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GBE Durability Gap (Opinion) G#41218

Brian Murphy aka BrianSpecMan BRM @ Build4 CAPEM Showroom

GBE Durability Gap (Opinion)

GBE > Encyclopaedia > Opinion > State of the Industry > G#41218

About:

Scope/Extract:

  • These Opinion Posts have the potential to contribute to filling part of the ‘knowledge-gap’ and I am planning to ring every bit of 50 years of experience in violet construction, 40 years of specification consultancy and 24 years of green construction into its content.
  • GBE Continuing Professional Development (CPD) seminars will also be created and published to support this paper and its promotion.

Durability-Gap:

Problems

    • Marketing campaign (6-page advert) by the plastics sector focussed on:
      • Challenge of unique characteristics of timber needing knowledge and know-how to avoid failures.
      • Failures in forest and plantation certification and chain of custody.
      • Need for and environmental impact of, fire and preservative treatments, protective and decorative coatings.
      • Weatherboarding not having a ‘Manufacturer’ and not having a ‘Certificate’ or ‘Guarantee’.
    • The architectural education ‘Knowledge-gap’ leaves architects:
      • Without the confidence to engage with timber
      • ‘Going in blind’ and falling foul of these complexities.
      • Not having the confidence to adopt a major solution to the climate crisis.
      • Lack of use of timber due to fear of failure (JR)
    • Water or moisture vapour ingress:
      • Affecting timber durability.
      • Building durability.
      • Leading to mould and rot affecting timber structural integrity.
    • Long term maintenance costs of incompetent construction (JR)
    • Wasted material due to need to replace defective materials (JR)

Solutions:

    • Timber Development UK (TDUK) is former TRADA and marketing organisation Wood for Good WFG to challenge competing sector marketing.
    • Improved Architectural Education for competency and employability?
      • Improving confidence in the use of timber solutions
        • (including designer, user and insurance perspective) (JR)
      • Reducing replacement/upgrade needs/cost (JR)
    • Sources of competency know-how:
      • Competent construction:
        • National Building Specification (NBS) Guidance Notes a good starting point.
          • But an expensive subscription service unless you need specifications.
        • Continuing Professional Development (CPD) seminars:
          • Offered by: BM TRADA, TDUK, ACAN, SCAN, ASBP, etc.
        • Competent design guide publications:
          • TRADA, TDUK, Edinburgh Napier University.

Design Life & Durability

  • Scope: BS 7543, Component Life, Guarantees, Track record, Lifecycle assessment.
  • Client’s expectations:
  • Meet Regulations and Legislation.
  • Company Annual Report.
    • Statements of intention on Environmental issues.
    • Commitment to BS EN ISO 14001.
  • But do we as designers give them the opportunity to put their money where their mouth is?
  • Life Expectancy:
  • Appropriate life for the product / building.
  • Made to all aspects of the standard?
  • Housing Association Property Mutual (HAPM) manual:
    • Got its ‘Green’ quotient for products.
  • Design Life & Durability
  • BS 7543:1992:Guide to durability of buildings and building elements, products and components.
    • Table 1,
    • Normal Life. 60 years
    • Table 2,
    • Maintainable with periodic treatment, will last for the life of the building.
  • BS 7543 Table 1
  • 120 Years Long Life
    • g. British Library Euston, Portcullis House, BedZED
  • 60 Years Normal Life
    • Traditional Loan/Mortgage Period
  • 30 Years Short Life
    • 2023: BRAD 30 years: Normal Life!!!
  • 15 Years Temporary
  • BS 7543 Table 2
  • Maintainable with periodic treatment,
  • Will last for the life of the building.
  • Durability & Design Life
  • Add Shells diagram.
  • Guarantees?:
  • Developers require Guarantees.
  • Employers want them too.
  • Tenants want Collateral Warranties.
  • Manufacturers offer guarantee on products.
  • Applicators offer guarantee on application.
  • Some offer back-to-back guarantees.
  • Warranties: For how long?
  • Developers want 25 years.
  • Private Finance Initiative (PFI) want 25 years.
  • Build Own Operate Transfer (BOOT) want 25 years.
  • What they get is short life products and warranties paid for by monthly premiums.
  • Insurance Policy: For how long?
  • National House Building Council (NHBC) covers for 10 years.
  • Zurich covers for 15 years.
  • Insurability: for how long?
  • Housing Association Property Mutual (HAPM), Building Life Plans (BLP), Building Performance Group (BPG), SPON all developed:
  • Component Life Manuals (CLM) which include insurable ranges:
    • U uninsurable.
    • 5, 10, 15, 20, 25, 30, 35 years.
    • 35 years +.
  • Manufacturers: What is on offer?
  • Polyester Powder Coatings (PPC) offered 25 years on matt recipe.
  • PPC offered less years on gloss recipe.
  • Back-to-back guarantees for product and installation are available from best operations.
  • Most manufacturers offer a lot less.
  • 10 years should be the minimum.
  • 1 years is commonplace.
  • Some guarantees are not worth the paper they are written on.
  • Legal Departments work hard to make sure get-out clauses exist.
  • Some Directors boast about it in front of supply chain whilst specifiers look on.
  • Track Record:
  • Building Inspectors were asking for:
  • ‘Proper Materials’ or 20 Years Tracks Record.
  • If you are inventing new products, there is no track record.
  • Or including reclaimed materials they have already had a life; can they survive another? Why not?
  • Life Cycle Costing:
  • Pay now, Save later.
  • Consider initial cost.
  • Running costs in use.
  • Maintenance costs in use.
  • Weigh up the benefits:
  • Cheap price and short life or high maintenance or replacement(s) costs.
  • Expensive and cheap to run and maintain.
  • CAPEX = Capital Expenditure, OPEX = Operational Expenditure, TOTEX = Total Expenditure.
  • CAPEX + OPEX = TOTEX
  • Icebergs
  • Initial costs above the waterline.
  • Long term costs below.
  • Whole Life Costing:
  • Increasingly expected to be considered,
  • But QS trade does not offer it without another fee.
  • Life Cycle Costing (LCC):
  • Incredibly complex equations.
  • Building Magazine Series of articles.
  • DL&E Davis Langdon & Everest as was.

