BRITISH STANDARD BS EN 460 1994 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 The European[.]
BRITISH STANDARD 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 The European Standard EN 460:1994 has the status of a British Standard UDC 674.03:620.193.8:620.193.91 BS EN 460:1994 BS EN 460:1994 Cooperating organizations The European Committee for Standardization (CEN), under whose supervision this European Standard was prepared, comprises the national standards organizations of the following countries: Austria Belgium Denmark Finland France Germany Greece Iceland Ireland Italy Luxembourg Netherlands Norway Portugal Spain Sweden Switzerland United Kingdom Oesterreichisches Normungsinstitut Institut belge de normalisation Dansk Standard Suomen Standardisoimisliito, r y Association franỗaise de normalisation Deutsches Institut für Normung e.V Hellenic Organization for Standardization Technological Institute of Iceland National Standards Authority of Ireland Ente Nazionale Italiano di Unificazione Inspection du Travail et des Mines Nederlands Normalisatie-instituut Norges Standardiseringsforbund Instituto Portugs da Qualidade Asociación Espola de Normalización y Certificación Standardiseringskommissionen i Sverige Association suisse de normalisation British Standards Institution This British Standard, having been prepared under the direction of the Technical Sector Board for Building and Civil Engineering, was published under the authority of the Standards Board and comes into effect on 15 August 1994 Amendments issued since publication © BSI 07-1999 Amd No The following BSI references relate to the work on this standard: Committee reference B/515 Draft for comment 91/51885 DC ISBN 580 22911 Date Comments BS EN 460:1994 Contents Cooperating organizations National foreword Foreword Text of EN 460 National annex NA (informative) Committees responsible National annex NB (informative) Cross-references © BSI 07-1999 Page Inside front cover ii Inside back cover Inside back cover i BS EN 460:1994 National foreword This British Standard has been prepared under the direction of the Technical Sector Board for Building and Civil Engineering and is the English language version of EN 460:1994 — 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, published by the European Committee for Standardization (CEN) EN 460 was produced as a result of international discussion in which the United Kingdom took an active part A British Standard does not purport to include all the necessary provisions of a contract Users of British Standards are responsible for their correct application Compliance with a British Standard does not of itself confer immunity from legal obligations Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, the EN title page, pages to 6, an inside back cover and a back cover This standard has been updated (see copyright date) and may have had amendments incorporated This will be indicated in the amendment table on the inside front cover ii © BSI 07-1999 EUROPEAN STANDARD EN 460 NORME EUROPÉENNE May 1994 EUROPÄISCHE NORM UDC 674.03:620.193.8:620.193.91 Descriptors: Wood, tests, durability, classifications, biodegradability, hazards, pest resistance 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 — Durabilité naturelle du bois massif — Guide d’exigences de durabilité du bois pour son utilisation selon les classes de risque Dauerhaftigkeit von Holz und Holzprodukten — Natürliche Dauerhaftigkeit von Vollholz — Leitfaden für die Anforderungen an die Dauerhaftigkeit von Holz für die Anwendung in den Gefährdungsklassen This European Standard was approved by CEN on 1994-05-18 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 Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member This European Standard exists 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 Central Secretariat has the same status as the official versions CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom CEN European Committee for Standardization Comité Européen de Normalisation Europäisches Komitee für Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels © 1994 Copyright reserved to CEN members Ref No EN 460:1994 E EN 460:1994 Foreword Contents This European Standard has been drawn up by WG “Natural durability” of Technical Committee CEN/TC 38, Durability of wood and wood-based products, with AFNOR as Secretariat This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by November 1994, and conflicting national standards shall be withdrawn at the latest by December 1996 This European Standard was adopted by CEN and in accordance with the Common CEN/CENELEC Rules, the following countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom Page Foreword Introduction Scope Normative references 3 Definition Hazard classes Durability classes Durability for use in the various hazard classes Annex A (informative) Important factors in the relationship between expected service life and natural durability Annex B (informative) Hazard classes and general service situations taken from Table of EN 335-1 Annex C (informative) Bibliography Table — Wood-destroying fungi — Guidance on the durability classes of wood species for use in hazard classes Table B.1 — General service situations and hazard classes given in EN 335-1 (extract of Table of EN 335-1) © BSI 07-1999 EN 460:1994 Introduction Definition Where wood-destroying organisms are likely to attack timber in service, either a timber of sufficient natural durability should be selected or the durability characteristics of the timber should be enhanced by preservative treatment Guidance on the various classification systems used to describe the natural durability of timber to attack by wood-destroying organisms is given in EN 350-1, and the system used to classify preservative-treated timber is given in EN 351-1 The need for specific durability characteristics for a timber will depend on its conditions of service (as defined by the class of biological hazard, see EN 335-1 and EN 335-2) For the purposes of this standard, the following definition applies 3.1 glued laminated timber structural member formed by bonding together timber laminations