kSIST FprEN 460:2022

Durability of wood and wood-based products - Guidance on performance

This document gives guidance on the selection of wood of wood and wood based products for use in situations where they may be subject to degradation by fungi or wood destroying insects. This guidance includes information on factors that can influence the service life of a wood or wood-based product when considering biological degradation. This document is a step toward the evaluation of the service life of a wood product.
This document does not consider:
1)   the durability characteristics of the glue used in wood-based products;
2)   the aesthetic function of wood products (discoloration, surface weathering, mould).

Dauerhaftigkeit von Holz und Holzprodukten - Leitfaden zur Bestimmung der Leistungsfähigkeit

Dieses Dokument gibt eine Anleitung zur Auswahl von Holz und Holzprodukten zur Verwendung unter Bedingungen, in denen sie der Zerstörung durch Pilze oder Holz zerstörende Insekten ausgesetzt sein können. Diese Leitlinien enthalten Informationen über Faktoren, die die Gebrauchsdauer eines Holzes oder Holzproduktes unter Berücksichtigung des biologischen Abbaus beeinflussen können. Dieses Dokument ist ein Ansatz zur Bewertung der Gebrauchsdauer eines Holzprodukts.
Dieses Dokument berücksichtigt nicht:
1)   die Dauerhaftigkeit des Klebstoffs, der in Holzprodukten verwendet wurde;
2)   die ästhetische Funktion von Holzprodukten (Verfärbung, Oberflächenverwitterung, Schimmel).

Durabilité du bois et des matériaux à base de bois - Guide pour déterminer la performance

Le présent document fournit des recommandations relatives à la sélection de bois et de matériaux dérivés du bois pour une utilisation dans des situations où ils peuvent être soumis à une dégradation par des champignons ou des insectes xylophages. Ces recommandations incluent des informations sur les facteurs susceptibles d'influer sur la durée de service d'un bois ou d'un matériau à base de bois, compte tenu de la dégradation biologique. Le présent document constitue un progrès vers l'évaluation de la durée de service des éléments en bois.
Le présent document ne traite pas :
1)   des caractéristiques de durabilité de la colle utilisée avec les matériaux à base de bois ;
2)   de la fonction esthétique des éléments en bois (décoloration, vieillissement d’aspect de la surface, moisissure).

Trajnost lesa in lesnih proizvodov - Navodilo za učinkovitost

General Information

• Status: Not Published
• Public Enquiry End Date: 27-Feb-2022
• ICS: 79.040 - Wood, sawlogs and sawn timber
• Technical Committee: LLZ - Les, lesni izdelki in zaščita lesa
• Current Stage: 5020 - Formal vote (FV) (Adopted Project)
• Start Date: 04-Nov-2022
• Due Date: 23-Dec-2022
• Directive: 305/2011 - Regulation (eu) No 305/2011 of the European Parliament and of the Council of 9 march 2011 laying down harmonised conditions for the marketing of construction products and repealing council directive 89/106/eec
• Mandate: M/112 - Mandate to CEN/CENELEC concerning the execution of standardization work for harmonized standards on structural timber products
• Ref Project: FprEN 460 - Durability of wood and wood-based products - Guidance on performance

RELATIONS

• Revised: SIST EN 460:1995 - Durability of wood and wood-based products - Natural durability of solid wood - Guide to the durability requirements for wood to be used in hazard classes
• Effective Date: 14-Oct-2020

Standards Content (sample)

SLOVENSKI STANDARD
oSIST prEN 460:2022
01-februar-2022
Trajnost lesa in lesnih izdelkov - Naravna trajnost masivnega lesa - Zahteve po
trajnosti lesa, ki se uporablja v posameznih razredih ogroženosti

Durability of wood and wood-based products - Natural durability of solid wood - Guide to

the durability requirements for wood to be used in hazard classes

Dauerhaftigkeit von Holz und Holzprodukten - Natürliche Dauerhaftigkeit von Vollholz -

Leitfaden für die Anforderungen an die Dauerhaftigkeit von Holz für die Anwendung in

den Gefährdungsklassen

Durabilité du bois et des matériaux dérivés du bois - Durabilité naturelle du bois massif -

Guide d'exigences de durabilité du bois pour son utilisation selon les classes de risque

