IS 5539 : 1969Specification for preservative-treated plywood

IS 5539:1969 is the Indian Standard for Preservative Treatment of Trees Posts and Poles, and Sawn Timber for Outside Use. It covers the chemical impregnation methods for transmission / distribution poles, telephone poles, fencing posts, marine piles, and outdoor structural timber in India.

Use it when: - Procuring electrical / telephone distribution poles (the dominant Indian application — millions of poles installed annually for rural electrification) - Specifying fencing posts for plantation / agricultural / boundary applications - Specifying outdoor sawn timber for garden structures, pergolas, exposed timber framing - Auditing pole / timber treatment quality — chemical retention, depth of penetration, treatment certificate verification

Use with companion codes: - IS 401:2001 — Code of Practice for Preservation of Timber (the master treatment-and-process code) - IS 1141:1993 — Code of Practice for Seasoning of Timber (pre-treatment moisture conditioning) - IS 287:1993 — Recommended moisture content limits for timber by application - IS 12896:1990 — Specification for treatment with copper-chrome-arsenic (CCA) — the dominant preservative chemistry

Approved preservatives (Clause 4):

• CCA (Copper-Chrome-Arsenic): the standard for transmission poles, fencing posts, marine piles. Highly effective against fungi, insects, marine borers. Now restricted in some countries (US, EU) due to arsenic content — Indian use continues for utility poles.
• CCB (Copper-Chrome-Boron): similar to CCA but boron substitutes for arsenic; less environmental concern; comparable performance against fungi and insects.
• ACQ (Alkaline Copper Quaternary): arsenic-free; modern alternative; growing acceptance.
• Copper-azole: modern formulation; excellent fungal resistance; arsenic-free.
• Creosote: traditional; petroleum-based; effective for railroad ties, marine piles in heavy biological-attack environments. Distinctive black colour + tarry odour.
• Boron compounds: less aggressive; for indoor / dry-service timber only.

Treatment methods (Clauses 5-7):

1. Full-Cell (Bethel) Process — for transmission poles, marine piles: - Timber loaded in pressure vessel (cylinder) - Vacuum applied → removes air from wood cell cavities - Preservative solution pumped in under pressure (10-15 bar) - Pressure held until specified retention achieved - Final vacuum + bleed → removes excess from surface - Retention: 8-25 kg/m³ for utility poles; up to 30+ for marine

2. Empty-Cell (Lowry / Rueping) Process — for above-ground exposure: - Pre-pressurise vessel without vacuum (air remains in cells) - Preservative pumped in under pressure - Pressure released → air expands, pushing preservative out of cell cavities into cell walls - Cell-wall absorption only; cell cavities empty - Retention: 5-10 kg/m³; suitable for above-ground service

3. Hot-and-Cold Open-Tank Process — for short pieces of timber: - Timber placed in hot preservative bath (60-80°C for 2-4 hours) - Then transferred to cold bath (ambient temperature) - Wood cells contract on cooling, draw in preservative - Less effective than pressure treatment; OK for fencing, garden structures

Retention requirements (Clause 6) — kg of preservative per m³ of treated timber:

| Application | Retention (kg/m³) | |---|---| | Internal indoor use | 4-5 | | Above-ground outdoor | 5-8 | | Ground-contact fencing | 8-12 | | Distribution / transmission poles | 12-15 | | Marine submerged piles | 20-25 |

Penetration requirements (Clause 7) — depth of preservative in wood: - For utility poles: ≥ 13 mm penetration with ≥ 80% of the sapwood (the outer layer; heartwood is inherently more durable but harder to treat) - For other applications: depth varies; sapwood penetration generally required - Verified by incision test — cut a section; observe preservative coloration depth

Indian electrical utility pole standards:

• 8 m pole: for low-voltage distribution lines; typical at street-corner / residential
• 9 m pole: for HT distribution; standard for 11 kV / 22 kV lines
• 11-13 m poles: for higher voltage transmission (33 kV, 66 kV)
• 15-22 m poles: for 132 kV and higher (specialised)

Pole diameters: - Tip diameter: typically 150-180 mm (the smaller end, at top) - Butt diameter: 250-350 mm (the larger end, at base, where greater bending strength needed) - Taper: typically 12 mm per metre of length (i.e., diameter reduces by 12 mm for each metre of pole length)

Common species for poles: - Eucalyptus — most widely used in India for poles; readily available; treats well; low cost - Casuarina — coastal supply; good for marine + saline regions - Sal (Shorea robusta) — historically the gold standard; now scarce and expensive - Babool / Acacia — short-distance fencing - Teak (Tectona grandis) — premium; only for high-value applications

Inspection checklist: 1. Pole length + diameter: tape measure verification at top, middle, base 2. Straightness: bow / curvature within tolerance (typically 1% of pole length) 3. Surface defects: dead knots, surface checks > 25 mm depth, fungal staining 4. Treatment certificate: from BIS-licensed treatment plant; details retention, chemistry, batch number, treatment date 5. Incision test: cut a 25 × 25 mm sample at end of pole; observe depth of preservative penetration 6. Retention test: lab analysis of preservative content in extracted core sample 7. Bend test (occasional, on sample poles): static + impact load testing

Service life: - Properly CCA-treated eucalyptus pole: 25-40 years in Indian climate (most regions) - Improperly treated (low retention, poor penetration): 5-10 years - Cost differential: treated pole costs ~3-5× the cost of untreated; lifetime cost-of-service is 5-10× lower than untreated

1. Buying poles from non-licensed treatment plants — informal treatment yards do partial / no treatment; reported retention is fictitious. Always procure from BIS-licensed treatment plants with documented quality systems.

