raising plate

A raising plate is a horizontal timber laid flat on top of a wall or beam to provide a bearing surface for the lower ends, or heels, of roof rafters. It sits between the top of the wall and the rafters themselves, typically running the full perimeter of the building. The plate distributes the concentrated downward load and outward thrust from the rafters across a wider area of the wall, preventing point loading that could crack or crush the masonry or timber beneath.

Raising plates are usually made from softwood such as pine or spruce, sized to match the depth of the rafters or slightly less. A common dimension is 50 mm by 100 mm (nominal), though this varies by local practice and building code. The plate is fixed to the wall using foundation bolts set into the mortar bed, or by nailing through into the brick or stone. In timber-frame construction, the raising plate may be part of a larger wall plate assembly that also carries interior load-bearing walls.

Variants and alternatives

In some regions, the raising plate is called a rafter plate, wall plate, or bird's mouth plate. Some builders integrate it into a continuous structural beam system. In modern construction with engineered trusses, a single raised bearing plate may support multiple trusses. Cold climates sometimes require a slightly thicker plate to accommodate the additional thrust from steeper roof pitches and snow loading.

A common failure point occurs when the plate is undersized, poorly secured, or laid on damp or uneven masonry. Movement here causes the rafter heel to slip, creating gaps that allow water penetration and allowing the rafter to split where it bears. Conversely, if the plate is not thick enough or the bearing is too narrow, concentrated pressure can crush the timber. The interaction between raising plate, rafter heel, and wall top is critical to weather-tightness and structural integrity.

The name reflects its literal function: it raises the rafters up and away from the wall surface. This elevation allows for ventilation of the roof space and creates a small air gap that helps manage moisture. In modern practice, the raising plate sits just below a soffit vent or breathable membrane, forming part of a deliberate thermal and moisture management strategy rather than simply a bearing device.