Proceedings IRG Annual Meeting (ISSN 2000-8953)
© 2018 The International Research Group on Wood Protection
IRG/WP 18-50338
THE INTERNATIONAL RESEARCH GROUP ON WOOD PROTECTION
Section 5 Sustainability and Environment
Enhancing knowledge transfer in the wood protection sector
Christian Brischke
1, Gry Alfredsen
2, Susanne Bollmus
1, Miha Humar
3, Dennis Jones
4, Linda Meyer-Veltrup
5, Lina Nunes
61University of Goettingen, Wood Biology and Wood Products, Buesgenweg 4, D-37077 Goettingen, Germany
2Norwegian Institute of Bioeconomy Research, Box 115, NO-1431 Ås, Norway
3University of Ljubljana, Biotechnical Faculty, Dept. of Wood Science and Technology Jamnikarjeva 101, SI-1000 Ljubljana, Slovenia
4DJ Timber Consultancy Limited, Neath, United Kingdom / Luleå University of Technology, Forskargatan 1, SE 931 87 Skellefteå, Sweden
5Heinz-Piest-Intitute for Skilled Crafts, Wilhelm-Busch-Straße 18, 30167 Hannover, Germany
6LNEC, Structures Department, Av. do Brasil, 101, 1700-066 Lisboa, Portugal and cE3c, Centre for Ecology, Evolution and Environmental Changes / Azorean Biodiversity Group and University of the
Azores, 9700–042 Angra do Heroísmo, Portugal
Paper prepared for the IRG49 Scientific Conference on Wood Protection Johannesburg, South Africa
29 April – 3 May 2018
IRG SECRETARIAT Box 5604 SE-114 86 Stockholm
Sweden www.irg-wp.co
Disclaimer
The opinions expressed in this document are those of the author(s) and are not necessarily the opinions or policy of the IRG Organization.
Enhancing knowledge transfer in the wood protection sector
Christian Brischke
1, Gry Alfredsen
2, Susanne Bollmus
1, Miha Humar
3, Dennis Jones
4, Linda Meyer-Veltrup
5, Lina Nunes
61University of Goettingen, Wood Biology and Wood Products, Buesgenweg 4, D-37077 Goettingen, Germany, christian.brischke@uni-goettingen.de; sbollmu@gwdg.de
2 Norwegian Institute of Bioeconomy Res., Box 115, NO-1431 Ås, Norway, Gry.Alfredsen@nibio.no
3 University of Ljubljana, Biotechnical Faculty, Dept. of Wood Science and Technology Jamnikarjeva 101, SI-1000 Ljubljana, Slovenia, Miha.Humar@bf.uni-lj.si
4 DJ Timber Consultancy Limited, Neath, United Kingdom / Luleå University of Technology, Forskargatan 1, SE 931 87 Skellefteå, Sweden, dr_dennisjones@hotmail.co.uk
5 Heinz-Piest-Intitute for Skilled Crafts, Wilhelm-Busch-Straße 18, 30167 Hannover, Germany, meyer@hpi-hannover.de
6 LNEC, Structures Department, Av. do Brasil, 101, 1700-066 Lisboa, Portugal and cE3c, Centre for Ecology, Evolution and Environmental Changes / Azorean Biodiversity Group and University of the
Azores, 9700–042 Angra do Heroísmo, Portugal, linanunes@lnec.pt
ABSTRACT
In order to meet the needs for the developing bio-based economy, maintaining and expanding the market potential for wood raw materials and wood products in indoor and outdoor construction uses remains a key activity for industries in the biotechnological and forestry sector respectively.
A major restraint in this respect is the drastically deviating views and expectations on quality and performance of the material. Such differences can be found between producers and consumers, between architects and engineers, between planners and approval bodies as well as between academia on the one hand and industry and traders on the other hand. The wood protection and wood preservation sector is located exactly within this area of deviating opinions. To overcome the barriers due to different perceptions and therewith strengthen the standing of wood as a desirable building material in the future, new strategies and methods for communication, knowledge transfer and education are needed.