Ta slovenski standard je istoveten z: prEN 460
ICS:
79.040 Les, hlodovina in žagan les Wood, sawlogs and sawn
timber
oSIST prEN 460:2022 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN 460:2022
DRAFT
EUROPEAN STANDARD
prEN 460
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2021
ICS 79.040 Will supersede EN 460:1994
English Version
Durability of wood and wood-based products - Natural
durability of solid wood - Guide to the durability
requirements for wood to be used in hazard classes

Durabilité du bois et des matériaux dérivés du bois - Dauerhaftigkeit von Holz und Holzprodukten -

Durabilité naturelle du bois massif - Guide d'exigences Natürliche Dauerhaftigkeit von Vollholz - Leitfaden für

de durabilité du bois pour son utilisation selon les die Anforderungen an die Dauerhaftigkeit von Holz für

classes de risque die Anwendung in den Gefährdungsklassen

This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee

CEN/TC 38.

If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations

which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other

language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC

Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,

Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are

aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without

notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 460:2021 E

worldwide for CEN national Members.
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Contents Page

European foreword ....................................................................................................................................................... 3

Introduction .................................................................................................................................................................... 4

1 Scope .................................................................................................................................................................... 5

2 Normative references .................................................................................................................................... 5

3 Terms and definitions ................................................................................................................................... 5

4 Performance ..................................................................................................................................................... 7

4.1 General ................................................................................................................................................................ 7

4.2 Exposure ............................................................................................................................................................. 8

4.2.1 Climate ................................................................................................................................................................ 8

4.2.2 Use class .............................................................................................................................................................. 9

4.2.3 Design .................................................................................................................................................................. 9

4.2.4 Quality of site work ........................................................................................................................................ 9

4.2.5 Maintenance ...................................................................................................................................................... 9

4.2.6 Usage ................................................................................................................................................................. 10

4.3 Service life ....................................................................................................................................................... 10

4.3.1 Limite state ..................................................................................................................................................... 11

4.4 Consequence of failure ............................................................................................................................... 11

4.5 Materials .......................................................................................................................................................... 11

4.5.1 Natural durability ........................................................................................................................................ 11

4.5.2 Conferred durability ................................................................................................................................... 11

4.5.3 Guidelines ....................................................................................................................................................... 12

5 Requirements on biological durability in different end use conditions .................................. 12

5.1 General ............................................................................................................................................................. 12

5.2 Durability against wood-destroying fungi .......................................................................................... 13

5.3 Durability against beetles ......................................................................................................................... 13

5.4 Durability against termites ...................................................................................................................... 13

5.5 Durability against marine borers ........................................................................................................... 13

5.6 Durability against combined biological hazards .............................................................................. 13

Annex A (informative) Consequence of Failure (COF) ................................................................................... 14

Annex B (informative) Example of durability classes of wood species in use class ............................ 16

Annex C (informative) Important factors in the relationship between expected service life

and biological durability ........................................................................................................................... 18

Bibliography ................................................................................................................................................................. 21

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European foreword

This document (prEN 460:2021) has been prepared by Technical Committee CEN/TC 38 “Durability of

wood and wood-based products”, the secretariat of which is held by AFNOR.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 460:1994.

The main technical changes compared to the previous edition EN 460:1994 are the introduction of a

decision process for performance specification of wood and wood-based products based on (i) materials

and exposure, (ii) presentation of design life and (iii) articulation of consequence of failure.

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Introduction

There is increasing need to understand the service life of wood products, especially in construction.

Service life in the Construction Products Regulation: Regulation (EU) N°305/2011 (CPR) can be

understood as performance within an economically acceptable period, under typical exposure and

maintenance scenarios.

This document is concerned with the service life of wood products, especially in construction. The

purpose of this document is to provide information that will help to guide the user to select an

appropriate wood or wood-based material based on information about the end use environment and the

target service life.

In many end uses, design, workmanship and maintenance will significantly influence the service life of

the wood or wood based product.

The standard EN 350 is focused on the classification of durability of heartwood of different wood species.

In practice, wood-based building products will also contain sapwood and often different treatments, like

coatings, wood modification or wood preservation.
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1 Scope

This document gives guidance on the selection of wood of wood and wood based products for use in

situations where they may be subject to degradation by fungi or wood destroying insects. This guidance

includes information on factors that can influence the service life of a wood or wood-based product when

considering biological degradation. This document is a step toward the evaluation of the service life of a

wood product.
This document does not consider:
1) the durability characteristics of the glue used in wood-based products;

2) the aesthetic function of wood products (discoloration, surface weathering, mould).

