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EN 335-2-2006 | Wood | Lumber
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Wolman_AG
Trends in World Population and Use of Wood
ICS 71.100.50
Supersedes EN 335-2:1992
Durability of wood and wood-based products - Definition of use classes - Part 2: Application to solid wood
Durabilit du bois et des produits drivs du bois Dfinition des classes d'emploi - Partie 2 : Application au bois massif Dauerhaftigkeit von Holz und Holzprodukten - Definition der Gebrauchsklassen - Teil 2: Anwendung bei Vollholz
Ref. No. EN 335-2:2006: E
EN 335-2:2006 (E)
Foreword......................................................................................................................................................................3 Introduction .................................................................................................................................................................4 1 2 3 4 4.1 4.2 4.3 4.4 4.5 4.6 Annex A.1 A.2 A.3 A.4 Scope ..............................................................................................................................................................5 Terms and definitions ...................................................................................................................................5 Use classes: application to solid wood.......................................................................................................6 Use class 1 .....................................................................................................................................................6 Use class 2 .....................................................................................................................................................6 Use class 3 .....................................................................................................................................................6 Use class 4 .....................................................................................................................................................6 Use class 5 .....................................................................................................................................................6 Summary of use classes for solid wood .....................................................................................................7 A (informative) Guide for the application to solid wood in relation to durability ...................................8 Introduction ....................................................................................................................................................8 General decision making ..............................................................................................................................8 General precautions ....................................................................................................................................12 Natural or conferred durability of solid wood...........................................................................................12
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Normative references ....................................................................................................................................5
Bibliography ..............................................................................................................................................................13
This document (EN 335-2:2006) has been prepared by Technical Committee CEN/TC 38 Durability of wood and derived materials, the secretariat of which is held by AFNOR. 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 February 2007, and conflicting national standards shall be withdrawn at the latest by February 2007. This document supersedes EN 335-2:1992. EN 335 is divided into three parts, Part 1 gives general definitions of use classes in different service situations, Part 2 concerns their application to solid wood and Part 3 concerns their application to wood-based panels The revision of EN 335-2 is in accordance with ISO 21887 (under preparation).
NOTE Attention of users is drawn to the need to avoid misinterpretation of any numbering system using classes for timber which cannot correspond exactly to the European use classes defined in this part of EN 335.
The classes described in this part of EN 335 are based on an existing classification agreed by the European Homologation Committee (EHC) in 1981 and published in the EHC reference document in 1984. Proposals for altering the five classes of EHC classification have been considered, particularly the possibility of harmonisation with other classes used outside Europe. It has, however, been judged that five classes are the most appropriate solution to European conditions. The possibility of harmonisation between the three moisture categories of Eurocode 5 (EN 1995-1-1) and the five classes of all parts of EN 335 has been carefully studied. The latter have been adjusted as far as possible. Nevertheless, it is important to note that the two systems use different criteria to achieve different ends. Any user may utilise the appropriate part of EN 335 to identify the "use class" of a given service environment and geographical location. Table 1 will assist in determining the biological agents that can attack timber in that situation. The user can then consider the type and duration of performance required, select an appropriate level of durability and ensure that the timber or wood-based product specified has that durability either, as a natural (see EN 350-2) or an acquired characteristic as the result of appropriate preservative treatment (see EN 351-1). NOTE At the moment EN 350-2 gives information with regard only to solid wood. EN 351-1 considers only the performance of preservative-treated solid wood.
This part of EN 335 offers guidance on the application to solid wood of the use classes, as defined in Part 1 of EN 335, in relation to the biological agents that can attack solid wood and solid wood panels.
NOTE Due to their specific behaviour against biological agents, solid wood panels are considered in this part of EN 335, as solid wood.
This Part shall be used in conjunction with Part 1 of EN 335. Annex A gives information and guidance for the user to determine the appropriate use class and to select a suitable level of durability (either natural or conferred by preservative treatment). It does not give guidance on protective measures other than preservative treatment.
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. None applicable.
For the purposes of this European Standard, the following terms and definitions apply. 3.1 protected subject to design and construction measures intended to prevent excessive exposure to the direct effects of the weather 3.2 solid wood wood, sawn or otherwise machined which may include finger jointed and/or laminated wood
NOTE Adapted from EN 1001-2:2005, 1.39
3.3 solid wood panel wood-based panel consisting of pieces of timber glued together at their edges and, if multi-layer, on their faces [EN 12775:2001, 4.1]
Use classes: application to solid wood
In this environment the moisture content of solid wood is such that the risk of attack by surface moulds or by staining or wood-destroying fungi is insignificant (that is the wood shall have a moisture content of maximum 20 %1) in any part for practically the whole of its service life). However, attack by wood-boring insects, including termites, is possible although the frequency and importance of the insect risk depends on the 2) geographical region .
