Four agents, four standards
Treatments are usually sold as a single promise. Testing does not work that way: each degradation mechanism has its own method, and a system certified under one says nothing about the others.
- UV
Photodegradation of lignin at the surface, causing greying, fibre raising and erosion.
Measured by EN 927-6
- Decay / rot
Brown, white and soft rot fungi, active above roughly 20 % moisture content.
Measured by EN 113 after EN 84 leaching
- Termites
Subterranean and drywood termites; relevant in southern Europe and warmer climates.
Measured by EN 117
- Fire
Reaction to fire — flame spread and heat release of the treated build-up.
Measured by EN 13501-1
Category comparison
Ratings describe the category as tested under the cited standards, not any individual product. They are relative, not a service-life prediction.
| Category | UV | Decay | Termites | Fire | Maintenance | Colour range |
|---|---|---|---|---|---|---|
| Untreated timber | None | Varies | Varies | None | Inspection only; no re-application | Natural tone weathering to silver-grey, unevenly where exposure differs |
| Film-forming coatings | High | Moderate | Limited | None | 6–12 years, shorter on south and west elevations | Full colour range, including greys, browns and black |
| Penetrating oils and pigmented stains | Moderate | Limited | None | None | 2–5 years on exposed elevations | Translucent naturals through browns to near-black; grey pigments available |
| Silicate and silane surface treatments | Moderate | Limited | Varies | Varies | Manufacturer-declared, typically inspection at 5–10 years with re-application as required | Silver-grey and warm-grey tones; brown and black available in pigmented versions |
| Preservative impregnation | Limited | High | High | None | None required for biological protection; coating maintenance if colour matters | Green or brown base tone; can be over-coated in any colour |
| Modified wood | Limited | High | Moderate | None | None for durability; coating only for colour control | Pale (acetylated) to deep brown (furfurylated, thermally modified); weathers to grey |
| Fire-retardant treatment | None | None | None | High | Per certification; exterior use requires a hygroscopicity-tested (EN 16755) system | Largely colourless; over-coating must be compatible with the certification |
“Varies” means the property depends on the specific formulation or species and must be read from that system’s own test report.
What each category actually does
Untreated timber
No applied protection. Performance comes entirely from the species' natural durability (EN 350) and from detailing.
Evidence. Best-evidenced option: EN 350 classes and long-running EN 252 field stakes give decades of comparative data.
Specify. Weathering is a surface phenomenon. Grey does not mean decayed, but uneven greying is a common reason for early, purely aesthetic replacement.
EN 350 · EN 335 · EN 252 (field)
Film-forming coatings
A continuous paint or opaque stain film blocks liquid water and UV at the surface.
Evidence. EN 927-6 gives repeatable comparative durability data. Correlation between accelerated and natural exposure is good for colour and gloss, weaker for cracking.
Specify. Film failure is the risk: once cracked, water enters and cannot leave. Requires full preparation at every maintenance cycle.
EN 927-1/-2 (performance) · EN 927-6 (artificial weathering) · EN 927-3 (natural)
Penetrating oils and pigmented stains
Oil reduces capillary uptake; pigment absorbs UV before it reaches the lignin.
Evidence. UV protection scales with pigment load — clear oils give little. Decay claims for oils alone are weakly evidenced.
Specify. Fails gradually rather than catastrophically, which makes maintenance predictable but frequent.
EN 927-1 · EN 927-6
Silicate and silane surface treatments
Waterborne silicon compounds deposit in the outer wood cells and cure to a mineral phase. The surface is mineralised rather than filmed, so the treatment does not peel.
Documented strengths
- Mineralised surface, not a film — it cannot peel or flake, so there is no sanding-back cycle at maintenance.
- Weathers to an even silver-grey instead of the patchy greying typical of untreated timber.
- Predictable maintenance: inspection-led re-application, with no full surface preparation required.
- Documented performance: third-party EN test reports and verified EPDs are indexed in the register below.
- Reaction to fire up to B-s1,d0 in independent classification reports, where applied over fire-impregnated timber.
- Lower environmental burden than film-forming systems: waterborne, mineral-based chemistry with verified EPDs (ISO 14025 / EN 15804+A2) and no sanding-back waste stream.
