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)
- Marketing campaign (6-page advert) by the plastics sector focussed on:
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)
- Improving confidence in the use of timber solutions
- 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.
- National Building Specification (NBS) Guidance Notes a good starting point.
- Competent construction:
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
- Hard Copy, CD and on-line service:
- BS 7543 refers to Building Design life:
- Structural integrity:
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.
- Use of durability classes to avoid preservative treatment:
© GBE GBC GRC GBL NGS ASWS Brian Murphy aka BrianSpecMan ****
30th November 2023
About:
GBE Opinion
GBE State of the Industry
- Knowledge-Gap (Opinion) G#41163
- Current Architectural Education (Opinion) G#41163
- Absence or inadequate Architectural Education (Opinion) G#41163
- GBE Finance Gap (Opinion) G#41199
- GBE Time-Gap (Opinion) G#41207
- GBE Skills Gap (Opinion) G#41209
- GBE Performance Gap (Opinion) G#41216
- Building Regulations Approved Documents A-Z & 7
- Durability-Gap (Opinion) G#41218 (this page)
Sectors
- Barriers Drivers towards more Sustainable Profitable UK Cement Industry G#182
- Barriers Drivers Sustainable Profitable UK Cement Industry G#1920 N#1771
GBE Greenwash
- GBE Greenwash (Navigation) G#734 N#756
- Polished Concrete Floors (Greenwash) G#737 N#759
- Green Cement (Greenwash) G#735 N#757
- Fibre Cement Cladding (Greenwash) G#948 N#966
GBE CPD
- I used to be a Master Builder v Architect’s don’t do that
- Universal man v One Planet Woman
- Green or Violet materials Which do you use (CPD) #G15560
- Violet (CPD) G#408 N#409
GBE Jargon Buster
- Violet (Jargon Buster) G#1583 N#1516
© GBE GBC GRC GBL NGS ASWS Brian Murphy aka BrianSpecMan ****
30th November 2023