Hempcrete inside a Perth suburban renovation

A 1960s brick-and-tile house in Perth’s inner north had the familiar limitations of its era: small, separated rooms, poor winter warmth, and little protection from summer heat. Its owners wanted to open the plan without losing the calm, tactile character of the original building. They also wanted materials with a lower environmental impact than conventional plasterboard and steel stud partitions.

The resulting renovation used hempcrete for selected internal walls rather than treating it as a universal replacement for every lining system. The material became part of a carefully considered wall assembly, helping divide living spaces, soften acoustics, regulate humidity, and give the interior a distinctive mineral texture.

This case study examines the reasoning behind that decision, the practical details of the installation, and the compromises required when a natural building material is introduced into an existing Perth home.

The house and the brief

The single-storey home had a solid masonry perimeter, a concrete slab, and a series of lightweight internal partitions added during earlier alterations. Some walls were out of square, while the ceiling heights varied subtly between the original rooms and a later rear extension. Rather than demolish the entire interior, the design team mapped the existing structure and retained as much of the usable fabric as possible.

The brief centred on a new kitchen, dining, and living zone connected to the garden. Two new internal walls were required: one to separate a quiet study from the living room, and another to form the edge of a guest bedroom and bathroom. These partitions did not carry roof loads, so hempcrete could be considered as an infill material within a timber frame.

The owners were drawn to the material’s appearance, but performance mattered just as much. Perth’s hot summers, cool nights, and occasional winter dampness made thermal moderation and moisture behaviour important. The walls also needed to accommodate electrical conduits, provide a degree of acoustic privacy, and meet the relevant building requirements.

Why use hempcrete indoors

Hempcrete is generally made from the woody inner core of the hemp plant, known as hemp hurd, combined with a lime-based binder and water. It is lightweight, vapour permeable, and usually installed around a structural frame. Unlike concrete, it is not normally used as a load-bearing material in a domestic internal partition.

Inside this Perth house, the material was selected for its ability to buffer small changes in temperature and humidity. It does not function like mechanical air-conditioning, and its thermal mass is modest compared with dense masonry. Its value lies in the combination of insulation, breathability, and surface comfort. Rooms lined with lime plaster over hempcrete can feel less harsh during temperature shifts, particularly when ventilation and shading are already working well.

The material also offered an alternative to highly reflective, hollow partitions. The hemp-lime mix absorbs and diffuses sound more effectively than a thin plasterboard skin, although it cannot provide the same acoustic performance as a purpose-built multi-layer wall with insulation, resilient channels, and separated frames. In the study, the owners noticed a reduction in conversational noise from the living room, while the bathroom wall required additional acoustic treatment.

Material character was another factor. The softly mottled surface had enough variation to register as a finish rather than disappear beneath paint. This approach sits comfortably within a broader design culture that values material honesty, whether the project involves a new natural wall or the careful reuse of an existing structure, such as this heritage co-working space.

Building the wall assembly

The first step was resolving the junction between hempcrete and the existing brick shell. The new partitions were kept independent of the external walls, with a small separation that allowed the old masonry to continue drying naturally. A treated or appropriately durable timber frame was fixed to the slab and ceiling structure, with openings planned for doors, cabinetry, and service routes.

The hempcrete mixture was placed in lifts between temporary shutters. Each layer was lightly tamped rather than heavily compacted, preserving the pockets of air that contribute to its insulating performance. The wall was allowed to dry progressively before the shutters were removed. In Perth’s dry climate, this process was faster than it might be in a cool, damp region, but the team still avoided sealing the surface prematurely.

Service coordination was essential. Electrical conduits were positioned before the mix was installed, and plumbing was kept out of the hempcrete wherever possible. Wet services were concentrated in a conventional framed section beside the bathroom, reducing the risk of future leaks inside the natural wall. Heavy joinery was also planned in advance, with plywood reinforcement incorporated into the frame where shelves and wall-mounted fittings would be fixed.

