What is Clay Lump?

Whilst you might expect earth buildings to be commonplace around the world, they are also common in the UK, where earth buildings have been constructed for hundreds of years. The type of earth construction varies, such as ‘cob’ in the West Country and ‘clay lump’ in East Anglia (mostly concentrated around South Norfolk and North Suffolk).

Similar to solid brick work, this building technique used large, un-fired, clay bricks set in a clay mortar. The bricks were made of local clays usually containing a mixture of sand, chalk, lime, straw or animal hair and then shaped using a simple wooden mould and air-dried. Often termed mud bricks, or adobe in the Spanish-speaking world).

The sizes could vary from about 22 x 12 x 5 inches to 18 x 6 x 6 inches. The wall surfaces were originally finished with a clay plaster, which was often tarred for weatherproofing and then sanded to take a colour-wash.

Current evidence suggests that the technique first made its appearance in this region in the late 18th century, and becoming very popular in the clayland parts of Norfolk and Suffolk in the first half of the 19th century when there was a tax (repealed 1850) on fired bricks. It was particularly used for farm buildings and cottages.

There was a slight revival of interest in the technique in the first quarter of the 20th century but by the 1920s cement rendering was the most frequent surface treatment. 

How to Identify a Clay Lump Construction

It is common for clay lump properties to be rendered externally, leaving the gable walls within the roof space as the only area where exposed clay lump can be spotted. In many cases, the clay lumps were hidden behind a brick facing, particularly in town environments. A brick or stone plinth was usual to give the blocks a dry foundation. This facing increased the thickness of the external wall to more than a traditional solid brick wall and is therefore another good indicator of a clay lump property.

Buying a Clay Lump Property

Clay lump properties are readily mortgageable, but not with all lenders, and therefore it is important to ensure that your mortgage lender is aware of the construction type.  This will also be the case with buildings’ insurance.  Local brokers will have experience in properties of this construction type and will also have a knowledge of lender and insurance criteria. The main enemy of clay lump is water and the introduction of modern cement renders.  It is therefore important to commission a survey in order to highlight the need for current repairs and any future maintenance.