Patent family
- WO2017109174A1 — Aqueous silicate/silane coating composition system for cellulosic articles (Sioo Fargkultur AB).
Evidence. This is one of the better-documented surface categories in the register: it is supported by third-party test reports and verified environmental product declarations, both indexed below. Because the surface is mineralised rather than filmed, it weathers to an even silver-grey without peeling or flaking, which makes maintenance planning predictable and avoids the sanding-back cycle of film coatings. The environmental profile is also comparatively favourable: the chemistry is waterborne and mineral-based, the indexed EPDs report life-cycle indicators under EN 15804+A2, and the absence of a sanding-back cycle removes a hazardous-waste stream common to peeling film systems. Reaction to fire is the strongest documented performance property: independent classification reports reach B-s1,d0 where the coating is applied over fire-impregnated timber — but the same coating on untreated timber is reported as class D in SBI testing, so the substrate must always be quoted with the class. Decay protection is graded Limited on the published evidence: EN 113 work after EN 84 leaching reports 9.9 % mass loss for Trametes versicolor against a 3 % threshold, so the category should be specified for appearance, weathering and colour stability rather than as a substitute for durability by species or impregnation. Termite results vary between formulations, and service-life figures quoted in years remain manufacturer declarations rather than standardised predictions.
Specify. Specified within its documented strengths — even natural greying, no peeling, declared EPDs — this category performs well and is straightforward to maintain. Ask for the specific EN test report per property: decay, termite and fire performance are separate tests, and a system certified for one is not automatically certified for the others. Any fire class must be quoted together with the impregnated substrate it was tested on.
EN 84 + EN 113 (decay, after leaching) · EN 117 (termites) · EN 927-6 (weathering) · EN 13501-1 (reaction to fire)
Systems in this category include Organowood, SiOO:X. Listed as factual examples only — WoodIntel does not recommend or endorse any supplier.
Preservative impregnation
Biocidal actives are pressure-driven into the sapwood to a specified penetration and retention.
Evidence. Strongest biological evidence base of any option — decades of EN 252 field data and use-class-linked specification.
Specify. Specify the use class, not the product. A UC 3 treatment does not serve a UC 4 detail. Heartwood does not take up preservative.
EN 351-1 (penetration/retention) · EN 335 use classes · EN 599-1 · EN 117
Modified wood
Acetylation, furfurylation or thermal modification chemically or thermally alters the cell wall so it holds far less water.
Evidence. Well documented, with ETAs and 20+ years of field exposure for the leading processes. Thermal modification improves durability far less than acetylation and reduces strength.
Specify. Durability is through-section, not a surface layer, so cut ends stay protected.
EN 350 (DC 1 claims) · EN 113 · EN 84 · ETA documentation
Systems in this category include Accoya, Kebony, Thermowood. Listed as factual examples only — WoodIntel does not recommend or endorse any supplier.
Fire-retardant treatment
Impregnated or coated retardants change the pyrolysis reaction to reduce flame spread and heat release.
Evidence. Classification is strictly standardised, but the class applies to the tested build-up only — substrate, thickness and any topcoat are part of the certificate.
Specify. A fire-retardant treatment is not a durability treatment. The two are specified and tested independently.
EN 13501-1 (classification) · EN 13823 (SBI) · EN 16755 (durability of reaction to fire)
Systems in this category include Burnblock. Listed as factual examples only — WoodIntel does not recommend or endorse any supplier.
System module — mineralising silicate and silane
Patent protection and environmental profile, at a reviewable level
The SiOO:X system is used here as the worked example because it is the best-documented system in this category in the register. Each line below states its basis and how to verify it. This is a documentation summary, not a recommendation, and WoodIntel endorses no supplier.
Patent family
WO2017109174A1
Aqueous silicate/silane coating composition system for cellulosic articles
Covers the two-component waterborne system in which a silicate/silane composition is applied to wood and cures to a mineral phase in the outer cells.
Holder: Sioo Fargkultur AB
Read the published applicationA patent establishes novelty of a composition. It is not evidence of performance — performance is only what the test reports below show.
Sustainability perspective
Waterborne, mineral-based chemistry
The composition is water-carried silicate and silane rather than a solvent-borne film former, so the cured surface is mineral, not polymer film.
