From Loudin's Encyclopædia of Architecture - 1833:
"The cob walls of Devonshire, which are formed of clay and straw trodden together by oxen, have been known to last above a century without requiring the slightest repair; and we think there are many farmers, especially in America and Australia, who, if they knew how easily walls of this description could be built, would often avail themselves of them for various agricultural purposes. We shall therefore here describe the Devonshire practice, as furnished by a Reverend gentleman who has himself built several houses of two stories with cob walls in the manner which he details in the following paragraph; and who, moreover, informs us that he was born in a cob-wall parsonage, built in the reign of Queen Elizabeth, if not a few years earlier, which was only taken down in 1831 to be rebuilt. Our correspondent writes:
Cob walls, as they are called, are composed of earth and straw mixed up with water like mortar, and well-beaten and trodden together. The earth nearest at hand is generally used and the more loamy the more suitable it is considered for the purpose. These wall are made two feet thick, and are raised upon a foundation of stonework. The higher the stonework is carried the better, as it elevates the cobwork from the moisture of the ground.
After a wall is raised to a certain h eight, it is allowed some weeks to settle, before more is laid on. The first rise, as it is called, is about four feet; the next not so high; and so every succeeding rise is diminished in height as the work advances. The solidity of cob walls depends much upon their not being hurried in the process of making them; for, if hurried, the walls will surely be crippled; that is, they will swag, or swerve from the perpendicular. It is usual to pare down the sides of each successive rise before another is added to it. The instrument used for this purpose is like a baker's peel (a kind of wooden shovel for taking the bread out of the oven) but the cob-parer is made of iron.
The lintels of the doors and windows, and of the cupboards or other recesses, are put in as the work advances (allowance being made for their settling), bedding them on cross pieces, and the walls being carried up solid. The respective openings are cut out after the work is well settled.
In Devonshire, the builders of cob-wall houses like to begin their work when the birds begin to build their nests, in order that there may be time to cover in the shell of the building before winter. The outer walls are plastered the following spring. Should the work be overtaken by winter before the roof is on, it is usual to put a temporary covering of thatch upon the walls to protect them from the frost.
In forming cob walls, one man stands on the work to receive the cob, which is pitch up to him by a man below; the man on the work arranging it and treading it down. Each workman generally uses a common pitchfork, though sometimes a three-pronged fork is employed. Cob houses are considered remarkably warm and healthy and they are generally covered with thatch. The durability of cob is said to depend upon its having "a good hat and a good pair of shoes"; that is, a good roof and a good foundation.
Devonshire thatching is very superior to that in most parts of England. it is done with combed wheat straw called reed, consisting of the stiff, unbruised and unbroken stalks, which have been carefully separated from the fodder straw by the thresher, and bound up in large sheaves called nitches. In this way, the thatcher is enabled to finish his work much more neatly than in other counties where no reed is made. Instead of brick nogging for partitions, cob is used for filling in the framework, which is previously lathed with stout slit oak or hazel. This sort of work is called rab and dab."
Cottages built with this material, if afterwards rough-cast and white-washed, are certainly capable of being rendered very clean and comfortable. The expense of building one with a fire-place and oven in the principal room, which may be stated to be about 14 feet square; two small rooms behind the larger one for stowing away fuel and provisions; the upper storey divided into two apartments, the one for the parents, the other for their children, may be made very comfortable, and decently furnished for about £60."