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Focus on the European standardization - Towards a revision of the EN 350 natural durability standard: a different approach to the inherent resistance and performance of wood and wood-based materials
2013 - IRG 13-10811
The European standard EN 350 “Natural durability of solid wood”, Parts 1 and 2, is one of the fundamental standards developed by the CEN/TC 38 “Durability of wood and wood-based products”. This standard is widely used by wood industries as the reference document which provides information on the resistance of wood species used in mainly the construction sector against decay fungi, wood-boring beetles and termites as well as information on wood species’ capacity to be impregnated with wood preservatives. The standard also refers to the appropriate standards for testing these properties of wood and provides criteria of interpretation of such tests’ results. The changes that have occurred over the last few decades on the European market, including the appearance of new wood-based products such as modified wood, the publication and application of new regulations (Biocidal Directive/Regulation, Construction Products Directive/Regulation) and the evolutions of customers’ expectations in terms of the service life of the wood-based products which they may use, make it crucial to initiate a deep revision of the EN 350 standard. The new version would take into account the revisions made recently in related existing standards, the modifications that have occurred on the European market of wood products, and the outcomes of recent national and European research projects in order to provide a robust and relevant decision tool to all those who rely on wood.
M Kutnik


Interspecific variability of European oak durability against white rot fungi (Coriolus versicolor): Comparison between sessile oak and peduncle oak (Quercus petraea and Quercus robur)
2001 - IRG/WP 01-10393
The knowledge of wood natural durability against biologic predators enable its external use. The resistance of European oak wood was reported like durable according to the EN 350-2. However, some individuals may contain high durable wood. Our research was focused to understand this variability in oak population that represent the first french species (4.1 millions of ha). Natural durability of European oak heartwood (Quercus petraea and Quercus robur) against white rot fungi (Coriolus versicolor) was tested according to european standard EN 113. The experimental material consists in 23 oaks robur and 26 petraea oaks sampled from 9 French regions. For each tree, 3 twin samples were taken off from heartwood situated at 1.30 m from the bottom of the tree. Different effects were tested by hierarchic variance analysis: "species", "forest within species" and "tree within forest". The tree effect is very significant for biologic natural resistance. Variability between species was also demonstrated. Although the species effect is significant, it's relatively weak compared with tree differences (it was declared significant 5%). Durability classification was determined according European standard EN 350-1. 69.2% of petraea oak trees are classified as high durable, 19.2% durable, 7.7% moderately durable and 3.8% slightly durable. In the case of robur oak 91.3% of trees are classified as high durable and 8.7% durable.
N Ayadi, B Charrier, M Irmouli, J P Charpentier, C J Allemand, F Feuillat, R Keller


CEN Draft Standard (38 N 460F): Méthode d'essai pour determiner l'efficacité d'un produit de préservation du bois en milieu marin
1986 - IRG/WP 4132 F
G Castan


Assessing the performance of wood preservatives from biological tests - the European approach
1994 - IRG/WP 94-20040
The impetus for the European Standardisation Committee to undertake the development of a performance standard for characterising the effectiveness of wood preservatives from biological tests, lies in the Construction Products Directive. This is effectively the European Community law which provides the basis for Construction Products to be traded across all member states without technical or regulatory barriers and without having to undergo further testing or re-certification. The performance standard covering wood preservatives is EN 599 and it defines the performance which preservative products will be required to achieve in specific laboratory and field tests, in order to be accepted and marketed as suitable for particular conditions of use. Five hazard classes of use are defined in another standard (EN 355-1) and EN 599 lists the specific biological tests required for each hazard class, the maximum amount of the product that can be applied in each test, the need for pre-leaching or pre-ageing and the rationale for deriving a value (the biological reference value) for the minimum amount of product deemed effective in each test. The highest biological reference value determined from all the tests is defined as the critical value and it is this value which is carried forward to the standard covering treated wood (EN 351) to provide the basis for defining the minimum amount of product required for effectiveness within treated commodities. EN 599 lists the minimum testing requirements for each hazard class together with optional additional tests to provide efficacy assessment against a wider range of target pests or to increase confidence in the critical value by incorporating data from longer-term field tests. The standard also describes the requirements for marking and labelling preservative products to describe their suitability for specific uses. Work on EN 599 commenced in 1988 and its development has required negotiated agreement between the 18 member states of the CEN/CENELEC region with 12 different working languages and 3 different official languages for documentation. EN 599 is now at the final stage of submission to vote and the decision on its adoption and implementation will be announced before the end of 1994.
A F Bravery