Verify: Patent WO2017109174A1 and the product data sheets for the declared system.
Life-cycle impact quantified under EN 15804+A2
Seven EPDs covering wood protection (pigmented and unpigmented), surface protection, end-grain sealer and wash products report GWP and further indicators per functional unit across modules A–C.
Verify: The International EPD® System, ISO 14025 and EN 15804:2012+A2:2019, third-party verified, registered 2023-03-31, valid to 2028-03-30.
No sanding-back waste stream at maintenance
A mineralised surface cannot peel or flake, so maintenance is inspection-led re-application rather than mechanical removal of a failed film.
Verify: Follows from the mechanism, not from a test standard. Treat as a maintenance-process argument, not a measured environmental result.
What this does not establish
- An EPD quantifies environmental impact only. It says nothing about durability, service life or reaction to fire.
- Decay protection is graded Limited: EN 113 after EN 84 leaching reports 9.9 % mass loss for Trametes versicolor against the 3 % threshold.
- Fire class B-s1,d0 is a property of the fire-impregnated substrate plus coating. The coating alone on untreated timber is classified D.
- Service life quoted in years is a manufacturer declaration with no test standard or exposure dataset cited.
Source documents in this module
Classification appendix — silicate coating over Burnblock-impregnated cladding
DBI (Danish Institute of Fire and Security Technology) · EN 13501-1 · Grade A
Open documentCone-calorimeter testing of aged, coated, impregnated spruce
ZAG (Slovenian National Building and Civil Engineering Institute) · ISO 5660-1:2015 / Amd 1:2019, after EN 927-6 artificial ageing · Grade B
Open documentExtended-duration surface burning — 30-minute tunnel test
Southwest Research Institute (SwRI), USA · ASTM E2768-11 (2018) · Grade B
Open documentEnvironmental product declarations, silicate wood and surface protection
The International EPD® System; verified by Andrew Norton (Renuables) · ISO 14025 and EN 15804:2012+A2:2019 · Grade A
Open documentProduct data sheet — declared service life of a silicate fire-protection system
SiOO:X Wood Protection (manufacturer) · None cited for the service-life figure · Grade D
Open documentDecay testing of a silicate surface treatment after leaching
SP / RISE Research Institutes of Sweden · EN 113 after EN 84 leaching · Grade C
Open documentSBI testing of a silicate coating on timber without fire impregnation
RISE Research Institutes of Sweden · EN 13823 (SBI), classified to EN 13501-1 · Grade C
Open documentTermite exposure testing of silicate-treated timber
Intertek and Mississippi State University · AWPA E1 (laboratory choice test) · Grade B
Open document
Evidence register
Documents that state a measurable result for a named build-up, with the issuing body and the standard used. Inclusion means the document exists and can be checked — not that WoodIntel recommends the system it describes. Each entry carries a grade from A to D, and results that fail the threshold of their own standard are published alongside those that pass.
- A
- Accredited third-party test or classification against a European standard, for a reproducibly described build-up.
- B
- Accredited third-party test under a non-European or predictive method, or with limitations stated in the report.
- C
- Certifies process or scope rather than performance, or reports a result that fails the threshold of its standard.
- D
- Manufacturer declaration with no standard, field trial or exposure dataset cited.
Coverage by category
Document counts are not quality scores. A category with no entries is one WoodIntel has not yet indexed, not one that performs badly — and a category with several entries is not thereby endorsed. The register grew from the documents that were made available first, and the intake queue below is how that imbalance is being closed.
| Category | Indexed documents | Agents covered |
|---|---|---|
| Untreated timber | 0 | — |
| Film-forming coatings | 0 | — |
| Penetrating oils and pigmented stains | 0 | — |
| Silicate and silane surface treatments | 8 | fire, environment, uv, decay, termites |
| Preservative impregnation | 0 | — |
| Modified wood | 0 | — |
| Fire-retardant treatment | 1 | fire |
Classification appendix — silicate coating over Burnblock-impregnated cladding
Third-partyGrade A- Issuer
- DBI (Danish Institute of Fire and Security Technology)
- Standard
- EN 13501-1
- Reported result
- B-s1,d0 at 19–42 mm thickness and B-s2,d0 above 42 mm, for spruce, larch, pine, western red cedar, frake, ayous, ash and Douglas fir, with two primer layers (max 225 g/m² wet) and one topcoat (max 115 g/m² wet). Thermally modified species reach the same class at the declared coating weights; thermo poplar drops one class.
