Timber Frame Construction

A timber frame is a building that shows its work. The posts carry compression to the ground. The beams span between them in bending. The braces triangulate the frame against racking. Every member is visible, and every joint declares the path of the load. There is no concealment and no redundancy. What stands is what is needed, and nothing more.

The distinction between timber framing and conventional wood construction is worth being precise about. A stud wall is an assembly of small, interchangeable members — typically 38 by 140 millimeters — spaced closely and sheathed to create a composite structural surface. The individual studs are not significant; the system is. A timber frame is the opposite. Each member is large — 200 by 200 millimeters or more — individually selected, individually jointed, and structurally legible as a discrete element carrying a specific load. The frame is an assembly of named parts: sill, post, girt, plate, brace, rafter, ridge. Each has a role, and the role is readable from the geometry.

This legibility is not decorative. It is diagnostic. A timber frame that is functioning correctly looks correct — plumb posts, level beams, tight joints, no visible deflection. A frame that is in trouble shows it: joints opening, posts leaning, braces no longer making firm contact. The structure communicates its condition continuously, and the information requires no instruments to read. The eye is sufficient.

Joinery

The joints are where the intelligence of a timber frame resides. A mortise-and-tenon connection transfers load through bearing surfaces cut into the timber itself, secured with hardwood pegs driven through offset holes — a technique called draw-boring, which pulls the joint tight as the peg is driven home. No metal. No adhesive. The geometry of the cut holds the assembly together, and the peg prevents withdrawal.

There are dozens of joint types, each suited to a specific structural condition. A tying joint resists tension — the dovetail, which widens toward its end and cannot be pulled free without breaking the timber. A bearing joint transfers compression — the housing, where one timber sits in a shallow mortise cut into another, transmitting load through direct contact. A lapping joint connects members that cross — half the section removed from each, interlocking to maintain the plane. The vocabulary is large because the structural conditions are varied, and the material does not forgive a poor choice. A joint that is adequate in compression may fail catastrophically in tension. The selection must be correct.

What makes these joints remarkable is their tolerance for movement. Wood shrinks and swells with moisture content, and a pegged mortise-and-tenon accommodates this movement without loosening. The joint tightens in one direction as the timber shrinks and relaxes in another as it swells, but the peg maintains the connection through the full range. A bolted connection, by contrast, may loosen as the timber dries and the bolt hole enlarges. The wooden joint is designed for a material that moves. The metal connection tolerates it.

Species and Selection

The choice of species determines much about the frame's character and performance. Oak is the traditional framing timber in northern Europe — hard, heavy, durable, and workable when green. It is typically framed unseasoned — cut joints in green oak tighten as the timber dries, because the shrinkage is greatest tangentially to the growth rings, pulling the cheeks of the mortise inward against the tenon. A green oak frame gains strength as it ages, reaching a settled equilibrium after several years of drying in place.

Douglas fir is the primary framing timber in western North America — straighter-grained than oak, lighter, and available in longer lengths. Eastern white pine serves a similar role in the northeast, softer and easier to cut but adequate for moderate spans. Each species carries its own working properties: how it cuts, how it holds a peg, how it responds to moisture, how it ages. The selection is made not in the abstract but in relation to the specific frame — its span, its load, its exposure, and the tools and skills available for the work.

Raising

The frame is assembled in sections — called bents — on the ground, where the joints can be cut and fitted with the precision that gravity working in the builder's favor allows. Each bent is a cross-section of the building: two posts, a connecting girt or tie beam, and the braces that triangulate the assembly. When the bents are complete, they are raised into position — historically by hand, with pike poles and coordinated effort; now typically by crane, though the principle is the same.

The raising is the moment when the frame reveals its geometry as a whole. Individual joints that were cut flat on the ground now bear load for the first time. The connecting members — plates, purlins, ridge — tie the bents together into a three-dimensional structure. If the layout was accurate and the joints were cut correctly, the frame stands plumb and square without forcing. If not, the errors become immediately visible and must be corrected before the frame is loaded further. There is no cladding to conceal a misalignment, no sheathing to stiffen a racked frame. The structure must be correct in itself.

Enclosure

A timber frame is a skeleton. It requires an enclosure system — walls, roof, insulation — that is structurally independent of the frame or that works with it as a composite assembly. The frame carries the primary loads; the enclosure manages weather, thermal performance, and light.

The range of enclosure options is broad precisely because the frame does not depend on its walls for structural integrity. Straw bale infill between the posts provides exceptional insulation with minimal embodied energy. Structural insulated panels applied to the exterior create a continuous thermal envelope without interrupting the interior expression of the frame. Stone or brick infill between the lower posts adds thermal mass and weather resistance at grade level. Each approach produces a different building, and the frame accommodates all of them because it asks nothing of its enclosure except that it keep the weather out.

Duration

The oldest surviving timber frames are measured in centuries. Medieval barns in England, temple structures in Japan, stave churches in Norway — these are not preserved specimens but working buildings that have been maintained continuously, their frames inspected, their joints re-pegged where needed, their roofing replaced on the cycles appropriate to its material. The frame endures because it was designed to be maintained: each member accessible, each joint inspectable, each component replaceable without dismantling the whole.

This maintainability is perhaps the most significant property of the system. A timber frame does not age silently. It creaks, settles, shows its stresses in the grain. A joint that is working loose can be seen and addressed before it becomes a structural concern. A member that is deteriorating — from moisture, from insect activity, from sustained overload — can be sistered or replaced while the surrounding frame continues to carry its load. The building persists not because it is indestructible but because it is legible, and what is legible can be tended.