Terminology aligns with EN 124 and BS 5834. Descriptions have been adapted for clarity and consistency in Wrekin Product Information and are not intended to replace or restate the standard.
A-D
Term
Definition
Adaptor slab
Component at chamber top supporting surface box.
Base wall unit
Lowest wall unit with slots for utility entry/exit.
Bearing slab
Component at chamber base providing support.
Bedding load
Load applied to a surface box to achieve bedding-in of the load‑bearing parts.
Captive hinge
Integral hinge allowing access while resisting unauthorised removal.
Cementitious content
Cement and pozzolanic additions in mix (kg/m³).
Chequer pattern
Cast raised pattern on cover surface.
Clear area
Unobstructed area between seatings.
Clear opening
Largest inscribed circle diameter within clear area.
Combination unit
Cover and frame set in a concrete surround suitable for seating on a utility chamber.
Concrete cover
Thickness of concrete above reinforcement.
Cover
Movable part(s) closing the manhole or gully opening.
Cover (BS 5834)
Movable part of a surface box that covers the access opening.
Cushioning insert
Accessory improving stability and noise.
Depth of insertion
Distance from frame top to bottom of cover/grating at seating.
Designation
Categorization of a small surface box by grade and type.
Dirt bucket
Removable debris-collecting component of a gully top.
Dirt pan
Removable debris-collecting component of a manhole top.
Double triangular
Two triangular units providing stable seating and non-rock performance.
E-H
Term
Definition
Element
Frame or cover or grating (hinges/locks not included).
Frame
Part which receives and supports a grating and/or cover.
Frame bearing area
Underside area of frame resting on supporting structure.
Frame depth
Distance between top and bottom surfaces of the frame.
Grating
Movable part(s) allowing passage of water through to the gully/manhole.
Gully
Assembly that receives water for discharge into a drainage system.
Gully top
Upper part of a gully consisting of a frame and grating, with or without a cover.
Horizontal disc
Theoretical disc used to assess clear opening for small surface boxes.
Horizontal rectangular plate
Theoretical rectangular plate used to assess clear opening for large surface boxes.
I-L
Term
Definition
Indexed covers
Covers installable in one orientation only.
Inspection chamber
Structure with a removable cover for cleaning/inspection equipment but not personnel.
Intermediate wall unit
Wall section extending chamber height.
Kerb hinged
Hinge located adjacent to kerb.
Keyways (closed)
Blind lifting pockets preventing debris ingress.
Keyways (open)
Open lifting keyway holes.
Loosely coupled
Halves connected to prevent dropping during lifting.
M-P
Term
Definition
Manhole
Structure on a drain or sewer with a removable cover that allows personnel entry.
Manhole top
Upper part of a manhole/inspection chamber with frame + cover/grating.
Mass per unit area
Total mass of cover/grating / clear area.
Mortar sympathetic features
Features reducing strain in bedding material.
Nominal size
Integer approximating internal length/width.
Non-rock
Stable seating performance with minimal movement.
Permanent set load (FP)
Load = 2/3 FT applied for permanent set test.
Planar surface
Horizontal plane of a cover based on raised/recessed pattern coverage.
Pressure-relieved cover
Cover design reducing pressure build‑up.
Prising slot
Slot allowing lever/prising tool insertion.
Q-S
Term
Definition
Raised pattern
Areas raised above the cover planar surface providing traction.
Recessed pattern
Areas recessed below the cover planar surface providing traction.
Recycled polymer
Polymer comprised predominantly of recycled material.
Routine inspection
Inspection by sampling at intervals.
Safety grid
Grid preventing objects/people falling into shaft when cover removed.
Safety keyway
Retains lifting keys securely while lifting.
Sample
One or more units selected randomly.
Seal plate
Plate beneath cover preventing gas/water passage.
Seating
Surface on which cover/grating rests in the frame.
Securing feature
Feature preventing unintended lifting/ejection.
Set
Pair of covers referred to as one unit.
Single-piece
Cover/grating formed as one piece.
Solid top
Cover with no open slots or recesses.
Switching rules
Rules to adjust inspection intensity.
T-Z
Term
Definition
Test load (FT)
Load applied for testing load-bearing capacity.
Total clearance
Sum of maximum clearances between frame and cover/grating.
Unit
A single chamber component.
Utility chamber
Vertical structure housing utilities and access.
Vent
Opening in cover to provide ventilation.
Ventilated cover
Cover with openings for air movement.
Wall unit
Vertical hollow component forming chamber walls.
Waterway area
Free flow slot area for drainage/Effective drainage inlet area.
