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Timber cladding

Product specification guide: advances in treatment and preservation are increasing timber’s sustainability

Increasingly timber is being specified as a rainscreen cladding system for external walls. It is commonly thought of as a sustainable option due to being renewable, recyclable, biodegradable and having minimal embodied energy. This can, however, sometimes be counteracted by the treatments needed to protect it from excessive weathering.

Often when used outside, timber can deteriorate quickly. The main cause of this is usually moisture. As the moisture content of timber used externally for cladding often exceeds 20 per cent, it may need to be treated with a preservative; this can outweigh the sustainability benefits of the material. BS 8417, covering the preservation of timbers, draws on a number of European standards to facilitate the selection of timbers and the type of preservative treatment necessary for lifespans of 60, 30 or 15 years in different hazard classes.

Timbers that do not require preservative treatment include: Western red cedar, European larch, European oak and Douglas fir. These woods are naturally resistant to insects, moisture and rot. Spruce, fir and pine have to be treated, which involves impregnating them with chemicals such as boron. A preservation method that is becoming increasingly popular is one that involves heating the wood. Originating in Finland, the process thermally modifies
the properties of the timber improving its lifespan, strength, durability and stability.

The design of a building can make a large difference to the durability and lifespan of timber cladding. The cladding should be protected from exposure to high levels of moisture but designed with the presumption that water will penetrate it. When using other natural materials, the ‘good hat and boots principles’ is often cited. This should be the same for timber cladding: it should be raised away from the ground by a minimum of 250mm to avoid excessive damage at the splash line at ground level, and a good roof overhang should be provided to minimise the impact of weathering.

With the introduction of the government’s Green Deal scheme there is likely to be an increase in thermal upgrades, with solid-wall properties being insulated externally and additional rainscreen cladding added. This could see a rise in the use of timber cladding.

ThermoWood

ThermoWood

ThermoWood by Metsa Wood

ThermoWood is heat treated, making it more stable than untreated softwood. The heat treatment changes the chemical make-up of the timber so it is less able to absorb moisture. This restriction of moisture movement limits any potential for swelling, shrinkage or distortion.

Manufacturer Metsä Wood
Type of cladding Horizontal and vertical
Profiles available Tongue and groove shiplap, channel cladding, tapered cladding, battening and cornering
Wood species Scandinavian Redwood
Treatment Heat treated at 200°C
Life expectancy 30 years
Country of origin Finland
Maintenance Annual inspection recommended
Certification PEFC certified

www.metsawood.co.uk

Accoya

Accoya

Accoya by Accys Technologies

Accoya wood is made from softwood but has the qualities of hardwood, produced via a process called acetylation. Acetylation transforms the free hydroxyls in the wood into acetyl groups, reducing the wood’s ability to absorb water, making it more dimensionally stable and more durable.

Manufacturer Accys Technologies
Type of cladding Horizontal and vertical
Wood species Softwood, for example Radiata pine
Treatment Acetylation
Life expectancy 50 years
Maintenance Low frequency due to increased dimensional stability as coatings do not stretch and shrink
Certification FSC, PEFC certified and cradle-tocradle gold standard
Recyclability Can be reused or used as a biofuel to produce heat and power

www.accoya.com

Imported External Cladding System

Imported External Cladding Panel System

Imported External Cladding Panel System by BCL Timber Products

This external timber cladding panel system allows the cladding to be prefabricated, which means large areas can be constructed in a fraction of the time of traditional site-fix methods. All BCL cladding panel systems have concealed fixings, creating a smooth and continuous finish.

Manufacturer BCL Timber Products
Type of cladding Horizontal and vertical
Profiles available Horizontal: open harfield, shiplap, feather edge. Board on board
Wood species Western red cedar, Siberian larch, European oak, South American hardwoods
Treatment Protim or similar
Finishes Translucent or clear lacquer, paint
Maintenance Lacquer: 5-7-year repaint cycle Paint: 15-year warranty
Certification FSC or PEFC certified

www.bcltimberprojects.co.uk

Homegrown External Cladding System

Homegrown External Cladding Panel System

Homegrown External Cladding Panel System by BCL Timber Products

These prefabricated cladding panels minimise the amount of work that must be done on site when installing the cladding. They are produced using home-grown timber species, thereby reducing their carbon footprint and environmental impact.

Manufacturer BCL Timber Products
Type of cladding Horizontal and vertical
Profiles available Horizontal: open harfield, shiplap, feather edge. Board on board
Wood species Sweet chestnut, cedar, larch
Treatment Protim or similar
Country of origin UK
Finishes Translucent or clear lacquer, paint
Maintenance Lacquer: 5-7-year repaint cycle. Paint: 15-year warranty
Certification FSC or PEFC certified

www.bcltimberprojects.co.uk

Thor Torrefied Wood

Thor Torrefied Wood

Thor Torrefied Wood by Silva Timber

THOR torrefied wood is a thermally modified, solid-wood cladding product. This natural method of treatment gives the wood enhanced durability and increased resistance to decay, as well as water repellence and weather protection.

Manufacturer Silva Timber
Type of cladding Horizontal
Profiles available Rabbeted bevel
Treatment Heat treated to 200°C through torrefacation
Life expectancy 60 years
Country of manufacture Canada
Finishes Factory applied clear stain or custom solid paint colour

www.silvatimber.co.uk

Siberian Larch Cladding

Siberian Larch Cladding

Siberian Larch Cladding by Silva Timber

Siberian larch is a sustainable old-growth timber, which is durable, dimensionally stable and long lasting. It is naturally resistant to decay, meaning it has a long lifespan and requires minimal chemical treatments.

