An Introduction to Timber-Framed Construction

Dr Annabelle Hughes

During the period 1275 to 1550, most houses in this region were built on box-frame principles, from barely seasoned oak. The size of these houses is described by the number of bays  a bay being the distance between two pairs of principal posts. Principal posts extend from ground cill to eaves-plates and are held together at the top by a horizontal timber called a tie.

Medieval (pre-1550) houses of this type in this area generally have a crown-post roof. A crown-post stands upon the middle of each tie that connects a pair of principal posts. A timber running the length of the house in the middle of the roof space - a purlin - is supported on these crown-posts. Each pair of rafters is connected by a collar, which rests across the purlin. The collars are generally halved with a dove-tail to the rafters, less often tenoned into a mortice.

The assembly of two principal posts, tie and crown-post is called a truss. These trusses were either closed, as at each end of the hall, and filled with wattle and daub, or open, as over the centre of a two-bay open hall. The crown-post on a closed truss was usually braced down to the tie, and up to the collar-purlin, with the principal posts braced down from the jowl to the mid-tie. Principal posts were generally jowled or thicker at the top, in order to accomodate the complicated jointing of eaves-plate, post and tie. This thickening was achieved by using a quartered tree-trunk with the root end at the top, and is sometimes described as a root-stock. The profile of these jowls often helps towards determining a date range.

On an open truss the crown-post was usually braced up four ways, to collar-­purlin and collar, and the tie is often cambered. The bay posts of an open truss were braced from about half-way down the posts, up to the tie, to form an arched shape over the hall. There are always exceptions to prove the rule. Crown-posts braced up four ways can also feature over the middle of two-bay floored cross-wings, although the up-bracing from the posts in these cases is usually in the form of two short brackets rather than long braces.

All the joints of the frame were fastened together with oak pegs. The spaces between the timbers of the frame were originally filled with wattle, made from woven sticks or split laths and sprung into place, covered thickly with daub, a mixture of clay, animal hair, dung and water. A coat of lime-wash would probably have covered both timber-frame and infill on the outside. If the pitch is fairly steep it may have been thatched originally, although this is not an infallible guide. Otherwise the roof would have been covered with tiles or Horsham stone.

The principal part of a medieval house consisted of a single room of one or two bays, open from ground to rafters - the open hall of the hall house. In addition there could be floored bays at either or both ends of the hall. As an alternative to a floored bay, a framed 'box' of two or more bays could be built at right-angles to the open hall, forming a cross-wing. These often survive when a hall has been rebuilt or replaced.

The only form of heating would have been an open hearth towards the centre of the hall. Hipped roofs with small open triangles at the apex of each end - the gablets - helped speed the escape of smoke, given a good draught, as did the tall window on one or both sides of the hall. These had wooden mullions and shutters. Sometimes there were small mullioned vents or louvres just under the eaves instead of one of the tall windows. In houses that have been altered and adapted over hundreds of years, soot deposits on roof timbers from decades of an open fire are often the only firm clue to the existence and extent of an open hall.

There were nearly always two opposing doors at one end of the hall, linked by the cross-passage, which was sometimes part of the hall, sometimes partially screened, sometimes within a narrow bay of its own, sometimes undershot within the floored end. This passage almost always abutted the service or 'low' end of the hall, lying beyond the single open hearth. Where there was a separate solar, it would lie beyond the opposite end of the hall - the 'high' or 'dais' end, so called after the raised platform found in the halls of larger houses like Penshurst Place. In smaller houses the partition wall at the high end would sometimes be treated decoratively, with wooden panelling below a moulded or carved timber running the width of the house just above head-height - the dais beam and screen. Evidence can sometimes be found for a fixed bench against this wall.

The solar tended to contain superior with-drawing rooms for the house-owner and his family above a parlour, and the service to be where provisions were kept and food prepared with more storage above. If there was only one floored end, it would serve as a combined solar/service.

Studies of buildings and associated documents increasingly suggest that in many cases much of the cooking and preparation of food went on in detached kitchens set some feet away from the main house. Sometimes these detached kitchens become incorporated into the house as part of later extensions, and in urban situations they sometimes become developed as separate dwellings.

The desire to control smoke, coupled with changes in social requirements, drove developments in house construction. At first this might be a framed smoke-bay or smoke hood introduced into the open hall at first-floor level, pre-dating the eventual chimney. Once some kind of smoke control was introduced it was no longer necessary to have an open hall, and these were either floored over in stages, or all at once, to give extra first-floor rooms. A difference in first-floor levels is often the indicator of the extent of an insertion or alteration.

New houses were then built with smoke-bays or chimney stacks, and were fully floored from the start. Changes in roof construction made it possible to use the attic space. Instead of a central collar purlin, supported by crown-posts, and collars linking each pair of rafters, a purlin was laid along each side of the roof, supported with struts (and sometimes a collar) at each tie. This did away with the need for a collar to each pair of rafters, and opened up the potential of the roof space for storage, and much else. This was the through or clasped side-­purlin roof, with queen struts, or raking struts. A time went on, these purlins were morticed (butted) into principal rafters, at first in-line or later, staggered, to spread the strain of the joints with the rafters.

With side-purlin roofs over fully-floored houses and smoke-bays or chimneys came the development of lofts, attics and garrets, for both storage and additional living space, and the proportions of houses began to change.

The sixteenth century tended to be a period of transition, as old houses were converted to meet rising expectations and new houses built incorporating these changes from scratch. Often houses were built that still reflected traditional plans and methods of construction, but incorporated 'modern' innovations. Some were 'experimental' solutions to new demands and have either disappeared or survived as 'oddities', because they were seen as unsatisfactory. Those new styles and plans that were successful, survived and developed into the standard buildings of the seventeenth century and beyond.

As time went on, timber-framing became less socially desirable, and those who could afford to, built in brick and stone. These materials were also used to repair and up-date old framed buildings, underbuilding and encasing, where frames had rotted and weathered. One method used in the eighteenth century to disguise a framed house was to use mathematical tiles, hung on battens; these looked like bricks, but were less costly. There are many examples to be seen in Lewes.






Building survey

An introduction to timber-
framed construction