Massively on the go for ten years

Perhaps the most remarkable feature of cross-laminated timber is its diversity. The industrial market of the size of half a million cubic meters of CLT annually also leaves room for smaller manufacturers who do not use chemicals to manufacture their product. Most of them work with the system solid wood wall (MHM) of Hundegger, Hawangen/DE. It consists of grooved side boards, automatically nailed with aluminum pins and joined. Nearly 30 companies in Europe have invested in this technology in the past ten years. Another six lines are in Russia. Last year, the MHM-lines operating in Germany, Switzerland, Austria, Italy, France and Belgium alone produced almost 35,000 m³ of wall elements. This year the manufacturers report a "very good product placement on the construction sector." For 2013, the MHM-GmbH (MHM Limited) therefore predicts a 30% growth to 45,000 m³. This success has two fathers: First, more and more MHM-lines are installed. Perhaps more importantly, the second reason: "As soon as the sale begins, all manufacturers report back production up to capacity", says mastermind Hans Hundegger who is very pleased with the success of his idea.

Alternative for cheap side boards

2003 has been a good year for Hundegger. For it was then when the pioneer in the field of CNC joinery was awarded the first ever Schweighofer Prize for his achievements in CNC joinery. At the same time an idea caught on which the Hundegger experts in the Allgäu had been working at for many months – that of the solid wood wall (MHM). At this point, the solid wood construction was still hardly known. But Hundegger wanted to offer an alternative to the conventional post and beam or block construction – as well as to brick and concrete (more on this topic in an interview with Hans Hundegger, see below).
In 2004, Mayr+Sonntag, Legau/DE, became to be the first customers in Germany. Italy followed in 2006. In 2009, France and Austria appeared on the MHM map. Today there are lines in seven countries. All operate on the same principle: The MHM line uses dry side boards. There simply are no less expensive elements with a solid wood cross-sections on the market. What is more, the strength of the wood is the highest at the periphery of the stem. Even though there are many knots: When connected to a multi-layered wall in cross layers, knots are no issue. The element is a wood based material, is dimensionally stable and predictable.

Three steps to the finished element

Feedstock of the process are 23 mm thick, rough sawn, dried boards. They undergo the following steps:
Planing: Sorting to width is not necessary. The boards are groove-planed on one side and thus levelled. The other side is rough sawn. The grooves also increase the U-value of the finished wall element.
Forming panels: "Wandmaster" (wall master) is the name of the unit which nails the cut-to-length slats to form solid walls. One person feeds in the boards by hand. A roller conveyor forwards them into the machining zone. There the wall master portal seizes the slats and places them correctly. Now the automated nailing machine comes from above and presses the slats against eachother – ideally without leaving joints between them – shooting aluminum groove pins into the boards. When one layer is complete, the operator simply feeds in the next layer which is placed at right angles to the previous. The components have thicknesses between 11.5 an 34 cm.
Joining: A key element of the line is the well-tried portal joining unit Hundegger PBA. It cuts to size formats of 2 by 2 m up to 3.25 by 6 m to the millimeter.
These systems are reliable and proven. Hundegger's market share of over 90% in CNC joinery is based on the quality of engineering. But the service of the MHM-GmbH goes far beyond that. "We supply the European Technical Approval ETA right along with the machine and support our partner companies in marketing", explains project manager Rainer König. At request, this may include website design, brochure design and production, advertising and trade shows, event management, presentations and client consulting for the building system. More often than not, companies welcome this kind of support. They invest in a proven product and get valuable support in the critical period of market preparation.

A lot of added value for little money

It is a paradox. The current difficult situation in the sawmill industry seems to put the MHM technology in a good position. The complete line is relatively cheap. However, the investment alone will not suffice. Wall panels do not sell without some effort. But synergies can be found when cooperating with timber construction companies.
Today's sawmill halls often provide enough room to accommodate an MHM-line. Sales and engineering, on the other hand, are perfectly located at a carpenter's shop. There are already a number of such cooperations. It is important that the companies no longer have to acquire a license themselves: That is all included in the MHM package.
Alternatively, MHM is an ideal model for backward integration in timber construction. Those who work with ecologically smart massive wood elements often rather do without adhesives. In relation to industrial CLT, purchasing glueless elements is costly and there is only a limited range of manufacturers. But there is an abundant supply of side boards and it is available locally. As for the quality of construction, MHM walls easily stand up to comparison. This is demonstrated in more than 4,000 houses that have already been realized. An impressive model building was recently put up at the company's headquarters. The walls of the new building with sawtooth-shaped layout is composed entirely of MHM elements. Yet not enough, in Hawangen one can admire a second Hundegger solid wood construction product: the ceiling.

Stacked plank ceiling elements made of side boards

The MHM elements carry in their very name ("Mauer" = "wall") a reference to the fact that they are made for walls. The load bearing capacity for a ceiling looks completely different. Here, bending stiffness is key. For this, the inventors from the Allgäu have developed the profiled wood element-line (PHE). Again, dry 23 mm side boards are used here.
The PHE production line integrates a finger-jointing unit which joins the boards to form a continuous strand. To make the bottom side look nice (see pictures above), a planing unit applies a one-sided profile. Then, a cross-cut saw cuts the strand at lengths of 4 to 12 m. The PHE-line stacks the lamellae automatically, compresses and again connects them with aluminum groove pins. The elements are 7.5 to 25 cm thick and up to 1.2 m wide.

"It had to be cheap, healthy, easy to machine and massive"

Timber-online: Mr. Hundegger, what prompted the development of the solid-wood wall technology?

Hans Hundegger: In the early 2000s, many saw timber construction just as hollow walls, post and beam or as log houses. But I asked myself: How can I make a stable solid wood wall that is affordable and requires no chemicals? The search began with the cheapest product that comes from the sawmill: chips. But you cannot do without glue there. So I came across the side boards. From my professional past in the sawmill, I knew that these are hard to sell.

TO: Why are the side boards connected with aluminum pins? This is an unusual connection material in timber construction.

Hundegger: Aluminum has two advantages. It is not ferromagnetic and harmless in terms of building biology. In addition, it can be easily processed with modern CNC joining units. We manufacture our own aluminum nails.

TO: What are the benefits of the MHM technology compared to glued solid wood walls?

Hundegger: In addition to the above we have natural advantages in the U-value. Grooves are planed into each board. These standing air cussions insulate very well. We reach a thermal conductivity ? of 0.094 W/mK, as the MFPA Leipzig has confirmed.

TO: Are you satisfied with the market response?

Hundegger: The start was surprisingly difficult. Actually, I was just trying to sell the machine. But in 2001 we decided to make the first walls ourselves to prove that it works. Meanwhile, we build about 400 houses a year with it, and I expect further growth. Expecially for sawmills this is an easy and cheap way to increase their added value.

No license fee to be paid

The MHM and PHE-production processes are protected by patents. To produce the MHM-solid wood wall and the PHE profiled wood elements, to obtain the approvals and to get marketing support, there is only one requirement: The aluminum groove pins must be purchased at the manufacturer. As Hundegger confirms, this works very well. The producers can concentrate fully on production and sale. Therefore, there is virtually no producers whose MHM and PHE-line are not satisfactorily utilized. In addition, the portal processing sysem PBA can do more than just cut to size CLT panels. With a longer table it is capable of joining components for small to large volume timber constructions. This includes components as they were used for the 100m high observation tower on the Pyramidenkogel in Carinthia.