Design Life:

  • Definitions (See Appendix Jargon Buster)
  • Design Life:
  • Should be part of the briefing process, employer’s requirements or performance specifications.
  • Having been set at an early stage should inform the competency of the detailing and specification:
    • Structural integrity:
      • g. Creep = sagging after deflection or shrinkage over time (affects timber and concrete).
    • Durability:
      • g. choice of materials, protective or proofing measures
      • g. Vapour open construction: passive drying of the building fabric over time.
    • Climate change:
      • Anticipating changing exposure conditions over the life of the building
      • Future anticipated weather data is already available to designers.
      • Future Proofing the building and its services can be part of the design process.
      • Anticipating and making provision for installing additional systems as the climate evolves and buildings need help maintaining conditions.
    • Running costs:
      • Why create a building that needs heating or cooling if it is possible to avoid them both.
      • Anticipate increasing heating or cooling fuel costs and insulate accordingly initially.
    • Retrofitting insulation can be difficult:
      • New building’s detailing may make retrofitting insulation difficult; puncturing many proofing layers in the process, that are impossible to mend.
      • Do not make and leave cavities that could be insulated later, saving money now; insulate them now.
    • Case study: Future Proofing Services
      • British Library Reading Room Readers Desks:
      • American white oak furniture, plywood carcass, in laid linoleum writing surface, inlaid leather linings.
      • Back-to-back desks have a raised services outlet panel with many occupied and unoccupied pop-out brass plates.
      • Counter-staff book ready call light, 13-amp power, USB cable access to BLE Library database, wi-fi, internet, etc.
      • And a cable management hub to hide all cables inside the furniture.
      • As new technology arrives, they can be accommodated easily in an unoccupied brass plate.
    • Codes of Practice (BSI/ISO)
      • BS 7543 refers to Building Design life:
        • Temporary: 15 years, short: 30 years, normal: 60 years and long life: 120 years
      • ISO 15686-1 refers to Building Design life:
        • Temporary: 10 years, short: 25, normal: 50 years and long life: 100 years, 150 years and unlimited
      • In contradiction to these standards Building Regulation 2022:
        • Calls for 30 years for a Normal life (Short life!)
      • BS 7543 refers to Component Design Life:
        • Replaceable (shorter than building life),
        • Maintainable (with maintenance for the life of the building),
        • Life Long (For the life of the building)
      • Design life of the components of the building:
        • Need not be the same as the design life of the building that they are part of.
        • Detailing can hinder replacement by damaging more surrounding materials.
        • Detailing can readily permit disassembly and reassembly.
        • Design for assembly, adaptability, maintainability, reclaim ability and reuse.
        • Methods of fastening or fixing prevents or enables easy replacements.
        • Visible fixings enable easily removable parts.
        • Fixing may need to accommodate thermal and moisture movement.
        • Expressed (shown) fixings can accommodate movement and adaptability.
      • Component Life Manuals (CLM)
        • Hard Copy, CD and on-line service:
          • Housing Association Property Mutual (HAPM),
          • Building Life Plans (BLP),
          • Building Performance Group (BPG),
        • After decades of insuring buildings and assessing materials and components failures.
        • Component life can be anticipated and classified.
        • Failure modes can be identified, to guide the designer away from issues.
        • Classifications: Uninsurable, 5, 10, 15, 20, 25, 30 years to 35 years plus.
        • CLM: Schedules classify all materials in all applications:
          • Long life: comes from BSI & Electrical Kitemarks & BBA Certified products.
          • Short life: materials not made to a standard.
        • Designers can use the CLM to help determine standards and quality marks to include in specifications to ensure long life building is achievable.
        • Project Insurance Assessments/Audits:
          • Design Stage: Specifications of products and materials: classified.
          • Insurers seeks:
            • Longest life (aiming for match project Design Life expectations).
            • Consistency of life (replacing short life components to level out expectancy)
            • Advises review and improvement of specification items.
            • Less likely pay-outs over building’s insured life.
          • Site stage: revisit the reviewed items.
            • Inspecting the specification updates since first audit.
            • Checking on site for compliance with specification.
            • Checking for substitutions and surreptitious substitutions on site.
            • Highlighting any departures to Contract Administrator.
            • Insured can expect lower premiums.
          • Designer/Supervisor role:
            • Competent component choices.
            • Competent building design.
            • Avoiding reduced design life (JR)
            • Achieving the intended design life (JR)
            • Robust Specification against substitution.
            • Proactive Substitution management.
            • Supervision to check competency of building, materials and products.
            • GBS Green Building Specification A90 clauses
            • URL to specification

