Buying the apartment next door can seem an appealing way to gain space without leaving a building you like. The two homes already share a wall, and a new opening may appear to be the only missing ingredient. In practice, the wall sits within several overlapping arrangements: the structure, fire strategy, services, strata ownership and approved use of each apartment.
A related guide to consider while planning this work is Missing Building Approvals: How to Check Property Records.
A useful feasibility study tests those arrangements before the combined floor plan becomes fixed. It should establish whether a connection can be approved and built, what happens to the two existing entrances and service systems, and whether the proposed legal arrangement matches how the home will be occupied. These questions matter even when both apartments already have the same owner.
Define what combining the apartments means
Write a short description of the intended outcome. You might want a permanent single home with one main kitchen, or an approved internal connection that retains some independence between the two sides. That distinction influences the investigations your advisers need to undertake.
A physical opening and a formal consolidation of titles are different matters. Ask a property solicitor and, where needed, a registered surveyor to explain the available arrangements in the relevant jurisdiction. Do not assume that removing a wall automatically changes the registered lots, their entitlements or their financial obligations.
Similarly, retaining separate titles does not establish that any proposed internal connection is permissible. The building and planning assessment must consider the actual layout and use. The ownership advice and design advice need to refer to the same proposal.
Consider the future without designing around a promise
If future separation is important, tell the design team at the beginning. Ask what reinstatement might involve and which approvals would need to be revisited at that time. Retaining a second kitchen or entrance may assist a particular design, but it does not guarantee a future right to sell or occupy the spaces separately.
Keep this preference in the brief as a design objective rather than an assumed legal outcome. A project can be more coherent when everyone understands which decisions are permanent and which options the owner hopes to preserve.
Record the questions for the title review
Request advice on the registered lot boundaries, any common property involved, relevant interests recorded on title and the consents needed for the intended arrangement. Ask separately how any proposed title change could affect financing, insurance, levies and later dealings. These answers are property specific and should come from the appropriate advisers.
Investigate before relying on the second purchase
If the adjoining apartment has not yet been purchased, discuss the feasibility investigation with your solicitor before making commitments that depend on successful combination. The design team may need access, drawings or information that the seller cannot immediately provide.
Early investigation need not produce a fully detailed construction package. Its purpose is to identify significant constraints: a structural wall, an important service riser, a difficult approval pathway or a layout that works poorly once the two homes are joined.
Ask the advisers to distinguish confirmed facts from unresolved assumptions. For example, an original plan may show a wall position without proving its present construction. An informal conversation with a building manager may reveal useful history without constituting permission for work.
Decide what level of uncertainty you are prepared to accept before proceeding. That decision becomes clearer when the feasibility report lists the investigations still needed and the possible consequences if their results are unfavourable.
Assemble the building and strata records
Obtain the strata plan, relevant by-laws or scheme rules, available approved building plans and records of alterations to both apartments. Ask for information about structural systems, fire-safety arrangements and shared services that may be affected by the proposed connection.
Do not rely solely on sales floor plans. They are useful for discussing room relationships, but they may simplify walls, shafts and dimensions. The proposed combined home needs a measured survey that identifies the actual junction between the apartments.
NSW Government strata repair guidance identifies boundary walls and certain plumbing locations as common-property considerations and directs owners to their strata plan and by-laws when responsibilities are unclear. For a joining project, that reinforces the need to establish ownership of the affected elements before assigning work or maintenance.
Other states and territories use their own legal frameworks and terminology. Have the relevant local adviser interpret the documents rather than applying another jurisdiction’s process to the building.
Test the connecting wall with the structural engineer
Ask a structural engineer to assess the proposed opening and the building around it. The investigation should establish the wall’s role, the feasibility of the location and any implications for adjoining construction. An apparent partition on a sketch is insufficient evidence that it can be removed.
The preferred position may not be the easiest buildable position. A structural element, building movement detail or concealed service can require the opening to shift, narrow or take a different form. Keep more than one layout option available until the assessment is sufficiently developed.
If structural changes are feasible, the engineer and builder should explain the resulting design, construction access and likely disturbance at a planning level. Temporary support, demolition methods and structural installation belong to qualified professionals and the approved construction documentation.
Ask whether investigation or work requires access to the apartment above, below or a common area. That can affect permission, scheduling and the completeness of the feasibility assessment long before the opening itself is priced.
Have the building’s separating functions reviewed
The wall between two apartments may have functions beyond carrying load. Ask the relevant building and fire professionals to assess what the proposed change means for the building’s approved fire and acoustic arrangements, including the relationship to corridors and adjoining dwellings.
Do not assume that common ownership makes those functions irrelevant. The project needs an assessment of the resulting home within the whole building. Requirements depend on its classification, existing approvals, jurisdiction and proposed work.
The review should address the two front doors, any fire-safety equipment within the apartments and the treatment of service penetrations. If an entrance is to be removed or changed, include its corridor face and any required wall reinstatement in the design.
Ask which professional is responsible for coordinating these matters with the certifier or building surveyor. A structural report alone may not answer them, and an interior drawing should not be mistaken for a complete compliance assessment.
