Loft renovation - additional storey

Project background: a mezzanine above the kitchen

The project involved a two-bedroom apartment in Melbourne's CBD with five-and-a-half-metre ceilings, located within a mixed-use building. The owner wanted to add a mezzanine level above the kitchen, converting unused overhead space into accessible storage. Access was to be via a ladder, and the intent was to keep the ceiling height reduction to a minimum.

Kyle Conway of Aus Engineered was engaged by the builder at the concept stage, which meant the structural team was involved alongside the architect and town planner from the outset. Kyle noted that involving all disciplines at concept stage generally leads to more successful outcomes, as it shapes a buildable concept before any detailed design is committed to.

Gathering information on the existing structure

Before any design work could start, the team needed to understand what the existing structure could carry. On renovation projects, reliable as-built information is often the hardest part of the job. Buildings change hands, body corporates turn over, and record-keeping on older structures tends to be poor.

Kyle described the process of engaging the body corporate early to understand what documentation they held and what their requirements were for private building works. In this case, existing structural and architectural drawings were obtained, which gave the team the slab span, column orientations, and original design loads. Even with drawings in hand, Kyle stressed that on-site verification is essential: dimensions and member condition should be confirmed on site, not assumed from documents.

Where drawings are not available, the options include on-site measurement, accessing structural members through manholes, and non-destructive testing such as reinforcement scanning. These methods add cost and carry no guarantee that the renovation will ultimately be feasible. Kyle recommended keeping the client fully informed before committing to that investigation path, so there are no surprises if the outcome is that the existing structure cannot support the proposed addition.

Designing the primary steel beam and secondary timber beam

The design sequence started with the primary steel beam, because the secondary beam connection geometry depended on the primary beam's depth. The client wanted the secondary beams to sit within the web of the primary universal beam, bearing on the bottom flange, to avoid any meaningful drop in ceiling height. That meant the primary beam had to be sized first so its depth was known, and the secondary members then had to fit within approximately 200 mm.

Kyle used the Calcs.com steel beam calculator for the primary beam, entering the span, bearing lengths, and tributary width so that distributed loads were calculated automatically. The traffic-light utilization display let the team cycle through section options quickly, with instant feedback on bending, shear, and deflection as parameters changed.

For the secondary beam, the Calcs.com member selector was used with a maximum depth filter of 200 mm and a filter for the builder's preferred manufacturer, Hyne. The tool returned a list of GluLam sections meeting both the dimensional and structural requirements, with utilization figures shown immediately. Kyle contrasted this with spreadsheet-based design, where each section would need to be entered individually and results recalculated from scratch for every trial.

Column design, connections, and project deliverables

With the beam sizes fixed, the column design had to accommodate the beam-to-column connection geometry. The connection required a column flange of sufficient width to bolt up to the primary beam end plate, which drove the section choice toward a square hollow section. Calcs.com links loads between calculations, so the beam reactions were passed directly to the column input rather than being re-entered by hand.

Three connections were designed: the timber secondary beam bearing on the steel primary beam's bottom flange, the steel primary beam connecting to the column via a bolted end plate, and the column base connecting into the existing concrete slab using a proprietary anchor system. Bolt capacity, weld size, and plate thickness were all verified in Calcs.com against AS 4100-2020.

The final deliverables to the builder and client were structural drawings, a Victorian Form 126 building permit structural compliance certificate, and detailed structural calculations exported from Calcs.com. The export walks through every design assumption and the step-by-step method for each member, and includes a member schedule summary that the builder used for material orders. The actual design work, once all information was in hand, took about a week. The total project duration from first engagement to completion was closer to two to three months, with the main delay being procurement of reliable as-built drawings from the body corporate.