Furfurylated Wood: Durability, Fire and Carbon Data for Designers

Furfurylated wood is ordinary softwood that has been impregnated with furfuryl alcohol and cured. Kebony says its process permanently alters the wood cell structure, and its datasheets report lower swelling than untreated wood; a 2017 review notes that whether furfurylation is a true chemical modification of the cell wall is still an open question.^[1][18] In the documents we found it appears as Kebony cladding, decking and roof boards: a dark, hard, low-movement board that greys outdoors.

This guide sets out what Kebony's datasheets, declarations of performance, safety data sheet and EPDs, one national technical approval and one review say. Almost every figure comes from the manufacturer, so we label it that way. We found no other maker with documents of its own, and the name Visorwood did not appear in any document we opened.

What is furfurylated wood and how is it made?

A bio-based liquid cured inside the cell wall

Kebony's technology page says a biobased liquid reacts with the OH-groups present in the wood, which it says reduces water sensitivity and raises durability, and that the liquid also forms a polymer inside the wood that contributes to hardness and gives the brown colour.^[10] An earlier Kebony EPD (2016) shows furfuryl alcohol and catalysts as inputs and lists the production steps as impregnation, drying and profiling.^[7] The safety data sheet gives the composition of the finished wood as 20 to 50 % furfuryl alcohol polymer.^[11] The 2022 EPDs give the share by mass: for Kebony Clear decking 480 kg of radiata and 190 kg of bio-based chemicals per m³ (28 % chemicals, 670 kg in total), and for Kebony Character cladding 490 kg of Scots pine and 80 kg of chemicals (14 %, 570 kg in total).^[5][6] The 2016 EPD for Kebony Clear gives 480 kg of radiata and 200 kg of bio-based chemicals (29.4 %, 680 kg in total) in its material table, while its biogenic-carbon note states 286.6 kg of furfuryl alcohol per m³; we show these figures and do not decide between them.^[7]

Where the furfuryl alcohol comes from is stated only in a review: Mantanis (2017) writes that it is a liquid made from agricultural waste such as sugar cane and corn cobs. We read the relevant passages of that review in the full text on the journal's page; Kebony's own documents do not say it, so we treat it as that author's description.^[18]

Clear and Character

Kebony Clear is made from radiata pine, with a primarily clear front surface and treatment through the board.^[2] Kebony Character is made from Scots pine. The SINTEF approval says the modification gives a 35 % weight gain in the sapwood and increases sapwood durability against biodegradation, and also that it does not change the durability of the heartwood.^[8] Ask which range and which species a project is quoted in, because the documents give them different values.

How does furfurylated wood perform?

Durability, hardness and movement

According to Kebony's Clear datasheets of 15 February 2022, the modified wood has EN 350 durability class 1 against class 5 for untreated wood, use class 3 against 1, Brinell hardness 4.2 against 2.5 (EN 1534), density 670 against 480 kg/m³ and maximum tangential swelling 4 against 8 %. The rough-sawn sheets state that machining which reveals pale areas wider than 3 cm may mean insufficient treatment, and that the board or the affected portion shall then be discarded; all the sheets say the values are averages for the original profile and may change without notice.^[1][2] The cladding DoPs disagree on durability: DoP-002 (signed 5 November 2021) states class 1 and DoP-006 (October 2024) states class 2, with use class 3 in both.^[3][4] The Kebony Character cladding EPD states class 1–2, swelling of 6 % and a Brinell value of "20 - 30 N/mm²".^[6] We did not find a document that explains the difference between the two Clear DoPs.

The SINTEF approval says Kebony Scots Pine has strength properties similar to ordinary Scots pine except for cross-tensile strength and impact bending, which are reduced, and that shrinkage and swelling of the sapwood fall by about 50 %.^[8] The Mantanis review describes the wood as having greater hardness and moduli than untreated wood but being more brittle.^[18] We found no document that grades Kebony as structural timber and no strength values in the documents we opened. All the Kebony cladding and decking documents describe use above ground.

Heat flow and vapour

Both Kebony Clear cladding DoPs give vapour resistance values: µ 41 wet and 155 dry in DoP-002, and 37 and 140 in DoP-006, with the thermal figure of 0.14 printed under the thermal resistance label described above.^[3][4] We checked the pairing of labels and values on the rendered DoP pages.