Networking and scientific exchange between different disciplines is needed, such as forest science, silviculture, applied forestry, material sciences, wood technology, building technology, architecture and engineering. Consumer demands and preferences, which might serve as limit states to develop service life prediction and performance models, need to consider aesthetical aspects as well as the functionality of timber building assemblies. Finally, teaching students, craftsmen, and salesmen is the key to enhance the acceptance of renewable and carbon-storing products, which are both biodegradable and highly variable in their properties. All these peculiarities require a deeper understanding of their nature and characteristics to improve their purpose-related usage.
Keywords: Forest wood value chain, quality percipience, consumer preferences, knowledge
transfer, performance-based design
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1. BACKGROUND: MISCONCEPTIONS ALONG THE FOREST-WOOD-VALUE- CHAIN
Wood utilisation is accompanied by numerous groups along the forest-wood-value chain (
Figure 1) that can have drastically different viewpoints, traditions, and philosophies clash leading to potential inefficient use of timber, loss in yields and quality, and finally, impairing the reputation of wood as raw and building material.
Figure 1: Forest-wood-value-chain.
Wood is a natural material, and as such, is exposed to various degradation factors. In the past, biological degradation was prevented predominately with application of biocides and/or import of durable tropical wood species. Due to increased environmental awareness of producers and consumers, the sustainability of the above-mentioned solutions has been questioned. Nowadays, the key goal is to use domestic wood species with sustainable forest management practice as a premise. Utilisation of local materials not only stimulates rural economic growth, enables jobs in rural areas and maintains rural population, but also reduces emissions related to transport.
Typically, many of these wood species do not have sufficient durability, which may be overcome if special emphasis is given to proper use and understanding of durability. Mechanical, physical, biological, and aesthetical performances are key for the successful use of bio-based building products. If wood is not used correctly, its benefits can become detrimental. With the increased focus on sustainable material choices and a more circular and bio-based economy the time is right for an interdisciplinary effort to facilitate and customise the use of wood resources.
Taking Europe as an example, the main challenge is to achieve a better and common understanding of the quality and service capacity of timber and timber-derived building materials. To achieve this, an interdisciplinary forum needs to be established through which ideas and knowledge can be exchanged through collaborative activities across Europe and associated countries.
2. CHALLENGES AND OBJECTIVES
An interdisciplinary approach is sought to overcome the current discrepancies in quality
assessment and quality control of wood and wood-based products to avoid misconceptions and
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erroneous marketing along the forest-wood-value-chain. To achieve this, several aspects like the following must be addressed:
Quality
Sales of round timber based on growth characteristics versus product-oriented sorting
Strength-oriented grading and optimization of cutting yields
Sorting criteria for sawn timber
Quality control of semi-finished products (sawn and processed timber, treated and modified
timber, use in hybrid materials and composites)
Performance classification of wood-based products
Durability-based design of timber structures
Consumers and performance
Examining consumer expectations and preferences regarding aesthetic and technical service
life of wooden constructions and other wood products
Evaluating existing quality control tools and identifying gaps and improvements if needed
Developing tools for knowledge transfer
Providing education and training tools to guide consumers to understand the peculiarities of
wood as a renewable but also bio-degradable material
Improving harmonized assessment protocols for grading of wood materials
Providing educational tools customized for different user groups
Providing guidance how to introduce new materials to different user groups
Competence
Providing guidelines on good practice regarding wood destroying insects, discolouring fungi
and decay fungi
Increase knowledge on the performances of domestic wood species in order to promote a fit-
for-purpose end use
Therefore, experts from various disciplines such as forest sciences, forestry, saw mill industry, woodworking industry, polymer (adhesives and surface coatings) industry, material and building sciences, architecture and civil engineering, should be brought together for sharing knowledge about quality perceptions established in different sub-sectors of the building trade and the wood- producing forestry area and to provide synergistic effects. Alongside, experts from educational and pedagogical disciplines covering all levels between primary school, secondary school, vocational schools, and finally universities should be encouraged to provide best methods for education and knowledge transfer with the overall aim to increase the acceptance of timber and other wood-based materials for building purposes.
3. SITUATION TODAY
The value of forests globally and within Europe is immense, 117 million Ha according to the European Commission (2017). Their ecological importance is outstanding and the range of health and recreational services they provide to human societies is without controversy. Also, the economic impact of forests is highly significant and wood as the main resource in forests and thus the main product of the forestry sector is appreciated all over the globe. Nevertheless, modern building regulations in Europe as well as the public consumer-driven perception have led to an image of wood as building material which is tarnished from within its own sector and from competing material sectors (e.g. Jonsson 2006, Wyżga et al. 2009, Høibø and Nyrud 2010).
