Combining Two Apartments: Two Floor Plans, One Home Without a Seam

Combining apartments: when it is worthwhile

Combining apartments is a common solution in Vienna when families grow, when couples need more space, or when someone wants living and working under one roof. It pays above all when the location is right and a move would cost more than the conversion, and not only in financial terms.

Waiting has a cost of its own: queues for the bathroom, work at the dining table, children with nowhere to retreat. And a combination begun without a plan costs more later: a wall opened in the wrong place, a bathroom that cannot move, a seam in the floor that never disappears.

The simplest is the horizontal combination of two apartments on the same floor that share a wall. More complex is the vertical variant, in which two apartments one above the other are joined by a new staircase. That requires an opening in the floor slab, which has to be planned for structure and fire safety.

For our family it is the horizontal variant. The shared wall is also the border between two ways of life: tight family life on one side, the quiet apartment of an elderly lady with a living room facing the park on the other.

First, the question: what should the new apartment be able to do?

The most common mistake is to start with the wall. You open it up, and suddenly you have a large apartment with two of everything and no clear order. So the question comes first, as in every one of our projects: how do you want to live?

For the family, the answer runs roughly like this. The children should get rooms of their own, close together. The parents would like a quiet area with a bedroom and a bathroom of their own. One of the two works from home three days a week and needs a room that can be closed off. And everyone wants a large kitchen with a dining table where the whole family and guests have space.

Picture the first Saturday in the finished apartment. The children's doors stand open at the far end of the corridor. In the kitchen the long table catches the morning sun from the park, the whole family around it at once. Down the corridor a door closes softly, and the study begins its quiet working day.

From these wishes a life concept emerges, as described in the article A life concept instead of furnishing. Only after that is it decided which part of the combined floor area takes on which role.

A sober look at both apartments helps. Which rooms have the better light, which are quieter, where do windows face the courtyard and where the street? Here the small neighbouring apartment has the loveliest room on the entire floor, with two windows onto the park and morning sun. It would be a pity to turn it into a storeroom just because it lies at the end of the corridor. Observations like this decide where cooking, sleeping and working will happen. But how do two floor plans become one?

The floor plan: two logics become one

Two apartments have two logics: each its own hallway, kitchen, bathroom and routes. When combining, you decide which logic wins and what becomes of the duplicate rooms.

For our family the decision falls like this: the entrance of the larger apartment stays the main entrance, with a newly planned hallway, as described in the article on arriving well in the entrance area. The second front door is kept, but becomes the direct access to the study. This way clients can be received without walking through the apartment.

The old kitchen of the small apartment becomes the parents' bathroom, because water and drainage are already there. The family's existing kitchen moves into the neighbour's former living room, with its view of the park, and becomes the large kitchen-diner there. The former kitchen space becomes the pantry and utility room. How to plan such a thing is shown in the article on the pantry.

The parents' area, with bedroom, small dressing room and bathroom, lies at the quiet end of the new apartment, the children's rooms close to the family bathroom. How such private sequences of rooms work is described in the article on the private area of sleeping, dressing and bathing. Yet all of this depends on one wall.

Combining does not make one large apartment from two small ones. It makes a new apartment that happens to live in two old ones.

The wall in between: structure, fire safety and sound

The wall between two apartments in a Viennese Altbau is often a load-bearing masonry wall, frequently also a fire-protection and sound-insulation boundary. An opening is therefore always a matter for the structural engineer. He clarifies how wide the opening can be, which beam is needed and how the loads are transferred.

A generous opening with a lintel is often a better solution than complete demolition. It joins the rooms without blurring the character of the apartment, and it is simpler structurally. The opening can be closed with a floor-to-ceiling sliding door, for instance with a glass sliding-door system. More about openings and costs can be found in the article on the load-bearing wall in Vienna. How transitions are designed is described in the article Designing transitions between rooms. At Richard Atelier the opening, door and built-ins come from one hand, our own workshop Tischlerkultur, family-run since 1935. And who decides whether you may open the wall at all?

Legal matters: owners, share allocation and authority

Anyone who combines two owner-occupied apartments changes not only the floor plan but also legal units. The details depend on the building and should be discussed early with the property management, a notary or a lawyer. Typical questions are:

• Consent of the co-owners: If common parts of the building are affected, for example a load-bearing wall, the consent of the other owners is generally required in condominium ownership.
• Nutzwert and land register: Two condominium units become one. This usually requires a new Nutzwert report (the allocation of value shares in the building) and an amendment to the land register.
• Building authority: Interventions in load-bearing elements require a submission to the building police in Vienna. Whether a permit for the combination itself is also needed, we clarify with the master builder and the structural engineer.
• Financing: If one of the apartments is mortgaged, the bank should be involved early.
• Meters and connections: Electricity, gas and water meters are combined or re-registered in coordination with the network operators.

These steps take time, and they should run in parallel with the planning, not after it. An overview is given in the article on permits for conversions in the Viennese Altbau. Once the paperwork is moving, what waits behind the walls?

Building services: making two systems one

Two apartments bring two distribution boards, two heating systems and two plumbing stacks, and they have to be brought together. This is often the moment to decide on complete renewal, because old pipes and cables rarely meet current standards anyway.

For the electrics, a shared distribution board is created, with enough circuits for kitchen, study and lighting. The planning follows the future furnishings, as described in the article Electrical planning: why the socket is planned in front of the sofa. For heating, one gas boiler is usually decommissioned, and the second has to be sized to supply the whole floor area. Whether this is possible, or another system would make more sense, is clarified by the plumber.

The position of the risers determines where bathrooms and kitchen can sensibly go. That is why our family's parents' bathroom was placed in the old kitchen and not in just any room. If you are planning a new kitchen, you will find more on our page about fitted kitchens; for bathrooms there is the page on bathroom renovation. And what does the route from first call to handover look like?

The course of an apartment combination

A combination proceeds in these steps:

1. Free initial conversation (30 minutes, by phone or video, with an honest first assessment) about your wishes and the starting position of both apartments.
2. Survey with measuring and inspection of the dividing wall, pipes and cables, and heating.
3. Clarification of the legal questions with the property management, notary and authority.
4. Concept: layout, zones, role of the duplicate rooms, material palette.
5. Detailed design with structure, building services, built-ins and cost schedule.
6. Conversion: opening, strip-out, installations, bathrooms, kitchen, floors.
7. Fitting of the built-ins by our joinery workshop Tischlerkultur, furnishing, handover.

Because legal matters, structure and lead times come together, a combination usually takes longer than an ordinary renovation. A realistic framework is shown in the article on the schedule for an apartment renovation. On costs there is no fixed price; the design fee depends on the scope of the services commissioned. You will find an honest breakdown in the article What does a whole-home concept cost?. Once it is done, how do you make it look as though it was always one?

Material and floor: so the seam does not show

The greatest compliment for a combined apartment is when guests do not notice it was once two. A continuous material concept makes that possible. Parquet on one side and tiles on the other, and you see the old border at once.

Imagine your first guests. They walk from the hall through the wide opening, past the long table, into the study, and ask where the old border ran. The floor is continuous underfoot, every door is the same height, the timber carries from room to room.

The floor has the strongest effect. A continuous finish without thresholds joins the areas and makes the apartment feel larger, as described in the article on continuous floor coverings. If the two apartments are at different levels, a levelling layer is sometimes needed, which is allowed for in the planning.

Doors, built-ins and colours come on top. If all doors have the same height and finish and the built-ins are made from the same timber, you read the apartment as a whole. How to lay down this common thread is explained in the article on the material concept. Examples of completed projects can be seen in our references. Questions remain? The ones we hear most often are answered next.