Working with Cob

Cob is one of the oldest and most established building materials in the world, broadly consisting of mud and straw. Locally, especially Devon, Cob is the most common original building material with many thousands of the surviving local vernacular constructed with this material.

Having much experience and skill working traditionally with Cob makes us ideally suited to preserve and maintain your period property.

As you can see in the images - Cob comes in two main forms;

  • Blockwork (compressed, dried Cob formed in to blocks) - widely accepted by conservation and building regulatory bodies, allows a fast and strong build that can be utilized for pretty much any application; like garden walls, chimneys, house and barn exterior walls (both construction and repair) etc.
  • Natural Cob (clay based soil and straw - generally mixed on site) which is layered in lifts of approximately 16" per layer - gradually built up to allow for drying and curing which maintains the structural integrity.

Lime mortar is used in conjuction with the Cob Blockwork and Lime plasters are the recommended protective outer layer for both forms of Cob construction.

Cob repairs often involve stitching new material into existing with 'Helibars' which are twisted lengths of Stainless Steel that help to bind the different layers together. Clay Pantiles, Bricks and other natural mediums are also utilized in the repair of Cob.

Conservation and Building regulatory bodies will for the most part stipulate that Cob must be repaired and/or restored with a 'like for like' attitude - as oposed to simply making good with modern building materials such as concrete blocks or cement render. This is due to the properties of Cob requiring the ability to breathe and move naturally to maintain its integrity and longevity.

Much of the damage caused to Cob is through water penetration, once the Cob has been repaired and the reinstatement of Lime as the correct plaster or mortar is completed, the Cob is properly protected, able to breathe and thus stabilise to it's correct humidity levels.

Examples of Work