organic / Timber / Millwork

Charred Timber (Shou Sugi Ban) Millwork

Japanese charring technique creating 2-3mm protective carbon layer on hardwoods. The char layer resists moisture, UV, insects, and fungi without chemicals. Available on Australian hardwoods achieving BAL-12.5 to BAL-29 bushfire ratings. Distinctive black aesthetic for architectural millwork with 40-80 year service life on appropriate species.

Atlas code

ORG-TBR-MW-001

organictimbermillworkcharred-timbershou-sugi-banyakisugifire-resistant

At-a-glance signals

Overview

Executive summary

Charred timber millwork utilises the traditional Japanese Shou Sugi Ban (Yakisugi) technique, applying controlled charring to create a 2-3mm protective carbon layer on premium hardwoods. This ancient preservation method, originating in 18th century Japan for cedar siding, enhances timber's natural durability while creating a distinctive architectural finish. The charring process transforms the wood surface into a carbon-rich barrier that resists moisture, insects, UV degradation, and fungal decay without chemical treatments. In Australia, the technique is applied to native hardwoods including Spotted Gum (BAL-29), Jarrah (BAL-19), and imported Burnt Ash, suitable for cladding, screening, and architectural detailing where superior weathering performance and unique aesthetic are required.

Best when…

Chemical-free preservation - no toxic treatments or leaching risk
Enhanced resistance to UV, moisture, insects, and fungal decay
Distinctive black aesthetic with natural grain texture
BAL-29 achievable with Spotted Gum substrate (AS 3959)
40-80+ year service life on durable hardwood species
Low maintenance compared to painted/stained timber alternatives
Eliminates recurring VOC-generating paint/stain maintenance cycles
Carbon storage in timber plus reduced replacement frequency
Multiple Australian manufacturers and suppliers available
Suitable for Australian climate zones and bushfire areas

Top advantages

01 Chemical-free preservation - no toxic treatments or leaching risk
02 Enhanced resistance to UV, moisture, insects, and fungal decay
03 Distinctive black aesthetic with natural grain texture
04 BAL-29 achievable with Spotted Gum substrate (AS 3959)
05 40-80+ year service life on durable hardwood species

Top limitations

01 Charring does NOT increase fire rating - BAL depends on base timber species
02 Char layer is soft and wears away, especially on softwood substrates
03 Higher cost than conventional timber ($255-350+ AUD/m2 supply only)
04 Surface carbon may transfer on contact (handling/touch)
05 Colour consistency challenges across batches

Technical

Physical ·8

Density: 650-1100 kg/m3 Depends on base timber species. Spotted Gum ~1100 kg/m3 (Durability Class 1), Jarrah ~820 kg/m3, Burnt Ash ~650-700 kg/m3. Charring reduces surface density marginally (2-3mm char layer). Source: Australian Timber Database, Mortlock Timber.
Specific gravity: 0.60-1.13 Based on species: Spotted Gum 0.95-1.10, Jarrah 0.78-0.85, Ironbark 1.05-1.13, Burnt Ash 0.60-0.70. Source: Australian Timber Database.
Porosity: 5-15 % Charred surface creates a carbon barrier reducing surface porosity. Internal timber structure unchanged. Estimated based on hardwood porosity ranges.
Water absorption: 2-8 % Charred surface significantly reduces water absorption compared to untreated timber. Carbon layer acts as hydrophobic barrier, enhanced by factory-applied Cutek or WOCA oil finish.
Hardness: 6.1-14.0 kN Janka hardness of base timber. Spotted Gum 11.0 kN, Jarrah 8.5 kN, Ironbark 14.0 kN, Burnt Ash ~6.1 kN. Note: the char layer itself is soft (charcoal) and wears under abrasion. Source: Australian Timber Database.
UV resistance: Excellent Exceptional UV resistance from carbon layer protection. The charred surface absorbs UV radiation rather than allowing photodegradation of underlying lignin. Significantly reduces greying compared to untreated timber. Source: Mortlock Timber, reSAWN TIMBER co.
Chemical resistance: Good Enhanced chemical resistance from carbon barrier compared to untreated timber. Carbon layer is chemically inert and resists acid rain, mild chemical exposure. Not suitable for prolonged chemical contact.
pH tolerance: 4-8 pH Natural timber pH tolerance with carbon surface protection. Standard hardwood range.