Durability classes of timber species:

  • Timber comes in a wider variety of species and each species has different durability characteristics.
  • Durability is influenced by a number of factors:
    • Hardwood (generally more durable with exceptions)
    • Softwood (generally less durable, with exceptions e.g. Douglas Fir)
    • Indigenous climate zone (where it grows naturally)
    • g. Tropical are generally more durable,
    • But durability potentially modified if species is grown in another climate zone.
    • g. Wester red cedar grown in UK is less durable that grown on N America.
    • Higher levels of natural resin can improve durability. E.g. Douglas Fir, Western Red Cedar.
    • If species is acidic or not: Oak and Western Red Cedar are acidic.
  • Application durability classes (BM)
    • Each species and variations are given durability classes that relate to application exposure.
    • Application exposure includes:
      • Climate zone: Tropical, Rainforest, Desert, Temperate, Polar,
      • Site exposure conditions: Marine, Urban, Rural, Industrial,
      • External v Internal application.
      • External exposure to weather conditions including precipitation, wind and sunlight.
      • Internal exposure to dry, wet or humid conditions.
      • Relative humidity levels and Moisture Content
    • Schedule of timber species and durability according to TRADA classification of durability
Timber Durability Reclaimed prior use
Ekki 25 yrs + 50 to 100 yrs
Greenheart 25 yrs + 50 to 100 yrs
Jarrah 25 yrs + 50 to 100 yrs
Opepe 25 yrs + 50 to 100 yrs
Balau 25 yrs + 50 to 100 yrs
Oak 25 yrs +
Sweet Chestnut 15 – 25 yrs +
Pitch Pine 10 – 15 yrs +
Douglas Fir 10 – 15 yrs +
  • Add Schedule of building Use Categories (BM)
    • There is a risk that ill-informed specifiers choose species for colour and figuring.
    • A mismatch of durability and application can reduce the life expectancy of the installation.
  • Strength and Stability:
    • Unrelated to durability but related for fitness for purpose of furniture over time.
    • Strength and stability relate to building use, occupant robustness and level of care or misuse.
    • Prisons and inmates fall in the highest category, houses and families in a lower category.
  • Appearance:
    • Unrelated to durability but people’s perception of materials:
    • Solar exposure will fade the timber’s natural colour and turn it silver, grey, brown or black.
    • Differential exposure to sun and weather can leave patches of natural or faded timber.
    • Splash zone staining.
    • Perpetually wet areas due to close-proximity and capillary action.
    • Green timber drying shrinkage and distortions.
    • Clear or coloured stains or paints, choice of colour and gloss levels.
    • These and other issues can encourage building owners to replace parts sooner than needed or sooner because needed.

