Kangaroo housing is appealing, but many projects stall. Starting from an extension designed by STARC in Rhisnes, here are the design choices that make a secondary dwelling acceptable, approvable and pleasant to live in.
Housing an elderly parent or an adult child on your own plot is something many families consider at some point. On paper, kangaroo housing ticks every box. In practice, many projects stall before the first spade hits the ground, and it is very often the design that makes the difference.
Why so many projects never get off the drawing board
The observation is not new, but it has just been forcefully restated. In a feature published in late May 2026, La Libre Immo explains that co-housing, shared solidarity housing and kangaroo housing all have their appeal, yet the obstacles remain numerous.
The obstacles cited are very concrete:
- Parking. According to a lawyer interviewed, parking standards are often a concrete obstacle.
- Recognition of two households. Councils often remain very reluctant, notably for fear of fraud linked to social benefits.
- The neighbourhood's view. This way of living can meet with reluctance in certain neighbourhoods or from local authorities.
The issue is also on the table of policymakers. On 1 October 2026, the Union des Villes et Communes de Wallonie (the Walloon association of towns and municipalities) wrote to the ministers for Town and Country Planning and for Housing. Among other things, it is asking for a simplified procedure for certain forms of housing that meet social needs, such as kangaroo dwellings, drawing inspiration from the Flemish Zorgwoningen (care dwellings). For now, this remains a request rather than a rule in force.
What the CoDT says and what it means for the design
In Wallonia, the starting point is Article D.IV.4 of the Code du Développement territorial (CoDT, the Walloon spatial planning code). The Walloon Parliament summed it up clearly: dividing a single-family house into an existing main dwelling plus a separate kangaroo dwelling requires planning permission. Conversely, creating a room for an elderly or young relative within a single-family house, sharing one or more rooms that contain the basic functions (bathroom, kitchen, toilet), does not require planning permission.
The very first design decision, therefore, is whether you are creating a genuine second dwelling or simply extending the family home. Both are legitimate choices. But they lead to a different procedure, a different design and a different budget.
Two pitfalls come up again and again:
- Relying on rules found online. A single doorbell, a unit limited to a fraction of the volume: these conditions belong to the Flemish zorgwonen regime. In Wallonia, they do not exempt you from needing planning permission.
- Assuming time will sort everything out. A specialist lawyer points out that the CoDT's limitation mechanisms have all been disabled where the offence consists of creating a dwelling. A dwelling created without permission remains a problem, including when you come to sell.
Rhisnes an extension designed as a fully fledged dwelling
In Rhisnes, in the municipality of La Bruyère, a family wanted to house a relative without turning the existing house into an uncomfortable compromise for everyone. We chose not to carve up the interior. Instead, we added an extension designed from the outset as a self-contained secondary dwelling.
This choice changes the nature of the application. You are no longer presenting a divided house, with the suspicions that can raise. You are presenting a legible project: one volume, one use, one household. The planning application becomes easier to defend because every question the council might ask is already answered in the drawings.
The three decisions that unlock a kangaroo project
What we applied in Rhisnes holds true for most projects of this kind.
A separate entrance. This is essential for each household to truly feel at home. It also makes the existence of two dwelling units visible, which makes it easier to register two separate households at the same address. Some councils have even organised themselves to support this. In Wavre, the town has introduced a model agreement under which the parties obtained the town's agreement to assign a sub house number, thereby recognising the two separate dwelling units.
A dedicated volume. A well-proportioned extension reads as an annexe on the scale of the house, not as a second building. For neighbours, this is often decisive. We work on:
- massing, height and roof pitch, in keeping with the existing building;
- materials, in dialogue with the brick, stone or render of the house;
- sightlines, to preserve everyone's privacy, for both households and for neighbours;
- single storey living, where the occupant is elderly, so the dwelling remains suitable in ten or fifteen years.
Independent utilities. Separate meters for water and electricity, a dedicated heat source or at the very least individual metering, independent drainage. This is less eye-catching than a fine picture window, but it is what keeps everyday life calm: each household pays for what it uses, and the independence of the two households is easy to demonstrate. These choices are made at sketch stage. Adding them later costs considerably more.
That leaves parking, which La Libre identifies as an obstacle. We build it into the site layout at a very early stage, rather than discovering the issue once the planning application is being examined.
Questions to ask yourself before you start drawing
Before meeting us, take the time to answer these questions. They shape the whole project.
- Who will live in this dwelling, and for how long? An ageing parent and a twenty-five-year-old do not have the same needs.
- Should the dwelling be able to change use later? Office, guest room, rental: reversibility needs to be planned for in the design.
- How much independence do you want? A complete second dwelling or shared rooms, the procedure is not the same.
- Does your plot allow for it? Siting, setbacks, access, parking, local planning rules: we check this from the very first visit.
- What is the overall budget? It includes the building works, but also connections, fees and surveys.
- What legal framework applies between you? Ownership, gift, occupancy agreement: a visit to the notary is often worthwhile.
On the technical side, a heated extension must meet PEB (EPB, energy performance of buildings) requirements. For a project involving an existing building, we rely on Optibim, our partner design office based at the same address, for the energy performance study and for a precise survey of the existing structure using 3D scanning. This allows us to design on reliable foundations from the sketch stage onward.
What the architect really brings
A kangaroo dwelling is not simply a studio tacked onto a house. It is a project that must convince three audiences at once: your family, your council and your neighbours. The architect's role is to translate these expectations into a clear design, then into a coherent planning application, and finally into a well coordinated building site.
Are you considering housing a relative on your plot, by extending or converting your home? Let us talk about it early, before the first ideas set the project in stone. An initial meeting with the STARC team in Gembloux allows us to check feasibility, clarify the procedure and lay the right foundations.
Rudy Brogniet, for STARC