Map the services on both sides
Prepare a schedule of existing electrical supplies, water connections, hot-water arrangements, drainage, ventilation, communications and air conditioning. Some may be independent; others may connect to shared building infrastructure. Their ownership and maintenance arrangements need to be confirmed.
Ask the relevant licensed trades whether systems will remain separate or can appropriately be altered. Two switchboards or water accounts should not be assumed unnecessary simply because the rooms become one home. Any change needs technical and administrative coordination.
- Identify service risers and access panels near the proposed opening.
- Confirm how retained equipment will remain accessible for maintenance.
- List the fixtures and appliances that will be removed or relocated.
- Record proposed changes to metering, controls and account arrangements for review.
- Identify work that could interrupt services to other apartments.
Keep the schedule linked to the drawings. If a kitchen becomes a study, its service changes should appear in the same revision as the room change, rather than remain an informal instruction to the trades.
Make the combined floor plan feel like one home
The opening location determines whether the two apartments connect naturally or through an awkward private room. Trace the route from the proposed main entrance to living areas, bedrooms and bathrooms. A larger total area does not guarantee better circulation.
A related guide to consider while planning this work is Combining Back-to-Back Wet Rooms into One Larger Ensuite.
Look for duplicated corridors, remote storage and rooms that become thoroughfares. A connection through a former bedroom may sacrifice the very bedroom count that made the purchase attractive. A connection near two living areas may work more easily but still needs the structural and service assessment.
Decide how many kitchens, laundries and living areas the household genuinely needs. Retaining everything can preserve flexibility while consuming useful space and creating a fragmented home. Removing duplicated facilities can improve the plan but adds service and finishing work.
Test different daily routines
Use the plan to follow a visitor arriving, someone working from home and a family member moving between bedroom and bathroom at night. Consider whether one side of the home can remain quiet while the other is active.
If the home is intended for several generations, discuss privacy and independence explicitly. An extra entrance might be useful in a particular approved design, but access control, door operation and household expectations still need to be clear.
Resolve the two entrances as part of the project
Choose which entrance will function as the everyday front door and what will happen to the other. The answer affects internal circulation, corridor appearance, intercoms, locks, deliveries and emergency access arrangements.
Any proposed external alteration to an apartment entrance needs review within the scheme and building requirements. A redundant door should not be concealed behind furniture without understanding whether it must remain accessible or operational.
Where both entrances are retained, consider how visitors will identify the correct door and how the household will manage keys and intercom calls. Where one entrance is formally closed, include all associated finishes and equipment changes in the scope.
Ask the relevant parties how apartment numbering and building records should be handled. Avoid making informal changes to common-area signage or shared systems while the approved arrangement remains unresolved.
Plan the finish across the former boundary
The two apartments may have different floor levels, ceiling heights or wall alignments. A measured section through the proposed connection can reveal these issues before a seamless finish is promised.
Have the flooring and design team assess the existing build-ups and any movement considerations at the junction. The desired visual continuity must work with the actual substrates and the building’s requirements. A surface finish should not be used to disguise an unresolved construction detail.
Lighting, skirting and joinery also influence whether the connection feels intentional. If only a small area is being disturbed, discuss whether existing materials can be matched or whether a deliberate transition would look better.
Retain realistic expectations about colour and ageing. Two apartments renovated at different times can require broader decoration than the opening alone suggests, even when their original specifications were similar.
Prepare one coordinated approval proposal
Ask the project lead to assemble the design and specialist information into a consistent submission. The strata body, planning authority and building approval process may require different material, but each should describe the same intended work.
NSW Government renovation guidance treats structural and waterproofing work differently from minor renovations and notes that common-property changes may require by-law attention. The local process for your building must be confirmed, including who will maintain any altered common property.
Separate an early indication of support from a formal approval. Meeting discussions, design comments and contractor availability are useful steps, but the project should not proceed on the assumption that one replaces the others.
Track conditions as well as approvals. Access restrictions, inspection requirements, protection of common areas and record-keeping obligations can influence the programme and construction price.
Budget for the interfaces, not just the opening
Request a cost plan that separates investigation, design, approval work, construction, services and reinstatement. Title-related professional work, if proposed, should also be identified. Use actual project advice and quotations in Australian dollars, with GST treatment and exclusions clear.
The construction allowance should account for building access, material handling, waste removal, protection and any agreed work in common areas. An apartment project can require considerable coordination even when the visible alteration is compact.
Consider a hypothetical pair of apartments where the preferred opening conflicts with a shared riser. Moving the connection might preserve feasibility but require a different circulation plan and more internal alterations. A contingency cannot replace that design decision; the revised scope needs to be understood before it is approved.
Close the project with records that match the home
Agree on the completion documents required from the project team and the scheme. Keep the approved drawings, relevant professional records, service information and any updated ownership or maintenance documents together.
Check that retained access panels, controls and entrances work as intended. Walk through the combined home using the daily routines tested during design, and inspect the floor and ceiling transitions around the former boundary.
Joining apartments is most successful when the legal arrangement, approved building design and lived layout describe the same home. Establishing those connections early gives the attractive idea of more space a practical basis for proceeding.