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Lifetime costs
Softwood boardingÌý
Permeable softwood such as European Redwood. Copper Chrome Arsenate pressure impregnated to British Wood Preserving and Damp Proofing Association (BWDPA) schedule P2; or creosote to schedule T4; or double-vacuum impregnated with organic solvent to schedule V1 or V2Capital cost £35/m²
Net present value for 60-year life £65/m²
Service life 35 years
Non–permeable softwood boarding such as European whitewood. Preservative treatment: double-vacuum impregnated with organic solvent to BWDPA schedule V3; or pressure impregnated with CCA to BWDPA schedule P4; or creosote to BWDPA schedule T5 Capital cost £34/m²
Net present value for 60-year life £64/m²
Service life 35 years
Untreated softwood of a species designated as suitable without preservative treatment (SW) or suitable without preservation if covered (SWC) to Table NA1 of BS EN 942, such as Western red cedar and Douglas firCapital cost £31/m²
Net present value for 60-year life £39/m²
Service life 30 years
Non-permeable softwoods. Preservative treatment: double-vacuum impregnated with organic Capital cost £34/m²
Net present value for 60-year life £81/m²
Service life 20 years
Permeable softwoods dipped or immersed in organic solvent for a minimum of three minutes Capital cost £32/m²
Net present value for 60-year life £78/m²
Service life 20 years
Non-permeable softwoods dipped or immersed in organic solvent for a minimum of three minutes Capital cost £31/m²
Net present value for 60-year life £91/m²
Service life 15 years
Plastic boarding Ìý
Extruded cellular PVCu boarding with third-party assurance, manufactured to BS 7619 manufactured to BS 7619 Capital cost £44/m²
Net present value for 60-year life £56/m²
Service life 30 years
Glass-fibre reinforced plastics (GRP) boarding with minimum wall thickness of 1.5 mm Capital cost £49/m²
Net present value for 60-year life £66/m²
Service life 25 years
Extruded PVCu boarding. Wall thickness 2 mm or greater Capital cost £42/m²
Net present value for 60-year life £57/m²
Service life 25 years
High-pressure laminate boarding Ìý
Thermosetting resins homogeneously reinforced with cellulose fibres, with an integral decorative surface of polyurethane acrylate. Third-party assurance for external use Capital cost £72/m²
Net present value for 60-year life £84/m²
Service life 35 years
Table notes:
Costs are based on a functional unit of 1 m² of horizontal boarding. The m² rate is an average for a typical three-bedroom house clad at first-floor level only, and includes treated battens, detailing around windows, corners and abutments. The building is located in a non–polluted, inland, low-exposure environment.
Costs include initial supply and installation; removal and replacement of cladding at the end of its service life.
Costs are discounted to net present values at a discount rate of 6%.
Maintenance activities and component replacements are as follows:
  • Softwood should be painted with organic solvent treatment at five-year intervals – analysis based on this scenario where more than one treatment option is given. Creosoted softwood should be recoated every three years.
  • Softwood such as Western red cedar, suitable for use without preservative treatment, or CCA treated timber has no allowance for a recoating cycle.
  • Plastics and high-pressure laminate boarding should be cleaned annually.
Service lives represent typical average lives to enable a comparison of the lifetime costs. The ultimate lives achieved may cover a range of years greater or less than the typical service lives used in this analysis.
The 60-year period reflects a typical design life to BS ISO 15686 – 1:2000, Service life planning: general principles.