In this environment the moisture content of solid wood occasionally exceeds 20 %, either in the whole or only in part of the component and thus allows attack by wood-destroying fungi.
NOTE For timbers whose use includes a decorative function, disfigurement can also occur as a result of the growth of surface moulds and staining fungi.
Risk of insect attack is similar to that for use class 12).
In this environment solid wood can be expected to have a moisture content above 20 % frequently, and thus it will often be liable to attack by wood-destroying fungi.
Risk of insect attack is similar to that for use class 1 .
In this environment solid wood has a moisture content in excess of 20 % permanently and is liable to attack by wood-destroying fungi.
NOTE Termites may be an additional problem in certain geographical regions. Additionally, the above-ground (or 2) above-water) portion of certain components, for example fence posts, may be attacked by wood-boring beetles .
In this environment solid wood has a moisture content in excess of 20 % permanently. Attack by invertebrate marine organisms is the principal problem, particularly in the warmer waters where organisms such as Limnoria spp., Teredo spp. and Pholads can cause significant damage.
NOTE The above water portion of certain components, for example harbour piles, can be exposed to wood-boring 2) insects, including termites .
1) Determined according to ISO 3130. 2) Beetles are present throughout Europe (including overseas regions of European countries), but the risk of attack varies greatly from high to insignificant. Local or national experts should be consulted for advice on the risk of insect attack
Summary of use classes for solid wood
Table 1 gives typical moisture content levels for solid wood and a summary of the biological agents which may attack it in the various use classes. Table 1 Summary of use class moisture content conditions and attacking biological agents for solid wood General service situation a Description of exposure to wetting in service dry max 20% occasionally > 20% occasionally > 20% Uc U L Uc U L Occurrence of biological agentsa Fungi Beetles
Marine borers -
interior, covered interior, or covered
3.1 exterior above ground, protected 3.2 exterior, above ground, unprotected 4.1 exterior in ground contact and/or fresh water 4.2 exterior in ground (severe) and/or fresh water 5 in salt water
frequently > 20% Uc U L -
predominantly or permanently > 20%
permanently > 20% permanently > 20%
U = universally present in Europe and UE territories L = locally present in Europe and UE territories
Due to only locally criticality of exposure and the need of targeted prescription, sub-classification of biological agents is possible locally.
The risk of attack can be insignificant according to specific situations and geographical locations. Disfiguring + decay fungi. Disfiguring + decay + soft rot fungi. The above water portion of certain components can be exposed to wood-boring insects, including termites..
Annex A (informative) Guide for the application to solid wood in relation to durability
The purpose of this annex is to facilitate the use of this standard by providing: information on decision making; general considerations related to the durability of wood components made of solid wood; information on assigning use classes.
A.2 General decision making
Using the decision sequence represented in Figure A.1, the user may select suitable material for the intended end-use environment. The steps may be summarized as follows: a) b) Consider the performance required of the component. Determine the use class of the situation in which the wood component will be used and the biological agents that threaten it (see Figure A.2 for wood above ground and Figure A.3 for wood in ground or water contact). Assess whether the natural durability of the wood to be used is sufficient or if preservative treatment is required. Select for the component a more durable species of wood or choose another solution (design) or preservative protection. If preservative treatment is required, select the appropriate treatment taking into account the biological agents against which protection is necessary.
Determine use class EN 335-1 and EN 335-2
Select wood species if possible or appropriate Determine natural durability EN 350-2 - select another wood species - change design
Is natural durability appropriate to use class ?
