We have recently written a blog on Constructing with Cob, but in order to do this you will need to learn how to make Cob! Making Cob the traditional way can be a lot of fun, so let’s have a look at how it’s done.

Cob Brick

What you will need:

Subsoil - The soil beneath the thin layer of top soil is called subsoil. Subsoil has very little organic material and should be rich in clay, and this is what you need to make Cob. Clay is the binder that holds all of your materials together. When clay is wet it is sticky and pliable, when it dries out it is strong and hard.

Straw - Straw is the fibre of the Cob. During the mixing process, straw acts as a conduit for the distribution of clay and binds the mixture together. Commonly, barley straw is used in Cornwall cob walls. Wheat straw, generally a thatcher’s favourite, is considered too brittle for cob making.

Water - This is the crucial ingredient in Cob as it turns your clayey subsoil and straw into a sticky, but workable building material.

A Mould - This can be made out of wood into the size you want your Cob brick to be.

Tarpaulin - This is an ideal surface to mix your ingredients on and for turning your materials during the mixing process.

Mixing the Cob:

1. Lay out your tarpaulin.

2. Distribute your clayey subsoil and straw on the tarpaulin.

Mixing Cob 1

3. Add some water to your mixture and get your feet dirty by stomping the mixture together.

4. Turn the mixture from time to time to ensure it is mixed well.

Cob Mixing 3

5. During the mixing process add water, as needed, to keep the mixture manageable.

6. When the clayey subsoil, straw and water is thoroughly mixed it can be left to ‘mature’ for a day before use.

Mixing Cob 2

Making your brick:

1. Fill your mould with your Cob, ensuring the mixture is compacted.

2. The Cob can remain in the mould for a day or two.

Cob Brick Making 1

3. Release the Cob brick and allow to dry in an aerated environment for at least 2 weeks.

4. If achievable, leave your cob bricks in the sun (but not in the rain)!

 Cob Brick 2

For more information about Cob, please visit our Website.

Cob and Lime Specialist Cornwall & Isles of Scilly-Cob Repairs, Cob Re-Builds and Cob New Builds Cornwall & Isles of Scilly-Cob Structural Reports and Assessments Cornwall & Isles of Scilly

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Contact us

Leslie Cornell
Unit 13/14 St Austell Bay Business Park
Par Moor Road
St Austell
Cornwall
PL25 3RF

Tel: 01726 337577
Mob: 07851 153 683
Email: cornellcob@outlook.com