2. Visual acceptance only — green-tinted poles (CCA-treated) look impressively treated. Visual colour says nothing about retention or penetration depth. Mandate lab analysis of one sample per shipment.

3. Inadequate penetration in heartwood-only poles — heartwood (the central core) is naturally durable but doesn't accept preservative readily. Many tropical species (sal, teak) have very small sapwood fraction. For such species, treat 'as good as possible' (typically less retention/penetration than codes mandate) but ensure heartwood quality is verified.

4. Re-using poles — old poles taken down during line upgrades sometimes get re-treated and re-sold. Pre-service damage + fungal initiation aren't reversed by re-treatment. Avoid re-used poles for permanent lines.

5. Storage post-treatment — treated poles must be stored on raised supports (not on ground; not in soil/mud) for at least 14 days for surface curing. Some yards stack on ground; surface moisture re-activates chemistry; treatment partly leaches.

6. Field cutting / drilling — when poles are cut to length or drilled for fittings on-site, the exposed cut/drill faces are untreated raw timber. Apply brushable CCA or copper-naphthenate to these spots; mandatory but routinely skipped. The cut/drill location becomes the initiation point for decay.

7. Inadequate ground-line protection — at the soil-air interface (the 'ground line'), oxygen + moisture conditions are most favourable for decay fungi. This is where 80% of pole failures occur. Provide additional barrier treatment (bituminous coating, sleeve) at ground-line zone.

8. Wrong chemistry for application — CCA in food-processing facilities: chromium contamination risk. Use boron-only or copper-azole for sensitive applications.

9. Disposing untreated waste as biomass — CCA-treated wood off-cuts and discarded poles contain heavy metals (Cu, Cr, As). They are NOT biomass-acceptable for fuel; must be disposed in licensed hazardous-waste facilities. Many sites burn off-cuts; pollutes soil + air.

• IS 401:2001 — Code of Practice for Preservation of Timber (master code)
• IS 287:1993 — Recommended moisture content for timber
• IS 1141:1993 — Code of Practice for Seasoning of Timber
• IS 12896:1990 — Specification for treatment of timber with CCA
• IS 1850:1986 — Treatment of timber with creosote
• IS 6313 Part 3:2001 — Anti-termite measures for timber and bamboo
• IS 1708:2014 — Methods of testing small clear specimens of timber
• IS 883:2016 — Code of Practice for Design of Structural Timber in Building
• IS 2911 Part 2:2021 — Code of Practice for Timber Pile Foundations
• IS 4017:1976 — Code of Practice for Selection of Timber for Marine Wharves
• CEA Regulations — Central Electricity Authority safety standards (mandate IS-treated poles for distribution / transmission)
• IRC 73:1980 — Geometric design standards for rural roads (covers protective treatment of roadside timber elements)

IS 5539:1969 is 56 years old but remains the working code. Methodology is mature; chemistry has been updated by amendments (most recently 2008 — added copper-azole and arsenic-free alternatives).

Where preservative-treated timber is still relevant in 2026 India:

• Rural electrification distribution poles: ~70% of all preservative-treated timber demand; eucalyptus + CCA dominates. Major Indian DISCOM tenders specify IS 5539 conformance.
• Plantation / agricultural fencing: extensive use in citrus + sugarcane belts
• Boundary fencing for industrial sites, farms, animal enclosures: bulk demand
• Coastal jetty wood components (above-water portions): casuarina + CCA
• Heritage restoration: replacement of original treated-wood components in colonial-era buildings, docks, railway stations

Where it's being replaced: - Transmission poles > 11 kV: increasing shift to RCC (IS 1678 for concrete poles) and steel lattice towers. Treated wood gradually losing market share. - Telephone poles: shifting to fibre-optic cable installations; aerial poles still mainly wood - Suburban distribution poles: mixed wood / concrete; cost determines

Indian treatment industry: - Major BIS-licensed plants (in eucalyptus-growing regions: Karnataka, Andhra, Tamil Nadu, Kerala): consistent CCA treatment per IS 5539 / IS 12896. Quality verified. - Tier-2 / regional treatment yards: variable quality. Pre-qualify with sample tests. - Informal / unlicensed yards: best avoided for utility-grade poles.

Environmental & health considerations: - CCA disposal issue: arsenic content makes used poles a long-term liability. Many countries have moved to arsenic-free chemistries; India is gradually transitioning but slowly. - Workers' health: CCA treatment workers should use PPE (gloves, masks, eye protection); some unlicensed yards don't. Treated wood handlers should avoid skin contact with green-wet poles. - Recommended modernisation: copper-azole and ACQ treatments are gaining market share — comparable efficacy, no arsenic. For new tender specifications, request 'arsenic-free preservative' option.

For specifiers: insist on IS 5539-compliant treatment from BIS-licensed plants. Mandate batch certificates + sample lab testing. Cost premium over informally-treated wood: ~30-50%. Lifetime cost-of-ownership: 3-5× lower than failure-prone informally-treated poles.

Future: IS 5539 has been on the BIS revision agenda since 2018 — expected updates include explicit listing of newer preservative chemistries, clearer environmental / disposal guidance, and modernised acceptance test methods. No public draft yet.