Colour change and weathering

Kebony's use and maintenance guide states that the boards have a deep brown colour that turns to a silver-grey patina, usually gradually over several months, faster with intense sun and rain, without affecting decay resistance or other technical properties. It adds that oil, stain or paint reduces the greying or changes the colour, and that a surface coating is possible if the original colour should be kept as long as possible. We read this in the guide's Dutch-language section, because the text of the English pages did not extract.^[12] The datasheets say natural colour and grain variation appear on delivery and after installation, and that surface cracks and checks may appear on the weathered surface.^[1][2]

Cleaning and maintenance

The datasheets say the wood needs no maintenance beyond normal cleaning.^[1][2] The use and maintenance guide asks for cleaning of dirty exterior surfaces, a deck at least once each spring, discourages pressure washers (brushes are acceptable, and never a direct jet on the wood), and notes that strong cleaners can lighten the surface of cladding.^[12]

How does furfurylated wood behave in fire?

Both Kebony Clear cladding DoPs state D-s2, d0 under EN 13501-1, with the product mounted with an open air gap behind; DoP-002 names Efectis as the testing body and DoP-006 names none.^[3][4] The SINTEF approval gives the same class for 21 mm Kebony Scots Pine cladding with a ventilated gap of 40 to 80 mm over an A2 substrate, and says Kebony Scots Pine roof boards of at least 28 mm, and decking laid as a roof terrace, meet B_ROOF(t2) in the build-ups it describes. It lists use as exterior cladding in risk classes 1 to 6 in fire class 1, with further conditions for fire classes 2 and 3. The approval's stated validity ended on 1 October 2025, and a search of SINTEF Certification's register for "Kebony" on 14 October 2026 returned no approved product, so we could not confirm a renewal.^[8]

Kebony's fire page says its Clear and Character cladding reach D-s2, d0 as standard, that Clear shiplap and tongue-and-groove profiles with a fire-retardant treatment applied by partners reach B-s1, d0, and that a low FIGRA value was measured in an SBI test.^[9] This is a manufacturer's web page: we saw no classification report for B-s1, d0, no FIGRA figure and no document naming the retardant, so a build-up that needs class B should ask for the report. The page also compares Kebony with other modified woods, and we did not check those comparisons. For another route see our thermally modified wood profile.

How much carbon does furfurylated wood hold?

What the EPDs show

We opened two EPDs from EPD Norway, both owned by Kebony AS, based on EN 15804+A2 with the PCR NPCR 015 rev4, verified by Silvia Vilčeková and declared per m³. Kebony Clear decking (NEPD-3659-2604, issued 5 August 2022, valid to 5 August 2027) shows A1–A3 GWP-total of −1,080 kg CO₂e: fossil +401, biogenic −1,510, land-use change +25.4. It declares A4 transport +61.1 and A5 +3.85 and, because its functional unit is 60 years with the decking replaced after 30 years, B4 replacement +437.^[5] Kebony Character cladding (NEPD-3513-2106, issued 25 May 2022, valid to 25 May 2027) shows A1–A3 of −715 (fossil +328, biogenic −1,050), A4 +38.7 and A5 +2.75, with a 60-year product service life and B1–B5 reported as zero.^[6] The Clear EPD notes that selected key indicators were revised in March 2025 using a recalculation method from the Norwegian Institute of Wood Technology, intended to make wood EPDs more comparable; we did not read that method.^[5]

Read the number with care

The negative A1–A3 total does not mean the board removes carbon from the atmosphere for good. Both EPDs model the end of life as energy recovery of all the wood (670 and 570 kg), with C3 at +1,030 and +1,060 kg CO₂e per m³, mostly biogenic, and credits for substituted heat in module D of −682 and −692.^[5][6] The two EPDs differ in species, density, functional unit and service-life assumptions, so we do not set them against each other. We found no EPD for Kebony Clear cladding, and the older Kebony EPD cited on the 2022 datasheets, NEPD-407-287, was valid to 21 June 2021.^[1][7] Do not set these figures beside EPDs from another programme or PCR version, such as those in the thermally modified wood profile, without checking declared unit, modules and PCR.

Which standards and certificates apply?

The shiplap datasheet states CE marking according to EN 14915 (solid wood panelling and cladding), and the cladding DoPs cite the same standard and assessment system 3.^[2][3][4] We did not read EN 14915, EN 350, EN 335, EN 1534 or EN 13501-1. The datasheets also state that Kebony products are exempted from the EU biocide directive and comply with the EU Timber Regulation.^[1][2] Kebony's technical-data page lists FSC, PEFC and Nordic Ecolabel certificates, an ICC-ES report (ESR-3756, which we did not open) and the EPDs.^[19]

