Sod roofs of norway

sod roofs of norway

The extreme climate of sub-arctic Norway is an ideal study site for cold and moist climate zones. Living and surviving in this extreme environment, the local population has developed sophisticated climatic architecture that is more explicitly responsive to the environment than in more temperate climate zones. The subject farmhouses are located in the southern center of Norway in the Oppland County area, including the towns of Vagamo and Lom. They are located in the foothills of the 6,000 foot high Jotunheimen National Park. Sod-roofed structures, both new and old are plentiful in this area, with this ancient technology still currently in use and actually experiencing a renaissance as Norwegian citizens are becoming more concerned about global warming. Some farmhouses have been relocated and are well preserved at museums at Lom District Museum in Presthaugen, Maihaugen in Lillehammer and the Norsk Folkemuseum at Oslo.

Materials:

Available materials from the slopes of Lillehammer, Vagamo, and Lom at Oppland County in 18th century were and remain limited, whether the purpose was for construction or any other activity. The land is formed largely from granite covered with a thin layer of topsoil, resulting in little arable land. Cut through by retreating glaciers over the eons, Norway is made up almost entirely of extremely high mountains woven through with correspondingly steep and narrow fjord valleys. Nonetheless, trees and water are plentiful. Trees are tall and straight with a few branches, making them ideal for construction.

Creating a comfortable living environment in this sub-arctic climate with its very cold and moist conditions requires good insulation to keep the heat in the structure. In these circumstances, engineering becomes literally a series of life or death decisions with the building's ability to do the following among its most important considerations:

• Shed rain and snow

• Use snow to also act as insulation, keeping the heat inside

• Avoid water damage and mildew problems from ground water and moisture from melting snow

• Keep frost (frozen ground water) from lifting and destroying the foundation

• Keep the living environment and food storage areas dry, for both humans and animals.

Soil does not provide much insulating value but snow on top of a roof does provide good insulation against heat loss, as known from traditional arctic snow shelters such as igloos. However, soil does provide heat storage mass that is equivalent to stones and bricks which means that it stores the heat longer than other materials. In addition, logs as much as 12" in diameter provide excellent insulation.

sod roof

The three traditional roofing materials in this area were slate, wood shake, and sod. However, precisely cut slate tiles were expensive, and in the absence of nails, it was not easy to keep wood shake permanently in place. Iron was available but nails were scarce and not often used as fasteners. Iron was more often used for hinges and supports around fireplaces. Made of soil and turf which were readily available and requiring less manual labor to install, sod roofs became the obvious choice and the most common roof in this area to protect against the combined threat of wind, sun and water. Nonetheless, sod roofs required special materials and knowledge to install, and would be required to be upgraded and reinstalled over time.

The base of any roof was supported by logs placed about 24" on center, with wood planks about 2" thick placed above. To support the short overhang at the low end of the gable roof, outrigger beams were cut into the top of the wall logs and the direction of the roof planks were perpendicular to the roof slope. Some houses had a right angle key at the end of the outrigger to support the fascia board. This end of the roof fascia board supports the weight of about 4" soil and turf with water in it and keeps the sod from sliding off the roof.

The sod roof is a particular and unique feature in the traditional Norwegian farmhouse, providing several benefits beyond availability of materials and ease of construction:

1. Thermal insulation against bitter winter cold;

2. Thermal insulation against humid summer heat and shade from the summer sun;

3. Moisture retention and weight to hold the water-repellant birch bark underneath;

4. Water shedding properties.

The traditional sod roof was constructed in three layers, beginning with a bottom layer of water repellant birch bark. Prior to the use of oil based, waterproof membranes, birch bark was readily available and water repellant, as long as it was kept moist. The oil in the bark itself protected against moisture, kept cracking to a minimum, and kept the bark's water shedding properties alive. Birch trees that grow in this area tend to be quite narrow and so the strips of bark were layered to reduce gaps and the possibility of leakage.

Grass growing on the roof is important because their roots will act as binder for the soil. Without it, the soil will wash off with heavy rain and sliding snow. During winter, the grass will be dormant but the roots will continue to hold the soil together. Under the freezing temperature, the water in the soil will freeze. Snow could cumulate up to 8 meters in the area and will actually act as insulation keeping the heat within the building.

Conclusion

Ages before automobiles, supertankers, and power plants, people lived within their means, ate what they could produce or exchange, and built homes with materials harvested from the ground in the surrounding area. Today, we enjoy manufactured products, water, and energy from halfway around the world in the name of economy, efficiency, and profit. We have learned through economic downturns that our everyday lives are a fragile balance of politics, natural events, and the economy, creating both inconvenience and security issues. A single political or natural event can profoundly influence supply causing disorder and hardship for people, particularly as it affects the price of oil and gasoline as well as food and water. Peace of mind moves outside of our control when our access to everyday needs is out of our control. We need to find ways to balance the convenience and comfort of today's technology with a truly sustainable way of living.

The strategy of vernacular architecture is unique to the climate zone and the materials available in the area. Local structures predating the industrial revolution provide useful sustainable solutions that fit into the environment and are unique to the area. I chose a climate zone that is somewhat extreme in order to articulate the unique features and methodology developed by the local population throughout their long history. It is true that currently, few people live in these extreme environments. The majority of people live on the coastline or near a large body of water that provides food, rich arable land, and a tempered climate. However, the current trend is that overcrowding and high living expenses of waterfront cities combined with the population growth is causing a shortage of living spaces and will push new developments inland where the climatic condition is more extreme than on the coastlines.