2 Normative references
There are no normative references in this document.
3 Terms and definitions

For the purposes of this document, the terms and definitions given in EN 1001-2 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— IEC Electropedia: available at https://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
3.1
coating

surface treatment intended to provide a physical protection of the wood surface normally applied in

liquid form
3.2
component

product manufactured as a distinct unit to serve a specific function or functions

3.3
conferred durability

improved resistance of a wood species to biological degradants provided by a treatment process

(chemical, physical, etc.) such as wood preservation or wood modification
3.4
consequence of failure (COF)

the significance of the product failure in service. The outcome of a failure can be expressed in terms of

safety to personnel, economic loss, and/or damage to the environment
[SOURCE: EN 60300-3-11:2009, 3.1.23]
3.5
critical biological hazard

biological hazard or hazards that are most significant for the end use application and its geographical

location
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3.6
likelihood of failure
probability that a wood component will reach its limit state at a given time
3.7
limit state
point where a product is deemed to have failed

Note 1 to entry: The limit state is commonly reached before loss of function is complete.

3.8
material resistance

inherent ability of a material to endure a specific biological hazard through a combination of natural

and/or conferred durability and moisture dynamic behaviour relevant for the different biological agents

3.9
moisture dynamics

physical characteristic of a wood material or wood product to respond to changing environmental

conditions and take up and release moisture (vapour or liquid)
3.10
natural durability
inherent resistance of wood to attack by wood-destroying organisms
3.11
overlay

one or more sheets or films, for example impregnated paper, plastics, resin film, metal that protect a wood

surface
3.12
performance

ability of a wood species or a wood-based material to withstand deterioration over time and fulfil

essential function
3.13
permeability to water

ease with which water penetrates a wood-based matrix (wood of a particular species, wood-based

material)

Note 1 to entry: The permeability to water of a wood species or a wood-based material can be tested using the

method described in CEN/TS 16818.
3.14
service life

period of time after installation during which a building, structure or component parts meet or exceed

the performance requirements
3.15
wood modification

non-biocidal process of a chemical, biological, or physical alteration of the cell wall substance of wood,

resulting in a permanent desired property enhancement to primarily enhance biological durability and

dimensional stability
Note 1 to entry: Examples are thermal or chemical modification.
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3.16
wood preservative treatment
treatment to improve the resistance of wood to biodeterioration

Note 1 to entry: Application of wood preservative products in liquid form for the preventive treatment of wood

resulting in a desired permanent improvement of their properties in order to protect them from degradation by

wood destroying fungi, xylophagous insects (termites and beetles) or marine borers.

Note 2 to entry: The usual processes are surface treatment (soaking or spraying) or penetrating treatment

(double vacuum autoclave or vacuum autoclave and pressure).
4 Performance

When wood-destroying organisms are likely to degrade wood in service, a suitable approach for meeting

service life needs to be selected. There are principally two approaches:

1) by design - minimizing the moisture risk the wooden component is exposed to or by denying the

access for organisms through construction measures;

2) by durability - either select a wood species of sufficient natural durability or ensure sufficient

conferred durability by treatment with a wood preservative, wood modification or non-biocidal

treatment to manage the challenge presented in the use environment.
Typically it is a combination of both.
4.1 General

A schematic diagram to illustrate the performance of a wood product is shown in Figure 1. The features

defining the exposure of a material or product are multifacteted. An exposure when compared with the

service life required for the product is the framework for identifiying suitable wood and wood based

materials to meet these requirements.
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Figure 1 — Schematic illustration of a decision process for performance specification linked to

clauses in this document

This document provides information to aid the user in the choice of a wood or wood-based material for

a product, knowing its use class end use environment and the target service life. No attempt has been

made to quantify the service life that could be expected from a particular combination. This is reflected

in national interpretation documents.
4.2 Exposure

The exposure is the challenge presented to the wood material or product and comprises many features.

Building guidelines and conventionally accepted performance (4.5.3), which should be respected in the

design, often minimize the risk of a wood-destroying organism degrading wood in service. This can lead

to lower requirements concerning durability to cover the residual risk.

