Every leased office sits on a boundary between two scopes of work. The landlord owns and maintains the base building; the tenant designs, funds and builds the fitout. Where that line falls determines who pays for what, who approves what and which contractor is allowed to touch which system.
Most budget surprises in a fitout trace back to a misunderstanding of that boundary. Clarifying it before a lease is signed is one of the most valuable things an office fitout architect can do for a tenant.
The base building is the landlord’s asset: structure, façade, roof, the core with its lifts, stairs and amenities, central air-conditioning plant, main switchboards, hydraulic risers, sprinkler mains and the building’s fire detection backbone. These systems serve every tenancy and are maintained under the landlord’s contracts.
Base building quality varies widely between buildings, which is why we stress testing it early in commercial office design in Brisbane. Floor-to-ceiling height, core position and air-conditioning capacity all constrain what the fitout can achieve.
Many leases describe the handover condition as Category A: a shell with ceilings, base lighting, floor finishes or raised floor, and air-conditioning distributed for an open-plan layout. Category B is the tenant’s adaptation of that shell—partitions, meeting rooms, kitchens, joinery, finishes, furniture and data.
The terms are not used consistently, so the actual handover schedule matters more than the label. A lease that promises Cat A may still exclude ceilings in some zones or leave base lighting to be reworked, and those gaps fall to the tenant unless negotiated.
Air-conditioning is where disputes most often arise. The landlord supplies plant sized for typical office density and distributes it across an open floor. As soon as the fitout introduces enclosed rooms, high-density meeting spaces or a comms room, additional zones, supplementary cooling and duct modifications are required—typically at the tenant’s cost and by the landlord’s nominated mechanical contractor.
Rooms dense with screens and people, such as those described in meeting room technology for hybrid collaboration, are frequent triggers. Engaging the mechanical engineer through consultant engagement before the layout is fixed avoids rework.
Sprinklers, detectors, occupant warning systems and exit signage are base building systems, but every new partition changes how they must be arranged. Sprinkler heads may need relocating, detectors added inside enclosed rooms and exit paths re-verified—all within the tenancy, at the tenant’s cost, by the building’s fire contractor.
The certifier assesses the fitout against the building’s existing approvals and fire engineering basis, a process explained in certifier requirements for office fitouts.
The landlord typically provides a tenancy distribution board with a defined capacity and base lighting in a regular grid. The tenant extends power to workstations, rewires lighting to suit the new layout and installs data cabling, comms racks and security.
Lighting upgrades—tunable systems like those in circadian lighting design—replace base building fittings, which affects what is reinstated at lease end.
Core amenities belong to the landlord. Any kitchen, tea point or additional amenity inside the tenancy is a tenant item, and its location is governed by where hydraulic risers, floor penetrations and grease or waste connections can realistically reach.
Positioning a kitchen and breakout space near existing services can save a significant sum in core drilling and plumbing runs, so it is worth resolving during space planning rather than detailing.
Most commercial buildings issue a fitout guide or tenant design manual that defines technical standards, nominated contractors for base building systems, working hours and the approval process. Drawings must usually be submitted for landlord review before works begin, and a building manager will sign off on any penetrations or roof access.
This review adds time and must be built into the program alongside the considerations covered in fitouts for Brisbane CBD buildings. Thorough construction documentation that already reflects the guide shortens the landlord’s turnaround.
Landlords often offer a fitout contribution as a lease incentive, but it rarely covers base building modifications the fitout triggers. Identifying those costs during feasibility—and the reasoning outlined in office fitout feasibility studies—strengthens the tenant’s position in lease negotiations.
At lease end, make-good clauses usually require reinstatement to base building condition. A photographic and documented dilapidation record at handover, and a fitout designed to be removable, reduce that liability—one of the trade-offs in cost versus value in office design.
Commercial interiors at ISA™ are delivered under a management system certified to ISO 9001 for quality, alongside ISO 45001 for occupational health and safety—important in occupied buildings—and ISO 14001 for environmental management. The quality policy outlines how responsibility matrices and landlord submissions are checked.
Browse our office projects to see fitouts delivered within very different base buildings.
Base building covers the landlord’s structure, façade, core, lifts, central plant and primary fire services. Tenant fitout covers everything the occupier adds to make the space usable for their business—partitions, joinery, finishes, furniture, data and modifications to services within the tenancy.
Category A generally describes a landlord-delivered shell with finished ceilings, base lighting, raised floor or floor finishes and air-conditioning distributed to an open-plan layout. Category B is the tenant’s work that adapts that shell to a specific business, such as offices, meeting rooms, kitchens and fit-for-purpose services.
Usually the tenant. The landlord provides base building plant and distribution to an open-plan layout, and any additional zones, supplementary cooling for comms rooms or meeting rooms, or ductwork changes caused by the fitout are typically a tenant cost, carried out by the landlord’s nominated contractor.
Yes. Most leases require landlord approval of fitout drawings before works start, and many buildings have a fitout guide setting out technical standards, approved contractors and submission requirements. Building that review time into the program avoids delays at the start of construction.
Make-good clauses typically require the tenant to return the space to its base building condition. Understanding and recording that condition at the start of the lease, and designing a fitout that is straightforward to remove, has a direct effect on what the tenant pays when they leave.
The boundary between base building and fitout is written into the lease, the fitout guide and the building’s approvals—but it is rarely laid out clearly in one place. A responsibility matrix prepared before signing turns assumptions into agreed scope.
Know what the landlord is handing over, what the fitout will change, and what must be returned. Most of the cost certainty in a fitout is won or lost at that point.
Copyright © 2026 ISA™. All Rights Reserved.
