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Air dried jointed oak cladding

©Gareth Gardner | Jointed oak halflap | VHL2Jointed oak halflap | VHL3

VHL2 ©Gareth GardnerVHL5 from VHL3

Oak grows widely across the whole of the British Isles and continental Europe and for centuries has been used in all aspects of construction. Despite the loss of much of our native woodland, there continues to be a viable supply of British oak and we make every effort to ensure that all oak logs supplied to Vastern Timber originate from either independently certified woodlands or those managed under the strict guidelines of the Forestry Commission. English oak has many environmental benefits, including a reduction in carbon emissions from transport and the contributing of funds to our native forest management.

Dry oak is normally used for profiled cladding sections and is either naturally dried or kiln dried to a moisture level of 15 – 25%. A wide range of colours is common in newly machined English oak, with tones including golden honey and chocolate brown. As the cladding weathers, the colour variation between the boards will decrease and they will turn to a natural silver.

The jointing process
These jointed boards, supplied in standard 4.0mt lengths, are created by mechanically bonding a number of shorter lengths together in a high pressure press using moisture resistant glue.

The process of jointing oak allows us to offer cladding boards with fewer of the problems associated with oak and more of the environmental benefits that make timber cladding such an attractive building material. Utilising shorter lengths of oak allows us to increase the yield (and therefore the value) of the forest resource and reduce the waste in our sawmills – all of which is good news!

Furthermore, jointed boards are longer, less prone to distortion and of a better and more consistent quality than standard oak boards.

Tannic Acid
One feature of oak decking that must be considered is the high tannin content. During the first few months after the decking has been attached, tannin will exude from the boards, resulting in streaks and stains where it comes in to contact with masonry or render. Tannin also corrodes ferrous metal, so it is therefore important to use either stainless steel fixings. Additionally care should be taken to keep other ferrous metal such as scaffolding away from the decking to avoid staining of the boards.

Technical Specification

Produced to comply with the harmonised standard for construction products regulation BSEN14915:2013 and to conform to BS8605-1:2014 External timber cladding: Method for specifying.

Trade Name Air-dried oak
Base timber English oak
Species Quercus Robur
Process Finger jointed
Origin Legal and well-managed forests in England and Wales.
Intended use External cladding
Other uses None
Appearance Newly machined boards will display the full range of yellowish-brown colours associated with oak. Being jointed from shorter lengths, the colour variation will be more exaggerated and the zigzag joints will be noticeable. As the boards weather, the colour variation will even out and will change to a silver-grey patina.
Weathering As the boards weather the colour will change to a silver-grey. On shaded elevations or in areas of higher pollution the oak may weather to more of a black colouring. In semi-shaded areas such as under eaves the exuding tannin may leave unsightly stains.
Profiles All machined profiles available
Dimensions 20×70, 20×95, 20×120, 20x145mm
Lengths Jointed at either 4.0mt or 6.0mt allowing for a small % of cutbacks
Moisture content 16 – 20%
Natural durability (EN350-2) Durable Class 2
Insect attack Sapwood can be attacked by the powder post beetle (Lyctus spp). However, sap is normally excluded from cladding boards.
Desired service life:(BS8417) Occasionally wet 60 yrs
Frequently wet 30 yrs
Treatability class Resistant
Movement class Medium (Effect reduced due to finger-jointed format)
Resistance to impact Medium to high
Resistance to fixing High. Pre-drilling recommended.
Mean density 670 – 760 kg/M3
When to fix Ideally Autumn / winter only. Avoid hottest months.
Grading BS1186-3 1990 Class 2. EN942:2007. J30. CE grade A. Clean with a few sound knots up to 30mm and regular small pips.
Working properties Average workability. Takes fixings satisfactorily.
Extractives Oak contains tannic acid, which will corrode ferrous metals. When the two come into contact, a blue sludge is formed that will stain the oak and anything else it meets. All fixings used in conjunction with oak should be stainless steel. Tannic acid could also leave unsightly brown stains on the surface of the cladding and will stain any porous materials below the cladding. The reactivity of tannin makes oak cladding unsuitable for polluted areas and shaded areas.
Emission of formaldehyde (EN14915) E1 (Not significant)
Reaction to fire (EN14915) Euroclass F (Untested). D-s2, d0
Fire treatment Possible by impregnation
CE compliant Yes
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