Towards harmonisation of regional approaches for an International Standard for the approval of wood preservatives
1997 - IRG/WP 97-20122
Recent proposals from the European Standards body (CEN) for an ISO Standard on wood preservatives has initiated debate on whether there is any prospect of an acceptable common approach among ISO member countries, to a harmonised framework of hazard classes, with agreed supporting biological tests, leading to a unified rationale for demonstrating compliance with minimum performance standards for specific preservatives in specific end-uses. This paper discusses a potential framework for developing an International Standard prescribing hazard classes and the biological test methods capable of supporting a common approach to the approval or standardisation of a wood preservative system. An approach is proposed which incorporates elements of existing standards or protocols used in Europe, Japan, Australasia, South Africa and North America based on the framework of European Standard EN599 but adopting regional variants with incorporation of field testing for the suggested Hazard Classes 2, 3, 4a, 4b and 5. The proposals are intended to initiate development of a consensus process rather than to suggest a solution in itself. However, it is hoped that the framework provided will allow the discussion process to advance more effectively and harmoniously.
A F Preston, A F Bravery


The natural durability of wood in different use classes
2003 - IRG/WP 03-10457
The natural durability of important European wood species has been tested on 3970 specimen in field trials. The wood was exposed at five test fields in Germany with different climates at each site in European hazard class 4 and 3 (with and without soil contact). Within EHC 3 it was distinguished between tree different expositions (end grain sheltered, unsheltered and with water trap). The test is now running for 3 years. The results have shown that the type of exposition (EHC 3 or EHC 4) has a strong influence on both: the decay activity and the durability determined as the quotient of decay of tested species and of decay of Scots pine sapwood. The test site had a strong effect on decay activity and time to failure, whereas the effect on durability was minor. Up to now it is not yet possible to calculate the final durability classification, but so far the field tests in soil confirmed the natural durability given in EN 350 (with the exceptions of Quercus robur and Robinia pseudoacacia, both were less durable than said in the standard). Whereas so far the above ground tests revealed a higher durability for all softwood species with coloured heartwood (heartwood of Larix, Pseudotsuga and Pinus) than classified in the standard EN 350. It is obvious that the current classification of natural durability is only valid for use in soil contact. Future amendments of the standard EN 350 seem to be reasonable. It is proposed to list durability class separately for in ground and for above ground use in the future.
U Augusta, A O Rapp


Physiological properties of fungal test strains according to the European Standard EN 113
1986 - IRG/WP 2258
For the discussion of the European standard EN 113 the EMPA's procedure of culturing the test fungi and the corresponding virulence of the test fungi as well as the wood moisture content at the end of the test are shown. It is mainly shown that within the standard the choice of the solvent may not be left at the test lab if reproducible results shall be obtained. The different solvents influence in different form the wood decomposition values due to fungal attack. A water leaching of the wood specimen impregnated with solvents generally Further increases the negative effect of the solvent on the fungi. It is therefore the task of the Technical Committee of the European Committee for Standardization (CEN/TC3B) to agree to a standard solvent and to evaluate this in the original state as well as after a leaching followed by uniform drying periods by means of an interlaboratory test.
E Graf, B Zgraggen, P Manser


Resistance of DMDHEU-treated pine wood against termite and fungi attack in field testing according to EN 252. Results after 30 months
2006 - IRG/WP 06-40354
The aim of this study was to determine the effectiveness against decay and termite attack of pine sapwood treated with pure and modified DMDHEU in a field test according to European Standard EN 252. Some of the treatments tested were able to increase, within the period of the test reported (30 months), the resistance of the wood both to micro-organisms and termites. The curing process seems to be the key factor for this increase as WPG (weight percent gain) of the modified wood alone was not sufficient for the prediction of the long-term performance.
S Schaffert, L Nunes, A Krause, H Militz


Fouling and Boring Organisms Deteriorating Various European and Tropical Woods at Turkish Seas
2010 - IRG/WP 10-10741
This study aims to investigate the diversity of fouling and boring organisms damaging wood material at Turkish coasts. Trials were carried out at six harbour sites throughout the seas surrounding Turkey. Wood samples were hanged down at a depth of six meters in the sea, for a period of one year. Identification of the organisms obtained from wood plates revealed the presence of five wood borer and 26 fouling species. Iskenderun harbour had the highest boring organism diversity (five species), followed by Trabzon, Finike harbours (three species) and Bandirma, Eregli and Alaçati harbours (two species). The two molluscan boring species, Teredo navalis and Lyrodus pedicellatus were present at all harbour sites, but Nototeredo norvegica occurred only at Trabzon and Iskenderun harbours, Bankia carinata only at Iskenderun harbour, and the crustacean wood borer Limnoria tripunctata at Finike and Iskenderun harbours. All native tree species, except for the olive, were significantly impacted from fouling and boring organisms.
S Şen, H Sivrikaya, M Yalcin, A Kerem Bakır, B Öztürk