Mechanical ·5

Tensile strength: 80-150 MPa Longitudinal tensile strength of base timber. Spotted Gum ~125 MPa, Jarrah ~90 MPa. Charring only affects 2-3mm surface, not structural core. Source: AS 1720.1, Australian Timber Database.
Compressive strength: 40-80 MPa Compressive strength parallel to grain. Spotted Gum ~70 MPa, Jarrah ~55 MPa. Structural properties fully maintained in underlying timber. Source: AS 1720.1.
Flexural strength: 90-150 MPa Modulus of Rupture (MOR) for Australian hardwoods. Spotted Gum ~130 MPa, Jarrah ~100 MPa, Ironbark ~150 MPa. Source: AS 1720.1.
Impact resistance: 30-80 J/m Impact resistance varies by hardwood species and grain density. Dense hardwoods like Spotted Gum and Ironbark have high impact resistance. Charred surface layer absorbs minor impacts but is soft.
Creep resistance: Excellent Excellent creep resistance typical of seasoned Australian hardwoods. Charring does not affect internal structural properties. Source: AS 1720.1.

Sustainability & Health

Embodied carbon & energy ·7

Embodied carbon: -50 to 200 (species and accounting dependent) kg CO2-eq/m3 No charred-timber-specific EPDs currently available. Timber stores biogenic carbon (approximately 250 kg CO2/m3 for hardwood). The charring process adds minimal energy input compared to chemical treatment manufacturing. Net embodied carbon likely negative when biogenic storage is included. Source: WoodWorks, BAUWN, NIST SP 1324.
Carbon footprint: -50 to 200 kg CO2-eq/m3 Potentially carbon-negative when biogenic carbon storage is included. Hardwood stores ~900 kg CO2/m3 (biogenic), processing emissions ~200-400 kg CO2-eq/m3, net = carbon negative. Extended service life (40-80 years) reduces replacement-related emissions. Source: WoodWorks EPD methodology, BAUWN.
Embodied energy: 500-1200 MJ/m3 Includes harvesting, seasoning, milling, and controlled charring. Charring adds approximately 50-100 MJ/m3 additional energy vs uncharred timber. Total significantly lower than chemical treatment alternatives. Source: estimates based on timber EPD frameworks.
Water footprint: 50-200 L/kg Forest growth water requirements and minimal processing water. Charring process uses no water. Comparable to standard timber products.
Recycled content: 0-30 % Typically 0% recycled content (virgin timber). However, reclaimed timber can be charred as a value-adding restoration technique. Some suppliers offer reclaimed timber charring services.
Renewable content: 95-100 % 100% renewable content from sustainably harvested timber. Cutek/WOCA oil finishes are plant-based. Source: supplier specifications.
Circular score: 8.5 /10 High circular economy value: renewable resource, 40-80 year lifespan, no chemical contamination enabling composting/biomass recovery at end-of-life. Can be recharred or refinished to extend service life. Fully biodegradable.

Health & emissions ·1

VOC emissions: <50 ug/m3 No chemical treatments — eliminates toxic leaching risk. Factory oils (Cutek, WOCA) are low-VOC. Eliminates recurring VOC from repainting cycles. Source: BAUWN.

