Proprietary Shaft Wall Systems: Lift Shafts, Service Risers, Fire Ratings and Installation from One Side

Quick Answer: Shaft wall systems (e.g. British Gypsum GypWall SHAFT, Knauf Shaft Wall) are specifically designed to line the inside of lift shafts, service risers, and stairwells where installation is only possible from one side. The systems use proprietary J-track, C-H (cellular) studs, and solid or laminated boards installed vertically from within the shaft — no access to the back of the construction is required. Fire ratings from EI 60 to EI 120 are achievable; systems must be installed strictly to the tested configuration.

Summary

A conventional double-sided metal stud partition requires access from both faces during installation — you screw boards to the stud from each side. In lift shafts, service risers, and duct enclosures, only one face is accessible: the inside of the shaft. Proprietary shaft wall systems solve this by inverting the construction logic: the boarding is installed first (slotted vertically into floor and ceiling tracks), then the stud structure is built behind it, engaging with the boarding from the one accessible side.

This is counter-intuitive compared to standard drylining, but the system has been developed and tested over decades. British Gypsum's GypWall SHAFT and Knauf's Shaft Wall system are the two dominant products in the UK market, and both are backed by third-party fire test data. Lift shaft enclosures in buildings with habitable space alongside them are almost always required to achieve 60-minute (EI 60) or 120-minute (EI 120) fire resistance — the shaft wall system is designed specifically for these applications.

Installation requires specific training and familiarity with the proprietary system. Unlike standard metal stud where substitution of similar products is common, shaft wall systems must use the manufacturer's specific components — the J-track, C-H stud profile, and board type are all engineered to work together to achieve the tested fire rating.

Key Facts

• One-side installation — entire system installed from within the shaft; no access required to the external face
• J-track — proprietary floor and ceiling track with an inward-facing leg that boards slot into; standard UW track cannot be used
• C-H stud (cellular stud) — a C-stud with the web perforated or slotted to engage with the J-track and hold the boards in position; heavier gauge than standard CW stud
• Board types — shaft wall boards are typically thicker (25–32mm) or are laminated composites; Gyproc SoundBloc or Gyproc Shaft Wall Board
• Fire ratings — EI 60 achievable with standard shaft wall configuration; EI 120 requires heavier or additional board layers
• Height capacity — systems tested to 5m and above without intermediate support (dependent on stud size and wind/seismic loading)
• Acoustic performance — shaft walls also provide significant acoustic isolation; important for lift shafts alongside habitable rooms
• Lift shaft requirement — Building Regulations Part B requires the lift shaft to be enclosed in fire-resistant construction where it passes through more than one storey; the shaft wall provides this
• Service riser — shaft wall systems are equally applicable to service risers (plumbing, HVAC, electrical riser shafts)
• Access doors — proprietary access door frames with equivalent fire rating are required at all access points to the riser; same fire rating as the shaft wall
• Structural independence — shaft wall systems should be structurally independent of the lift guide rails; guide rail vibration must not be transmitted through the shaft wall to occupied space
• Floor clearance — bottom track must clear the finished floor to allow shaft drainage; typically 25–50mm gap; fill gap with intumescent sealant for fire rating
• Head-of-wall (HOW) detail — the shaft wall must accommodate inter-storey deflection; the J-track and C-H stud system allows vertical movement of the boards within the track

Quick Reference Table

Verify exact system data in current British Gypsum White Book or Knauf Technical Manual; system heights depend on loading

Detailed Guidance

Installation Sequence — One-Side Method

The shaft wall installation sequence is the reverse of standard drylining:

1. Install floor J-track: Fix to the structural floor slab at the shaft perimeter; this is the base into which the boards will slot
2. Install ceiling J-track: Fix to the structural soffit (ceiling) at the shaft perimeter; this provides the upper restraint for the boards
3. Mark stud positions: Mark the J-track flanges at the stud spacing (typically 600mm centres)
4. Install boards: Each shaft wall board is slotted vertically into the floor J-track first, then tilted upright into the ceiling J-track; the board hangs between floor and ceiling track
5. Continue boards: Add boards one at a time, maintaining tight vertical joints between them (butt joint, no gap)
6. Install C-H studs: After all boards in a bay are in position, C-H studs are pushed horizontally through the board joints and engaged with the J-track at floor and ceiling; the stud flange captures the board edges and provides structural restraint
7. Crimping/fixing: C-H studs are crimped or screwed to the J-track at top and bottom
8. Apply additional board layer (if required for higher fire rating): fix additional boards to the face of the C-H studs from the same accessible side; joint staggered from first layer

This is a highly coordinated operation. The sequence cannot be reversed — studs cannot be installed before boards. Coordinating the width of boards with stud spacing is essential; boards must be wide enough to be supported by two adjacent studs when the stud is inserted.