Position in Log:

  • Choosing timbers:
    • Ideally, we only use heartwood (older core of tree trunk/branches).
    • Not sapwood (living outer layers of trunk/branches, moisture transport route from roots to leaves).
    • Different species have different proportions of heartwood to sapwood.
    • Ideally all sapwood is removed since it is lower strength, more perishable and less durable, different appearance.
    • Preservative treatment of sapwood can make it more durable.
    • When cutting a circular trunk into rectangular sections of heartwood, some softwood may be present.
    • Joiners will probably choose their pieces of timber to ensure exclusion of sapwood.
    • Carpenters may not make the same kind of choices.
  • Applying timbers:
    • Wet ‘green’ timbers need to dry or be dried to a safe moisture content to avoid rot and infestation.
    • Sections of timber from different positions in the log will distort in different ways when drying.
    • Tree log milling will adopt a cutting sequence and orientation to optimise the amount of sound timber obtained that are not compromised by their position in the log.
    • The position in the log is revealed in each section of the timber by way of reading the grain pattern in the end of the section.
    • The position in the log should be taken into consideration when applying timber sections.
    • Due to their differential drying shrinkage rates sections can curl as they dry and flatten as they wet.
    • This curling can compromise the integrity of an assembly:
    • Board on board weatherboarding can curl, joints open and let rainwater in through the open joints.
    • Placing board front to back, front to front or back-to-back will result in different curl patterns.
    • Curling can be predicted by inspecting end grain and arranging curls to close gaps, not open them.
    • Curling in many details can lead to gaps where tree debris and bird droppings can lodge and expose the timbers to conditions conducive to failure.
    • Applying water repellent and moisture permeable stains or coatings on all hidden faces of timber can help resist those failures for longer.

Design to avoid preservative treatment:

  • Scope:
    • All timber applications in exposure conditions worse than ‘internal’.
    • Water soluble preservative treatments exposed to weather can be washed out of timbers.
    • Preservative treatments washed out of timbers can pollute soil or water bodies below timbers.
    • Natural Tanning from acidic timbers can leach out and stain absorbent materials below.
    • Natural Tanning from acidic timbers can leach out and pollute soils or water bodies below.
  • Problem:
    • Timber exposed to weather precipitation is vulnerable to absorbing water and moisture vapour.
    • Timber that absorbs water and moisture vapour is vulnerable to increasing moisture content.
    • Timber with moisture content above 20% is vulnerable to mould, rot and infestation.
    • Preservative treatment is necessary if using less durable timber species in more onerous conditions.
    • Preservative treatments have high potential negative impact in manufacture, application, in use and after first life as a waste.
  • Solution:
    • Use of durability classes to avoid preservative treatment:
      • By determining the exposure conditions of an application, the designer can choose a species that has a durability class that is suitable or better in that exposure condition.
      • Thus, voiding need for preservative treatment in timber.
      • Having matching durability class for exposure conditions does not result in endless life expectancy.
      • There may be a limitation E.g. English Oak will only have 25 years life expectancy in contact with soil.
      • If the durability class is unaffordable, use of preservative treatment of vulnerable species will be necessary.
      • Defining the life expectancy required by the treatment.
      • Be sure to check:
        • Unseasoned, Unregularized, Untreated, Unfinished Oak
        • Can be as cheap as seasoned or kiln dried, regularised, preservative treated, finished softwood.
      • Detailing to avoid need for preservative treatment:
        • See also (Below) from:
        • ‘Avoiding water or moisture vapour from entering construction’.
        • Through to:
        • ‘Adding moisture via internal wet trades.’
      • Cross reference to other TDUK Technical paper.

© GBE GBC GRC GBL NGS ASWS Brian Murphy aka BrianSpecMan ****
30th November 2023

Images:

HiiGuru At GDL 2023 NEC BrianSpecMan & Kevin McCloud talking Bats and Birds in buildings

© GBE GBC GRC GBL NGS ASWS Brian Murphy aka BrianSpecMan ****
30th November 2023

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© GBE GBC GRC GBL NGS ASWS Brian Murphy aka BrianSpecMan ****
30th November 2023

GBE Durability Gap (Opinion) G#41218 End.

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