Manufacturer Silva Timber
Type of cladding Horizontal
Profiles available Rabbeted bevel
Treatment Heat treated to 200°C through torrefacation
Life expectancy 60 years
Country of manufacture Canada
Finishes Factory applied clear stain or custom solid paint colour

www.silvatimber.co.uk

Certigrade Western Red Cedar Shingles

Certigrade Western Red Cedar Shingles

Certigrade Western Red Cedar Shingles by Silva Timber

These cedar shingles are produced from waste from British Columbia’s main logging and sawmilling industry, providing a sustainable and environmentally friendly product. The natural effects of aging and weathering will give the product a silvery grey colour in time.

Manufacturer Silva Timber
Type of cladding Tiled cladding and roofing
Length of shingle 405mm
Width of shingle 75mm-365mm
Butt thickness 10mm
Wood species Western red cedar
Treatment Natural oils act as preservatives against decay and insect attack
Life expectancy 50 years
Country of origin Canada
Certification FSC certified

www.silvatimber.co.uk

Fraser Timber Cladding

Fraser Timber Cladding

Fraser Timber Cladding by Arnold Laver

Fraser Timber cladding is available in a large range of colours and profiles. The timber is finished in the factory where it is dried and then stained before it reaches site.

Manufacturer Arnold Laver
Type of cladding Horizontal and vertical
Profiles available Bevel with shiplap, cove, channel
Wood species Pine
Life expectancy 20 years
Country of origin Canada
Maintenance Re-staining required after 15 years
Certification PEFC certified

www.frasertimbercladding.co.uk

Kebony

Kebony

Kebony

Kebony is a sustainable alternative to hardwoods from tropical regions. Wood is made more durable and stable using liquids from biowaste material. The wood is dark, resembling teak and acquires a silvery grey patina over time.

Manufacturer Kebony
Type of cladding Horizontal and vertical
Profiles available Rectangular, shiplap, grooved
Maximum length available 5,400mm
Wood species Pine, beech, southern yellow pine, ash
Treatment Kebonisation modifies the wood, forming locked in polymers in the cell walls
Country of origin Norway
Finishes None needed
Maintenance None
Certification FSC and PEFC certified

www.kebony.com

Garapa Cladding

Garapa Cladding

Garapa Cladding by Wood Trend

Garapa - more commonly referred to as Brazilian ash - has a light honey brown colour, which weathers to a silver grey. Strong and durable, it can be left untreated.

Manufacturer Wood Trend
Type of cladding Horizontal and vertical
Profiles available Tongue and groove
Wood species Brazilian ash
Treatment None necessary - naturally resistant to rot, insect attack, mould, fungus and decay
Countries of origin Argentina, Brazil, Bolivia, Columbia, Peru, Guyana, Paraguay, Peru, Suriname, Trinidad & Tobago, Venezuela
Finishes None

www.woodtrend.com

Ipe Cladding

Ipe Cladding

Ipe Cladding by Wood Trend

Brazilian walnut - or ipe as it is more commonly known - is dark brown in colour, with a reddish tint. As it weathers, this turns to a dark grey. The cladding boards come with a chamfered top and a square bottom.

Manufacturer Wood Trend
Type of cladding Horizontal and vertical
Profiles available Tongue and groove
Wood species Ipe
Treatment None necessary - naturally resistant to rot, insect attack, mould, fungus and decay
Country of origin Argentina, Brazil, Bolivia, Columbia, Peru, Guyana, Paraguay, Peru, Suriname, Trinidad & Tobago, Venezuela
Finishes None

www.woodtrend.com

Cemwood

Cemwood

Cemwood by Cembrit

Cemwood is not strictly a timber cladding product, but a cement fibre board designed to look like wood. This gives it added fire-resistant properties and removes the occurrence of any irregularities or knots in the timber.

Manufacturer Cembrit
Type of cladding Horizontal and vertical
Profiles available Shiplap
Maximum length 3,660mm
Maximum width 209mm
Material Cement fibreboard
Country of origin UK
Finishes Boards can be supplied grey for on-site painting or staining, or pre-coated

www.cembrit.co.uk

Western Red Cedar Shingles

Western Red Cedar Shingles

Western Red Cedar Shingles by John Brash

Shingles can be laid in straight lines, giving a clean regular appearance to the roof or wall; alternatively, random butts can be used to give a much more irregular aspect. The shingles are light, reducing both the carbon footprint of transportation and the structure required to support them.

Manufacturer John Brash
Type of cladding Tiled cladding and roofing
Length of shingle 400mm, 450mm, 600mm
Width of shingle Random
Wood species Western red cedar
Treatment Untreated or treated with Osmose Naturewood preservative treatment
Life expectancy 40-60 years
Country of origin Canada
Certification FSC and PEFC certified

www.johnbrash.co.uk

Western Red Cedar Shakes

Western Red Cedar Shakes

Western Red Cedar Shakes by John Brash

Shakes differ from shingles in that they have a split, rather than a sawn, face and have a low-carbon footprint. When used, they create an aesthetic akin to that of traditional log cabins, and have a low carbon footprint.

Manufacturer John Brash
Type of cladding Tiled cladding and roofing
Size of shake 600mm x 19mm
Width of shake Random
Wood species Western red cedar
Treatment Untreated or treated with Osmose Naturewood preservative treatment
Life expectancy 40-60 years
Country of origin Canada
Certification FSC and PEFC certified

www.johnbrash.co.uk

 

 

 

Readers' comments (2)

  • I love the look of some of these, I really feel that cladding makes a building look a lot more modern and at the same time more green and friendly. I am considering getting some timber cladding from this website as they are local to me http://www.vastern.co.uk/cladding/ does anyone have any suggestions on which to pick?

    Unsuitable or offensive?

  • gain new envelop from nature. excerllent!

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