Compliance & Fire

Fire performance ·6

Combustibility class: Combustible - BAL rating per species Combustible material (timber). Charring consumes surface cellulose, leaving fire-resistant charcoal and lignin, but does NOT make the material non-combustible. BAL rating depends entirely on base timber species. Source: Mortlock Timber lab testing, AS 3959.
Fire resistance level: BAL-19 to BAL-29 (species dependent) minutes BAL ratings achieved per AS 3959: Spotted Gum = BAL-29, Jarrah = BAL-19, Ironbark = BAL-29 to BAL-40. These ratings are inherent to the species, NOT the charring process. The Blackwood Project (NZ) pursuing BAL-40 certification. Source: Mortlock Timber, Adelaide Timber Cladding, Eco Timber Group.
Ignition temp: 400-500 (char layer) degC Charcoal (char layer) requires higher temperatures to ignite than cellulose. Charcoal ignition ~400-500 degC vs cellulose ~250-300 degC. However, once char is consumed, underlying wood ignites at normal timber temperatures. Source: Nakamoto Forestry, NELMA.
Flame spread index: 0-25 (Class A charred cypress) FSI Non-charred cypress tests ASTM/UL Class C; charred cypress achieves Class A flame spread. For Australian hardwoods, flame spread characteristics depend on species density and BAL rating. Source: Nakamoto Forestry, NELMA.
Smoke dev. index: 100-200 SDI Natural timber smoke development. Char layer may reduce initial smoke generation as cellulose already consumed. Hardwood species generally produce less smoke than softwoods.
Heat release rate: 150-300 kW/m2 Heat release rate typical of hardwood timber. Charring does not significantly change fire properties of the timber — Mortlock lab testing confirms this. The char layer has already consumed cellulose but does not provide fireproofing. Source: Mortlock Timber, US Forest Service FPL.

Cost & Lifecycle

Capex & lead time ·6

Material cost (range): 255-350 AUD/m2 Supply only, 19mm thick, excluding GST. Jarrah $255-320/m2, Spotted Gum $285-330/m2, Burnt Ash $320-350+/m2, Irongum (most cost-effective). WOCA finish adds $10-20/m2 over standard Cutek. Source: Mortlock Timber 2025 pricing.
Material cost (per unit): 13400-18400 AUD/m3 Based on 19mm boards at $255-350/m2, equivalent volume pricing approximately $13,400-18,400/m3. Premium pricing reflects specialised charring process. Source: calculated from Mortlock Timber m2 pricing.
Lead time: 14-42 days Australian manufacturers (Mortlock, Hurford's) produce domestically, reducing lead times. Standard profiles typically 14-28 days. Custom profiles or large orders may extend to 42 days. Source: Mortlock Timber.
Lifecycle cost: 280-450 AUD/m2 Excellent lifecycle value. Higher upfront cost offset by 40-80 year service life and reduced maintenance vs painted/stained timber (which requires repainting every 3-7 years with associated VOC emissions and labour costs). Source: BAUWN, Mortlock Timber.
Annual maintenance: 1.50-5.00 AUD/m2/year Re-oiling every 5-10 years at approximately $15-25/m2 per application. Annualised = $1.50-5.00/m2/year. Significantly less than painted timber requiring repainting every 3-7 years. Source: Mortlock Timber.
Market availability: Good - multiple Australian manufacturers Multiple Australian suppliers: Mortlock Timber (manufacturing in-house), Hurford's, Greenhill Timbers (QLD), Eco Timber Group, Nationwide Timber (Melbourne), Adelaide Timber Cladding, Rustic World Timbers, Timber & Rose. Good national availability with delivery networks covering metro and regional areas. Source: supplier websites.

Service life & durability ·3

Expected lifespan: 40-80 years Char layer lifetime estimated 20 years before significant erosion (subject to exposure). Underlying durable hardwood (Durability Class 1-2) provides 40-80+ year structural life. Thousands of Japanese buildings retain 40+ year old charred cladding. Source: Mortlock Timber, BAUWN.
Maintenance interval: 5-10 years Re-oiling recommended every 5-10 years with Cutek or WOCA exterior oil. Visible char erosion expected around 4-5 years in exposed conditions. Burnt Ash requires less maintenance than Spotted Gum or Jarrah. Source: Mortlock Timber.
Warranty period: 5-25 years Varies by supplier and species. Char finish warranty typically 5-10 years; structural timber warranty 15-25 years. Mortlock Timber offers product warranties on species-specific basis.

Layer D

Where it's used

External timber cladding and screening

Architectural millwork and detailing

Feature walls and accent panels

Pergola and outdoor structure elements

Garden and landscape architecture

Bushfire-resistant construction (BAL zones)

High-end residential and commercial projects

Heritage and Japanese-inspired architecture

Where it's used

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