Multi-Tenant Commercial Evacuation Diagrams: Who Owns What Under AS 3745 (Australia)

In a single-tenancy commercial building, evacuation diagram ownership is straightforward. The landlord covers the common areas, the tenant covers the interior of their space, and the boundary line is the tenancy demise marked on the lease plan. Multi-tenant buildings break that simplicity in three predictable ways: more parties, more shared infrastructure, and more chances for one party to assume the other has it covered when neither does.

This post maps the actual ownership chain for evacuation diagrams in multi-tenant commercial buildings in Australia, the way it should be documented in the lease, the common cost-sharing models, and the disputes we have seen on real engagements. It is the commercial-tenant counterpart to the strata and body corporate guide (which covers residential strata governance) and the single-tenant landlord-tenant post (which covers the simpler case).

Three diagram layers in any multi-tenant commercial building

Before any conversation about who pays for what, draw the boundaries clearly. A multi-tenant commercial building, whether it is a strip mall, a 3-storey office walk-up, a CBD tower, or a sub-regional shopping centre, contains three distinct layers of evacuation diagrams. Each layer has its own owner.

• Layer 1: building-wide common-area diagrams. These cover the main lobby, lift lobbies on every floor, fire stair entries on every level, car park entries and exits, and any plant rooms, switch rooms, or back-of-house corridors. They show the building-scale exit routes from any point in the common areas to the assembly area.
• Layer 2: tenancy-interior diagrams. Each leased tenancy has its own internal floor plan, its own exit routes (which often pass through common areas before reaching the street), and its own fire equipment. The diagrams inside a tenancy show only the tenancy boundary, the exits leading out into common areas, and the internal fire equipment.
• Layer 3: sub-tenancy diagrams. When a tenant subleases part of their leased area to a third party (a serviced-office operator subleasing individual suites, a head retailer subleasing a kiosk, a head fit-out tenant subleasing a back-of-house workspace), that sub-tenancy needs its own internal diagrams in addition to the layer 2 diagrams of the head tenancy.

Who owns the common-area diagrams (layer 1)

Building owner or landlord. In a privately-owned multi-tenant commercial building, the building owner is responsible for diagrams in common areas. This is not a lease term, it is a direct consequence of who controls the space. AS 3745:2010 clause 3.5 requires the owner of the area to provide compliant diagrams for that area, and "common area" is by definition the owner-controlled portion of the building.

In a strata-titled or body-corporate-titled commercial building (commercial strata, common in low-rise office and retail), responsibility for common-area diagrams shifts to the body corporate or owners corporation. The mechanism is the same as residential strata, governed by state strata legislation (Strata Schemes Management Act in NSW, the Owners Corporations Act in Victoria, the Strata Property Act in WA, and equivalent acts in other jurisdictions). The body corporate engages the diagram supplier and pays through the levy structure.

For mixed-ownership buildings (a strata building where the ground-floor retail is one lot owned by the original developer and the upper floors are individually-strata-titled offices), the boundary between body-corporate responsibility and lot-owner responsibility is whatever the strata plan defines as common property. The body corporate handles common property, lot owners handle the interior of their lot. Both follow the same AS 3745 obligations, just within their respective boundaries.

Who owns the tenancy-interior diagrams (layer 2)

The leaseholder. In Australian commercial leasing practice, the diagrams inside a tenancy are the responsibility of the tenant currently leasing that space, not the landlord. The lease typically requires the tenant to maintain the tenancy in compliance with relevant standards and regulations, and AS 3745 obligations sit within that requirement.

The tenancy boundary is the demise marked on the lease plan, which is normally the inside face of the perimeter walls. Anything outside that line is common area (landlord) or another tenancy (other tenant). Anything inside is the tenant's problem, including diagrams. A common practical pattern: the diagram supplier needs both the tenancy floor plan (from the tenant or fit-out drawings) and the demise plan from the lease to draw the boundary correctly.

There are two clean exceptions to the tenant-pays rule. The first is when the landlord operates the building as a serviced or managed model (managed offices, food-court precincts inside a shopping centre, co-working operators) and the landlord-as-operator effectively occupies and controls the tenancies. In that case the operator covers all the diagrams. The second is when the building is brand new and the landlord delivers diagrams as part of the base-build handover, before any tenant has fit-out drawings. Those base-build diagrams cover the empty shell of the tenancy and then get replaced by the tenant's own diagrams after fit-out completes.

