This site uses cookies to provide you with a great experience. By using Vastern Timber, you accept our use of cookies.

2021 Lockdown update

Following Government guidelines we are open to service trade customers, who can select and collect timber by appointment. We ask that all visitors wear masks indoors and outdoors when on our premises.

Our customer showroom is closed. For cladding, beams, plank and flooring we can take orders by phone and email. Collections only by appointment. Deliveries are limited to sites with easy access and forklift offload or a minimum of two people on site for manual offload.

Please do not visit our sites without an appointment and a mask.

Contact us to book a visit


Request a quote



    Information about your project

    I consent to having Vastern Timber collect and store my personal information via this form.

    Brimstone Ash

    Weathered Brimston Ash CladdingBrimstone Ash Cladding

    Weathered Brimstone ash cladding Brimstone ash cladding | VHL4

    Produced from ash (Fraxinus excelsior), the most prolific white wood in our mixed woodlands, and enemy of the keen gardener, Brimstone Ash is the most popular item in the range. Once prized for its strength and flexibility, ash was one of the staples of the British furniture making industry. However with the demise of the furniture industry ash trees are in much less demand and often go to waste.

    Of all the thermally modified hardwoods on the market, ash is the most popular. The strong grain and deep dark chocolate colour (think 70% cocoa) offer a fantastic alternative to tropical hardwoods. The majority of the thermally modified ash on the market is from either the US or mainland Europe. Brimstone Ash is produced from ash logs sourced from English and Welsh woodlands, the majority of which are within 100 miles of the Vastern Timber Sawmill.

    Being the hardest and strongest of the Brimstone range, the ash is suited to the widest variety of end uses. Brimstone Ash is ideal for cladding and decking, and in both cases offers a local alternative to imported and particularly tropical timber species. However when designing pieces remember the product is more brittle than natural wood and may require different jointing and gluing techniques.

    Like all thermally modified timber, Brimstone is durable above ground but it will not last well when in contact with the ground.

    Brimstone overview


    Technical Specification

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

    Trade Name Brimstone Ash
    Base timber English ash
    Species Fraxinus Exclesior
    Process Thermal modification. 210 degrees centigrade.
    Origin Legal and well-managed forests in England and Wales.
    Intended use External cladding
    Other uses Decking, external joinery and furniture
    Appearance Consistent dark chocolate brown colouring with a clearly defined grain pattern. The colour is further enhanced by the application of a clear oil such as Osmo UV resistant oil.
    Weathering The modification process removes most natural extractives resulting in relatively consistent weathering largely free of staining. Weathering to a grey colour occurs more quickly than on non-modified timber.
    Profiles All machined profiles
    Dimensions 20 x 95mm, 20 x 120mm, 20 x 145mm
    Lengths Random. 1.5 – 3.0mt+
    Moisture content 2-4% (Moisture content is stable in exterior conditions)
    Natural durability (EN350-2) Very durable. Class 1
    Insect attack Thermally modified wood is resistant to insect attack when used above ground contact.
    Desired service life (BS8417) Occasionally wet 60 yrs
    Frequently wet 30 yrs
    Treatability class Resistant
    Movement class* Small
    Resistance to impact* Medium to high
    Resistance to fixing High. Modified wood is brittle and should be treated with care.
    When to fix Year round. Very stable in all conditions.
    Grading BS1186-3 1990 Class 1. EN942:2007. J20. CE grade A. Clean with a few small sound knots.
    Working properties Thermally modified woods are more brittle than untreated wood. Care should be taken when cutting and nailing to prevent chipping and break out. Pre-drilling is advised. Test glues before large-scale use. Water based glues do not work well. PU glues have tested well. Otherwise treat as a normal hardwood.
    Extractives The modification process involves no chemicals and any natural chemicals in the wood are removed during the process. Thermally modified wood can be treated as inert.
    Emission of formaldehyde (EN14915) E1 (Not significant)
    Reaction to fire (EN14915) Euroclass F (Untested). D-s2, d0
    Fire treatment Untested
    CE compliant Yes

    While the utmost care has been taken to provide accurate information, Vastern Timber shall not be held responsible for any consequences arising from any errors or omissions on this website nor for any damages resulting from the use of the information.