GBE H21 Timber Weatherboarding Checklist

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GBE H21 Timber Weatherboarding Checklist

Issues:

Timber is a natural material with natural variation and an amazing range of properties and applications
Standards are being kept up to date and familiar British Standards are being replaced by unfamiliar Euro Norms
It is relatively easy to get out of date and get specifications wrong
TRADA employs one man full time to address the many calls from Architects with failed timber weatherboarding

Problems:

There are too numerous problems to describe here now (but I will keep coming back to add more)
Despite NBS Guidance enabling competent specification of Timber Weatherboarding
- Users of NBS still get it wrong from time to time
Poor detailing, poor specification, poor choice of timber, substitution and poor workmanship and maintenance all contribute to failures.

Example:

BRE Campus’ Innovation Village, one demonstration building had failed timber weatherboarding where two adjacent boards expanded then burst out of the cladding surface.
The T&G joints had been installed upside down creating a channel to collect water, the boards absorbed water and expanded until failure. That demonstration building is gone now.

Misunderstandings:

If an architect chooses to do ‘radical timber weatherboarding’ and the detailing is questioned by the tradesman the Architect should learn to listen and not insist on his details be followed without question.

Solutions:

Don’t be radical for the sake of being radical; learn to be competent instead
Subscribe to NBS and use H21 Timber Weatherboarding Specification read and use the guidance notes carefully
Purchase the TRADA Book on Timber weatherboarding, read it and follow its guidance
Consider using the GBE H21 Timber Weatherboarding (Outline), read it and follow the guidance
Use askTRADA website
Seek TRADA advice/consultancy
Purchase the more technical Napier University Book on Timber Weatherboarding, read it and follow its guidance
If you want to do open joint rain screen weatherboarding, consider using the following specification and editing to suit your project GBS H21 Timber Weatherboarding Rain screen (RSWS)
Listen to the tradesman

GBE Outlines

GBE H21 Timber Weatherboarding (Outline) G#10281

GBS Specification

GBS H21 Timber Weatherboarding (RSW) G#625

Consider:

Durable species without preservative treatment
Locally sourced durable softwood or hardwood
Unseasoned, untreated, unfinished oak can be as cheap as treated softwood
Architect to design joinery to minimise waste, be aware of position in log, sections sizes and lengths, before deciding use and joint patterns of hardwoods
FSC approved timber sources, timber board products and timber based materials See G20, Z10

Substitute:

Architects are prone to choose their favourite species of timber; availability of the species varies in the supply chain, due to numerous issues including:
- Long growing time
- Seasonal harvesting
- Drying/Seasoning time
- Availability, stock levels and delivery times
- Matching quantity available to size of project
- Reclassification of scarcity and endangerment, etc.
- FSC timber or other Certification scheme requirements
Some favourite species have the wrong characteristics for some application
Most species unfinished and exposed to the sun will fade to silver/grey so the original colour becomes irrelevant
There is a growing preference for timber species to be specified by performance characteristics and colour range
- enabling legal and sustainable timber to be sourced with chain of custody more readily
- offering a few examples of species available with characteristics that match the requirements
- leaving the final species choice to the Architect by samples

Minimise:

Timber miles shipping tropical hardwoods to the construction site

Avoid:

Preservative treatment by choosing species for durability to match the application
Treated softwood if a durable softwood is available
Treated softwood if a durable hardwood is available
Transporting durable hardwoods cross the globe if a local durable hardwood will do the job
Indonesian Hardwood
- Recently most has been illegally logged, destroys forests, biodiversity, communities and habitation
- Only use FSC certified
Preservative treated perishable softwood. See G20, Z10 and Z12
PVC substitute for timber cladding See Z50
Coated aluminium substitute for timber landing
Virgin Plastics See Z50

Health:

Avoid the use of preservatives which need touching up on site wherever the timber is cut or drilled on site

Environmental:

Avoid the use of preservatives, they are hazardous if released to the environment (air, land or water) or to nature

Wellbeing:

Use unfinished untreated timber in preference to treated, painted, stained, oiled, waxed timber, any of which may off-gas VOCs to the environment
The smell of fresh paint is often welcomed but it invariably is not making your health better
Recent (2011) changes to EU Directives saw a significant reduction in VOC releases from paint to the atmosphere but this does not mean they are all gone.
Low-VOC can also mean more/different chemicals to limit VOC releases to atmosphere
There are many manufacturers who have always made VOC-free natural plant-based or mineral-based paints

Biophilia:

Being able to see, feel, hear and even smell timber is very welcome by most occupants, visitors and passers-by
There is growing evidence that natural materials in the built environment can enhance their sense of wellbeing

Biodiversity:

Designing for Biodiversity: A Technical Guide for New and Existing Buildings G#1328 N#1316
This guide includes how to incorporate bat boxes in the timber weatherboarding cladding zone without compromising the building’s external envelope.

Safety:

Precautionary principle:

Avoid using preservative treatments to avoid risk of loss to the environment and nature

Resourceful:

Resource Efficiency:

Architect to design joinery to minimise waste: be aware of position in log, sections sizes and lengths, before deciding use and joint patterns of softwood and hardwoods
Choose and reserve the log with the right amount of figuring (more or less), for your project,
- don’t condemn the installation with too much or too little figuring
- Avoid sending finished materials to landfill

Industry/Sector Initiatives:

Consider having excess to requirement collected by one of the nationwide social enterprise sites

Reduce:

Reclaim:

Reclaimed cladding timber: Supplier:
Architectural Salvage: via Salvo website Salvo
Construction reclaim: via Community Wood Recycling

Reuse:

Offer ‘excess to requirements’ materials to exchange websites

Recycle:

Recycling of timber usually means reducing to wood chips or particles and adding a synthetic binder to make chipboard or particleboard, with or without other salts for fire or preservative treatments
Recycling of timber can also mean reducing to wood flour and adding recycled plastics to make a conglomerate wood-plastic
C2C or Cradle to cradle principles advise against mixing technical (plastics) and natural (wood) since separating them at the end of life is currently economically nearly impossible and are likely to end up in landfill, with a shorter than plastic life and a longer than timber life

Recover:

Consider heat recovery if burning untreated and unfinished timber on site
Use damaged untreated pallets to construct on-site composting bins to compost landscape waste