Aluminum Formwork for Mid-Rise Apartment Walls and Slabs

Project Background

A mid-rise residential development in Southeast Asia, built as a twelve-storey apartment block over a two-level podium car park. The frame is cast-in-place reinforced concrete: perimeter shear walls and columns, flat slabs at every typical floor, and two cast-in-place stair flights serving each level. The architect called for fair-faced concrete on the exposed slab soffits and on the corridor-facing wall surfaces, so the formwork had to leave a finish that could be accepted as final, with no plaster or skim coat applied afterwards. The plot sits between a live access road and an existing row of three-storey buildings, which left the contractor a narrow working corridor and no permanent crane position along the long side of the block.

Challenges

Laydown space drove the formwork decision. A steel panel set for one typical floor would have required crane lifts for nearly every panel movement, and the neighbouring buildings ruled out the crane radius the tender schedule had assumed. The site also sits in a monsoon belt, where rain arrives in short, heavy bursts through the afternoon, so any panel set that could not be stripped, cleaned and re-erected quickly would have exposed the floor cycle to weather delays the program had no float for. The labour force was a mixed crew rather than a specialist formwork team, which meant assembly had to be driven by a marked-up layout and numbered panels instead of individual trade judgement. The stair core added a further complication: flights, landing, walls and slab had to be formed inside one repeating sequence rather than handled as separate packages with their own cycles.

Solution and Product Configuration

A complete aluminum formwork system was specified for the typical floor, built from 6061-T6 extruded profiles with friction stir welded frames, a 4 mm panel skin and a 65 mm edge frame at 8 mm thickness, keeping a standard panel at roughly 24 kg so two workers can carry and set it by hand. Wall panels at 600 mm standard width and 2400-2600 mm height were laid out from a numbered installation drawing, tied through the wall thickness with tie rods and PVC sleeves, and located on kickers fixed to the slab before assembly started. Slab panels of 400-600 x 1200 mm were set on slab prop heads and carried by adjustable steel props with an 1800-3300 mm adjustment range, so one prop stock served the typical slab, the podium soffit and the stair landing. Stair flights used dedicated staircase panels formed in the same cycle as the surrounding slab. Square column buckles and square spacers held column and wall corners true where the perimeter stepped, while back edge connectors and strengthen back edges kept panel edges straight under pour pressure.

All panel-to-panel connections were pin and wedge, which meant no bolted joints to re-torque between pours and no loose fixings left in the slab. Stripping followed the method statement sequence: wall panels first, then beam panels, then slab panels, then kickers, tie rods and PVC sleeves, with T type and Y type panel pullers used to release panels without levering against the fresh concrete. Conduits, embedded pipes and roof bars were checked and adjusted before the wall section was poured, and every panel carried an installation code so it returned to the same position on the floor above instead of being redistributed at random.

Typical floor formwork configuration:

Outcome

The typical floor settled into a repeatable routine once the crew had completed two full repetitions. From the third floor onward, stripping, cleaning and transfer to the next level were finished inside the same working day, and the wall-and-slab sequence ran ahead of the allowance the contractor had carried in the tender for conventional timber and steel formwork. Panels came off the concrete with their edges still true, so the corridor wall faces and the slab soffits were accepted as fair-faced surfaces; that removed the plaster and skim-coat trades from the finishing program and cut the volume of wet work on each floor.

The site team's other observation concerned reuse. Because the frames are friction stir welded and each panel was cleaned and returned to its installation code, pin and wedge holes stayed round and panel edges stayed straight through the height of the block. There was no rust treatment between pours, as steel panels would have needed, and no plywood swelling or delaminated edges to repair in the humidity. Waste on the floor was largely limited to packaging, since board offcuts and edge damage were no longer part of the cycle. The contractor's project engineer described the result as a fixing and stripping job the crew could run from a drawing rather than from long experience, which is what allowed a mixed labour force to hold the floor cycle.

Contractors and developers planning repetitive wall, slab or stair work on residential, hotel or institutional projects are welcome to send their typical floor drawings and sections for a formwork configuration review and a project-specific quotation.