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EN 350:2016

Durability of wood and wood-based products – Testing and classification of the durability to biological agents of wood and wood-based materials

Note: This new standard replaces EN 350-1 and EN 350-2 which have now been combined into one document.

It gives guidance on methods for determining and classifying the durability of wood and wood-based materials against biological wood-destroying agents.  as well as wood species and wood-based materials, these methods also apply to those which have been heat-treated, preservative treated as well as to modified wood.

The wood-destroying agents considered in this standard are:

  • Wood-decaying fungi (basidiomycete and soft-rot fungi)
  • Beetles capable of attacking dry wood
  • Termites
  • Marine organisms capable of attacking wood in service.

EN 350 provides the durability classes of wood-based materials to various wood destroying organisms in four separate tables:

Table 1: Durability Classes of wood-based materials to attack by decay fungi  
 Durability Class1  Description

DC 1

DC 2

DC 3

DC 4

DC 5

Very durable

Durable

Moderately durable

Slightly durable

Not durable

 Note: ¹ The durability classes refer only to the heartwood. Sapwood is classed as not durable (DC 5).

 Table 2: Durability Classes of wood-based materials to attack by wood-boring beetles1

 

 Durability Class  Description

DC D

DC S

Durable

Not durable

 Note: ¹Beetles = hylotrupes bajulus, Anobium punctatum, Lyctus brunneus and Trichoferus holoscericeus.  Rossi (= Trichoferus holosericeus cinereus).

 Table 3: Durability Classes of wood-based materials to attack by termites 

 Durability Class  Description

DC D

DC M

DC S

Durable

Moderately durable

Not durable

 Table 4: Durability Classes of wood to attack by marine organisms 

 Durability Class  Description

DC D

DC M

DC S

Durable

Moderately durable

Not durable

 Durability of wood-based materials is further  covered in the standard’s Informative Annexes.

Annex B gives the biological durability of selected wood species considered of economic importance in European countries as follows:

  • Table B.1 – Durability of heartwood and treatability of softwood species
  • Table B.2 – Durability and treatability of temperate hardwood species
  • Table B.3 – Durability and treatability of tropical hardwood species
  • Table B.4 – Classification of commercial groupings

Annex C gives the classification of treatability of wood with aqueous wood preservatives i.e. the ease with which wood can be penetrated by a liquid applied during a process of wood impregnation. Depending on the formulation, the achieved penetration may be different.

Table C.1 – Classification of the treatability of wood

Treatability Class  Description1 Explanation
1 Easy to treat Easy to treat; sawn timber can be penetrated completely by pressure treatment.
2 Moderately easy to treat Fairly easy to treat; usually, complete penetration is not possible, but after 3 or 4 hours by pressure treatment more than 6 mm lateral penetration can be reached in softwoods and in hardwoods a large proportion of the vessels will be penetrated.
3 Difficult to treat Difficult to treat; 3 – 4 hours by pressure treatment may not result in more than 3 mm to 6 mm lateral penetration.
4 Extremely difficult to treat Virtually impervious to treatment; little preservative absorbed even after 3 – 4 hours by pressure treatment; both lateral and longitudinal penetration minimal.
Note:   Historically treatability data may use other descriptive terms which approximate to the treatability classes as follows:

  • Class 1   Permeable
  • Class 2   Moderately resistant
  • Class 3   Resistant
  • Class 4   Extremely resistant.

Annex D deals with the classification of permeability to water – the ease with which water penetrates a wood-based material and is released by evaporation. The term permeability differs from that of treatability as the latter measures penetration of a aqueous solution following a defined treatment schedule whereas permeability to water reflects both the spontaneous uptake and release of water during defined exposure conditions.

 Annex F covers classification by performance i.e. the ability of a wood species or wood-based material to withstand deterioration over time. It provides an understanding of the performance of wood in service.

Measuring durability class – advice from British Standards Institution (BSI)
  • Annex F of EN 350:2016 states that field tests and aging procedures are required where performance is a consideration.  However, changes from the previous version of EN 350 mean that field testing is no longer a requirement to measure durability class.
  • BSI believes that ‘testing in accordance with Informative Annex F (section F.2 paragraph 2) is essential to deliver a useful durability measure’ and advises UK specifiers to follow this more stringent practice.
  • Under the new standard, laboratory testing may now be used but ageing procedures are not required for these. Durability classes can therefore be assigned to wood without needing to take aging into account.
  • The BSI believes that durability class is only a useful measure if it is used in the context of how a material may perform in use. Durability classes calculated using the normative text of this standard may therefore not be useful when considering how a wood species or a wood-based material might perform.

 

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All Questions OSBPlywood

What are the main changes to the FSC Chain of Custody Certification standard?

Download What’s New in FSC revised COC standard.   Also, the previous FSC compulsory verification programme has been replaced by a due diligence protocol with a new risk assessment system. Learn more.  North American good forestation practice supports the aims of EUTR.  Its sustainably managed forests comply with one or more of the five leading certification agencies responsible for verifying proper forestry practices.

