Shaft Wall Calculator — Liner Panels, C-Studs & J-Track

A shaft wall (or shaft liner) system is a fire-rated plasterboard enclosure built around service risers, lift shafts, stairwells and vertical ducts. It uses 19mm shaft liner panels (British Gypsum Gyproc CoreBoard or Knauf Coreboard, 600mm wide and up to 3000mm long) slotted into C-studs within J-track, with FireLine face boards on the accessible side. The system can be installed from one side only, which is its key advantage — no access to the shaft interior is needed during construction.

Under Approved Document B, the structural fire-resistance period follows the building height: 60 minutes up to 18m, 90 minutes between 18m and 30m, and 120 minutes above 30m (where a life-safety sprinkler system is also required). The shaft wall enclosing a service riser or lift shaft is generally provided to the same period as the structure it serves. British Gypsum and Knauf publish tested build-ups for each period — for the GypWall Shaft system tested to BS EN 1364-1 (insulation rating EI), the non-shaft-side FireLine build-up is two layers of 12.5mm Gyproc FireLine for EI 60 (spec A306002 / A306012), two layers of 15mm for EI 90 (A306003) and three layers of 15mm for EI 120 (A306030). The single layer of 15mm (spec A306001) is the BS 476: Part 22 build-up only — that is a single-direction test in which the corridor-side insulation drops to 30 minutes, so it does not give a full 60-minute BS EN 1364-1 rating. This calculator uses the BS EN 1364-1 layer counts. Always confirm the specific requirement with building control.

C-studs (also called I-studs) are C-shaped metal sections that hold the shaft liner panels in place. They are positioned at 600mm centres. J-track is a J-shaped metal channel fixed to the floor and soffit that receives the C-studs and liner panels. The liner panel slides into the J-track, then the C-stud is inserted to lock it in place. British Gypsum GypWall Shaft and Knauf Shaftwall are common UK systems.

Yes, wherever there are valves, dampers, access points or serviceable equipment within the shaft. Building Regulations and fire risk assessments determine the number and location. Inspection panels must maintain the fire rating of the shaft wall — use fire-rated access panels (e.g. Profab or Howe Green) tested to the same period as the surrounding wall.

Yes, this is the primary advantage of shaft wall systems over traditional block or stud walls. The liner panels slide into the J-track from the corridor side, and C-studs lock them in place. Face boards are then fixed to the C-studs from the accessible side. This means the shaft interior does not need scaffolding or access at each floor level, significantly reducing installation time and cost.