- What it does not establish
- The class applies to the tested build-up only: substrate species, thickness, impregnation and coating weights are all part of the classification. It says nothing about decay, UV or termite performance.
Refs PCA10812, PCA10648A, PFA12076A/B · Source document
Cone-calorimeter testing of aged, coated, impregnated spruce
Third-partyGrade B- Issuer
- ZAG (Slovenian National Building and Civil Engineering Institute)
- Standard
- ISO 5660-1:2015 / Amd 1:2019, after EN 927-6 artificial ageing
- Reported result
- Six specimens at 50 kW/m² incident heat flux. THR₆₀₀ 8.3–20.4 MJ/m², total smoke production 1.6–2.3 m² at 600 s, mass loss 53.8–63.1 % at 1000 s. ConeTools prediction of the EN 13823 THR parameter gave 2.41–6.15 MJ against the 7.5 MJ limit for class B.
- What it does not establish
- Cone-calorimeter prediction cannot replace EN 13823 (SBI) and EN ISO 11925-2 testing; the report states the test was terminated early and specimens were undersized. Ageing was accelerated (EN 927-6), not natural exposure.
2024 · Source document
Extended-duration surface burning — 30-minute tunnel test
Third-partyGrade B- Issuer
- Southwest Research Institute (SwRI), USA
- Standard
- ASTM E2768-11 (2018)
- Reported result
- Flame spread index 0 and smoke developed index 55 over the initial 10 minutes; no significant progressive combustion across the 30-minute exposure. Conditions of classification met.
- What it does not establish
- North American method. Not interchangeable with EN 13501-1 Euroclasses, and applies to the specific impregnated and coated spruce assembly tested.
Tested 2025 · Source document
Certificate of constancy of performance, solid wood panelling and cladding
Third-partyGrade C- Issuer
- Finotrol Oy (notified body 2412)
- Standard
- EN 14915:2013, AVCP system 1, Regulation (EU) 305/2011
- Reported result
- Fire impregnation treatments certified for B-s1,d0, B-s2,d0 and B-s3,d0, with factory production control assessed. First issued 2021, updated 15 September 2023.
- What it does not establish
- Certifies constancy of production for the listed treatments and plants — it is not itself a test result, and covers reaction to fire only.
2023 · Source document
Environmental product declarations, silicate wood and surface protection
Third-partyGrade A- Issuer
- The International EPD® System; verified by Andrew Norton (Renuables)
- Standard
- ISO 14025 and EN 15804:2012+A2:2019
- Reported result
- Seven declarations covering wood protection (pigmented and unpigmented), surface protection, end-grain sealer and wash products, with GWP and other indicators reported per functional unit across modules A–C. Registered 2023-03-31, valid to 2028-03-30.
- What it does not establish
- An EPD quantifies environmental impact. It carries no information about durability, service life or reaction to fire.
2023 · Source document
Product data sheet — declared service life of a silicate fire-protection system
Manufacturer declarationGrade D- Issuer
- SiOO:X Wood Protection (manufacturer)
- Standard
- None cited for the service-life figure
- Reported result
- States a life span of up to 15 years on fine-sawn or micro-structured surfaces, subject to correct application, installation, maintenance and local weather.
- What it does not establish
- No test standard, field trial or exposure dataset is cited for the 15-year figure, so WoodIntel records it as a declared input and does not use it as a service-life prediction.
Version 2.2, 2024-12-10 · Source document
Decay testing of a silicate surface treatment after leaching
Third-partyGrade C- Issuer
- SP / RISE Research Institutes of Sweden
- Standard
- EN 113 after EN 84 leaching
- Reported result
- Mass loss of 9.9 % for Trametes versicolor, against the 3 % threshold the standard applies for an effective result. Other test fungi in the same series performed better.
- What it does not establish
- The reported result does not meet the threshold of the standard, so the category is graded Limited for decay. It is published here because a register that shows only favourable results is not an independent register.