The FSC certificate copy (CU-COC-813689, issued to Kebony Norge AS, valid until 10 March 2030) and the PEFC certificate copy (valid until 7 February 2031) are chain-of-custody certificates; the FSC copy says it does not by itself show that a given product is FSC certified, which needs the claim on the invoice. We did not check the FSC or PEFC databases.^[16][17] The Nordic Swan licence copies on Kebony's site (product group 086, durable wood for outdoor use, criteria 2.10) say valid to 30 September 2026. On 14 October 2026 the Norwegian registry page returned an error and a Swedish registry search for "Kebony Norge" returned no entry, so we cannot say whether the licence has been renewed. The datasheets cite licence number 2086 0001, which the Norge copy carries.^[1][15]

Health and safety, and end of life

Kebony's safety data sheet of 14 October 2025 states that the product is not hazardous in itself, that the main health hazard is dust from sawing, sanding or machining (a P3 filter if extraction is not sufficient), and that the furfuryl alcohol monomer concentration is below the limit for classification as hazardous waste under Decision 2014/955/EU. It gives wood waste codes and says that in households it is safe to burn the wood in stoves and fireplaces.^[11] The use and maintenance guide says waste can be disposed of like untreated wood and burned with no other smoke components than untreated wood, and the EPDs assume energy recovery.^[5][6][12] We found no document on reuse, recycling or take-back of used boards.

Where is furfurylated wood used, and what are the limits?

When to specify it, and when not

Where the documents support it

• Cladding and decking above ground. The datasheets and DoPs state use class 3, and the installation guides describe above-ground exterior use under constructive wood protection.^{[1][3][4][13]} The maker's documents say no maintenance beyond cleaning is needed and also that the board greys; keeping the brown colour longer means a coating, applied to the coating maker's instructions.^[1][12]
• Hardness and movement. Against untreated softwood in the same datasheet, hardness is 4.2 against 2.5 Brinell and maximum tangential swelling 4 against 8 %.^[1] For Kebony Character the user guide gives about 6 %, measured differently (fully dry to fully saturated, across the board width).^[12] We found no independent test of these values.
• Facades with fire requirements. D-s2, d0 is documented for Kebony Clear cladding in the DoPs, and class B-s1, d0 is claimed by the maker for treated shiplap profiles; ask for the report before relying on the latter.^[3][4][9]

Where it needs care or may not suit

• Ground, water and structure. The SINTEF approval says the wood is used over terrain and not in contact with soil or seawater, and the decking installation guide says not in contact with the soil; we found no structural grading.^[8][14] For graded structural timber, see our glulam and cross-laminated timber profiles.
• Conflicting or lapsed documents. Two Clear DoPs give durability class 1 and 2 and density 660 and 635; the older EPD cited on the datasheets expired in 2021; the Nordic Swan copies end 30 September 2026; the SINTEF approval ended 1 October 2025.^{[1][3][4][7][8][15]} Ask for current versions.
• Metals and fixings. Stainless steel A4 or A2 only, with A4 near the coast or in chloride-exposed settings; galvanised or ferrous metal stains the wood dark, zinc can corrode, and run-off can discolour zinc and copper details.^[12][13][14]
• Character is not for re-machining. The user guide says Kebony Character must not be processed further, while Clear can be.^[12] The SINTEF approval for Kebony Scots Pine reads differently: it says the wood is processed with ordinary tools, that processing weakens its protection and that cut and machined surfaces should be treated with a wood preservative. It also says the modification does not change the durability of the heartwood. We show both and do not decide.^[8]
• Single source. Kebony is the only maker whose documents we found, and its process is described as patented, so the data come from one company and its certificates.^[10]
• Against named alternatives. We found no document that compares furfurylated wood with thermally modified wood or with other timbers under the same test, so any such comparison would be our own. Kebony's web page makes comparative claims about thermally modified and acetylated wood that we did not check.^[9]

We read no price, no independent field monitoring and no emission test report for Kebony products.

Technical data in Kebony's own documents

Only one manufacturer's documents exist in our reading, so the table below compares Kebony's documents with each other, not products of different makers. Values are as printed, with the standard or condition each document states. They come from documents of different dates and, for hardness, different scales, and we convert nothing.

The hardness values of Clear (4.2 Brinell) and Character ("20 - 30 N/mm²") are printed on different scales, and we do not know how they relate. The two Clear DoPs and the datasheets differ in density, and the DoPs differ in durability; we show them without deciding.

Suppliers whose documents we read

Frequently asked questions about furfurylated wood

The bottom line on furfurylated wood

Furfurylated wood is a hard, low-swelling softwood for cladding and decking above ground, and in practice it is Kebony's product. Its limits are real: documents from a single maker, no structural grading, no ground contact, a class B fire rating that rests on a retardant and a report we have not seen, and certificates and approvals whose dates have passed or whose values differ between documents. Ask for the current EPD, the DoP for your profile, the fire report for your build-up and the Nordic Swan licence status.

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