Performance classification of wood in construction – drafting a user friendly European standard
2014 - IRG/WP 14-20545
The performance classification for wood products in construction is an extremely important topic in Europe and beyond – warranty providers and end users demand service life and performance information in the face of competition with other materials. The European project PerformWOOD has formalised and drawn together the on-going research to focus on generation of a material resistance factor for performance classification and alongside WG28 is developing the first moisture dynamic test protocols in the Technical Committee’s history, again based on research work being drawn together. In this paper some of the early concepts around a future user friendly standard to enable wood and enhanced durability wood to be specified by construction professionals on the basis of performance are considered. A draft standard (EN460) for consideration of performance classification of wood in construction is underway and relies on concepts that are being road-tested with industry, construction professionals, researchers and the general public.
E Suttie, C Brischke, L Meyer, J Van Acker, M Kutnik, E Heisel, F Englund, J Jermer, S Thelandersson, M Polášek, D Lorenzo


Towards durability classification of preservative treated wood – first attempts using different European standards
2018 - RG/WP 18-20638
EN 350 (2016) gives guidance on methods for determining and classifying the durability of wood and wood-based material against biological wood destroying agents. “Wood-based materials are those derived from trees and include amongst others: untreated wood, heat treated wood, chemically modified wood, glue laminated wood, wood-based panels, wood polymer composites and wood treated with wood preservatives”. Very few data are yet available for assigning durability classes to preservative treated wood on the basis of results from test methods referred to in EN 350 (2016). In this study results from tests according to EN 113 (1996), ENV 807 (2001), and EN 252 (2014) were evaluated, for assigning durability classes of differently preservative treated wood, using different classification schemes. Specimens made from beech (Fagus sylvatica) and Scots pine (Pinus sylvetris) were treated with four different retentions of two wood preservative systems. Results show, that different tests lead to durability classification between 1 (very durable) to 5 (not durable) for same tested combinations. Most treated wood achieved higher durability classes based on test against basidiomycetes (EN 113) compared to tests against soil inhabiting micro-organisms (ENV 807 and EN 252). In summary, it became evident that durability classification of preservative treated wood strongly depends on both, the applied test method and the evaluation scheme used for assigning durability classes.
S Bollmus, A Gellerich, C Brischke, H Militz


Can CCA be substituted as reference preservative?
2018 - IRG/WP 18-20641
While field testing of wood protective formulations remains probably the best method to find out the effective preservative concentration, the use of chrome-copper arsenate (CCA) as reference becomes debatable due to environmental and legislative reasons. This emerges from the European standardization bodies who have discussed reference alternatives that can omit the use of CCA. The present debate article suggests one possible approach to cope with the problem. CCA has served in the tests fields of the Nordic countries for more than 50 years and thus, offers a solid database for modelling of its behaviour and service life in in-ground conditions. Based on data from the field of Simlångsdalen (Sweden), this paper outlines a simple but reliable model that can substitute the use of CCA. Seventeen tests were included into the model; some extremes, i.e. very short or long test durations were discarded. Statistical analysis shows that both logarithmic and linear regressions can describe the decay index in a similar way. Some applications of the model to real test data that the Technical Group at the Nordic Wood Protection Council works with have been compared to the standard method based on the European standard EN 599-1. Results demonstrated that the model generates similar data of formulation concentrations compared to the standard method. It is suggested that identical models, based on data from the other Nordic fields, could be developed and applied. The proposed method demands a wide discussion between the testing and standardization bodies for further practical implementation.
N Terziev, M Jebrane, P Larsson Brelid, N Morsing, P-O Flaete, P Torniainen, J S Kim, G Daniel


Proposed method for out-of-ground contact trials of exterior joinery protection systems
1981 - IRG/WP 2157
Methods for testing the efficacy of preservative treatments for exterior joinery are described using the format of a European Standard. Commercially used treatments applied to jointed test units (L-joints) which are then protected by conventional finishes are exposed to normal outdoor hazards out of ground contact. Assessment is made a) by determining eventual failure through decay and b) by destructive examination of replicate treated and untreated units, after increasing time intervals, rating comparative performance in terms of wood permeability increase and the progress of microbial colonisation.
J K Carey, D F Purslow, J G Savory


