A longitudinal frame (Dutch: langsgebint) is a timber frame whose posts stand in the length direction of the building: more than two posts connected by a continuous longitudinal beam, with wind braces at the top between post and beam. It therefore runs parallel to the ridge, where a transverse frame stands at right angles to it.
How it differs from a transverse frame
This is the key point and the source of most confusion:
- Transverse frame — stands at right angles to the ridge. Two posts with a tie beam or a collar between them. Carries the roof across the width and sets the cross-section of the building.
- Longitudinal frame — runs parallel to the ridge. A row of posts under a continuous longitudinal beam. Provides stability in the length direction above all, and carries the purlins.
A roof structure built on longitudinal frames generally consists of two such frames, one on each side, connected to one another by tie beams. Those tie beams are in turn braced back to the posts with knee braces.
Distribution
Roof structures using longitudinal frames are characteristic of Germany and the eastern Netherlands — Twente, the Achterhoek, parts of Drenthe and Overijssel. Across most of the Netherlands transverse frames are the norm. The construction type therefore says something about the region and the building tradition a structure belongs to.
Points to watch in restoration and alteration
- The wind braces are the stability. They form the triangles that stop the frame racking along its length. Never remove one to make a doorway, a stair or a cupboard without a structural engineer specifying replacement bracing or a steel portal.
- Check the post feet. The base of the posts often sits on a pad or straight on a floor and has endured centuries of rising damp. Rot and insect attack start there. Repair is by cutting out the affected length and splicing in a new foot.
- Mortice and tenon joints with pegs. The joints are held by timber pegs, not by glue or steel. A drawn or split tenon is a genuine structural problem; driving nails through it does not solve anything.
- Carpenters’ marks. Frames often carry assembly marks from the time of construction. Record them before anything is dismantled — they show how the roof originally went together.
Related terms
- Timber frame
- Transverse frame
- Wall plate
- Knee brace
- Roof structure
- Mortice and tenon joint
- Carpenters’ mark
Want to know more about building terms? Take a look at our knowledge base on fredsdiyplans.com.