Roofing - Sod Roofs

What is a sod roof?

A sod roof (also known as a turf roof) is a method of roofing using layers or birch bark covered in sod, which is grass with the soil beneath it containing the roots. 

What is the history of sod roofing?

A sod roofing is a traditional method of roofing in Scandinavia. Until the late 19th century it was the most common roof on rural log houses in Scandinavia. The weight of a sod roof is 250 kg per metre squared. This weight is an advantage as it helps to compress the logs and makes the walls more draft proof. In winter, this weight increases due to levels of snow fall. The birch bark underneath the sod ensures that the roof is waterproof. 

Building a sod roof

The main element of the roof is birch bark, which is held together by the sod. The materials are all natural and easily found in rural areas, which makes it suitable for its surroundings. Putting together a sod roof is labour intensive and requires a lot of manpower. They are usually completed during a roofing party where neighbours, family and friends all take part in.

Birch bark is water resistant, soil resistant and strong, making it perfect for making a sod roof. It is easily cut and can is commonly found in Northern Europe. When the sheets of bark have been cut, they are stored flat under pressure to prevent it curling, which if left naturally it would do. 6 or more layers of the flattened bark sheets are then laid from the eaves upwards, ensuring that they are overlapping.

Traditional sod roofing method, including a turf log which is held by wooden hooks

Sod is cut from good quality land with sandy soil with a deep root. Small pieces are cut for easy transport and then taken onto the roof and laid. Sod must be laid out immediately after the birch bark to keep it in place, which means that the whole process must be accurately timed and coordinated. The finished roof must be between 15cm and 20cm because the sod has to have enough water to survive a dry summer, but not too much as the weight would be excessive. 

Modern day sod roofing

Today, sod roofing has been adapted to our modern ways of living and is now referred to as 'green roofing.' Germany, Switzerland and in the US, green roofs are becoming more popular. The UK is too learning the benefits of these roofs and are always being encouraged to use them. There is a green roof Centre in Sheffield and London is now too encouraging the promotion of green roofs in the city.

Advantages of a green roof

Long lasting - due to the vegetation on the rooftop, the roofing materials are protected from the elements which would normally damage it. Green roofs can last more than 50 years.

Energy saving - high insulation which means less heating bills.

• Reduced drainage requirements - the vegetation will ensure that water is retained  which reduced run off and lowers the requirement for drainage systems.

Increases property value - they are more eco friendly and produces an extra recreational space, therefore more appealing to potential buyers.

Keeping traditional craft going - keeping history alive by using a roofing method thousands of years old!

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Thatching - Modern Day

Afterparty by MOS at P.S.1


In 2009, MOS Architects won the competition to build a temporary pavilion installation at MoMA's P.S.1. The brief required the design to incorporate bar areas, seating, provide shade and incorporate water, it was also required that the designers experiment with new shapes and materials. It will be used as a venue for events during the summer.

MOS partners Hilary Sample and Michael Meredith explained that the design was to 'honour and reflect current economic realities by using basic materials.' The main structure of the pavilion is a recycled lightweight aluminium frame which are easily assembled, which is covered in thatched palm-fibre from Indonesia. 

This specific thatch is loose and has a softer texture than thatch used in the UK.

Air is drawn across troughs of water, which cools, and upwards through the narrow structures, which also provide shade for visitors.


The use of thatch in this modern design is very different from traditional use, but it suits the design and is extremely eco friendly.

Roofing - Thatching

What is thatching?

 Thatching is the craft of building a roof with dry vegetation such as straw, water, rushes and heather. The method is to layer the vegetation so as to shed water away from the inner roof. It is a very old roofing method and has been used in both tropical and temperate climates. Thatch is still employed by builders in developing countries, usually with low-cost, local vegetation. It is also popular in some developed countries by the choice of wealthy people for aesthetic reasons for their home.

When did thatching begin?

In Europe, thatching has been used as a method of roofing at least since the Neolithic period, although it was probably used before this but there are no records to prove this. In most of Europe and the UK, thatch remained the only roofing material available to the bulk of the population in the countryside, and in many towns and villages, until the late 1800s. The number of thatched buildings in England decreased from one million in 1800 to 35,000 by 1960 because of machinery and transport enabling other materials to be used. Today there are around 24,000 listed thatched buildings in the United Kingdom. 5% of these are new builds and there are 1500 individuals engaged in thatching. Thatch has become much more popular in the UK over the past 30 years, and is now a symbol of wealth rather than poverty. Thatching is becoming popular again because of the renewed interest in preserving historic buildings, traditional crafting methods and using more sustainable building materials. There are more thatched roofs in the UK and Ireland than in any other European country.

Thatching Techniques

Here is a video showing the different techniques and stages of thatching:

http://www.youtube.com/watch?v=FrmhXww92Lk&feature=player_embedded

When applied by a skilled thatcher, a thatched roof can last to about 50 years until a new layer of straw needs to be applied over the original surface. This accumulates every 50 years to thatch around 2.1meters thick on old buildings. To begin with, roofs were thatched with wheat, rye or maslin, which is a mixture of both materials. 

Thatch is fastened together in bundles with a diameter of about two feet. These are then laid on the roof with the butt end facing out and secured to the roof beams, after which they are pegged in place with wooden or steel rods. The thatcher adds the layers on top of each other, finishing with a layer to secure the ridge line of the roof. This method means thatch roofs are easy to repair, can endure heavy winds and rain and only need a stable supporting structure.

Advantages of a Thatched Roof

• Accessible materials, readily available all over the world
• Can be combined with other materials such as roof tiles
• Versatile material and can cover irregular roof structures and shapes
• Extremely sustainable and eco friendly due to the materials being natural
• Gives a beautiful rustic feel to any building, old or modern

Disadvantages of a Thatched Roof

• Can only be applied by a skilled worker, therefore expensive as well as being time consuming
• Can be damaged by nature such as extreme weather or animals
• Hard to insure due to fire risks
• Has to be redone approximately every 50 years