Office partitioning glossary
Plain-English explanations of the terms you will come across.
- Cat A fit-out
- The standard landlord finish for offices to let, typically including ceilings, raised floors, lighting, air conditioning and toilets, but with an open floor and no tenant partitions.
- Cat B fit-out
- The tenant's fit-out added to a Cat A space, including partitions, meeting rooms, kitchens, furniture, IT and branding, tailored to how the business works.
- Ceiling void barrier
- An acoustic or fire-rated barrier installed in the space above a suspended ceiling, directly over a partition, to stop sound or smoke passing over the top of the wall.
- Deflection head
- A detail at the top of a partition that allows the structural slab above to move or deflect slightly without cracking or loading the wall, while keeping acoustic and fire seals intact.
- Demountable partition
- A partition system made from pre-finished panels set into floor and ceiling tracks, designed to be taken down and rebuilt elsewhere with little damage or waste.
- DnT,w
- A site-measured sound insulation figure between two actual rooms, including the effect of doors, flanking paths and junctions. It is usually lower than the partition's laboratory Rw rating.
- FD30S
- A fire door set tested to resist fire for 30 minutes, with S indicating smoke seals are fitted. The rating applies to the complete door set, including frame, hinges, closer and glazing.
- Fire stopping
- Materials such as fire-rated sealants, batts and collars used to seal gaps and service penetrations in fire-rated walls, so fire and smoke cannot pass through openings.
- Flanking transmission
- Sound that travels around a partition rather than through it, for example over the top through the ceiling void, under a raised floor or along ductwork and external walls.
- Frameless glazing
- Glass partitioning where panes are held in slim channels at the head and base and meet each other with a clear joint or narrow seal, rather than vertical frame members.
- Licence for alterations
- A formal written consent from a landlord allowing a tenant to carry out specified alterations, such as partitions, setting out the conditions and any reinstatement duty at lease end.
- Manifestation
- Markings applied to glass partitions and doors, such as frosted bands, dots or logos, so people can see the glass and do not walk into it. Usually placed at two set heights.
- Metal stud partition
- A wall built from galvanised steel channels fixed to the floor and ceiling with vertical studs between them, lined with plasterboard on both sides. It is the standard construction for solid office walls.
- Rw rating
- Weighted sound reduction index, a single number in decibels showing how well a partition reduces airborne sound in laboratory tests. Higher numbers mean better sound insulation.
- Safety glass
- Glass that breaks in a way that reduces the risk of injury, typically toughened glass that shatters into small blunt pieces, or laminated glass held together by an interlayer when broken.
Last updated 6 November 2026