Grünenfels 30 December 2010

Switzerland has a wealth of medieval castle ruins. In the Canton of Graübunden they are particularly numerous with, for example, the valley of Vorderrheintal (Surselva) displaying no less than about 50 ruins. Some are almost gone, others are kept in good repair and a few impressive structures are left to the elements.

Since ten years I have monitored some ruins and as 2010 is drawing to an end, the question is whether a “pinnacle” or Mauerzahn at Grünenfels by Waltensburg will survive 2011?

I’m fond of ruins. Not only because of their exciting history and placement in the landscape, but also since stone and masonry weathering is often fantastically displayed at such structures. And since I have the privilege of spending my family holidays in Surselva, I often take the opportunity to visit the nearby ruins.

Worrying and exciting

Grünenfels is a worrying and simultaneously an exciting sight. The ruin is located in dense forest at a spur between two ravines, one of which separates it from the village of Waltensburg with its famous medieval church displaying the mural paintings of the so-called Waltensburger Meister (master).

The outer part of the "Mauerzahn" with quoins made from green metaconglomerate (Verrucano)

Hidden in the forest, the ruin comes with the remains of a tower and surrounding wall, of which the southeast corner rises some 8 m above the ground. This is a classical Mauerzahn (literally “masonry tooth”); such perplexing pinnacles dot the landscape of ruins in Switzerland, but are – naturally – becoming ever rarer. And most are significantly more “sturdy” than the frail structure at Grünenfels.

Built from local rubble of small, naturally rounded gneiss boulders (Bollensteine) and hewn metaconglomerate (Verrucano) for the quoins, the small castle had its heyday in the 13th century, but was abandoned already by the late 14th century.*

Becoming undermined

The history from abandonment until modern times is poorly known and thus there are no records that can aid in understanding the masonry decay. The first (and last) archaeological excavation was carried out as a response to illegal digging in 1962, but no conservation measures were undertaken. Soon the forest invaded the ruin again – and the Mauerzahn was left to its own destiny. Clavadetscher & Meyer (1984) describe the condition in 1962 as “desolate”, and it is astonishing, indeed, that is still standing upright half a century later!

The "Mauerzahn" at Grünenfels in 1962 and 2009, with the red colour showing lost masonry. Source left image: Reworked from Clavadetscher & Meyer 1984

Monitoring of a part of ther masonry which shows small changes between 2004 and 2010

Over the last 50 years it is, surprisingly, not the upper part of the Mauerzahn that has fared the worst, but the masonry closer to the ground. Many stones have disappeared and though there has been little erosion over the last seven years, the structure is doomed since it is slowly becoming “undermined”. Or a hurricane or a little earthquake will topple the “tooth”. As of today, the whole structure is resting on a “base” measuring about one square metre only and it is leaning dangerously towards the north.

Built-in weaknesses

A masonry block fallen from the ruin with the leaning "Mauerzahn" in the background

Weathering is solely related to the joints; it is probably mostly caused by frost, but dissolution phenomena and salt may also play their roles. However, it is the building technique that plays the greatest role in the decay of the structure as such. With masonry faces of rounded boulders and cobble and hardly any binders to secure the one metre thick walls, there are numerous built-in weaknesses. Generally, boulders and cobbles simply loosen and fall when the joints become critically weathered. This is similar at many other Surselva ruins.

Can something be done? Yes, but it would require consolidating and supplementing lime mortar joints, securing loose stone and planning for very regular maintenance, all with no guarantee that the Mauerzahn will survive the next week. Given the numerous ruins in need of repair in the region, it’s a matter of priority – and money. It would be nice, though, if the structure could be kept for as long as possible; clear a bit of the forest around and it will be visible as a classical Mauerzahn – one of the few left locally.

The impressive "Mauerzahn" of the castle at Friberg by Trun in Surselva in 1911 before the collaps shortly after. Image source: Poeschel 1929.

Postscript

Does anyone know of a good English translation for Mauerzahn (literally “masonry tooth” or “wall tooth”)? I have searched in vain for some time and would be happy for any comment (also in German) that you may have.

Location

Sources

• Erwin Poeschel: Das Burgenbuch von Graubünden, Zürich 1929
• Otto P. Clavadetscher & Werner Meyer: Das Burgenbuch von Graubünden, Zürich 1984
• http://de.wikipedia.org/wiki/Waltensburger_Meister
• http://de.wikipedia.org/wiki/Burg_Gr%C3%BCnenfels