To save Norway’s Stave Churches, conservators had to relearn a lost art as these iconic wooden buildings require ancient weatherproofing technology.
image: for illustration – Tjensvoll stave Church from 1999 By Arne Kvitrud – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=89819139
… Nordic builders coated their stave churches with tar to seal and protect the wood from frigid winters…
Atlas Obscura writes:
TO STEP INTO ONE of Scandinavia’s surviving stave churches is to enter the past. Shadows shift and tell stories in the elaborate carvings of intertwined beasts that are hallmarks of the churches’ unique architecture. Sounds reverberate off the timber as if traveling across centuries. The air feels dense with the tang of hewn wood, peat smoke, and pine tar.
As early as the 11th century, builders began erecting these churches all over the region. Much of Europe was raising massive cathedrals of stone during this period, but the Scandinavians knew wood best. While each house of worship was unique, all of them had staves, or load-bearing corner posts joined to vertical wall planks with a tongue-and-groove method.
… there were once nearly 2,000 stave churches, or stavkirker. Today, fewer than 30 remain, mostly in western Norway. As the number of churches dwindled, so did knowledge of the complex ancient technology needed to maintain them. To preserve the surviving churches, researchers and conservators have had to piece together a lost craft through interviews, rediscovered documents, and mass spectrometers that discern the chemical composition of the churches’ ancient weatherproofing.
As they did with the ships that carried them as far as Africa and North America, the Nordic builders coated their stave churches with tar to seal and protect the wood from frigid winters, long days of summer sun, and Scandinavia’s full spectrum of precipitation. The special glaze, made from pine resin, took days to prepare in a massive peat-and-wood mound that Ole Jørgen Schreiner, a traditional tar expert, calls a mile. Creating one was a “complex and laborious project” in and of itself.
“The actual construction of the mile takes one to two days, and the burn itself takes (up to) three days,” says Schreiner… “Just building it requires accuracy … It’s not just sticks thrown in a pile, but precisely stacked and knocked together to avoid air pockets that can cause problems during the burn.”
The stacked wood would have been arranged on a hillside, and insulated with at least a double layer of cut peat. …
But “the knowledge was not at all handed down through generations. Some knowledge, however scarce, remained among builders of traditional wooden boats.”