Supply and demand of different wood species vary strongly between countries or even regions in
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Europe, which is driving the trade on the European market, but also beyond. Export to and import from all other continents is still increasing. In regions with an excessive supply of certain wood materials, such as beech (Fagus sylvatica) wood and large dimensioned softwoods in Central Europe, quality assessment and grading of lumber plays a significant role (e.g. Knoke et al. 2006, Beinhofer 2010, Wolfslehner et al. 2013). However, the quality criteria formulated by foresters and those formulated by wood technologists and engineers are not necessarily the same.
Furthermore, architects will have another perspective. It is of great importance that those who make the decisions, and set the price, regarding material choice of a new construction, understand and trust wood as a building material.
Strategies of cultivating, maintaining and harvesting forests have been overtaken by the increasingly fast developing technologies for wood processing during the last 50 years.
Silvicultural methods could not be adapted as fast as the change in requirements on the raw material over time and therefore quality grading needed continual adaptations during recent decades. Nevertheless, the understanding of wood quality is still a controversially discussed issue and harmonized conceptions will be needed to improve the general acceptance of the raw material and its peculiarities themselves (Pousette et al. 2012, Kotwicka and Krzosek 2013, Miyamoto et al. 2013). In particular, for mass assortments facing small markets clear and commonly accepted quality criteria are needed to save and enhance their value.
European building regulations – among others – require the consideration of different performance criteria for building materials to an increasing extent (Kutnik et al. 2014, Jones and Brischke 2017). This applies to wood and wood products as well. Compared to competing materials such as steel, concrete, glass, and plastics, wood-based materials usually suffer from higher variation of their physical and mechanical properties – this is not to say other materials are not without their own ”faults” in terms of energy consumption, water demands, end of life issues, use of non-renewable resources etc., as well as corrosion and non-biological deterioration. The use of wood and wood-based products benefits from their inclusion in the European activities towards a bio-based economy, ensuring markets from sustainable forest practices across the EU-28 countries and beyond. In addition, wood is prone to biological degradation, which has always affected its public perception in a negative way. On the other hand, there is also a highly negative perception of the import of durable wood species from tropical regions and wood treatments that were developed to overcome the deterioration problem (Ozanne and Vlosky 1997, Tacconi 2012).
It is therefore of utmost importance to: 1) provide hard and reliable performance data, and 2) transport this message to all relevant groups that use timber either as raw material in industry or as finished product in buildings, and 3) ensure this information is applied in practice as widely as possible to ensure failure in service is avoided. This would attract those groups which potentially would use (more) timber (for example in hybrid materials, e.g. wood/aluminium window systems) if its public standing as a reliable building material would be better. Therefore, information about material variation, use and particularly maintenance requirements, in combination with service life expectations of architects, specifiers and building regulators need to be delivered to assure a proper and purpose-related usage and to avoid premature failures due to poor constructions, bad maintenance or inappropriate allocation of materials.
To overcome the drawback of wood’s heterogeneous response to moisture, its often insufficient
dimensional stability and durability (too often resulting from poor choice and bad design),
various treatment methods were developed and have been in use for decades (Eaton and Hale
1993, Hill 2007, Schultz et al. 2007). Impregnation with different wood preservatives and fire
retardants, coating of wood surfaces, and finally thermal or chemical modification of the wood
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cell walls are among the most frequently used techniques to enhance the performance of wood in particular in the outdoor environment. However, all these processes are dramatically affecting the costs of wood building products and therefore the customer expectations about the quality of the products are increasing as well (Proverbs and Holt 2000).
Whenever and wherever organic material is exposed to favourable moisture and temperature conditions as well as to degrading organisms, e.g. as caused by a poor design of a certain component or missing maintenance, the overall functional and aesthetic service life of the components and potentially the larger construction unit, might get negatively affected.
Comprehensive, reliable and unadorned information about the product together with detailed information about necessary maintenance would raise appreciation and ultimately acceptance with the customer. All this information has to be incorporated into BIM (Building Information Modelling) what will enable better and safer construction of the buildings made of wood.
