Fire-Rated Corridor Encroachment on a Class 2 Residential Refurbishment
You are documenting a refurbishment of an existing four-storey Class 2 residential building. The public corridor serving each level is 1.35 m clear between finished wall faces. The client wants to add a 250 mm deep continuous services riser duct along one side of every corridor, fixed to the wall, to conceal new hydraulic and electrical services. The building has a single fire-isolated stair at the eastern end and a second stair at the western end, both discharging to the street. The corridor walls are existing 110 mm masonry with a 40 mm render finish; the new duct would be non-combustible framed and lined. The building surveyor has flagged the proposal and asked for your documentation to demonstrate compliance before the construction certificate is lodged. The project architect suggests reducing the corridor to 1.10 m and 'dealing with it as a performance solution later'.
1. Identify the code compliance issues raised by the proposed duct and explain how you would document the corridor width to support a construction certificate application.
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The core issue is that the duct reduces the clear corridor width from 1.35 m to approximately 1.10 m. In most Australian jurisdictions the deemed-to-satisfy provisions for a Class 2 building require a clear width of not less than 1.0 m in a public corridor, but the corridor is also part of the required egress path. Reducing a 1.35 m corridor to 1.10 m may still satisfy the minimum width, but the change affects the effective width available at doorways, at any projections, and at the point where occupants from both sides of the corridor converge on the stair. The duct also introduces a new surface into the corridor and may affect the required fire-resisting construction of the corridor wall if it penetrates or conceals it.
To document compliance you should: (1) prepare a dimensioned plan and section showing the clear width at every point along the corridor, including at door openings and at the stair landing, measured to the finished face of the duct; (2) confirm the corridor remains a compliant egress route by checking travel distance, egress width and the number and location of exits against the applicable deemed-to-satisfy clauses; (3) confirm the duct lining and framing achieve the required fire-resisting level for the corridor wall, or provide a tested system that maintains the wall's fire resistance; (4) show that the duct does not obstruct any fire hose reel, extinguisher, exit sign or emergency lighting; and (5) if any deemed-to-satisfy clause is not met, prepare a performance solution with a fire engineering brief, not a note saying it will be dealt with later.
Advising the architect to defer the issue is poor practice: the construction certificate cannot be issued on an unresolved non-compliance, and the drawing set must show the resolved geometry now.
2. The architect proposes a performance solution to retain the 1.10 m corridor. Outline the evidence you would expect to see and the drawing changes required before you would issue the documentation.
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A performance solution must be assessed against the relevant performance requirements, not simply asserted. I would expect a fire engineering report prepared by a suitably qualified fire safety engineer that addresses the specific performance requirements for egress and fire spread, and that uses a recognised assessment method such as a verified fire evacuation model, a comparison with the deemed-to-satisfy provisions, or another accepted method. The report should state the assumptions about occupant load, evacuation behaviour, and the presence and reliability of any compensatory measures such as additional exit signage, emergency lighting, or smoke detection.
The drawing changes I would require before issuing documentation are: a revised corridor plan showing the duct in its final position with the clear width dimensioned at every critical point; a reflected ceiling and services plan showing that the duct does not clash with sprinkler heads, detectors, exit signs or emergency lighting; a wall type schedule confirming the fire-resisting construction of the corridor wall and the duct lining; and a note referencing the fire engineering report and the specific performance requirements it addresses. I would also require the report to be listed as a referenced document on the drawings so that the builder and certifier know it forms part of the approved documentation.
Until those documents exist, I would not issue a construction certificate set, and I would record the outstanding items in a drawing issue register with a clear status.
3. What professional and ethical issues arise from the architect's instruction to 'deal with it as a performance solution later', and how should you respond as the draftsperson?
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The instruction asks you to document a non-compliance without resolving it, which is a professional and ethical problem. As a draftsperson you are not the certifier and cannot approve the design, but you are responsible for the accuracy and completeness of the documents you produce. Issuing drawings that show a corridor width that does not meet the deemed-to-satisfy provisions, without a performance solution in place, could mislead the builder, the certifier and ultimately the occupants. It also exposes you and your practice to liability if the building is constructed and later found to be non-compliant.
The correct response is to raise the issue in writing to the architect, set out the specific clauses and dimensions at risk, and request a written direction if the architect wishes to proceed on a performance basis. You should record that direction in the project file, issue the drawings with a clear 'for information only - not for construction' status, and list the outstanding fire engineering report as a hold point. You should not silently redraw the corridor to 1.10 m and present it as compliant. If the architect insists on proceeding without the performance solution, escalate to your principal or the project manager, and consider whether the matter should be referred to the certifier. The ethical principle is that you do not certify or imply compliance you cannot substantiate, and you keep a clear written record of advice given and directions received.