Five years ago a Bavarian sawmiller told TTJ that changing to KVH timber from regular sawn carcassing was like moving from a colour to a plasma TV.
He and other colleagues from the German sawmilling industry expressed confidence that KVH’s quality would win over many UK
importers and some have even gone as far as to suggest the product will "conquer" the UK. The economic crisis hindered the product’s increased use in the UK, but it is now being talked up again.
KVH – konstruktionsvollholz (solid wood construction) – is a value-added finger-jointed structural timber product designed to be more reliable and stable than normal sawn wood and particularly suited to long-length applications.
Spruce, fir, pine, larch or Douglas fir is visually or mechanically sorted and cut either with separate hearts or heart-free, with planing after drying to ensure dimensional accuracy. The product is S10 graded (equivalent to C24) and must be dried to 15% (+/-3%) and true to size.
The KVH Monitoring Group and the Confederation of German Master Carpenters provide a clear product definition to users and regulate a uniform product specification independent of manufacturers.
Other non-German finger-jointed structural timber products in the UK market share similarities with KVH – including Glenalmond Timber Company’s UK-produced Ultrajoist and a product manufactured by Latvian sawmiller Kurekss.
After visiting this year’s Timber Expo in the UK, Ante-Holz export manager Kai Oberlies reckons a breakthrough could be getting nearer.
Several seminar presentations focused on KVH and a feature wall at the exhibition was made from the product.
Currently, Ante-Holz is doing irregular KVH business to the UK – compared to its stronger glulam volumes.
"I think KVH is coming more and more," said Mr Oberlies. "It’s been a long wait and we keep trying with it but some of the market will accept it."
Harmonised standard
Tobias Wiegand, from the KVH Monitoring Group, said harmonisation of the European standard for structural finger-jointed solid timber EN 15497, performance requirements and minimum production standards would help drive interest in KVH.
He said a formal vote was due next spring, with the harmonised standard likely to be published in the Official Journal of the EU in the second half of the year.
"It’s a major benefit as, for the first time, we will have a harmonised production standard all over Europe," said Mr Wiegand.
"The harmonisation gives us an opportunity to export to other countries. At the moment there are national technical approvals. In some countries the use of finger-jointed timber is not allowed, is limited in use or is not known very much."
He added that while KVH’s use was commonin Germany, Austria and Italy, Denmark did not allow the use of structural finger-jointed timber, but a harmonised standard would be applied to any European country.
Mr Wiegand said specifiers should look at the performance of products and not whether they were finger-jointed.
Architects are becoming more aware of KVH and, as well as harmonisation increasing their interest, Mr Wiegand foresees it will lead to more companies starting production of finger-jointed structural timber.
A larger version of KVH is glued solid timber – duolam and triolam. The difference between these products and glulam is that they have lamellas of 45-85mm thickness, as opposed to glulam’s 6-45mm.
While glulam is often used for large and curved sections, duolam or triolam is often substituted for large cross-section solid timber which can’t be kiln-dried, such as 160x240mm.
One interesting use for the product is in large glass facades in profiles such as 90x240mm and 90x280mm. "The quality is better than solid timber," said Mr Wiegand.
"In Germany we have lots of different cross-sections in a building and you can use structural finger-jointed products or glued solid timber (duolam/triolam) depending on the cross-section. The more lines of glue there are, the higher the prices."
Mr Wiegand also referenced the first harmonisation of the European cross-laminated timber standard – EN 16351 – next spring, which he hopes will give some uniformity on panel thicknesses and surface quality.