Sub-tenancy: an edge case worth getting right

A serviced-office operator leases an entire floor from the landlord and then subleases individual suites to small businesses. A head retailer leases a 1,200 m2 shop and subleases a 60 m2 kiosk near their entrance to a third-party operator. A head fit-out tenant leases a warehouse and subleases part of the back-of-house to a delivery contractor. In each scenario, there is a head lease (between landlord and the head tenant) and a sub-lease (between the head tenant and the sub-tenant). AS 3745 obligations layer accordingly.

The default rule: the head tenant remains responsible to the landlord for everything inside the head-leased area, including the sub-tenancy portion. This is because the head tenant is the party in privity of contract with the landlord. If a fire authority issues a deficiency notice for an out-of-spec diagram inside a sub-tenancy, the notice typically lands on the head tenant first, who must then chase the sub-tenant.

The practical fix: the sub-lease should explicitly transfer evacuation diagram responsibility for the sub-tenancy interior from the head tenant to the sub-tenant, in writing. Without that transfer clause, the head tenant remains liable even when the sub-tenant has done the fit-out work that triggered a re-issue. The transfer does not absolve the head tenant from the landlord's perspective. The landlord still looks to the head tenant first. But it gives the head tenant a contractual mechanism to recover diagram costs from the sub-tenant.

What the lease should say (and often does not)

A well-drafted commercial lease names evacuation diagrams explicitly, allocates the cost between landlord and tenant, and specifies what triggers a re-issue. A typical lease either says nothing about diagrams (leaving the parties to argue when an audit hits) or uses generic "compliance with all applicable laws and standards" language that does not specify who pays the supplier invoice.

• Allocation: state explicitly that the landlord supplies and maintains diagrams in common areas, the tenant supplies and maintains diagrams inside the tenancy, and the boundary is the demise plan.
• Trigger events for tenant re-issue: list the events that require the tenant to commission new diagrams (any internal wall move, any change to exit routes, any change to fire equipment locations, any tenancy boundary change, the validity date on the diagram lapsing, which is 5 years out at most).
• Trigger events for landlord re-issue: list the events that require the landlord to commission new diagrams (common-area renovations, base-build fire equipment changes, the addition or removal of a tenancy, the validity date on the diagram lapsing, which is 5 years out at most).
• Make-good treatment: at lease end, specify whether the outgoing tenant must hand back diagrams in current condition (typical) or whether the landlord refreshes diagrams between tenancies (rarer, usually only for premium A-grade buildings).
• Cost-sharing for shared elements: if a single diagram serves both common area and the tenant's exit path through common area, specify which party commissions it and whether the cost is shared.

Cost-sharing models that actually work

In practice, three cost-sharing models cover almost all multi-tenant commercial leases in Australia. The right model for a given building depends on the lease type, the tenant mix, and the building owner's preferred recovery method.

• Model A: separate commissioning. Landlord commissions and pays for the common-area diagrams. Each tenant commissions and pays for their own tenancy diagrams. Cleanest from a contractual standpoint, most common in office buildings with a clear tenant mix.
• Model B: landlord-coordinated, tenant-funded. Landlord engages a single diagram supplier for the whole building (common areas plus every tenancy), then on-charges the tenancy-portion cost to each tenant either as a separate recoverable or as part of the next outgoings statement. Efficient for buildings with 5 or more tenants because the supplier can produce all diagrams from a single building floor plan with no duplicated work.
• Model C: landlord-included. Landlord absorbs all diagram costs (common areas plus every tenancy) as part of base rent or as a recoverable through outgoings. Most common in premium A-grade office towers and shopping centres where the landlord prefers single-source compliance over per-tenant billing. The economics work only when tenancy churn is low and lease terms are long.

Disputes we have seen on the ground

Four recurring patterns surface in commercial multi-tenant disputes, each with a clean resolution if the lease was drafted carefully and a messier one if it was not.

• Dispute 1: a fit-out tenant changes the internal layout, the diagrams in the tenancy are now wrong, and a fire authority inspection lands on the building. The deficiency notice goes to the landlord (because the inspector found the building non-compliant), but the underlying fault is the tenant's. Resolution: landlord pays the supplier, then recovers from the tenant under the lease's tenant-compliance clause. Cleanest when the lease names diagrams explicitly as a tenant compliance obligation.
• Dispute 2: a tenant moves out, the next tenant moves in, and no one commissions a fresh diagram for the new tenancy fit-out. Six months later an audit lands. Resolution: the incoming tenant pays for the new diagrams since they hold the lease at the time of the audit. Make-good clauses sometimes shift this to the outgoing tenant if the diagrams were out of date when they vacated.
• Dispute 3: a tenant subleases without a diagram-allocation clause in the sub-lease. The sub-tenant changes their fit-out, the head-tenancy diagrams are now wrong, the head tenant is on the hook. Resolution: head tenant pays the supplier, then chases the sub-tenant under the sub-lease's general compliance clause (weaker than an explicit diagram clause would be). Often partial recovery only.
• Dispute 4: a body corporate building, the common-area diagrams are missing on upper floors, no one on the committee remembers when they were last commissioned. Resolution: body corporate pays, levy through the next quarterly statement. The body corporate cannot recover from individual lot owners unless the lots had renovations that altered common-area exit routes.