no Preservative treatment necessary
Preservative treatment not necessary
Decide retention / penetration: EN 351-1
Is treatability appropriate ? yes Select wood preservative EN 599-1
Select appropriate treatment process
Figure A.1 General decision making sequence for selection of solid wood appropriate for the use class
Determine treatability of the selected wood species EN 350-2
Component above ground exposed to moisture no yes frequently exposed to weather or wetting no 1a 2a yes 3a
protected b 3.1 a Insect attack likely no yes both coleoptera and termites no Coleoptera yes No hazard 1c termites yes 1t 1ct 2f* yes no Insect attack likely yes both coleoptera and termites no Coleoptera yes 2fc* termites yes 2ft* 2fct* 3.1 or 3.2 f* yes no
not protected 3.2 a
Insect attack likely yes both coleoptera and termites no Coleoptera yes 3.1or 3.2 fc* termites yes 3.1or3.2 ft* 3.1or 3.2 fct* yes
f = fungi; c = coleoptera; t = termites Protection may be specified against all coleoptera (c)or against individual insects (Anobium, Hylotrupes or Lyctus). *Protection may also be specified against blue stain in service and moulds as an option where f applies. a 12-3 represent use classes; 3.1 and 3.2 represent service situations depending on the severity of the situation (climate or installation)
Figure A.2. General decision making sequence for the identification of use classes and associated agents : Solid wood - Above ground
Component in ground and/or in fresh water contact 4a Not severe Severe
Component in salt water
4.1 a Insect attack likely No Yes Both coleoptera and termites No Coleoptera yes 4.1 f* 4.1 fc* termites yes 4.1 ft* 4.1 fct* 4.2 f* yes No
4.2 a Insect attack likely Yes Both coleoptera and termites No Coleoptera yes 4.2 fc* termites yes 4.2 ft* 4.2 fct* 5f* yes No Insect attack likely Yes Both coleoptera and termites No Coleoptera yes 5fc* termites yes 5ft* 5fct* yes
f = fungi; c = coleoptera; t = termites Protection may be specified against all coleoptera (c)or against individual insects (Anobium, Hylotrupes or Lyctus). * Protection may also be specified against blue stain in service and moulds as an option where f applies.
4 and 5 represent use classes and 4.1 - 4.2, represent service situations.
Figure A.3 General decision making sequence for the identification of use classes and associated agents : Solid wood - In ground and/or in water contact
A.3 General precautions
If the use class for a component when in use cannot be accurately determined, or when different parts of the same component are deemed to be in different use classes, decisions should be taken with regard to the more severe of the possible use classes. In situations where wood components out of ground contact may permanently accumulate water due to their design or surface deposits, it may be necessary to consider that these situations are equivalent to contact with the ground or fresh water. This risk can vary from insignificant to significant. It has been recognized that some components in use classes 4 and 5 will not be completely in ground or water contact. The part protruding from the ground or water can be susceptible to attack from additional organisms not normally associated with these use classes. If a wood component is inaccessible or if the consequences of its failure would be particularly serious, it may be more appropriate to consider a more durable timber or a more intensive preservative treatment than usual for the perceived use class. The different durability and treatability of sapwood and heartwood should always be considered. For some wood preservatives, a risk of leaching exists if the treated wood component is not sufficiently protected from weathering after treatment and before being put into service. This applies particularly to components in use classes 1 and 2 that are exposed to the weather during construction. Under such circumstances and if the specified wood preservative is leachable, it is essential that the wood component is covered or otherwise protected after treatment and during transport and construction, as well as in service. Timber handling and building practice during construction, quality of maintenance, type and integrity of applied surface coatings and compatibility between treatments and coatings, are among the factors which can affect the performance of treated wood and which should be considered during the development of the specification.
A.4 Natural or conferred durability of solid wood
The natural durability of solid wood can depend to a large extent upon: species; presence of heartwood or sapwood.
Improved durability may be conferred on solid wood by preservative treatment. The methods of treatment that may be used depend upon: species; presence of heartwood or sapwood; preservative product used and the penetration and retention values selected from EN 351-1.
For the natural durability of wood, see EN 350-2. For the penetration and retention combinations available, see EN 351-1. For the performance of wood preservatives, see EN 599-1.
[1] EN 350-2, 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 Europe3) EN 351-1, Durability of wood and wood-based products Preservative-treated solid wood Part 1: Classification of preservative penetration and retention3) EN 460, 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 EN 599-1, Durability of wood and wood-based products Performance of preventive wood preservatives as determined by biological tests Part 1: Specification according to hazard class EN 1001-2, Durability of wood and wood-based products Terminology Part 2:Vocabulary ISO 3130, Wood Determination of moisture content for physical and mechanical tests ISO 21887, Durability of wood and wood-based products Definition of use classes (under preparation) EN 335-1, Durability of wood and wood-based products Definition of use classes Part 1: General EN 12775, Solid wood panels Classification and terminology [2]
3) Under revision.
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