 

Can US Underwriters Laboratories certified EPDs be used for environmental performance ratings under the BREEAM system?

Learn how APA products can count towards a building’s BREEAM rating.  The British Research Establishment and the US Underwriters Laboratories  now recognize each other’s certified EPD making it simpler for APA member mills to gain environmental performance ratings under the BRE Environmental Assessment Method  (BREEAM).

Does APA plywood meet the lowest category (E1) for formaldehyde release without need for further testing?

Under the harmonised European Standard for wood-based panels, EN 13986, Annex B, ‘wood-based panels glued with resins emitting either no formaldehyde or negligible amounts of formaldehyde after production as e.g. isocyanate or phenolic glue’ are to be classified as E1 (the lowest formaldehyde release class) without further testing.

See APA’s guide Formaldehyde and Engineered Wood Products.  APA plywood is designated under the lowest E1 category for formaldehyde release without needing further testing.  APA’s US PS 1 and PS 2 plywood have been tested to EN 717-1 and formaldehyde levels already meet the requirements for the E1 classification limit.

Also see:  Formaldehyde (plywood) and Formaldehyde (OSB).

 

 

Can APA plywood and OSB be used in non-construction applications?

US plywood and OSB are equally effective as sturdy, robust and cost-effective solutions  for non-construction applications – from shelving, site hoardings , protective linings in the cargo bay of delivery vehicles to packaging and furniture.   See APA’s Performance Panels.   Need help to decide what grade or type of panel to use for a specific application? APA’s Industrial Panel Selection Guide (Form T200) is another easy to use resource.

How do I equate product Use Classes with the Service Classes given in Eurocode 5 for the design of buildings using engineered wood products?

See APA’ s guide  to Service Classes and Use Classes. For maximum biological durability, both Service Classes and Use Classes must be considered when specifying US CE-marked panels .  This guide helps you make the right selection.

 

‘Hazard classes’ have been replaced (see updated EN 335:2013) by Use Classes covering plywood and OSB.  They will also cover LVL when the LVL standards have completed their current update.  Use Classes are based on different environmental exposures that can make the panel susceptible to deterioration. , as given in Eurocode 5, are used for assigning  strength values and calculating deformation in load bearing situations.  They are determined by the moisture content of the panel corresponding to the environmental humidity and temperature during service.

How do APA’s member’s products count towards a sustainability assessment for new construction or in refurbishment projects?

The British Research Establishment and the US Underwriters Laboratories  now recognize each other’s certified EPD making it simpler for APA member mills to gain environmental performance ratings under the BRE Environmental Assessment Method  (BREEAM).  This is the UK’s leading and most widely used environmental assessment method for buildings and communities. It sets the standard for best practice in sustainable design and has become the de facto measure used to describe a building’s environmental performance. Learn how APA products can count towards a building’s BREEAM rating.

What is a ‘life cycle stage’ and how do these link to the environmental assessment of whole buildings?

A good starting point is our Green Topics section and  Types of EPD and the five life cycle stages

How do core category rules link with environmental product declarations?

EN 15804:2012 +A1:2013 provides the core Product Category Rules (PCR) for the production of Environmental Product Declarations (EPD) for all construction products and services.  Review with main environmental standards.  For more details see: Core Product Category Rules (PCR) for Products and Services. 

Whose responsibility is it to check that wood products being imported into the EU do not originate from illegally sourced timber supplies?

The European Union Timber Regulation (EUTR) puts specific obligations on operators and traders . Operators (or importers) are any (natural or legal) person first placing timber on the EU market. They must maintain records of any traders that they supply timber to.  They must implement a due diligence system to minimise the risk of putting illegal timber or any of its derived products on the market.  Learn more.

Does the EUTR require mills to provide any extra documentation for customs entry into the European Union?

The European Union Timber Regulation (EUTR) puts specific obligations on operators and traders and applies to timber originating in the domestic (EU) market, as well as from third (non-EU) countries such as North America. The information it requires has to be retained for at least five years and be available on request.  See European Timber Regulation.

Must all plywood and OSB panels carry a CE marking?

Manufacturers of wood-based products  covered by either a harmonised European standard (hEN) or a European Technical Assessment (ETA) must apply for CE marking under the 2013 Construction Products Regulation.  See CPR & CE Marking  and our Official Guidelines section.

What is the definition of a construction product under the CPR?

This applies to any product or kit which is produced and placed on the market for incorporation in a permanent manner in construction works or parts thereof and the performance of which has an effect on the performance of the construction works with respect to the basic requirements for construction works.’

Products must clearly display the CE mark and have the correct Declaration of Performance documentation.  For more info: CPR & CE Marking.

What is a Declaration of Performance referred to under the Construction Products Regulation?

