Sod roof

Until the late 19th century, it was the most common roof on rural log houses in Norway and large parts of the rest of Scandinavia.

The load of approximately 250 kg per m2 of a sod roof is an advantage because it helps to compress the logs and make the walls more draught-proof.

A sod roof is well suited to the dynamics of a barter economy because the materials are ubiquitous and cost nothing, although the work is labour-intensive.

The Norwegian term dugnad denotes an established custom, where large undertakings were accomplished with help from the community.

At the same time, open-air museums and the preservation movement created a reservation for ancient building traditions.

Birch is common everywhere in Northern Europe, and its bark is easily stripped from the trunk in spring or early summer, while the sap is running.

One incision with a knife lengthwise down the trunk between two branches will produce a correspondingly wide sheet, its length equal to the circumference.

The outer, flaky (white) bark is pried loose from the inner (green or brown) layer, the bast.

On roughly hewn or sawn roof boards, the friction alone will hold the layers of birch bark in place.

The first layers project about 8 cm along the eaves, where they will curve down around the edge of the outer board to form a throating.

In very dry areas, it was customary to cultivate certain drought resistant plants - notably Rhodiola rosea, Allium fistulosum and Sempervivum tectorum.

These logs or beams (Norwegian: torvvol) come in a variety of shapes and sizes, depending on the quality and status of the building, and on local tradition.

The turf log was fastened to the roof boards and underlying rafters with naturally grown wooden hooks, preferably from durable juniper.

A more refined fastening device was the kolv, an elaborately shaped stick of wood, around 60 cm long, pegged to the roof and extended through a hole in the turf log.

[12] Erosion at the verges was in some districts prevented by means of similar logs, sometimes joined crosswise at the gable top.