The performance of each component will deteriorate at a rate depending on climate, use class, design,

quality of site work, maintenance and useage.
4.2.1 Climate

The environment and particularly the moisture availability from local climate, temperature and

proximity to sea all impact on the rate of deterioration of a wood material and components. Climate data

are utilized in service prediction tools.
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4.2.2 Use class

The service situations in which wood is susceptible to biological degradation have been divided into five

use classes which are defined in EN 335. Guidance on the application of these use classes to solid wood is

given in EN 335. (See ISO 15686-8:2008, Annex A, A.1.5 Factor D – Factor category – indoor environment

and A.1.6 Factor E — Factor category: outdoor environment).
4.2.3 Design

The design detailing and workmanship of the wood material in a product has a significant impact on the

performance of the product. Poor design features that enable water trapping increase exposure and can

accelerate degradation whilst good design that excludes moisture ingress can reduce exposure and avoid

degradation. National guidelines for product categories should be referred to for best practice design

features. (See ISO 15686-8:2008, Annex A, A.1.3 Factor B — Factor category: design level).

Enhancing performance by design means taking planning, constructive, building physics and

organizational measures which prevent or limit a reduction in the functionality of wood and wood-based

materials, especially by fungi, insects or marine animals during their service life, and also prevent damage

from excessive swelling and shrinkage of the wood and wood-based materials.

Some of these measures are enshrined in national building guidelines. Others restrict or limit access of

humidity, insects or marine animals to wood and wood-based materials e.g. by covering or coating,

calculations or simulations of moisture subject to climate conditions, protection against undesirable

changes in the moisture content of the materials during storage, transport, assembly and installation.

In many cases the desired performance of any measures adopted, can only be ensured if the measures

and the wooden component is maintained to an appropriate level (4.2.5).
4.2.4 Quality of site work

The activity of installing a wood product into service is known to have an impact on performance and

national best practice construction site guidance is available. (See ISO 15686-8:2008, Annex A, A.1.4

Factor C — Factor category: work execution level).
4.2.5 Maintenance

Maintenance is the combination of technical, administrative and organizational measures during the life

cycle of an object, which serve to maintain or restore its functional condition so that it can fulfil the

required function.

Basic measures of maintenance are regular servicing (e.g. cleaning of surfaces and gutters), inspection,

repair and improvement (EN 13306). A typical maintenance schedule, depending on the exposure and

the actual component, could be:
— servicing and cleaning every half to one year;
— inspection by the user or owner when servicing and cleaning;
— professional inspection after 2-5 years in service and then annually;

— repair following inspection, e.g. for an exteriror wood coating this might be a 5 year redecoration

cycle;
— improvement whenever necessary.
In many end uses, maintenance can significantly extend service life.

Regular inspection of wooden components can lead to the early detection of any detrimental changes,

damage or consequential damage. The earlier changes or damage are detected, the lower the effort

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required to repair consequential damage and the lower the cost of repairs or other conservation

measures.

Servicing includes maintaining the functionality of system parts, built-in parts and components, such as

coatings, drainage devices, ventilation, covers, enclosures, etc.. Servicing also includes the removal of dirt

deposits, growth of plants, moss and algae that may cause detrimental wetting of the wooden component.

Products in exterior use that are coated require coatings to be maintained to continue to provide a

protective effect to the wood material used in the product. The coating reduces the exposure of the wood

material and delays or avoids degradation. Poorly maintained coatings can exacerbate moisture risk

through water trapping. (See ISO 15686-8:2008, Annex A, A.1.8 Factor G — Factor category: maintenance

level).
4.2.6 Usage

The operation of the building or asset can impact on performance (e.g. high traffic areas get worn more

readily). (See ISO 15686-8:2008, Annex A, A.1.7 Factor F — Factor category: usage conditions).

4.3 Service life

Service life may be derived from national guidance, where specific features of national wood use, direct

experience and expectations are considered. Indications of years for short, medium and long service life

from published sources are given in Table 1. Regional or national guidance should be developed to

support this framework to take into account any regional or national features of material use, design and

experience that impact on service life uses of wood products. In Table 2, the suggested minimum design

service lives for building products are presented (ISO 15686-1).

Table 1 — Service life indications in years from national documents and other standards

Short Medium Long
EN 1990 <15 30 >50
BS 8417 15 30 60
DIN 68800-1 <10 <30 >30
FD P 20-651 <10 10-50 >50

Table 2 — Suggested minimum design lives for components (DLC) extract from ISO 15686-1

Design life of Inaccessible or Components where Major replaceable
building structural replacement is components
components expensive or difficult
Unlimited Unlimited 100 40
150 150 100 40
100 100 100 40
60 60 60 40
25 25 25 25
15 15 15 15
10 10 10 10
NOTE 1 Easily-replaced components may have design life of 3 to 6 years.

NOTE 2 An unlimited design life should rarely be used, as it significantly reduces design options.