Under the CPR, manufacturers wishing to trade in the European market are legally required to set down the levels of performance for any construction product.  They have to be listed in an official document called a Declaration of Performance.

What is the difference between Structural 1 and Exposure 1?

Exposure 1 is a glue bond classification.  It uses the same 100% waterproof glue as exterior panels and refers to a panel’s durability when long delays in construction are expected or when facing high moisture content. For plywood, see  https://apawood-europe.org/products-trademarks/plywood/trademarks/glue-bond/.  For OSB:  https://apawood-europe.org/products-trademarks/osb/trademarks/exposure-durability-classification/

Structural 1 refers to a panel’s superior performance characteristics.  For OSB, see https://apawood-europe.org/products-trademarks/osb/comparable-performance-requirements/

For Structural 1 plywood,  all panels have special improved veneer grades and if manufactured to the American PS1 standard, the veneer grades will be species with a Group 1 strength classification.  See group classification of species.

 

The CE-mark on an APA plywood panel means it conforms to European Standards – but which ones?

Plywood Design Information looks at the plywood grades A-A, A-B, A-C; B-B, B-C; C-C, C-D and the relevant standards that the trademarked panels comply with.

 

I want to use a Rated Sheathing panel for flooring/ roofing application, what info do I need to know?

For plywood, see Span rating.  For OSB, see Span rating. A full range of technical information in under Products and Trademarks.

What extra strength benefits do Structural 1 OSB panels provide over standard Rated Sheathing panels?

OSB Structural I  on an APA trademark indicates that the OSB structural-panel meets the requirements of a Performance Rated panel.  This delivers superior design capacity for these panels over OSB Rated Sheathing and Sturd-I-Floor.  Also see Comparison of Superior Design Capacities for OSB Structural I Sheathing with OSB Rated Sheathing.

What is the difference between a touch-sanded panel and sanded panel?

Veneer in a finished US trademarked plywood panel must conform to one of the six grades listed in the US PS 1-09 standard: N, the highest classification (rarely produced), followed by A, B, C-plugged, C and D.  Non-overlaid APA plywood panels come in three levels of surface finish – sanded, touch-sanded and unsanded.

Also see veneer grades for Popular APA Plywood Panels.

How do APA veneer grades match those given in the European standards

APA has produced two easy to follow guides to help match the grade numbers given on a US finished plywood panel with the requirements of  EN 635-3.

Detailed guide listing permissible defects – with maximum sizes.

Simplified guide to the US PS 1-09 veneer grading rules and appearance grades in EN 635-3 based on the appearance of the surface veneers. Equivalents cannot be exactly compared as two different sets of grading rules apply.

How do I correctly gauge the face appearance a plywood Siding panel?

I want to specify an APA panel for concrete formwork – what do I need to know?

See APA’s comprehensive Concrete Forming Design/Construction Guide for architects, engineers and contractors and the types of APA concrete forming plywood panels.

Are APA panels tongue and grooved on all four edges?

APA panels have a tongue and groove profile on their two long edges.  This eliminates the need for support (blocking) under adjacent panel edges to prevent them from deflecting independently of each other when load is applied.  See Tongue & Groove  (plywood) and Tongue & Groove (OSB).

I am not familiar with the term ‘Sized for Spacing’ – what is its significance?

‘Sized for Spacing’ on APA Rated Sheathing, APA Rated Sturd-I-Floor and APA Rated Siding trademarks indicates that the manufacturer has produced the panel to a size slightly less than the traditional nominal 2440mm (96″) by 1220mm (48″).  It is done to facilitate proper panel spacing during construction.  See Sized for Spacing  (plywood) and Sized for Spacing  (OSB).  For further technical details see Product and Trademarks.

How are Performance Category and thickness related?

Performance Category, Panel Thickness and Span Ratings are key categories that need to be considered together.  See Thickness, Performance Category  (plywood) and Thickness, Performance Category (OSB).

I’d like to know more about a panel’s Span Rating and how it links to thickness.

Plywood: Span rating
OSB: Span rating

What is Span Rating on the APA trademark and why is it important?

Span Rating denotes the maximum recommended centre to centre spacing of supports in inches over which the panel should be placed with its strength axis across two or more supports. Plywood: Span rating.  OSB: Span rating

What is the difference between Exposure 1 and Exterior plywood panels? What are their appropriate uses?

Bond classification relates to moisture resistance of the glue bond and therefore to the structural integrity of the panel.  See glue bond durability classification (plywood) and exposure durability (OSB).

What are the main OSB panels likely to be available in Europe?

See APA’s guide to panel grades  and also info on understanding the trademark.

What are the main plywood panels likely to be available in Europe?

What are the main European standards that I would need to be aware of for OSB panels?

The main standards are: EN 13986 and EN 300.   But also see the other relevant standards for OSB.

What are the main European standards that I would need to be aware of for plywood panels?

The main standards are: EN 13986, EN 636, EN 314, EN 635-3.  And for more details, see EU standards for plywood.