exterior detail of the stone and cob wall of a barn
Stone and cob wall of a barn in the Torridge district of Devon © Historic England
Stone and cob wall of a barn in the Torridge district of Devon © Historic England

Mud Walls – 5 Reasons Why You Should Love Them

Mud, (also called cob, chalk bats, and wychart in some regions) walls and buildings are built using mixtures of clay soils, chalk, and sand, with straw to bind it all together. They are found in many places around England, often associated with picturesque cottages or rural villages. Mud walls and buildings are a charming vernacular tradition that sheds light on the historic use of locally sourced natural materials.

Here are five fascinating facts about mud walls that you should know:

1. Mud or earth building is one of the oldest methods of construction in the world

Originating from the Middle East in the 8th century BC, in England 'clay lump' walls and buildings are first recorded in East Anglia in the late 18th century. For over a century afterwards, mud was the material of choice for nearly every sort of building and structure in the clay subsoil dominated parts of the East of England.

2. They're energy efficient, carbon neutral and good for wildlife

The only energy you need to make a mud wall is a hearty breakfast for the labourers who are building them. The mud was usually dug from the ground close to the building site, so it was and remains a very sustainable material. If, as was often the case, the walls were covered with a protective layer of lime wash, they absorb carbon dioxide, rendering them carbon neutral. Also, because the walls are usually thick and strong, they are great at insulating the buildings they were used for, keeping buildings warm in winter and cool in summer. Finally, clay lump and other mud walls are often a particularly attractive home for many different species of mining bees, including the Hairy Footed Flower Bee, which likes Cob walls in particular.

3. They were a tax avoidance scheme

The Brick Tax was introduced in 1784 to help pay for the costs of fighting the revolutionary war in the Thirteen Colonies. The tax was, unsurprisingly, unpopular, and there were many ways in which people tried to avoid paying. Building walls and buildings using the clay lump blocks avoided firing the clay to make normal bricks, and therefore was not subject to the tax [1].

4. Mud walls are quick and dirty

Mud walls are made using a number of methods, but all use a simple recipe and was a bit like baking cake.

John Curtis (from Norfolk), writing in the 1849 Encyclopaedia of Cottage, Farm and Villa Architecture, provided a detailed account of the ingredients that comprised the perfect mud wall mixture. He suggests that you need

"three loads of soft tender clay, as much water as [the mixture] will absorb, one or two horses (for treading), as much short old straw as can be properly mixed with it; [and] more water as required".

The mixture was trodden by the horses until the clay was completely broken down and mixed to a mortar-like consistency. Once the mixture was prepared, it was pressed into rectangular wooden box mould with a foot, and smoothed with a spade. The mould was removed, leaving a perfect mud brick. This was then left to dry, turning to ensure all sides were equally dry. They would be ready for use in 3 weeks.

The social campaigner John Denson, writing in 1821, was astonished by how cheap and quickly clay lumps could be fashioned into a cottage for a rural family. He noted that a cottage could be built for the minimal sum of £33, and that it would take about 1,000 clay lump blocks to build the cottage. He estimated that this would take two days to complete.

5. There are still a lot of places where buildings and walls using this traditional method of construction can be found

Some of the best examples in the East of England can be found in:

  • Whittlesey: There are over 25 sections of mud wall to be found in this beautiful Fenland market town, many of which are listed. Here, the mud walls are generally boundary walls that highlight historic plots in the town, and contribute to the unique character of the town [2]. The Whittlesey Mud Walls Group is an active local group that has catalogued all of the walls in the town, and provides advice and help to people who want to repair and maintain their mud walls.
  • Ashwell 'Bee Wall': Originally the kitchen garden wall of Ashwell Bury, this long section of cob wall on Gardiners Lane in Ashwell, Hertfordshire, derives its local nickname from the large number of different species of mining or masonry bees that make their home in it.
  • 1-16 The Crescent, East Harling: These cottages, designed by the architect George Skipper and built between 1918 and 1920 using rendered clay lump, were an experiment by Norfolk County Council in the provision of cheap housing.

Why not enrich the list with mud walls, or contribute examples to our architectural alphabet - #archalpha@HistoricEngland - "M" is for Mud Walls


[1] Whittlesey Mud Walls Group Walk leaflet

[2] Whittlesey Conservation Area Appraisal. Katie McAndrew (Fenland District Council Conservation Officer) 2018