction rating from 0 (sound) to 100 (completely destroyed) as defined in Table 1.
How are different timbers classified based on the test?+
Timbers are classified into four classes (Class I to Class IV) based on their average life in the test, as specified in Table 2.

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