Termites and other wood-destroying insects are among the most common concerns surrounding timber construction. For this reason, the answer should go beyond the general statement that “the timber is treated.”

Structural timber selected for Smart-Timber™ undergoes industrial preservative treatment before it is incorporated into the building, in specialised European facilities and according to a defined treatment specification.

The treatment is supported by a Treatment Certificate, documenting information relating to the treated timber, the treatment specification, the stated Use Class and the applicable treatment standard. The Treatment Certificate reviewed for the timber documents a specific timber order, its treatment specification and its declared Use Class, with reference to BS 8417.

The accompanying technical documentation for the preservation system states that correctly treated timber is protected against wood-decaying fungi and wood-destroying insects.

Protection is therefore not simply a claim made by ÖKOHAUS GER, but a documented process that can be verified.

Temporary wetting should not be confused with biological deterioration.

The critical issue for structural timber is prolonged exposure to moisture conditions capable of supporting biological activity, particularly when combined with unsuitable design, detailing or material management.

Within Smart-Timber™, protection is approached before the timber is incorporated into the building. Material selection, industrial treatment and the construction system work together as part of the overall durability strategy.

The treatment documentation identifies the relevant Use Class, connecting the treatment specification with the intended exposure conditions.

The technical documentation for the preservation system also states that correctly treated timber is protected against wood-decaying fungi, while prolonged excessive surface moisture can still create conditions in which surface mould may develop.

This distinction is important. Moisture exposure does not automatically mean timber deterioration. Long-term durability depends on the relationship between the material, its treatment, its intended conditions of use and the way the complete building system manages moisture. For this reason, ÖKOHAUS GER combines controlled preparation, industrial treatment and appropriate construction design, so that protection begins before the timber reaches the construction site and continues through the way it is incorporated into the complete Smart-Timber™ system.

The designation C24 is not a marketing term used by ÖKOHAUS GER. It is a recognised structural timber strength class under EN 338.

The structural timber selected for Smart-Timber™ carries identification indicating its C24 classification and product information.

Its production is also supported by Factory Production Control documentation for strength-graded structural timber. The certificate reviewed refers to EN 14081 and grading that includes C24.

It is important to understand that structural strength classification and preservative treatment are two different technical requirements.

• C24: documents the structural strength class of the timber.
• Treatment Certificate: documents the specified preservative treatment.

Timber may possess the required structural strength class without that classification proving that it has received the required preservative treatment. Conversely, preservative treatment does not, by itself, demonstrate that the timber possesses the required strength class for its intended structural function.

For this reason, Smart-Timber™ treats both as distinct but complementary elements of the overall structural timber specification. A properly specified structural timber system must document both structural performance and biological protection.

For ÖKOHAUS GER, simply describing timber as “treated” is not sufficient technical information. What matters is whether the treatment can be documented: where and how it was carried out, to which specification, and for which intended conditions of use.

Industrial timber preservation is a technical process that should correspond to the intended use of the material and an appropriate treatment specification.

The timber selected for Smart-Timber™ is industrially treated in specialised European facilities and supported by corresponding technical documentation.

The Treatment Certificate reviewed identifies the treated timber, the preservation system, the declared Use Class and the treatment specification.

This approach is consistent with the broader principles of BS 8417, which provides recommendations for determining when preservative treatment is required and for specifying treatment according to factors including natural durability, treatability, Use Class and intended service conditions.

The key difference is between a general claim that timber is “treated” and a treatment process supported by technical documentation.

Wood preservatives belong to the field of biocidal products and are subject to a specific regulatory framework.

Within the European Union, biocidal products are governed by Regulation (EU) No 528/2012, the Biocidal Products Regulation (BPR).

The important point for homeowners is that the assessment should not be reduced to a broad claim that a preservative is simply “safe” or “unsafe.”

What matters is whether the relevant active substances, product use and treated article comply with the applicable regulatory requirements.

Article 58 of Regulation (EU) No 528/2012 specifically addresses treated articles. Among other requirements, it establishes conditions concerning the active substances used in treated articles placed on the market and, where applicable, their labelling.

The technical documentation reviewed for the preservation system also identifies the treated timber as a treated article under Article 58 of the BPR.

For ÖKOHAUS GER, the important principle is controlled industrial application in accordance with the technical specification, together with the ability to document that treatment, rather than using the commercial name of a preservative as a marketing argument. The responsible approach is to specify and document the treatment within the applicable technical and regulatory framework, rather than describing every preservative treatment with an unqualified claim of harmlessness.

The quality of a structural material should not depend solely on what a builder says about it.

The structural timber selected for Smart-Timber™ carries identification relating to its C24 classification and product details, while separate documentation supports production control and preservative treatment.

This creates three distinct levels of verification:

• Structural classification: C24 identification and corresponding structural timber documentation.
• Production control: Factory Production Control documentation for strength-graded structural timber.
• Preservative treatment: a Treatment Certificate documenting the industrial treatment.

These documents do not all prove the same thing, which is precisely why the distinction matters. C24 marking should not be presented as evidence of preservative treatment, and a Treatment Certificate should not be presented as proof of a particular structural strength class unless that class is independently established by the appropriate structural documentation.

A Smart-Timber™ homeowner can request the available marking and technical documents supporting the timber's classification, production and treatment. The essential question is not only what timber the builder says is used, but what the builder can document is actually used.

Long-term structural quality cannot be reduced to a single label or to the general phrase “treated timber.”

Two homes may both contain timber and still differ substantially in the structural class of that timber, production control, preservative treatment, documentation and the way the material is incorporated into the complete building system.

This is why Smart-Timber™ approaches structural timber as part of an integrated specification.

Structural classification, controlled production, documented industrial treatment, material verification and construction design work together within the overall Smart-Timber™ system.

The distinction is important because the performance of a building is determined by the complete system, not simply by the generic material category used for its frame.

For this reason, the essential question is not simply whether treated timber is used, but what timber is actually specified and what documentation is available regarding its strength class, production and protective treatment.