Merryn and Graham Dineley, she an archaeologist specialising in exploring ancient ale-making, he a craft brewer specialising in actually making ancient ales, have produced a fabulous downloadable poster on the visible remains of Viking brewhouses in Britain, which you can find here.
The poster points out that structures which have been interpreted as Viking “bath houses” or “saunas” are much better interpreted as brewhouses, not least because they were right next to the site of the drinking hall, as at Jarlshof on the Mainland of Shetland and Brough of Birsay, a now uninhabited island off the Mainland of Orkney. And really, what do you think a Viking would rather have – a bath or a beer?
To quote from the poster:
We know that the Vikings drank ale. There are numerous references to it in the Sagas. We also know that the ale was made from malt. In the 10th Century AD, Haakon Haroldson, the first Christian king of Norway, decreed that Yule be celebrated on Christmas Day and that every farmstead “should brew two meals of malt into ale”. One brew was for family, the other for guests. There were fines for non-compliance. If they failed to brew for three years in a row their farm was forfeit.
Ale was an important part of the Yule celebrations. Every farmstead had the facilities to make it. The ale was stored in huge vats, close to the drinking hall. The Orkneyinga Saga tells us that Svein Breastrope was ambushed and killed by Svein Asleiferson, who had hidden behind a stone slab by the ale vats in the entrance of the drinking hall at Orphir, Orkney. Since huge ale vats are not easily moved, then the ale must have been mashed and fermented close to the ale store.
The products and by-products of brewing ale are ephemeral, leaving no trace in the archaeological record. Ale is drunk, spent grain is fed to animals and residues are washed down the drains. Only the installations and perhaps some equipment may survive.