The Accoya factory in Arnhem is now in its 11th year.

TTJ and other trade press were granted access to the facility during a press event held by the modified wood maker earlier this year.

Significant expansion is the story at the moment, with the 40,000m3 capacity plant expanded to 60,000m3 in a 2017 investment with plans for a further phase to raise capacity still further to 80,000m3.

Just a quick reminder about Accoya.

Put simply, it’s the result of New Zealand plantation radiata pine that goes through an acetylation modification process to modify its characteristics, giving it benefits that far exceed solid softwood and matching that of some of the best tropical hardwoods.

Durability and dimensional stability are two of its key attributes, lending itself to external applications including windows, cladding, decking and doors.

The product and its panel product variant – Tricoya MXT – have gained significant traction in recent years, with Accoya now supplied to over 60 countries across the world, including a strong base among distributors and joinery manufacturers in the UK.

The latest Accsys Group trading update for the year ended March 31 shows an 8% growth in total revenue to €61m, with Accoya sales volumes up by 7% to 42,676m3 with a 15% increase in the second half. After the EU Referendum the company sold products in euros to British customers, leading to a 17% increase in prices.

The company reports continued and strong pent up demand for Accoya with significant increased volumes largely from repeat customers.

Arnhem Expansion

Production at Arnhem takes place by batch treatment in a format similar to wood preservation, with each chamber having an annual 20,000m3 capacity.

A third treatment plant is currently being added to the two existing treatment vessels in a move which increases capacity by 50% to 60,000m3, with additional volumes expected to be available later this quarter.

Justin Peckham, sales manager at Accoya manufacturer Accsys Group, has been at the company the same length of time as the plant has been open.

“We will add a fourth chamber whenever the market demands it,” said Mr Peckham.

“The way the market is looking we are already beginning to plan for that even before the third chamber is complete.”

The modification process can work with a variety of species, but established favourite radiata pine (imported from New Zealand) is the easiest to use.

There is a large volume of radiata pine at the Arnhem site – with Mr Peckham estimating that 10,000-12,000m3 of timber is stored inside the two warehouses and currently in transit from New Zealand.

“Logistically, radiata pine has its challenges with a long lead time,” said Mr Peckham.

It arrives at Rotterdam with a 14% moisture content and the finished Accoya is much drier at 6% in part to avoid chemicals reacting with moisture in the wood.

“We are working with other species but that is a little bit further down the line,” he said. “Sitka spruce is not very porous and difficult to treat, so we’re not looking to use it for Accoya.”

However, it will be suitable for use in the production of Tricoya wood elements at the Hull production facility, which is currently being built and is due for completion in the summer of 2019. This modified fibre will be used to manufacture Tricoya modified wood panels.

Species that do also work well include European alder, Nordic pine and Scots pine.

One of the benefits of radiata pine is that it can be treated up to 100mm thick, while other species have to be laminated to achieve similar sizes.

“In terms of durability and stability there is very little difference from one board to another,” added Mr Peckham.

“But compared to a normal piece of timber there is a lot of variety. With a piece of oak you can’t tell which piece is going to last 15 years and one which will last less than this.”

Mr Peckham said people had not realised that they could do things differently with Accoya compared with other timbers.

“So we have had to do the investment in R&D and go out into the market and say here is a product opportunity for you. I think people are understanding more about it now.”

“The idea had been for people in the industry to come up with the ideas [for products].”

Another advantage of the dimensional stability of Accoya is it can be used as thin as 15mm in a cladding board, whereas 18mm is the industry standard. Usually, any boards thinner than 18mm might warp.

In a sample room at Arnhem, a huge range of Accoya product samples include Shigeru Ban charred cladding. “We see lots of interest in this at the moment,” said Mr Peckham.

There are also laminated window sections and acetylated veneers for acoustic guitars.

In total, 170 people are working for Accsys, with more staff joining to operate the extra chamber at Arnhem and the plant in Hull.

Accoya Tower Project

Some striking applications of Accoya exist in the Netherlands, with one notable example at Bergen op Zoom.

The 25m-high €1.4m Pompejus Tower, situated on the restored 17th century Fort de Roovere was created by RO&AD Architects.

Accoya was specified because of its durability, stability and low maintenance benefits in external applications.

The structure consists of steel triangles according to a mathematical design principle with Accoya wood plates mounted on the faces to create the voronoi pattern.

The 3D design plans were converted into data for CNC machines at VKP to fabricate the panels.

Some 100m3 of Accoya was used in the building, which incorporates an exhibition space and open-air theatre, with all 129 stairs also made from Accoya.

“The original idea was to have done the structure in engineered wood but for financial and technical reasons steel was chosen,” said architect Ad Kil, a self-confessed Accoya fan.

“We have selected Accoya in all our projects along the waterline,” he said.

“This consistent specification unites the projects and makes it a kind of family,” he added.

Another Accoya application at this site is the Moses Bridge which spans the fort’s moat.

Designed as a discreet bridge, RO&AD Architects designed a “sunken” bridge that follows the line of the fort slope and sits almost flush with the water line, making it practically invisible.

It is built with Accoya wood sheet piling on either side, with a hardwood deck/stairs in between.

Park 20/20

Another project making widespread use of Accoya is the Park 20/20 Cradle to Cradle (C2C) working environment located at Haarlemmermeer business park near Amsterdam.

Four key principles characterise the park design for disassembly, products of services, material banking and productivity and health.

Accoya was specified for the cladding on the park’s first building – the Bosch Siemens Home office, designed by cradle-to-cradle founder Michael Braungart.

C2C Gold certified since 2010, Accoya was chosen for the cladding and windows for its sustainable values, durability, dimensional stability and low maintenance properties.

Another application seen by TTJ on Accoya’s tour was Breakers Beach Bar & Restaurant, Noordwijk.

Designed to withstand the elements without requiring frequent maintenance, Accoya Wood was used for windows, doors, cladding, railings, trusses, mullions and planters. Sikkens coatings were used for the finish.

The building is part of the Grand Hotel Huis Ter Duin, a hotel often used by the Dutch national football team.

Accoya Velodrome

One of the most impressive recent applications of Accoya is the Omnisport Apeldoorn multi-sports arena, the site of the recent UCI Track Cycling World Championships.

The Accoya track is reputed to be one of the fastest in the world and was used at Apeldoorn to cope with humidity in the arena, which caused the previous larch wood track to shrink.

Accoya was also specified because the acetylation process means the boards will not splinter.