A head-beam bent is a load-bearing timber frame in which the head beam (the cross beam) is joined to the post with a halved, notched joint and passes the post so that its “head” projects beyond it. The name comes from that projecting head.
How the joint works
At the post the head beam is locally reduced in width so it can run past. Post and beam are joined with twin tenons — two tenons side by side rather than one — which allows the joint to resist rotation as well as direct load. The angle between post and beam is almost always supported by a brace, which stiffens the joint and keeps the bent stable in its own plane.
How the whole frame goes together
- Bents across the building — each bent consists of two posts carrying the head beam.
- Wall plates — these connect the bents along the length of the building, housed into the posts with mortice and tenon joints.
- Wind braces — braces at each post support the wall plate. They take the wind load along the building; without them a whole row of bents can rack over.
- Padstones — the post usually stands on a masonry padstone so the timber never touches damp ground. That is the single most effective measure against rot at the foot.
Difference from related frame types
| Type | Position of the cross beam | Characteristic |
|---|---|---|
| Anchor-beam bent | Passing through the post, wedged on the outside | Beam sits below the post head; the anchor pulls the posts together |
| Top-beam bent | Sitting on top of the posts | The beam caps the posts |
| Head-beam bent | Running past the side of the post, head projecting | Halved joint with twin tenons |
Points for restoration
- Rot at the foot — nearly all damage to historic frames is at the base of the post. A decayed foot is repaired with a scarfed-in new post foot, and the post is set on a dry padstone.
- Weakening at the mortices — twin tenons remove a lot of timber in one place. Always check the remaining section before adding load.
- Do not simply cut back the beam head — the projecting head is part of the joint, not surplus timber. Sawing it off to gain space weakens the frame.
- Record before dismantling — measure and photograph the carpenters’ assembly marks and the layout before anything is released. Without those marks a frame cannot reliably be re-erected.
Related terms
- Timber bent frame
- Anchor-beam bent
- Top-beam bent
- Brace
- Mortice and tenon joint
- Carpenters’ marks
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