Manual: Industrial Wood Preservation Specification and Practice 2nd edition April 2012 Publication ref: WPA/WPSM Manual: Industrial Wood Preservation - Specification and Practice 2nd Edition: April 2012 Published by: Wood Protection Association 5C Flemming Court Castleford West Yorkshire WF10 5HW www.wood-protection.org [email protected] Clicking on highlighted text will take you to the appropriate place in the The information contained in this publication is given in good faith. Every effort has been document or to a linked web site made during the consultation and publication process to ensure the guidance given is page if it begins with the prefix www. accurate. The Wood Protection Association cannot accept any liability for loss or damage arising as a consequence of the information given. © Wood Protection Association, April 2012 All rights reserved. No part of this publication may be copied, reproduced, stored in or introduced into a retrieval system or transmitted in any form by any means, electronic, mechanical or other without the prior permission of the Wood Protection Association. About the Wood Protection Association (WPA) The WPA is a not for profit technical and advisory organisation interested in the development and promotion of wood protection technology to support the use of wood as a cost effective, sustainable and low environmental impact construction material. The WPA acts as a technical advisor to British and European Standards setters on wood preservation, modified wood and the fire protection of wood. On the Regulations governing wood protection, the WPA enjoys lead body status with agencies like the Health & Safety Executive, Environment Agency, Scottish Environmental Protection Agency, the Department for Environment, Food & Rural Affairs and the Highways Agency. The roots of the WPA go back to the 1930’s with the formation of the British Wood Preserving Association which became the British Wood Preserving & Damp-proofing Association in 1989 and subsequently the WPA in 2006. As designers look increasingly to wood as a low carbon construction material the WPA is committed to providing guidance on the best ways to ensure wood is fit for the purpose intended. ARCHITECTS HELPLINE If you need help with a wood preservation specification then e-mail the WPA [email protected] © Wood Protection Association April 2012 1 Publication ref: WPA/WPSM Contents Page How to use this manual 3 Quick click to specifications 4 1. Objectives and practice of industrial wood preservation 5 2. Wood preservatives 5 3. Preservative treatment 12 Commodity Specifications C1 Timber to be used in cooling towers 18 C2 Timber for use permanently or intermittently in contact 19 with sea or fresh water C3 Fencing timber 21 C4 Agricultural and horticultural timbers 23 C5 Non load-bearing external softwood joinery and external fittings 25 (excluding cladding) not in ground contact C6 External timber cladding 27 C7 Timber for use in buildings in termite infested areas 28 C8 Constructional timbers (excluding walls of timber framed houses) 30 C9 Timber framed housing 31 C10 Hardwood external joinery 33 C11 Wood-based board and engineered wood products 34 C12 Decking timber 38 4. Treating timber 45 5. Using treated timber 47 6. Safety, health and the environment 49 7. Supporting information 50 Appendix 1 57 © Wood Protection Association April 2012 2 Publication ref: WPA/WPSM How to use this manual Treated wood in action This manual provides detailed guidance on industrial wood preservation for specifiers, timber treaters and those involved in using treated wood. Underlined links in this manual are designed to speed navigation and simplify access to the key information relevant to their particular interests. Specifiers The manual provides a user-friendly system of specifications on the type and level of treatment most appropriate for the desired life of timber commodities in UK service conditions. The WPA Commodity (‘C code’) Specification system covers many of the common uses for timber species whose natural durability is insufficient to deliver an adequate service life. Model specifications are presented that provide a simple and reliable way of specifying treatment without the need for detailed knowledge of the underlying Highways fencing principles. National Highways Sector Scheme for pre-treated fencing (Sector Scheme 4) Full details are also available to enable specifiers who prefer to either include a detailed requires that motorways and trunk road specification or simply wish to be assured that the model specifications are sufficient to fencing is treated to a 30 year service life cover all aspects of wood choice, preparation for treatment, treatment itself and post- specification. treatment handling. BSEN335:1 Use Class 4 (for posts), The manual also provides guidance on the allocation of timber components to Use Classes Use Class 3.2 (for rails). and Service Factors applying to end-use situations which also help to guide the decision on Treatment in accordance with BS 8417. whether treatment is required or not. Desired service life: 30 years. Information is also provided on quality assurance procedures that underpin confidence in Photo courtesy: Calders & Grandidge the performance of treated material. Treatment plant managers and operators The manual includes detailed information on preparing timber for treatment and the treatment to be achieved to conform to specifications received. While in many cases preservative suppliers will assist treatment companies with guidance on processes to achieve combinations of penetration and retention of preservative products, plant operators can also use the tables and techniques described to assess the conformity of their procedures with the requirements of preservative treatment specifications. Sections are also included on handling and storing treated timber, quality assurance and analytical procedures. Users of treated timber The manual provides information on characteristics of treated timber and guidance on the use, safety and disposal of treated timber. The relevant sections should be consulted by users to ensure that the full benefits of additional durability conferred by treatment can be obtained while conforming to safety, health and environmental protection rules. © Wood Protection Association April 2012 3 Publication ref: WPA/WPSM Quick click to Commodity Specifications Introduction The WPA Commodity (‘C’) Specifications provide a simple route to accurate specification based on the latest British Standard BS 8417:2011. Treatment is tailored to the risk faced by timber in five Use Classes: 1: Interior dry; 2: Interior – risk of wetting; 3: Exposed to weather, above ground; 4: In ground or water contact; 5: In sea water. The Commodity Specifications allocate timber commodities to appropriate Use Classes and identify suitable preservative treatments. Simple specifications based on the Commodity Specifications mean that no further detail is needed to ensure that a specification is comprehensive and calls up all the relevant detail on suitable timber species, preservatives and quality assurance. Example model specifications are given on page 18. The Commodity Specifications Preservative treatment of: For Model Specification clauses C1 Timber to be used in cooling towers go to page 18 C2 Timber for use permanently or intermittently in contact with sea or fresh water C3 Fencing timber C4 Agricultural and horticultural timbers C5 Non load-bearing external softwood joinery and external fittings (excluding cladding not in ground contact C6 External timber cladding C7 Timber for use in buildings in termite infested areas C8 Constructional timbers (excluding walls of timber framed houses) C9 Timber framed housing C10 Hardwood external joinery C11 Wood-based board and engineered wood products C12 Decking timber © Wood Protection Association April 2012 4 Publication ref: WPA/WPSM 1. Objectives and Practice of Industrial Wood Treated wood in action Preservation The fundamental objective of the pre-treatment of wood with preservatives is to ensure that, even when the wood is inherently vulnerable to biological deterioration, it remains sound throughout the design life of the structure of which it forms a part. Achieving this objective enables designers and specifiers to make maximum use of wood - the most environmentally acceptable construction material available. It is important to understand, however, that preservation is not a substitute for good design and appropriate maintenance programmes over the life of a structure, rather it is one component of a holistic approach to design, construction and maintenance. It is also an objective of pre-treatment to achieve the desired improvement in wood Roofing timbers durability with the minimum of environmental impact. It is a major advantage of pre- BSEN335:1 Use Class: 1 (dry) or treatment (which may often be precautionary in nature) that it is carried out in controlled Use Class 2 (where there is a risk of impregnation or application equipment which: wetting or condensation) a) gives minimum potential for exposure of either workers or the environment, to wood WPA commodity code specification: C8 preservative chemicals, and b) can impart greater durability than is possible with uncontrolled superficial processes, Photo courtesy: Lonza Wood Protection such as brushing and spraying. 2. Wood preservatives 2.1 Regulation of preservatives The sale and use of wood preservatives are governed in the UK by the Control of Pesticides Regulations 1986