with the grain running essentially parallel Scope This European Standard gives guidance on the selection of wood species based on their natural durability to attack by wood-destroying organisms for use as solid wood or as glued laminated timber (glulam) in the hazard classes defined in EN 335-1 This standard does not consider the durability characteristics of the glue used in glued laminated timber Normative references This European Standard incorporates, by dated or undated reference, provisions from other publications These normative references are cited at the appropriate places in the text and the publications are listed hereafter For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in it by amendment or revision For undated references the latest edition of the publication referred to applies EN 335-1:1992, Durability of wood and wood-based products — Definitions of hazard classes of biological attack — Part 1: General EN 335-2:1992, Durability of wood and wood-based products — Definitions of hazard classes of biological attack — Part 2: Application to solid wood EN 350-2:1994, Durability of wood and wood-based products — Natural durability of solid wood — Part 2: Guide to natural durability and treatability of selected wood species of importance in Europe © BSI 07-1999 Hazard classes The service situations in which wood is susceptible to biological attack have been divided into five hazard classes which are defined in EN 335-1 (see Table B.1) Guidance on the application of these hazard classes to solid wood is given in EN 335-2 Durability classes Classification systems for the natural durability of solid wood based on resistance to attack by various wood-destroying organisms are given in EN 350-1 Durability for use in the various hazard classes 6.1 General The natural durability of a wood species should be considered separately for each wood-destroying organism In practice supplies of sawn timber may include sapwood as well as heartwood 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 In addition to the natural durability, there are other factors that influence performance which should also be taken into consideration in the selection of a wood species and the decision whether or not it should be treated with a preservative EN 460:1994 For example wood with low permeability may acquire lower moisture contents under intermittent wetting conditions, compared to more permeable species, and will therefore have a reduced risk of fungal attack under such service conditions An indication of propensity to take up moisture may be obtained from the treatability classification of different wood species (see EN 350-2) Hence timbers having a particular natural durability classification for wood-destroying fungi and with a treatability classification of or may achieve an increased service life in out of ground contact conditions (hazard class or hazard class 3) compared to wood of similar durability classification but with a treatability classification of or Information on some further factors is given in Annex A 6.2 Natural durability to wood-destroying fungi Guidance on the use of a wood species in the various hazard classes depending upon their degree of natural durability is given in Table If the natural durability is inadequate, preservative treatment should be considered Table — Wood-destroying fungi — Guidance on the durability classes of wood species for use in hazard classes Hazard class Durability class o o o o o o o o (o) (o) o o (o) (o) — (x) (o) — (x) o (o) (x) x x o (x) (x) x x 6.3 Natural durability to wood-destroying beetles Wood-destroying beetles are present throughout the European area, but the risk of attack varies greatly from high to insignificant Reference should be made to local or regional expertise for advice on the risk of attack by wood-destroying beetles In situations where there is a significant risk of attack which would result in an unacceptable loss of strength or visual degradation, wood species classified as susceptible in EN 350-2 should be treated with a preservative 6.4 Natural durability to termites In situations where there is a significant risk of termite attack only the heartwood of wood species which is classified in EN 350-2 as “durable” (D) or “moderately durable” (M) to termites may be used untreated The choice between “durable” (D) and “moderately durable” (M) wood depends upon the specific requirements, for example for function, end use, expected service life, and the significance of failure 6.5 Natural durability to marine organisms In situations where there is a significant risk of attack by marine organisms, only the heartwood of wood species which is classified in EN 350-2 as “durable” (D) or “moderately durable” (M) to marine organisms may be used untreated The choice between “durable” (D) and “moderately durable” (M) wood depends upon the specific requirements, for example for function, end use, expected service life, and the significance of failure Key o natural durability sufficient (o) natural durability is normally sufficient, but for certain end uses treatment may be advisable (see Annex A) (o) — (x) natural durability may be sufficient, but depending on the wood species, its permeability (see 6.1), and end use (see Annex A), preservative treatment may be necessary (x) preservative treatment is normally advisable, but for certain end uses natural durability may be sufficient (see Annex A) x preservative treatment necessary NOTE Sapwood of all wood species should be regarded as durability class © BSI 07-1999 EN 460:1994 Annex A (informative) Important factors in the relationship between expected service life and natural durability A.1 Service life The service life of a timber component will depend upon many factors, not just durability classification against wood-destroying organisms For instance, in hazard class the design details of a timber component, which prevent water penetration and collection and encourage drainage and ventilation, together with local climatic conditions and maintenance procedures, may have an influence on long-term performance Similarly, in hazard class climatic conditions can have a