What is a wall plate?

A wall plate is a horizontal timber, typically 100x75mm or 100x50mm treated softwood, bedded in mortar on the top course of a masonry wall at eaves level. Rafters are bird's-mouth notched and nailed to it; ceiling joists rest on or are nailed to it. The wall plate distributes the concentrated point loads from each rafter pair evenly along the wall below, preventing localised overloading of the masonry. It also provides a continuous, level fixing surface for the base of the roof structure and anchors the roof to the wall against wind uplift.

How is a wall plate fixed?

A wall plate is bedded in a full bed of mortar on the top course of the masonry wall and levelled before the mortar sets. It is then strapped down to the wall with galvanised mild steel restraint straps (typically at 2m maximum centres) to resist wind uplift - these straps are built into the masonry below and bent up over the wall plate. Lengths of wall plate are joined with a half-lap joint (not a butt joint) and the joints are staggered on opposite sides of the building. For trussed rafter roofs, trusses are fixed to the wall plate with proprietary galvanised truss clips.

Can a wall plate rot?

Yes - wall plate rot is a common problem in older buildings. The wall plate sits on damp masonry and is often in contact with the outer leaf of the cavity wall, making it vulnerable to moisture. Symptoms include rafters dropping at the eaves, sagging fascias, and springy or soft areas of the ceiling near the eaves. Replacing a rotten wall plate is a significant structural repair requiring temporary propping of the roof. All new wall plates must be pressure-treated softwood to Use Class 3, and should be isolated from the masonry with a DPC strip to prevent moisture transfer.

Is a wall plate the same as a sole plate?

No - although both are horizontal timbers at the base of a timber frame, they serve different elements. A wall plate sits on top of a masonry wall and receives the roof structure (rafters and ceiling joists). A sole plate is the bottom horizontal timber of a stud wall partition, fixed to the floor. In timber-frame construction, the term 'wall plate' is sometimes also used for the bottom rail of an external wall panel - context determines the meaning. Both must be treated timber where they are in contact with masonry or concrete.

Structural noun

Wall Plate

/ wɔːl pleɪt /

Also known as: roof wall plate, eaves plate, timber plate

Definition

A wall plate is a horizontal timber bedded in mortar on the top course of a masonry wall at eaves level, providing a continuous fixing point for rafters and ceiling joists. It distributes the concentrated point loads from individual rafters evenly along the length of the wall below, and ties the roof structure to the wall against wind uplift. Typically 100x75mm or 100x50mm treated softwood, it is strapped to the masonry at regular intervals with galvanised restraint straps.

In practice

The wall plate is one of the first elements positioned when constructing a roof. It is bedded level in a full mortar bed on the top course of blockwork or brickwork, with a DPC strip below it to prevent moisture transfer from damp masonry into the timber. All lengths are joined with half-lap joints. Once set, galvanised mild steel restraint straps are fixed over the plate and built down into the masonry at 2m maximum centres to resist wind uplift - these are a Building Regulations requirement.

Rafters are bird's-mouth notched over the wall plate and skew-nailed. Ceiling joists rest alongside the rafters and are also nailed to the plate. The ceiling joists act as ties, preventing the rafters from pushing the wall plate (and wall) outward under the roof load - this outward thrust is one of the critical loads in a pitched roof. For trussed rafter roofs, proprietary galvanised truss clips are nailed to the wall plate and over the truss bottom chord at each truss position.

Building Regulations

Relevant PartPart A - Structure

Restraint strapsRequired at max 2m centres to resist wind uplift

Timber treatmentUse Class 3 treated softwood minimum

DPC below plateRequired to prevent moisture transfer from masonry

Approved Document A requires the roof structure to be adequately tied to the walls below to resist wind uplift. Galvanised restraint straps connecting the wall plate to the masonry satisfy this requirement. In high wind zones (Scotland, coastal areas, exposed upland sites), closer strap centres or heavier-gauge straps may be required. Replacing a rotten wall plate is notifiable building work requiring Building Regulations approval, as it involves altering the structural connection between the roof and walls.

Full Building Regulations guidance

Wall Plate

Just so you know...