4. EXAMPLES OF MISCONCEPTION IN THE WOOD PROTECTION SECTOR
For a better understanding of the general problem of misconceptions that can be found along the entire forest-wood-value-chain, a number of examples were gathered, all directly linked to the wood protection sector and located on different levels of construction.
4.1 Forestry / Silviculture level
The time of production in forestry easily overshoots the working life of humans by a factor of 3.
Thus, it makes it extremely difficult to estimate the demand and the quality criteria of the future customers. A forester barely, or never, experiences the use of the product that he planted and maintained during his lifetime. These special boundary conditions led to a time shift regarding quality assessment between producers on the one hand, and wood processor and users on the other hand. In addition, today’ forests have to fulfil many further functions apart from producing wood. But the portfolio and importance of forest functions is also significantly changing over time, often faster than silvicultural concepts can be changed or implemented.
In Central Europe, for several decades, it has been a forest political aim to increase the percentage of deciduous forests and mixed forests. In many regions the share of beech (F.
sylvatica) wood increased remarkably and nowadays beech turned into a mass product. In contrast, the demand for beech wood did not increase. During some periods it even decreased due to fashion cycles in the furniture and parquet flooring industry accompanied with the closure of relevant plywood factories in central Europe. As a consequence, beech trees are often reaching ages when they get very sensitive to the formation of false red heartwood (Fig. 2), which again is critical for impregnation, e.g. for use as railway sleepers.
Figure 2: Beech (Fagus sylvatica) forests in Central Germany and beech round-wood with portions of red false heartwood
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Complicated interrelationships between forest management, wood quality, and restrictions in the use of wood need to be identified and communicated between different groups along the forest- wood-value-chain. It is a matter of knowledge transfer and education.
4.2 Marketing/Trade level
Salesman and marketing people play a key role in transporting expert knowledge to customers and users of wood products. They are the main link between producers and end users, and therefore take high responsibility for the public opinion on the competitiveness of wood as a building material. Unfortunately, numerous examples point to the wrong strategy of taking advantage of short term profits regardless of the possible loss of confidence in wood as a building material that may raise on the long run. Frequently, expectations are raised, which the material is not able to fulfil. Figure 3 shows two examples of outdoor products made from Europe grown softwoods with coloured heartwood, i.e. European larch (Larix decidua) and Douglas fir (Pseudotsuga menziesii). The heartwood of both wood species is classified as
‘moderately to less durable’ (DC 3-4) based on results from tests with soil contact (EN 350, 2016). However, the sapwood of both species is classified as ‘non-durable‘ (DC 5), even though for instance the German standard DIN 68 800-1 (DIN 2011) allows sapwood percentages up to 5% and still considers it as heartwood. It does not surprise that the non-durable sapwood – even though smaller than 5 % of total wood - will decay significantly faster than the heartwood. If the sapwood happens to be distributed as shown in Figure 3, premature failure of the whole element can be expected within a short time frame. Knowledge transfer and fair-mindedness are closely connected and marketing can be an excellent instrument for educating users of wood and to improve the reputation of the latter.
Figure 3: Douglas fir (Pseudotsuga menziesii) boards (left) and European larch (Larix decidua) fence elements (right) containing high sapwood portions.
4.3 Design level
Proper design and an adequate work execution level is often lacking when wood is used for construction. Ideally from the user’s viewpoint, the durability of the selected wood material is high enough to mask any shortcomings in design, workmanship, and maintenance.
Unfortunately, it is often the opposite and materials which have the potential to perform well in a
particular use class situation fail due to poor design. Figures 4 and 5 show two examples of
bridge railings made from English oak (Quercus robur). The first railing showed severe decay
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after some years in service evolving from deep cracks and water trapping joints, which could have been avoided if tree ring orientation and execution of water draining gaps were carefully considered. Consequently, the expectations of the local authorities had been disappointed and for renewal of the railings coated steel was selected.
Figure 4: English oak (Quercus robur) timber bridge. Left: Severely decayed railing. Right: Replacement with coated steel.
Figure 5: English oak (Quercus robur) timber bridge. Left: Replaced element forming a lap-joint. Right:
Replacement in combination with ‘sound cutting’.