marked effect on performance Therefore, it is not appropriate to base an expected service life solely upon the durability classification For most constructional uses there is a generally accepted minimum level of natural durability, which in conjunction with the other factors gives a service life considered reasonable for a given component The selection of a wood with a higher durability classification than that recommended in this standard may be expected to provide an increased service life for a given end-use If constructional components are required to have only a short service life (temporary or semi permanent) or if extreme longevity is necessary, it may be appropriate to use wood species with lower or higher durability classifications than those given in Table An estimate of expected service life may be obtained by comparing the durability of the wood which is proposed for use with the known durability and service life of other well known wood species that have been used in the same location and for constructions with similar design and maintenance details Where fungal attack occurs on lateral surfaces, the service life of a timber component can be expected to increase in proportion to its thickness For example, a stake of cross-section 50 mm × 50 mm, embedded in the ground can be expected to have a service life approximately twice that of a stake of the same durability classification, but only 25 mm × 50 mm in cross-section However, in regions such as parts of central and southern Europe, which experience long, dry periods, it has been found that timber components having a relatively small cross-section in ground contact are likely to have a higher service life expectancy than similar components of larger cross-section due to their ability to dry rapidly This is true for similar reasons for fencing panels and exterior cladding © BSI 07-1999 Biological attack is often progressive, and the service life will therefore also depend upon the amount of deterioration that can be tolerated before the item fails A.2 Further factors influencing selection of durability class The selection of a wood species for use in a particular hazard class will require consideration of a range of factors, which may influence the level of durability deemed necessary Diminishing of the mechanical characteristics of a wooden component would compromise safety and economic requirements, a timber of a greater durability than that normally used may be specified This may be appropriate where: — the components to be used are load-bearing; — the components are difficult to replace or repair; — there is a need for extended service life; — the position of the building element presents a particular risk (for example a horizontal surface which is poorly drained); — there is a local, exceptional risk of attack by particular organisms (for example marine borers, termites); — the exposure to climatic conditions is severe (for example driving rain) The risk of weakening the mechanical characteristics may be diminished by structural protection of the building element, for example the overlaying of upper surfaces with more durable materials, or the protection of end grain EN 460:1994 Annex B (informative) Hazard classes and general service situations taken from Table of EN 335-1 Table B.1 gives an indication of the service situations associated with the hazard classes which are defined in EN 335-1 It is strongly recommended that EN 335-1 and EN 335-2 are studied to fully understand these service situations Table B.1 — General service situations and hazard classes given in EN 335-1 (extract of Table of EN 335-1) Hazard classes Above ground, covered (dry) Above ground, covered (risk of wetting) Above ground, not covered In contact with ground or fresh water In salt water EN 350-1:1994, Durability of wood and wood-based products — Natural durability of solid wood — Part 1: Guide to the principles of testing and classification of the natural durability of wood EN 351-1, Durability of wood and wood-based products — Preservative-treated solid wood — Part 1: Classification of preservative penetration and retention1) General service situations 1) Annex C (informative) Bibliography In course of preparation © BSI 07-1999 BS EN 460:1994 National annex NA (informative) Committees responsible The United Kingdom participation in the preparation of this European Standard was entrusted by the Technical Sector Board for Building and Civil Engineering (B/-) to Technical Committee B/515, upon which the following bodies were represented: British Telecommunications plc British Wood Preserving and Damp-proofing Association Chemical Industries’ Association Creosote Council Department of the Environment (Building Research Establishment) Electricity Industry in United Kingdom Institute of Wood Science Timber Research and Development Association Timber Trade Federation Wood Panel Products Federation National annex NB (informative) Cross-references Publication referred to Corresponding British Standard BS EN 335 Hazard classes of wood and wood-based products against biological attack EN 335-1:1992 Part 1:1992 Classification of hazard classes EN 335-2:1992 Part 2:1992 Guide to the application of hazard classes to solid wood BS EN 350 Durability of wood and wood-based products — Natural durability of solid wood EN 350-1:1994a Part 1:1994 Guide to the principles of testing and classification of the natural durability of wooda EN 350-2:1994a Part 2:1994 Guide to natural durability and treatability of selected wood species of importance in Europe BS EN 351 Durability of wood and wood-based products — Preservative-treated solid wooda EN 351-1:199Xa Part 1:199X Classification of preservative penetration and retentiona a In preparation © BSI 07-1999 BS EN 460:1994 BSI — British Standards Institution BSI is the independent national body responsible for preparing British Standards It presents the UK view on standards in Europe and at the international level It is incorporated by Royal Charter Revisions British Standards are updated by amendment or revision Users of British Standards should 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