CEN Draft (38 N 460E) Standard: Test method for determining the protective effectiveness of a preservative in the marine environment
1986 - IRG/WP 4132
This European Standard describes a marine test method which provides a basis for asseasing the effectiveness of a wood preservative used to prevent attack of timber in sea-water by marine borers. The method is only suitable for testing preservatives which are intended to prevent attack by marine wood boring organisms of treated timber for use in more or less permanent contact with sea-water. It is not suitable for assessing the effectiveness of preservatives against micro-organisms. The main objective of the method described is to evaluate the relative effectiveness of a wood preservative applied by vacuum/pressure impregnation. For this reason permeable timbers are used throughout so that the protective efficacy of various retentions of the preservative can be determined. However, it is recognized that modifications of the method may be used for other purposes, e.g. to determine the relative efficacy of a preservative treatment or to determine the natural durability of the heartwood and sapwood of a selected timber species. The method is primarily intended for testing in temperate waters where Teredine and Limnoria borers dominate. However, it is also capable of being used in tropics where attack by Pholads and specific Crustacean borers may be very destructive. It has to be considered that the test has to be run for a minimum period (usually for 5 years or until the point of failure) before any interpretation of the results can be made. Variations in the test conditions can be expected from one test site to another depending on temperature, salinity, population density of the various borer species etc. This will inevitably influence the general rate of attack. However, by comparing the results obtained for samples treated with the test product with those obtained with a reference preservative and those obtained with untreated control samples, the relative protective effectiveness of the product tested can be evaluated.
G Castan


Possibility of use of wood species per class of biological risks. Attempt to determine criteria based on Pr EN 350-1/2/3
1992 - IRG/WP 92-2409
M Rayzal


Comparison between the Hylotrupes bajulus strains of different European laboratories
1980 - IRG/WP 1118
In several European countries, wood preservatives of the same formulation are subjected for the quality label to particular tests according to standards established by the CEN. The different laboratories which carry out these tests have had their cultures for many years. The insects are kept in optimal nutritional and climatic conditions and have always mated amongst themselves. On the one hand, eradicant tests made with the same preservative in different laboratories have not always yielded the same results, and on the other hand, the Comitte of European Homologation has been trying to establish a single label for the European Community according to which it will be possible to carry out tests by any national laboratory of the participating countries. If the results are satisfactory, this will enable an approval certificate to be provided for the sale of these products throughout the countries of the Community. It is very important to be certain that the behaviour of insects and the insecticide resistance of the different insect strains are identical. For this, the best test seemed to be the determination of the toxic value of the wood preservatives against Hylotrupes bajulus (Linnaeus) new-hatched larvae, according to the European standard EN 47.
M-M Serment


Evaluation and approval of wood preservatives. Unification of European requirements
1988 - IRG/WP 2310
This paper reviews the current activities within the European Homologation Committee for Wood Preservatives (EHC) towards unification of the requirements on evaluation and approval of wood preservatives in Western European countries.
J Jermer


Rapport sur l'activité du CEN/TC 38 "Méthodes d'essais des produits de préservation du bois"
1982 - IRG/WP 2188
M Pottevin


Testing method for the treatability of wood
1994 - IRG/WP 94-40031
In order to test and classify the treatability of wood species in pressure treatment processes with water-based solutions, a laboratory method was developed which allows the testing of small samples and limited sections of a stem, e.g. sapwood. The penetration of different liquids was determined separately concerning the three anatomical directions of wood. The common parameters for pressure impregnation were used on sap- and heartwood of eight indigenous and tropical wood species. An elastic epoxy resin proved feasible for coating the samples on five sides. From the data of the testing method a measure for the treatability was calculated, allowing to classify wood species into four treatability classes analogous to prEN 350-2 (1993).
A O Rapp, R-D Peek


Information from the COIPM Wood Group
1986 - IRG/WP 4130
The Chairman outlined the progress of the co-operative work "testing the resistance to marine borers of heat shrinkable polyolefin sheathings and of wood treated by vacuum/pressure with polymers (polystyrene)". The first part of the work has been started: the samples of wood wrapped with shrinkable polyolefin sheathings have been prepared and sent to the stations participating. The second part of the programme has for the moment been stopped because in some preliminary trials samples treated with polystyrene have shown a light to moderate attack by molluscan and crustacean borers after 18 months' immersion. The results of these trials have been related and supported by photos and X-ray pictures. Four other stations are involved in this programme: three have been made available by Hempel Technology in Copenhagen (Denmark) and one by CNEXO (France). A presentation was given of the project for a European Standard "Field test method for determining the protective effectiveness of a preservative in the marine environment" which had been prepared by Professor Björn Henningsson (Sweden) and considered in the CEN meeting in September 1985. The participants were informed of the research being carried out by the IRG Marine Wood Preservation Group and the minutes of the 12th Meeting held in Brazil during May 1985 were presented.
A Gambetta