When the inspector arrives: who gets the deficiency notice

In multi-tenant commercial buildings, fire authority inspectors and council compliance officers typically issue deficiency notices to the building owner or managing agent first, regardless of which layer of diagrams is actually deficient. The reason is procedural: the inspector's primary contact at the building is the building manager, and the deficiency notice goes through that contact.

The building owner or manager then allocates the deficiency to the responsible party. Common-area deficiencies stay with the building owner. Tenancy-interior deficiencies get forwarded to the tenant with a remediation deadline. Sub-tenancy deficiencies get forwarded to the head tenant who forwards to the sub-tenant.

A practical implication: tenants who have ignored diagram obligations for years tend to discover the gap when the building manager forwards a remediation notice with a 14-day deadline. Last-minute commissioning is significantly more expensive than planned commissioning because suppliers prioritise scheduled work. The audit-failures post covers the 12 most common deficiency triggers and the inspector reasoning.

Practical checklists per party

Each party in a multi-tenant commercial building has a short, specific checklist for staying on top of diagram obligations. Walk these once a year and at every lease event.

• Landlord or building owner: maintain a current schedule of common-area diagrams with mount locations, last-issued dates, and the supplier file source. Re-issue on the 5-year cycle, on any common-area renovation, or on the addition or removal of a tenancy that changes exit routes.
• Tenant: maintain a copy of the tenancy diagram master file (so a future supplier can re-issue from it). Re-issue on any internal wall move, any fire equipment relocation, any change to exit doors, or the 5-year cycle. Treat diagram re-issue as part of fit-out close-out, not as an afterthought.
• Head tenant subleasing: include an explicit evacuation-diagram clause in the sub-lease allocating responsibility for the sub-tenancy interior. Hand the master file source to the sub-tenant on sub-lease commencement so they can commission updates from it.
• Body corporate or owners corporation in commercial strata: pass an annual diagram-review motion at the AGM, treat re-issue costs as a budgeted line item rather than a special levy, and document the building's common-property boundary clearly so the lot owners know where their responsibility starts.
• Fit-out contractor: include diagram commissioning in every fit-out scope of works (not as a separate line item the client forgets, but as a deliverable). The diagram should be drawn from the as-built plan, not the design plan, so it reflects what was actually installed.

Quick decision tree

If a diagram needs to exist somewhere in a multi-tenant commercial building, the responsibility allocation usually resolves to one of the cases below.

• Common-area diagrams (lobby, lift lobbies, fire stairs, car park, plant rooms): landlord or building owner. In commercial strata, body corporate.
• Diagrams inside a leased tenancy: the leaseholder.
• Diagrams inside a sub-leased tenancy: the head tenant, unless the sub-lease explicitly transfers to the sub-tenant.
• Diagrams for a tenancy that has changed hands recently: incoming tenant (subject to make-good clauses with the outgoing tenant).
• Diagrams in a brand-new building at handover: landlord (base-build), replaced by tenant diagrams after fit-out completes.
• Diagrams in a tenancy that has just been fit-out: tenant, commissioned from the as-built plan, mounted before occupation.

Get diagrams sized for multi-tenant scope

EvacPath produces AS 3745:2010-aligned evacuation diagrams for multi-tenant commercial buildings across Australia, working from architectural drawings, lease demise plans, or as-built fit-out plans. We can handle either layer alone (common-area diagrams for a landlord, tenancy diagrams for a tenant) or the full building stack (common areas plus all tenancies) where a landlord-coordinated model applies. Pricing starts at A$70 per diagram and is published on the pricing page.

For multi-site portfolios across several buildings, the multi-site procurement guide covers the planning side, and the supplier-switching guide covers the master-file handover.

For the related ownership scenarios this post does not cover in depth, see the strata and body corporate guide (residential and mixed-use strata), the single-tenant landlord-tenant post, and the tenant fit-out requirements post.