A ground frame is the lowest structural timber frame in a traditional post-and-beam building, resting directly on or near the ground. It forms the base of the load-bearing skeleton and transfers the weight of the entire structure down to the foundation. The term originates from traditional Dutch and Northern European timber construction, where it is known as an “aardgebint.”
Application
A ground frame consists of horizontal sills and vertical posts that together form a rigid structural bay at ground level. The sill beam sits directly on the foundation or on individual pier stones, while the posts support the upper frames and roof structure. Multiple ground frames are spaced at regular intervals along the length of the building, connected by purlins and wall plates.
Because the ground frame sits closest to the earth, it is the most vulnerable part of the timber structure. Rising damp, splashing rainwater, and poor ventilation can cause rot, fungal decay, and insect damage over time. In historic buildings, the ground frame is often the first element that requires restoration or replacement.
When restoring a ground frame, builders typically use durable hardwood species such as oak. A damp-proof course between the foundation and the sill beam prevents capillary moisture from entering the timber. Adequate ventilation around the base of the structure is equally important for long-term durability.
Traditional ground frames use mortise-and-tenon joints, a centuries-old woodworking technique that creates strong connections without metal fasteners. In new construction that follows traditional methods, these joints are still used to achieve both structural integrity and an authentic appearance.
Related terms
- Timber frame
- Foundation
- Timber
- Beam
- Truss
- Sill plate
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