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4.3.1 Limite state

An important aspect of service life is when the product has reached the limit state; its end of life. This can

be different for different products and tolerances vary amongst building and product owners.

4.4 Consequence of failure

Consequence of failure (COF) is an important element when considering service life of components.

Where there exists a high COF in service, for example where diminishing of the mechanical characteristics

of a wooden component would compromise safety and/or economic requirements, a timber of a greater

durability than normally indicated should be specified. This may be appropriate where:

— the components to be used are load-bearing;
— the components are difficult to replace or repair.

COF increases the factor of safety in critical timber assemblies in buildings and other structures of an

essential nature.

Although different components can fall into the same use class, the consequence of failure can be

different, and this should be considered in accordance with a recognized framework. An example is

presented in Annex A.
4.5 Materials

The exposure can be minimized by measures applied in the final product such as best practice design.

This can significantly enhance performance of the final wood product (4.2.3).

Alongside the exposure the performance of each component will deteriorate at a rate depending on

material properties and the interface with other materials. (See ISO 15686-8:2008, Annex A, A.1.2 Factor

A — Factor category: inherent performance level). For wood and wood-based materials the following are

relevant.
4.5.1 Natural durability

The classification for the durability of solid wood and wood-based materials to degradation by various

wood-destroying organisms are given in EN 350. For wood species, durability class refers only to

heartwood and sapwood is always regarded as not durable. If a range of durability classes is given in

EN 350 against the relevant organisms, the lowest durability class should be selected.

If the proportion of sapwood present is such that its loss would have adverse implications for the

performance of the component, or if the sapwood and heartwood cannot be distinguished, the durability

of the whole component should be regarded as equivalent to that of the sapwood.
4.5.2 Conferred durability

In some cases, the natural durability of a chosen wood species will be sufficient to meet service life

expectations. If the natural durability of the chosen species is inadequate, a means to enhance durability,

e.g. impregnation with wood preservatives, or a wood modification process must be considered. It is

essential for wood containing sapwood that it is treated to an extent that is appropriate for the critical

biological hazard or hazards present.

When specifying wood or wood-based material, a short service life should not require over specification

of durability or preservative treatment, a fit for purpose decision making principle should be in place. In

addition, a long service life in more challenging use classes maybe beyond what can be confidently

obtained by natural durability or conferred durability. Consideration should be given to protection by

design to exclude moisture (including, where valid, use of coatings) to meet service life.

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4.5.2.1 Wood preservation

The specification of wood preservatives is based on EN 351-1 and EN 599-1 with additional information

on treatability in EN 350. This document gives guidance on where preservative treatment, wood

modification or enhancing performance by design may be necessary.
4.5.2.2 Wood modifications

This specification of wood modification technologies is based on EN 350 and complemented by moisture

dynamics as part of material resistance. The use of natural durability and conferred durability using wood

modification links use classes to durability classes, based on a fit for purpose approach and taking into

account the variability of durability class rating. The approach should limit reliance on very durable wood

species in situations where it is not necessary, eg UC 1 and 2.
4.5.3 Guidelines

Material that conforms to regionally accepted performance guidelines (national or European standards)

or according to conventionally accepted performance (craftsmen guidelines) is another route to selecting

an appropriate material.
5 Requirements on biological durability in different end use conditions
5.1 General

The ability of wood or a wood-based material to achieve a particular service life will depend, in part, on

the durability of that material. Durability against the following should be taken into consideration: fungi,

termites, wood-boring beetles and marine borers. The durability to each of these biological agents should

be considered separately.

For each product application, the performance against biological agents needs to be considered, and the

critical biological hazard should be identified. Table 3 indicates the critical biological hazard in each use

class and shows the importance of basidiomycetes fungi.
Table 3 — Critical biological hazards for each use class
Basidiomycetes Soft rot a Beetles Marine
Termites
borers
UC1 - - X X -
UC2 X - X X -
UC3 X - X b -
UC4 X X X - -
UC5 c c - - X
X X
Specific regions of Europe only.
Lower impact of insects in outdoor environment.
Above waterline section only.

The following sections consider the biological hazards which, on consideration of the region and use class,

may represent the critical biological hazard.
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5.2 Durability against wood-destroying fungi

The requirement for durability of a wooden component depends on many factors, particularly use class,

the macro- and micro-climate where the component is used and/or by design detailing that can reduce

moisture levels to those unfavourable to decay fungi. A national or regional climate that results in lower

or higher risk of decay can result
...