Construction and Structural Details

Oak was the timber predominantly used in timber-framed construc­tion, for its strength and resistance to rot were unrivalled, and if it was allowed to dry naturally, it actually improved and hardened with age. Of the other timbers, elm is most commonly met, for when grown in woodland conditions it grew taller than oak and was therefore sometimes preferred to oak for longitudinal members, such as collar – purlins, where a single continuous length was an advantage. It is, however, somewhat inferior to oak in that it is less resistant to damp and insect attack, yet it was frequently used in the construction of barns and other farm buildings in the seventeenth and eighteenth centuries. At Houchins Farm, Feering, Essex (3), a house built in the second half of the sixteenth century, both oak and elm were used, oak for those timbers under stress, such as tie-beams and binding joists, but elm for all secondary timbers, such as studs. Sweet chestnut was another timber sometimes used – Polsteads Farmhouse, Bures Hamlet, Essex, built about 1590, is one example – and when weathered even experts find it difficult to distinguish it from oak. Chestnut, although it does not attract beetle infestation, is less resistant to rot than oak. Other timbers known to be used were ash (one of John Norden’s three ‘building trees’), willow, hornbeam, black poplar and even plum.

In the eighteenth century, when many of Britain’s forests were depleted, imported softwood was also used. Its use for flooring was, of course, widespread but in such places as Cambridgeshire, as well as in parts of the South-East, softwood began to replace oak as the traditional timber for wall-framing. An early example of the use of softwood in the structural frame was at the former White Horse Inn, in Castle Street, Cambridge, a seventeenth-century building. In Cambridgeshire it was not uncommon for oak and softwood to be used within the same building.

The oak was generally not seasoned, for timbers over about three inches thick took an extremely long time, and so the large scantlings required for structural purposes made it impracticable. In addition, when the oak was ‘green’, it was soft, allowing it to be cut and the joints made, but as the sap dried out, the timber hardened until eventually it was almost too hard to cut. Oak was, therefore, generally used within a year or so of felling, and this probably explains the warps

Construction and Structural Details

3. Houchins Farm, Feering, Essex

and twists to be seen on many old buildings. Even when oak has been fixed in a building for centuries, it will warp and twist, as if new, when cut up and used again. When oak was required to be seasoned, it was generally submerged in a running stream with butt-end upstream, the sap being flushed out.

Timbers from old buildings were often re-used, and it was common in Elizabethan and Jacobean periods, when so many of the timber – framed houses were built and rebuilt, to use timbers from old build­ings. In the main these timbers were cut up and often used to construct two or more smaller buildings. These old timbers can usually be identified because of the position of redundant mortices, peg holes and marks, and this may have led to the widespread and persistent belief that many houses are built of old ships’ timbers. There is nothing improbable about the idea, for up to about 1840 most ships were constructed of timber and at the end of their serviceable life were undoubtedly sold and broken up for their timbers, yet there is little evidence either ‘documentary or practically’ that the timbers were ever used in the construction of buildings. On closer examination the redundant mortices and peg holes can easily be explained.

The oaks were felled with a narrow axe, although a large tree was often cut around with a broad axe before the narrow axe was used on the heartwood. The larger trees were split into baulks by means of an axe and iron wedges, but for the smaller ones the baulks were often formed by roughly squaring the tree by means of an axe or adze. The baulks were then cut to length with a two-handled cross-cut saw, known as a ‘twart-saw’. The length of these timbers was usually between ten and twenty feet, but lengths up to thirty feet were not uncommon, and very occasionally timbers up to fifty feet were used. The conversion of these timbers varied depending on their use within the building (4). The principal timbers (posts, wall-plates and main beams) were boxed heart and simply squared by means of an axe before finally being trimmed with an adze. For smaller timbers (the studs,

Construction and Structural Details

A. boxed heart

B. halved 4. Timber conversion

C. quartered

braces, rafters and joists), the squared baulks were generally halved or quartered.

The timber would be either hand-sawn or cleft and squared by means of an adze. At first the logs rested on a trestle with the top sawyer, who guided the saw, sometimes standing on the log, with the bottom sawyer, who pulled the saw, underneath. It was not until the sixteenth century that saw-pits first began to appear; the principle was the same, the top sawyer standing above the log, with the bottom sawyer pulling the saw from within the pit. For high-quality work the timber was usually sawn, for it gave a good straight face, but for less important work the timber was cleft – split along its length. Cleft timber has an advantage over sawn in that, as it follows the grain, it is more durable, minimizing the likelihood of splitting caused by cutting across the grain. Cleft timbers were widely used up to the seventeenth century, providing many of the small timbers such as wattle staves, laths and tile battens, as well as the larger timber. Early weatherboarding, known as ‘clapboarding’, was also cleft, the baulks being quartered and then split into wedge-shaped planks radially from the centre. Floorboards too were cleft. The disadvantage with cleft timber, particularly with timber of large scantlings, was that the length obtained depended greatly on the quality of the timber available, and from the eighteenth century onwards, with the shortage of suitable timber to be cleft and the increasing number of power-driven sawmills producing precision-cut timber, its use declined.

Recent research undertaken by Dr Oliver Rackham indicates that more trees were needed for construction than was at first realized. In an article in Vernacular Architecture he estimates that at Grundle House, Stanton, Suffolk, a slightly larger than average fifteenth-century house, with two cross-wings, 330 trees were used; a large number were small trees, about half of them less than nine inches in diameter, and even the larger trees rarely exceeded fifty years’ growth, with only three exceeding eighteen inches diameter, the normal size of a mature oak. Similarly, the Royal Commission of Historical Monuments has found that, for a small three-bay, seventeenth-century, single-storey house at Swaffham Prior, Cambridgeshire, measuring some forty by 15 Vz feet on plan, about eighty oaks were used, varying in size from nine inches to eighteen inches in diameter.

Updated: 18th September 2014 — 5:53 am