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Similar decay problems occurred in a second bridge (same local authorities), but a different renovation strategy was applied. Only severely decayed elements were replaced. Slightly decayed parts were ‘sound cut’ (superficial removal of decayed portions) and new oak wood was used for replacements. Figure 5 shows that anything that could have been done wrong was done wrong: 1) Pre-infected wood was used for replacement, 2) old water traps were rebuilt, 3) new water traps were created, 4) water drainage was hindered, and 5) wood was exposed in direct contact with steel and concrete in the splash water zone. The performance of the repaired bridge will again be disappointing. The highly varying durability of English oak will not supersede the mistakes made by design. Deeper knowledge about wood durability under different moisture scenarios, about the effect of pre-infested wood and about basic rules of durability-based design are needed to avoid repeating mistakes. Such knowledge needs to be transferred to designers, planners, craftsmen, authorities, and other decision-takers.
5. STANDARISATION ISSUES 5.1 Standardisation level #1
Durability standards worldwide are using a classification system that is based on assigning intervals of relative values to durability classes ranging from ‘non-durable’ to very durable’ (e.g.
EN 350, CEN 2016). Relative values, sometimes called ‘x-values’, are needed to become independent from the actual rate of decay, mass loss, strength loss or whatever is considered to quantify ‘durability’. In fact, ‘durability’ is a non-absolute and still unit-less measure. However, codifying durability test results and expressing durability of wood as classes suggests that it is independent, not only from the geographical location, but also from the test conditions in terms of wetness, inoculum potential, and other factors more. Normalization of test results in durability testing is usually achieved through using reference materials such as pine sapwood with the aim to become independent from exposure related differences. Contrary to expectations, the relative durability does also vary significantly between test sites, test conditions and reference materials used for the test (Brischke et al. 2013, 2018). Figure 6 shows exemplarily the relative durability (resistance factor) for six wood species tested at different locations and corresponding durability classes, which differ in extreme up to five classes.
Figure 6: Variation of the resistance factors (relative durability) of six selected wood species and corresponding durability classes (DC) according to EN 350 (CEN 2016). Modified after Brischke et al.
(2013).
0 1 2 3 4 5 6 7 8 9 10
Western Red Cedar
Douglas fir White cypress European oak Brush box Northern silky oak
Wood species
Resistance factor [-]
- minimum/maximum xmean value s ▒ 95% confidence interval
x
x
x
x
x
x 5 4 3 2 DC 1
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A lot of expert knowledge is needed to fully understand the background of durability classification of wood and for interpretation of DCs obtained under different test scenarios.
Transporting this knowledge to planners, engineers, and users is a challenge.
5.2 Standardisation level #2
Standard guidance documents are rare in the wood protection sector. On the European level EN 460 (CEN 1994) provides some guidance on the durability requirements for wood to be used in hazard classes. However, as can be seen from Table 1, the question if natural durability of a wood species is sufficient for a use in a particular use class is not answered clearly. Numerous restrictions need to be considered and still the advice is very vague since often (preservative)
‘treatment may be advisable’. In summary, the guidance on durability classes based on EN 460 (CEN 1994) needs to be considered useless for decision-takers.
Table 1: Guidance on the durability classes of wood species for use in hazard classes (today defined as use classes - UC) according to EN 460 (CEN 1994)
DC 1 DC 2 DC 3 DC 4 DC 5
UC 1 ○ ○ ○ ○ ○
UC 2 ○ ○ ○ (○) (○)
UC 3 ○ ○ (○) (○) – (x) (○) – (x)
UC 4 ○ (○) (x) x x
UC 5 ○ (x) (x) x x
○ Natural durability sufficient
(○) Natural durability is normally sufficient, but for certain end uses treatment may be advisable
(○) – (x) Natural durability may be sufficient, but depending on the wood species, its permeability, and end use preservative treatment may be necessary
(x) Preservative treatment is normally advisable, but for certain end uses natural durability may be sufficient
x Preservative treatment necessary
The standard EN 460 (CEN 1994) is currently under revision and might be adopted in a way that allows more and better guidance for those who have not detailed knowledge about wood durability. A future vision might be to achieve a technical document similar to Eurocode 5 (EN 1995-1-1, CEN 2010) in structure and engineering thinking.
