Concrete is a common material used for many types of construction due to its strength, durability, water resistance and thermal mass. It can be used to form the structure of a house – floors, walls and roof – and when exposed, it contributes its own raw and industrial aesthetic. Concrete can also be more than just structural, and can be shaped to form kitchen islands, steps, benches, built-in seating and much more. This is done through what’s called formwork – moulds into which concrete is poured or placed – and the result is referred to as ‘off-form concrete’.
A variety of visual and textured effects and limitless shapes can be achieved with off-form concrete. Here’s a beginner’s guide to formwork and some inspired off-form results.
What is formwork?
Formwork gives concrete its shape. Concrete is poured into a mould, and the mould is removed when the concrete has hardened. The formwork is constructed and reinforced so the concrete doesn’t leak through its joints, and so that the formwork doesn’t sag, bulge or move. Off-form concrete can be produced on-site (otherwise referred to as ‘in situ’ or ‘site-cast’), or off-site (also known as ‘precast’ concrete).
The owners of this house, designed by Ian Bennett Design Studio
, are in the formwork business and have a great love of concrete, which they wanted their home to showcase.
Formwork is traditionally made with timber or plywood. It is flexible and easy to produce, but time-consuming for larger structures. Steel can also be used and typically has a longer lifecycle than timber formwork, meaning it can be used a greater number of times. Formwork can be custom-made and built or bought from formwork suppliers.In-situ concrete can be made even stronger by inserting steel reinforcement bars inside the formwork before the concrete is poured.
The choice of material will affect the look and feel of the concrete, as the surfaces of the formwork that come in contact with the concrete affect its final appearance. The concrete chimney on this house by Nixon Tulloch Fortey Architecture
has strong linear texture and a timber grain due to the choice of timber used in the formwork.Find a Singapore architect on Houzz
This three-storey Glendower Street house in Perth has an exposed concrete ceiling to evoke an industrial style, as well as to take advantages of the thermal properties of concrete.
“The formworker must cut and lay out the formwork just like they would if tiling a floor, having equal board widths against perimeter walls,” says Dean De Petra of Luxe Builders + Designers
. “At Glendower Street, we aligned the joints with the positions of the lights.”
Joints between adjoining panels or sheets of concrete can be difficult to disguise, and are sometimes accentuated as a feature. The off-form concrete in this Sydney home by TKD Architects
has very distinct joints, with a recess (or rebate) that creates a shadow line on the walls.
Be inspired by concrete
At Local House by Make Architecture
, the built-in seating and counters in this open-plan dining area is off-form concrete poured on-site, creating the visual effect of it almost emerging up and out of the floor.
“Because these forms are integrated into the structure and fittings of the home, they had to be poured and cured before the steel and timber framing could commence,” says Melissa Bright at Make Architecture.
Outside, recycled fence palings were used for the formwork to give texture and grain to the concrete seating and platforms.
At this Dawes Road House in Melbourne by Moloney Architects
, the concrete and timber cladding reflect the tones of the surrounding bush landscape. The monolithic concrete wall was made in-situ, and again features a timber-grained finish on both the interior and exterior.
At Long Courtyard House in Sydney by Scale Architecture
, the floors, ceiling and kitchen island are off-form concrete placed on site. The effect is softened with a backdrop of recycled bricks, salvaged from the demolished part of the house and reused along the south-western wall.
Cast Designs custom-made this monumental concrete kitchen island, which features distinct shadow lines and an integrated round concrete sink.
renovated and extended this Californian bungalow in Melbourne, placing a focus on materiality to break down spatial boundaries. Inside, the kitchen, dining and living areas are unified by a single slab of polished concrete flooring, and a solid-concrete countertop that was formed and poured in-situ by Rutso Concrete.Advantages of Concrete as a Kitchen Countertop Material
Likewise, Apex Landscapes & Pools
formed this outdoor table, polishing the off-form concrete after the formwork or boxing was removed.
These sculptural stairs by Sam Crawford Architects
were poured in-situ, and the plywood from the formwork of the stairs (and other concrete elements) was reworked into textured door panels, which conceal the wine cellar under the stairs.
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