Eleanor Hartley
Why Joints Tell You More Than the Timber Alone
Dendrochronology is a fine thing when it works, but it depends on finding enough rings, enough sapwood and a generous budget. The joints in a frame will often tell you more, faster and for nothing. Whoever cut them trained within a tradition, and the shape of a tenon, the angle of a shoulder, or the manner in which two lengths of oak were scarfed together can place a frame within a generation or two with reasonable confidence.
Do it gently. Take off later plaster and lath with care, never prise at a joint to see inside, and photograph pegs before you touch anything. You are reading evidence, not dismantling furniture.
Mortise-and-Tenon: The Workhorse of the English Frame
Nearly every historic frame leans on the mortise-and-tenon, and its variations are the clearest dating clues you will find.
- Draw-bored pegs. The hole in the tenon is set slightly back from the hole in the mortise, so driving the peg pulls the joint tight. Almost universal in medieval work and still used by hand carpenters today.
- Tusk tenons. The tenon passes right through the post and is locked with a wedge or a tusk-shaped shoulder bearing on the outside. Very common in floor joists and in trusses from the late medieval period through the eighteenth century.
- Fox-wedged tenons. Wedges driven into the end of the tenon inside a blind mortise, splitting it to lock the joint. Typical of close-studded walls and later partitions.
- Bare-faced and shouldered tenons. Where only one cheek of the tenon meets the shoulder, saving labour on lighter timbers.
Look at the peg. Square, slightly tapered, riven oak pegs driven from one side are early. Neat, round, uniform dowels suggest later work or an honest repair.
Dovetails: Reading the Tails
Dovetails in a timber frame rarely appear where you expect if your eye is trained on furniture. They turn up tying wall plates at corners, joining joists to summer beams and binding top plates in long runs. In early work the tails are often cut generously and left slightly proud, with the pins narrow and irregularly spaced. As you move into the eighteenth and nineteenth centuries, the spacing evens out, the angles soften and the shoulders become more defined.
A useful test is consistency. Hand-cut tails vary. If every pin is identical, spacing perfect and the saw marks are faint arcs from a circular blade, you are looking at a later insertion or a replacement section rather than original fabric.
Scarf Joints: Where Two Timbers Become One
Scarfs are the most regional and the most revealing joints in the building. A long wall plate or a tie beam is rarely one tree, and the way two lengths were united shows both the carpenter's training and the date.
- Stop-splayed scarf with under-squint. The tenon is set at a splay so the joint tightens under load. Strongly associated with medieval and early post-medieval work.
- Edge-halved and bladed scarf. Folding wedges driven in from both sides lock the joint. Common in the seventeenth century.
- Tabled scarf with wedges. A plain table with a key or folding wedges, widespread from the late seventeenth century onwards and much used in Georgian roofs.
Count the pegs. The more pegs a scarf carries, the earlier it generally is.
Tool Marks, Pegs and the Small Details
The surfaces around a joint are as informative as the joint itself. Pit-sawn timber shows faint, slightly irregular vertical scratches and a sometimes wavy face. Circular saw marks — shallow arcs — point to the 1830s or later. Adze-finished surfaces, dished and faceted, are earlier still. In mortises, spoon-bit auger marks are typical before roughly 1770; spiral-twist bits came later.
Also check for reused timber. Smoke-blackened rafters reset into a later roof, or a beam with empty peg holes where a previous joint once sat, will happily mislead you. Empty mortises are one of the most common causes of a wrong date.
Assessing What You Have Found
Read the frame as a whole. One unusual joint may be a repair; a consistent vocabulary across the building is a genuine date. Match joints to the carpentry around them, note any later additions in different species or sawn timber, and record everything before you cover it up again.
If the evidence conflicts — an early scarf beside machine-sawn joists — you are probably looking at an older core that has been reworked. That is not a problem. It is the story of the building, and it has been waiting in the joints all along.