Consideration Hempcrete internal wall Conventional plasterboard partition
Primary composition Hemp hurd, lime binder, timber frame Plasterboard, studs, insulation where specified
Structural role Usually non-load-bearing infill Non-load-bearing lining and partition
Moisture behaviour Vapour permeable and moisture buffering More dependent on coatings and cavity design
Surface quality Soft, textured, hand-finished appearance Smooth, paint-ready surface
Acoustic performance Good mass and absorption for its weight Highly variable; improves with layered systems
Installation Slower, with drying time and skilled labour Faster and familiar to most contractors
Service access Needs early coordination Easier to alter after installation
Environmental profile Low-impact agricultural by-product and lime system Established supply chain but more processed components

Once dry, the hemp-lime walls received a breathable lime-based plaster. The finish was intentionally left slightly irregular, with trowel marks and tonal shifts visible in changing daylight. In the study, the surface was finished in a warm chalk colour. The living area used a pale clay tone that connected with the existing jarrah flooring and the muted greens of the garden.

How the rooms perform

The most immediate change was sensory rather than technical. The new walls reduced the sharp echo created by the original hard surfaces, and the living room developed a quieter acoustic profile without becoming heavily carpeted or upholstered. Voices remained clear, but sound did not travel as aggressively into the study.

Temperature was more difficult to measure in isolation because the renovation also introduced external shading, ceiling insulation, cross-ventilation, and high-performance glazing. Still, the hempcrete partitions helped create a more stable internal atmosphere between the conditioned living room and adjacent rooms. In the evening, the walls did not feel cold to the touch in the way a thin painted partition often can.

The finish also changed how the owners used the rooms. The study became a comfortable place for focused work rather than an improvised desk in the kitchen. In the bedroom, the softly textured wall provided a backdrop for timber furniture and linen textiles. The design language remained restrained, allowing the natural material to contribute depth without becoming a decorative feature.

Maintenance required a different mindset. Small marks could be repaired with compatible lime plaster, but the surface was not intended to be scrubbed as aggressively as a standard acrylic-painted wall. High-contact areas were protected with timber trims, and the owners selected a more durable finish near doorways. This is similar to the way practical decisions shape material choices elsewhere in a home, from flooring transitions to pet-friendly stair carpeting.

Costs, limits, and lessons

The hempcrete walls cost more than basic plasterboard partitions at the installation stage. Labour was a significant part of the difference because the process required experienced installers, careful shuttering, and a longer programme. The lime plaster finish added further time, particularly where the owners wanted a hand-worked surface rather than a uniform skim coat.

That initial premium was balanced by several project benefits. The walls combined infill and finish in one material system, reduced the need for additional synthetic linings, and provided a strong visual identity. They also avoided the waste associated with repeatedly cutting and replacing plasterboard around irregular existing conditions. Offcuts and unused mix were kept low through detailed setting-out.

There were clear limits. Hempcrete is not suitable for every wet area, and it must be protected from prolonged liquid water. It is not a substitute for structural engineering, waterproofing, or proper termite management. Fixing heavy objects requires embedded reinforcement or carefully located structural supports. A contractor familiar with lime-based materials is particularly important because over-compaction, incorrect drying conditions, or incompatible coatings can compromise the wall.

The project also demonstrated that natural materials work best when included early in the design process. The owners initially considered hempcrete as a finish decision, but it affected door reveals, skirting details, electrical planning, wall thickness, and programme length. Treating it as an integrated construction system produced a better result than adding it late as a stylistic layer.

Practical decisions for a hempcrete retrofit

For architects, renovators, and homeowners considering hemp-lime partitions in Western Australia, the most useful lessons are specific and practical:

The Perth climate can support relatively efficient drying, but that should not lead to rushed work. Internal humidity, ventilation, and the moisture content of the timber frame still need to be monitored. The wall should be protected from rain during construction, and the building envelope must be resolved before internal finishes are applied.

It is also worth considering where the material has the greatest architectural value. In this renovation, hempcrete was used selectively in rooms where acoustic softness and tactile character mattered. Conventional systems remained appropriate for service-heavy zones and areas requiring easy future access. The result was a hybrid interior rather than a forced all-natural specification.

For the owners, that balance made the renovation feel grounded in its place. The walls respond to Perth’s light, the garden’s earthy palette, and the informality of suburban living, while the underlying construction remains legible and repairable. Hempcrete did not solve every performance problem, but it gave the project a coherent material and environmental strategy.

Contemporary’s coverage of residential experiments, adaptive reuse, and material innovation offers a useful lens for following this kind of work across Western Australia. Read more project stories, follow the people shaping the local design scene, and connect with the community through Contemporary Wine In Design.