European laboratory termite testing
1986 - IRG/WP 1299
As with all testing of wood preservatives the evaluation of the resistance to termites of treated wood requires methodology which is approriate to, and can be readily extrapolated to, the practical situation. Thus not only must the variations in possible treatment systems be taken into account (eg dip, brush or pressure application) so too must the range of termite species and the type of exposure of the treated wood (eg ground contact, internal or cladding). The European need for the testing of wood preservatives against termites is two-fold. Firstly there is a need to assess protective treatments against the termite hazard in Europe itself; this concerns only two naturally occurring subterranean termite species Reticulitermes lucifugis and Reticulitermes santonensis, as well as one introduced species Reticulitermes flavipes. Although the dry wood termite Kalotermes flavicollis does occur it is not regarded as a serious building hazard. Secondly there is a demand by preservative manufacturers or users for assessment of the termite resistance of formulations or treated materials exported to countries with substantial termite problems.
R W Berry


Fungi used in standard tests on the toxicity value of wood preservatives in various European countries
1975 - IRG/WP 255
The aim of the present paper is to make the comparative analysis of test fungi used in various European countries in order to define the toxicity value of wood preservatives against fungi of the Basidiomycetes class. Only the methods with national standard rank, present on the currently binding standards list are taken for consideration. The analysis of similarities and differences in the choice of test fungi used in these methods should be a further step in the investigation on the unification of the test methods
J Wazny


Protection of wood blocks treated with Trichoderma isolates selected on the basis of preliminary agar screening studies
1996 - IRG/WP 96-10154
Previously reported results of agar interaction screening studies for biocontrol agents of wood decay basidiomycetes showed two Trichoderma viride isolates, killed 16 of 19 target fungi (Tucker and Bruce, 1995). Testing of these isolates in wood was required to assess their performance at preventing decay of wood blocks. Standard testing of chemical wood preservatives is used to determine the toxic concentrations of preservative required to protect the wood against decay by basidiomycetes. As no ratified standards for testing biocontrol agents exist, two amended wood block testing standards were used to assess the two most effective Trichoderma isolates selected on the basis of preliminary agar screening studies. An agar based system similar to European Standard EN 113 (1980) and a soil block test based on the AWPA Standard 1413 (1977) were used with Scots pine and Sitka spruce pre treated with Trichoderma. Results indicated that wood blocks treated with Trichoderma isolates (T60) and (T110) were completely protected against decay by all the basidiomycetes tested irrespective of form of inoculum used (spores or mycelium) or timber species. Implications of the results for the use of agar plate interaction studies for screening biocontrol agents for subsequent use in wood block testing are discussed.
E J B Tucker, A Bruce, H J Staines


Eucalyptus globulus. Impregnability in relation with plantation and crop
1992 - IRG/WP 92-2402
Eucalyptus globulus Lasill is currently classified in Pr EN 350 on the basis of the characteristics of the first log. In practice, there are usually several following crops of branches developped on each stump in plantations. Up to a diameter of 8 cm, round wood of 2nd crop and further crops present a maximum of sapwood and characteristics which differ significantly from the basic classification and justify an amendment of the standard for the purpose of use in ground contact as impregnated stakes.
D Dirol


Evaluation of the european standard ENV 12038 for durability testing of plywood
2001 - IRG/WP 01-20237
The latest improved version of the standard ENV 12038 drafted as document N44 by CEN Technical Committee 38 (WG 7 - WG 23) is used to evaluate the effect of wood composition and structure on plywood durability. The method described is based on the agar-block test of the EN 113 standard used for the determination of the efficacy of wood preservatives and the assessment of the natural durability of timber. This test method differs from the soil-block test commonly used in North America and vermiculite test procedures used earlier for plywood testing. The ENV 12038 method is essentially developed to deviate minimal from the European basidiomycete tests currently established. Therefor it was important to evaluate whether or not vermiculite or soil as a test medium could be replaced by a malt- agar medium using an adequate preconditioning of panel specimens prior to fungal testing. Based on two consecutive experiments both test methodology and the assessment of plywood durability are investigated. Plywood is a material that allows a direct evaluation of test methods for assessing the durability of board materials in comparison with test methods used for solid wood. The presence of glue-lines and the layered structure based on solid wood veneers enables to investigate in detail the impact of wood composition as well as the type and amount of glue. Preconditioning plywood prior to testing according to ENV 12038 proved to be essential. However the impact of the glue is not entirely eliminated that way.
J Van Acker, M Stevens, E De Clercq


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