Brimstone Ash Cladding

Being durable, stable and relatively knot-free, Brimstone ash is an ideal choice for modern timber cladding designs and is sourced from local woodlands.


Contemporary / modern


All machined profiles


British woodlands



Brimstone Ash Cladding Features

Brimstone ash cladding is a thermally modified product using high quality ash grown in local woodlands. The modification process makes the ash very stable and confers a high level of durability, both of which are ideal characteristics for exterior timber cladding.
The strong grain, lack of knots and deep dark chocolate colour of Brimstone ash offer a locally grown alternative to imported hardwoods. The price and performance of Brimstone ash are similar to Canadian cedar.
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, decking and joinery.
Brimstone ash is transformed by thermal modification, a chemical free process that reconfigures wood by superheating it to over 200 degrees. The result is a stable and durable material, highly resistant to pests and rot, and certified to withstand the weather for over 30 years.

Call us to discuss your project


Brimstone ash Cladding from Vastern Timber

  • Thermally modified British ash
  • Sourced from legal and well-managed woodlands in England and Wales. GIB certified.
  • Supplied by Vastern Timber (
  • Grade BS1186-3 Class 1 / EN942:2007 J10
  • Finished thickness of 20mm
  • Overall finished widths 70mm / 95mm / 120mm / 145mm
  • Random lengths 1.5mt – 3.0mt+
  • Available in various profiles
  • Moisture content of 4 – 6%
  • Durability EN350-2 Very Durable. Class 1 (Above ground use only)
  • Supplied uncoated. No treatment required.


Brimstone ash has a consistent chocolate brown colouring with a strong grain pattern. Cladding boards may contain occasional small sound knots. 

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 for non-modified timber

Desired service life
Occasionally wet 60 yrs. Frequently wet 30 yrs.

Movement class

Resistance to impact

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.

563 Kg / M3

The modification process involves no chemicals and most natural chemicals in the wood are removed during the process. Thermally modified wood can be treated as inert.


How to fix
Hand nail with stainless steel nails through the face or through the tongue on suitable profiles.

Alternatively use a second fix nail gun and insert two nails per batten at opposing angles.

It’s important to include a 2mm expansion gap.

For more information, visit the resource centre

Batten type
Treated softwood. 35mm thick x 50mm wide

Batten spacing
400 – 600mm 

Nail type
Stainless steel only. 50mm ring shank nails for hand nailing or 50mm second fix brad nails if using a gun. Trim head stainless steel screws are also suitable.

When to fix
Year round.

Resistance to fixing
High. Modified wood is brittle and should be treated with care.


We machine timber cladding to the profile of your choice. View our full range of cladding profiles.

We recommend the following profiles for Brimstone ash.


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.

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