Design for Durability - Lunch & Learn

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This presentation, which includes termite management techniques, will help improve the specification and design performance of wood in construction. The presentation uses structural engineering criteria, years of experience and field trials and predictive modelling to provide guidance on methods to increase the service life of woods used in Australia. Also covered are the affects of natural variation between wood species, the effectiveness of wood preservative treatments and climatic conditions.

Text of Design for Durability - Lunch & Learn

  • 1. Design for Durability
  • 2. Learn more about wood at UTAS
    Centre for Sustainable Architecture with Wood
    Graduate Certificate in Timber (Processing & Building)
    4 units, part time, online
    Areas covered include:
    Wood science
    Design for durability and service for life
    Timber as a renewable resource
    Sustainable design and construction
    Engineered wood products
    International technologies and developments
    Plus, selected topics of individual interest
    More information: Associate Professor Greg Nolan
    (03) 6324 4478 or
  • 3. Learning Objectives
    After this presentation you should be able to:
    Understand the key timber hazards
    Understand the fundamentals of timber durability
    Understand the design factors that need to be considered to achieve satisfactory timber durability performance.
    For architects - AACA Competency:
    Elliot River Fire Tower, QLD
  • 4. Presentation Contents
    Design process
    Main timber hazards:
    Decay, insects, corrosion of fasteners & weathering
    Natural durability & treatment
    Design detailing
    Other hazards:
    Marine borer, chemicals, fire
  • 5. Design Process: 1
  • 6. Design Process: 2
  • 7. Design Process: Discussion
    To determine performance requirements you may need to consider:
    Target life expectancy (minimum regulatory, standards or contractual requirements)
    Level of reliability (life safety, cost or consequence of failure)
    Costs (initial vs ongoing maintenance, repair or replacement)
    In the context of building regulations, the Building Code of Australia (BCA) has implicit durability performance expectations:
    see Durability in Buildings Guideline Document at
  • 8. Design Process: BCA Design Life Guideline
    For normal buildings, the design life for most structural timber members is 50 years and for moderately accessible members 15 years.
  • 9. Timber Hazards
  • 10. From a durability perspective, the main hazards that need to be considered are:-
    • In-ground and above ground decay (including hazard or H levels etc)
    • 11. Insects (inc. termites)
    • 12. Corrosion (of fasteners)
    • 13. Weathering
    • 14. Marine borers
    • 15. Chemical degradation (not usually an issue), and
    • 16. Fire (subject of other resources)
    Hazard Classes (H)
    apply to these 3 agents
    Above ground durability trials, Beerburrum QLD
    Timber Hazards
  • 17. Decay
    The performance of timber with respect to decay is:
    • Highly related to the presence of free moisture in the wood above 20% moisture content (MC)
    • 18. Different with respect to decay when in-ground vs above ground (different timber durability ratings apply in each case)
    Macro climatic decay hazard maps have been developed to address these fundamental differences
    In-ground durability trials
    Wedding Bells, Nth NSW
  • 19. Decay: In-Ground Decay Hazard Zones
    In-ground decay hazard zones for Australia
    (Zone D has the greatest in-ground decay potential)
  • 20. Decay: Above Ground Decay Hazard Zones
    Above ground decay hazard zones for Australia
    (Zone D has the greatest decay hazard potential)
  • 21. Decay: Causes
    To thrive fungi need:
    • Moisture > 20% MC in wood
    • 22. Oxygen
    • 23. Temperature >25o to