Head-of-Wall and Structural Deflection

Lift shafts are typically concrete structures that deflect under load. The shaft wall system must accommodate this movement without cracking or loss of fire performance.

The J-track allows the boards to slide vertically — the C-H stud floats within the J-track slot, and the top of the board can move up and down without the track restraining it. This is an inherent feature of the system, unlike standard partitions where HOW details are a separate design consideration.

Critical detail:

• Do not fix the board face to the ceiling J-track; the board must be free to move
• The gap between the top of the board and the inside top of the J-track allows 25mm movement minimum
• Fill the HOW gap with mineral wool batt and intumescent sealant; do not use rigid filler

Fire Rating — Maintaining the Tested System

The fire performance of shaft wall systems is highly system-specific. The following substitutions invalidate the fire rating:

• Using standard CW stud instead of the specified C-H stud profile
• Using standard WallBoard instead of the specified shaft wall board
• Changing board thickness
• Changing board joint configuration (horizontal vs vertical)
• Changing stud spacing beyond the tested maximum

Third-party fire test reports for shaft wall systems typically run to 50+ pages. Building control may request the test report number and evidence that the installation matches the tested configuration.

For very high fire ratings (EI 120), two-layer board configurations are required. The boards must be installed in the tested sequence (first layer boards vertical, second layer horizontal or with staggered joints) — check the system data carefully.

Service Penetrations Through Shaft Walls

Service pipes and ducts passing through a shaft wall must be fire-stopped as for any fire-rated element:

• Plastic pipes: intumescent collar matched to pipe OD
• Metal pipes: mineral wool packed annular gap + fire mastic bead
• Ductwork: fire damper at the penetration or minimum 1m of intumescent duct wrap each side
• Electrical: proprietary cable transit block with ETA data

Access doors in shaft walls must match the fire rating of the wall. Proprietary fire door sets for riser access (Bradbury, Sertus, or equivalent) in EI 60 or EI 120 ratings are available and must be installed with intumescent seals and door closers.

Shaft Wall vs Conventional Fire Partition

Frequently Asked Questions

Can I use a shaft wall system for a standard partition where access is restricted (e.g. in a corner)?

No — shaft wall systems are designed for shaft applications and have different structural characteristics to standard partitions. For a restricted-access standard partition, the correct approach is to complete as much boarding as possible from both sides, then access the remaining section through a purpose-built access panel.

How do I achieve a flush junction between a shaft wall and a standard partition?

The shaft wall system terminates at the shaft perimeter. The abutting standard partition (or structural wall) is fixed to the shaft wall structure — typically with a closure stud at the junction and perimeter angle at the corner. The board face of the shaft wall becomes the face to which the adjacent partition is connected. Fire sealing at the junction (acoustic mastic or intumescent sealant) must be maintained.

Do shaft walls need engineering calculations?

For standard residential applications (building height under 11m, standard wind loads, lift shafts following standard geometry), published system tables from British Gypsum or Knauf should be sufficient. For taller buildings, or buildings in high wind exposure areas (coastal, high-rise), or where unusual loads apply (e.g. large access doors, equipment rooms), engineering calculations should be sought from the manufacturer's technical team or an independent structural engineer.

Regulations & Standards

• Building Regulations Approved Document B (Volume 1 and 2) — fire resistance of lift shaft enclosures and service risers passing through fire compartments

• BS EN 81-1:2019 — safety of lifts; fire performance requirements for lift enclosures

• BS EN 1364-1:2015 — fire resistance tests for non-load-bearing elements: walls

• BS EN 13501-2:2016 — fire classification of construction products; EI/REI definitions

• British Gypsum GypWall SHAFT Technical Guide — installation sequence, system data, and fire test references

• British Gypsum GypWall SHAFT — system data, tested configurations, installation guide

• Knauf Shaft Wall Technical Manual — Knauf equivalent system data

• Association for Specialist Fire Protection (ASFP) — technical guidance on shaft wall fire performance

• british gypsum systems guide — GypWall system overview and standard partition data

• building regs part b fire lining — fire resistance requirements for walls and ceilings

• drylining around services — fire stopping at service penetrations through shaft walls

• suspended ceiling grid systems — ceiling systems used at the top of shaft enclosures