SP/RISE test series · Source document
SBI testing of a silicate coating on timber without fire impregnation
Third-partyGrade C- Issuer
- RISE Research Institutes of Sweden
- Standard
- EN 13823 (SBI), classified to EN 13501-1
- Reported result
- Class D. The coating alone gives no measured improvement in reaction to fire over untreated timber.
- What it does not establish
- This is the counterpart to the B-s1,d0 classification above: the B class is a property of the fire-impregnated substrate plus coating, not of the coating. Any fire claim must state the impregnated substrate it was tested on.
RISE SBI reports · Source document
Termite exposure testing of silicate-treated timber
Third-partyGrade B- Issuer
- Intertek and Mississippi State University
- Standard
- AWPA E1 (laboratory choice test)
- Reported result
- Results differ between formulations and cannot be summarised as a single rating for the category.
- What it does not establish
- A North American laboratory method, not EN 117, and partial in scope. It does not support a European termite classification.
Test series · Source document
Open evidence gaps
Properties with no citable third-party report at time of review, in the order they would most change the picture if closed.
Priority 1
EN 16755 — durability of reaction to fire in exterior use
No public DRF classification for the coated build-ups above. Without it the fire class cannot be claimed for external exposure. This is the single most consequential gap in the register.
Priority 2
EN 113 re-test after EN 84 leaching
The published result reports 9.9 % mass loss for Trametes versicolor against a 3 % threshold. Until a re-test on a revised formulation is published, the decay rating stays Limited.
Priority 3
Full EN 117 termite report
Current evidence is AWPA E1, a North American laboratory method, and partial in scope. It does not support a European termite classification.
Priority 4
EN 927-3 natural exposure
Service-life figures quoted in years rest on manufacturer declarations with no field data. Either a natural-exposure trial is published, or the figure should be replaced with an inspection interval.
Intake queue
Documents WoodIntel is seeking for the categories with thin coverage, and the public register each is published in. This list exists so the current imbalance can be checked against a stated plan rather than read as a finding.
Modified wood
European Technical Assessments for acetylated and furfurylated solid wood
An ETA states the declared durability class and the assessment document it was measured against, which is what a grade A entry needs for modified wood.
Modified wood
EN 15804 environmental product declarations for modified timber
The silicate category already has verified EPDs in the register. Modified wood needs the same to make any environmental comparison legitimate.
Preservative impregnation
EN 252 field-stake results and EN 599-1 performance data for preservative systems
Preservatives carry the longest field record of any category, but the register currently cites none of it. Until it does, the High decay rating rests on the literature rather than on indexed documents.
Fire-retardant treatment
EN 16755 DRF EXT classifications for fire-retardant treated cladding
Reaction-to-fire classes do not survive weathering unless the durability of reaction to fire is classified separately. This gap applies to every coated or impregnated exterior build-up in the register, not only one supplier.
Film-forming coatings
EN 927-3 natural-exposure results for film-forming and penetrating systems
Accelerated EN 927-6 data is comparatively easy to obtain and already shapes the ratings. Natural exposure is what would let the maintenance intervals in the comparison table be stated as evidence rather than as convention.
Colour and appearance over time
Every exterior timber surface moves towards grey. The choice is whether that happens unevenly and unpredictably, or in a controlled way.
- Grey tones. Achieved either by letting the surface weather, or by specifying a pigmented system that pre-empts the shift so the elevation greys evenly.
- Brown tones. Available from pigmented oils, stains and silicate systems, and inherent in furfurylated and thermally modified wood.
- Black. Deep pigment loads absorb the most UV and typically hold colour longest, at the cost of higher surface temperatures and greater thermal movement.
Orientation dominates. South and west elevations in the same building can need twice the maintenance frequency of north and east.
Documents to request before specifying
- Decay: EN 113 result on leached samples (EN 84), stating the substrate species.
- Termites: EN 117 report, if the project sits in a termite region.
- Fire: EN 13501-1 classification for the exact build-up, and EN 16755 for exterior use.
- Weathering: EN 927-6 data, with the natural-exposure comparison if it exists.
- Service life: the basis for any figure quoted in years — field trial, model or warranty term. These are three very different things.
WoodIntel models service life from durability class, climate and exposure with explicit uncertainty; treatment effects are handled as a declared input, not an assumed benefit.