Announcing the arrival of a new family member is always a moment of pride for any parent and Ari Martonen, president and chief executive of Finnforest, looked suitably delighted at the launch of its latest Kerto LVL mill in Punkaharju, Finland, to over 150 guests from 15 European countries.

Finnforest has made no secret of its desire to become the leading European supplier of timber products by 2005 and the timber engineering division will be playing a major part in this plan. “We now have a family of products,” Mr Martonen explained, “that will allow us to provide every component needed for the timber building industry.”

This ‘family’ is large and certainly does cover each base, with sawn and machined timber, including truss material stock, plywood, I-joists, glulam and LVL, sold under the brand name Kerto. Continued acquisition and expansion of its own facilities will ensure that the Finnforest Group is able to meet the ongoing requirements of this fast developing sector, particularly in the UK, which is one of the largest growing markets for engineered wood in Europe.

Timber construction methods are becoming increasingly mainstream throughout Europe and, until recently, there were two quite distinct camps; mainland Europe has been at the forefront of timber engineering, with the main focus on larger structures, while mainstream housing has continued in brick and block. In the meantime, Scandinavian countries have developed timber frame housing. The UK has brought in many of the North American timber frame methods to this existing market, thereby adding I-joists and ancillary products to the core requirements, which include LVL.

While glulam plays an important part in many timber structures, LVL is a much more cost-effective product for straight columns and beams. It is produced from conventional veneers, scarf jointed together and laid up either with all of the plies running in the longitudinal direction (Kerto S), or with a small number of the intermediate plies running cross wise (Kerto Q). In effect this gives enormous slabs of very thick plywood, which can then be cut to size. Kerto S is the most popular variant, forming around 80% of total output, but Kerto Q is ideal for use as large panels and lintels, or in beam applications where a high shearing strength is needed.

Even though its main design purpose was as a covered structural component, Kerto LVL is rapidly becoming the product of choice for architects and designers in many aesthetic situations around Europe, forming columns, stairs, beams and trusses in some very prestigious buildings. The latest Opera Hall at Savonlinna, Finland’s centre of opera, is just one example of exposed LVL use, after the initial success of LVL in the Sibelius Hall

at Lahti.

Easy decision

The Punkaharju mill, situated in southern Finland, near to the Russian border, already incorporates one of the most modern peeling and plywood manufacturing plants in the world, which made the decision to add an LVL facility an easier decision. LVL has been around for some time and Finnforest has an existing plant in Lohja, Finland, with a 1.8m press width. Recent development of advanced pressing techniques and improved glues has allowed the new plant to operate at 2.5m wide, giving a far better flexibility and increased throughput, with the LVL veneer production line also feeding the plywood mill.

After initial soaking and debarking, logs are peeled and cut into 2.5m squares, which are then dried prior to grading into seven categories, of moisture, density and appearance. The closer a veneer is to the face, the stronger it needs to be and there has to be a trade off between good appearance and strength.

At the lay up stage the veneers are scarf jointed, to give flat sheets. This is one vital difference from some other LVL production, where the veneers are lapped over each other, causing ripples inside the sheet that remain, even after pressing. While it is not a major issue, lapped veneer LVL is not as consistent as Kerto and the edge appearance is not uniform.

Finnforest has spent a great deal of time researching the gluing process; by using a mixture of traditional resorcinol glues, which give a dark red colour, together with light resorcinols, which form a clear glueline, Kerto LVL can create face appearances that are very clean. As Markku Luhtasela, general manager, explained: “curing times on LVL are difficult; it’s like baking a thick cake and curing the inner veneer gluelines whilst maintaining the outer ones needs very precise glue application, software and pressing technology. We have developed the use of light resorcinol glues for the outer veneers, to give a clear glueline between the first two layers and any face scarf joints, ensuring clean faces on our LVL.”

A twin daylight cold press stage creates the basic panels, which are formed as 24m blanks in thicknesses ranging from 15-90mm. After initial curing the panel moves forward, through the hot press stage before being transferred automatically to the cutting and finishing lines.

Capital investment

“This line can already produce around 150m3 per day on three shifts, but our total workforce is just 12 people per shift,” continued Mr Luhtasela. “This gives some idea of the enormous capital investment set out by Finnforest, to ensure that ongoing production is highly efficient; the mechanisation and automation also gives very fine tolerances and precise quality control”. As the plant settles in, product volume per shift will climb, giving the Punkaharju plant an overall annual capacity of well over 70,000m3. When this is combined with the Lohja plant, Finnforest’s total LVL capacity will be around 175,000m3.

Once the LVL panels have been produced, they are transferred to the sanding, cutting and labelling line, producing a range of standard and special sections for customers throughout Europe. The entire sawing operation is fully automated, with ripping, cross-cutting and sanding options, before final wrapping. Even at this stage there are two choices: spiral polythene wrapping is standard, but for significant volume orders heavy-duty polythene sheet wrap can be applied, thereby increasing on-site protection.

The finished LVL components are then stored in a climatically controlled warehouse, prior to distribution to customers, for use together with the other products in Finnforest’s range of structural timber components.

While LVL is already in use throughout the UK there is an enormous growth potential for the product and the visit included a large British contingent from the timber frame and engineering industry. Neil McConnell, chairman of Donaldson & McConnell, is probably one of the longest serving providers of engineered timber in the UK.

“We have used Kerto for many years and this new wider panel size will give the industry a chance to increase LVL useage; it’s going to be even more versatile,” said Mr McConnell.

“We have invested around e50m in engineered timber plant,” said Heikki Castren, senior vice-president of engineered wood for Finnforest, “which gives some idea of our confidence in the growth potential that we see in LVL and associated products.”

As the market for engineered timber components develops, Kerto LVL will see a significant growth, but product development is a never ending process and Finnforest knows that it has to be at the leading edge of this, to ensure that it remains market leader, particularly in the Europe. Ole Salven, senior vice-president of western markets, brought the picture up to date: “The Punkaharju mill can create a wide range of finishes and we have developed techniques to bond other veneer species on as faces, to give Kerto LVL a radically different appearance.

“Our latest move has been bonding MDF faces as well, to give a paint surface option to our customers. After all, no-one asked for the Walkman until it was invented and now we just take it for granted, just like Kerto LVL in the future.”