6. FUTURE NEEDS AND PLANS
The need for robust performance data is becoming more and more evident. This derives from the European Construction Products Regulation (EC 2011) as well as from various consumer groups becoming increasingly sensible to safety and health aspects, but also to environmental friendliness. To compete with other building materials such as steel, concrete, glass or polymers, the lack of performance data for bio-based building materials needs to be resolved (Kutnik et al.
2014, Jones and Brischke 2017). Therefore, it seems indispensable to intensify networking between: 1) different research organizations and institutions as well as between disciplines such as material science (wood, lignocelluloses, agricultural products, and polymers), biology and plant pathology, engineering, biotechnology, and building physics, 2) between research communities, industry and education.
The wood sector is still lacking an adequate communication strategy that allows connecting
academia and science with industry and end-users. Better education and provision with relevant
data and information in the right format to craftsmen, engineers, planners, and architects is as
important as the establishment of building codes, standards, technical reports and finally design
guidelines. Vocational Sciences are still underrepresented in the wood building sector and are
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consequently becoming of increasing importance. Continuing Professional Education (CPD) (Nicol and Pilling 2005) for architects, engineers and other construction professionals is inconsistently provided across Europe. This is not only true for timber – although timber currently forms a very small part of the material and programmes currently on offer – but the quality of much of the existing information (being not always independent or objective) about timber can be seen to act as a disincentive to increased specification of timber and timber products. As a natural and highly variable material - and unlike many other building materials and products - timber requires sound knowledge of its characteristics and properties for effective design and construction to take place. With the engineered and modified timber sectors as well as other areas of timber construction undergoing rapid growth, together with ongoing regulatory changes affecting this industry, it is important that construction professionals are able to avail themselves of high quality CPD on timber from qualification through to retirement. In part this is necessary because education in material science and natural building materials forms only a small element – if any – within current undergraduate and post-graduate curricula for construction professionals, resulting in a minimal knowledge base about timber and timber products.
A second issue is that many existing CPD programmes are designed to be self-regulating with no testing of either learning or achievement. In many instances these courses and seminars are offered by producers or distributors of products, with a consequent lack of independence and objectivity often being a hallmark of the material on offer. The challenge therefore is to develop a high quality, pan-European CPD programme for construction professionals that covers all aspects of timber use.
Knowledge transfer and education along the forest-wood value chain is the key to an appropriate use and application of wood (on its own and as part of a hybrid material) and other bio-based materials to finally increase the acceptance of wood as a reliable building material for today and in the future!
7. CONCLUSIONS
The majority of the past European research projects focused on the exchange of information between experts coming from a rather narrow field. The current idea is to enable transfer of knowledge through the whole forestry-wood-construction value chain. Transfer of knowledge will enable better understanding of wood as building material and wider and safer use of wood for building applications. This is predominately important since not only in Europe forests are used ‘over-sustainably’, it is that stocks of timber are still increasing and many forests are still underutilized, while synthetic materials are superseding wood in more and more areas. In particular, the ban of extremely effective but harmful wood preservatives led to a loose of market shares – not at least because the wood industry lacked own alternatives.
To significantly improve the standing of wood as building material stakeholders along the whole forest-wood-value-chain need to be sensitized for the special character of wood. Concepts for knowledge transfer and education need to be developed and implemented. This needs to be a holistic approach starting at preschools age and ending in hardware stores and construction sites.
8. REFERENCES
Beinhofer, B (2010): Comparing the financial performance of traditionally managed beech and
oak stands with roomy established and pruned stands. European Journal of Forest Research,
129(2), 175-187.
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Brischke C, Gellerich A, Militz H (2018): Testing the durability of timber products above ground using the block-test method – A critical review. Proceedings IRG Annual Meeting, IRG/WP 18-20637, 17 pp.
Brischke, C, Meyer, L, Alfredsen, G, Humar, M, Francis, L, Flæte, P,O, Larsson-Brelid, P (2013): Natural durability of timber exposed above ground - a survey. Drvna industrija, 64, 113- 129.
Eaton, R A, Hale, M D, (1993): Wood: decay, pests and protection. Chapman and Hall Ltd.
EC (European Commission) (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 Text with EEA relevance EC (European Commission) (2017): Wood and other products. Available via:
https://ec.europa.eu/growth/sectors/raw-materials/industries/forest-based/sustainable-forest- management/wood-other-products_en
