Converting a Garage or Non-Habitable Space Into a Habitable Room in Auckland

A garage, basement or unused area can look like an obvious opportunity for creating more space within your existing home.

You might want another bedroom, home office, living room, teenage retreat or additional accommodation — without extending the footprint of the house.

But there's an important distinction to understand before you start:

Just because a space is already enclosed and looks like a room doesn't necessarily mean it is legally suitable to be used as a habitable room.

Garages, basements and storage areas are often built to different requirements from the parts of a home where people live, sleep and spend extended periods of time.

Converting one properly can therefore involve much more than adding carpet, lining the walls and replacing the garage door.

What Is a Habitable Room?

A habitable room is a space intended for activities normally associated with domestic living.

Bedrooms, living rooms and dining areas are common examples. Garages, storage areas and some basements are generally considered non-habitable spaces because they weren't originally designed or consented for people to occupy in the same way.

The important question isn't simply “Can we make this look like a bedroom?”

It's:

What needs to change for this part of the building to meet the requirements for how you intend to use it?

That is where a garage or basement conversion needs to start.

Can You Convert a Garage Into a Bedroom or Living Space?

Often, yes.

Whether it is practical — and what will be required — depends on the existing building.

Some of the first things that need to be considered are:

• Ceiling height

• Existing concrete slab and floor levels

• Ground moisture

• Wall, floor and ceiling insulation

• Natural light and ventilation

• Windows and exterior doors

• Fire safety

• Structural changes

• Weathertightness

• Plumbing, drainage and electrical services

• The existing consented use of the space

Some garages are relatively straightforward to convert. Others require considerably more work than homeowners initially expect.

1. Start With the Ceiling Height

Ceiling height can determine whether the space is suitable for the intended use before you've gone very far into the design.

For many habitable spaces, a ceiling height of around 2.4 metres will commonly need to be considered, although the exact requirements depend on the room and design.

If an existing garage or basement is too low, solutions may sometimes include altering the floor level or roof structure. But these can substantially change the scope and cost of what initially appeared to be a simple conversion.

This is one of the reasons feasibility should be considered before investing heavily in plans.

2. The Existing Floor Can Be More Important Than It Looks

The concrete slab is one of the most important things to investigate in a garage conversion.

A garage floor may not have been constructed with the same moisture protection, insulation or relationship to the surrounding ground as a floor intended for a habitable room.

That can create issues with dampness, moisture, warmth and potentially water entering the new living space, potentially affecting flooring, carpet and furniture and making the new living space difficult to keep warm and dry and free of mold and mildew.

Depending on the existing construction, solutions might involve specialist moisture-control systems, insulation or alterations to the existing floor.

The existing walls and roof may make a garage look almost finished, but what is underneath the floor can have a significant influence on whether the conversion is practical and what it will cost.

3. Insulation, Moisture and Warmth

Once people are going to regularly live or sleep in the space, the performance expected from it changes.

Depending on the existing construction and proposed work, this can mean upgrading insulation to the walls, ceiling and/or floor, as well as addressing moisture and ventilation.

This is particularly important in garages and basement areas, where the original construction may have been designed around storing vehicles or belongings rather than creating a warm, dry living environment.

Simply lining over an existing wall or putting flooring over a concrete slab doesn't necessarily resolve what is happening behind or underneath it.

4. Natural Light and Ventilation

Habitable rooms also need appropriate light and ventilation.

As a general design consideration, habitable spaces commonly need natural light equivalent to around 10% of the floor area, with openable windows or other openings providing ventilation equivalent to around 5%, although the Building Code provides different compliance pathways and alternatives depending on the design.

An existing garage may have very little glazing because it never needed to function as a living space. The conversion may therefore require new or altered windows or doors, or an appropriate mechanical ventilation solution.

Cutting new openings into an exterior wall can also introduce structural and weathertightness considerations, so this needs to be designed and constructed correctly rather than treated as simply installing a window.

5. Replacing the Garage Door

Replacing a garage door with a framed wall, windows or a new entrance is one of the most visible parts of many conversions.

But that new wall becomes part of the home's exterior envelope. It may need to provide appropriate structure, insulation and weathertightness and integrate correctly with the existing cladding, slab and surrounding building.

Depending on the work involved, parts of the conversion may also be Restricted Building Work and need to be carried out or supervised by an appropriately Licensed Building Practitioner.

6. Adding a Bathroom or Kitchen Changes the Conversation

Adding a bathroom introduces plumbing, wastewater, ventilation and waterproofing requirements.

Adding a kitchen can have an even greater implication.

Once kitchen facilities are introduced, the space has the potential to be used independently from the main house. That can change how the proposed use is viewed from a planning and compliance perspective.

This becomes particularly important when creating accommodation for family members, teenagers, elderly parents or tenants.

A bedroom or additional living area connected to the existing household and a self-contained dwelling are not necessarily the same project.

The good news is that this doesn't mean you can't create what you want. It means the intended use needs to be established early so the space can be designed, approved and built accordingly.

7. Creating Separate Accommodation Can Introduce Further Requirements

If different households could occupy separate parts of the property, additional requirements may need to be considered.

Depending on the design, this can include fire separation, acoustic performance and specific construction systems between different areas of the building.

Services may also need closer consideration, including:

• Wastewater and stormwater

• Water supply

• Electrical capacity

• Plumbing

• Drainage

• Fire separation

• Structural elements and retaining walls

This is where a project that initially sounds like “turn the garage into a flat” can become considerably more involved.

Thinking about how the space will actually be used from the beginning allows these requirements to be incorporated into the design rather than discovered halfway through the project.

Do You Need Building Consent for a Garage Conversion?

This depends on the existing building and the work required.

It isn't safe to assume that because you're working within the existing footprint of the house, the conversion won't require approval. Structural alterations, new exterior openings, plumbing, drainage, waterproofing and other building work can trigger building consent requirements. The intended use of the converted space can also introduce planning considerations.

For that reason, we prefer to establish the existing legal status of the space, what you want to use it for and the work required to achieve that before determining the approval pathway.

What If the Garage Has Already Been Converted?

This is something we regularly encounter in existing homes.

A previous owner may have installed walls, flooring, windows or even a bathroom and begun using the garage as living space without completing the appropriate approvals.

The room may look perfectly normal.

A finished room isn't necessarily an approved habitable room.

The property file and Council records can help establish what was originally consented and whether subsequent alterations were documented.

This can be particularly important when purchasing or selling a property, undertaking further renovations, arranging insurance or trying to resolve an existing unconsented conversion.

Is Converting Existing Space Better Than Building an Extension?

Sometimes.

One of the attractions of a garage or basement conversion is that the basic building footprint already exists. It can be an effective way to create additional bedrooms, living areas or accommodation without constructing an entirely new extension.

But existing doesn't automatically mean inexpensive.

If substantial work is required to the slab, structure, drainage, services or exterior envelope, the cost can increase quickly.

The useful comparison isn't simply: conversion cost vs extension cost.

It is:

What will each option cost to create the space you actually need — properly designed, compliant and finished to the standard you want?

Sometimes converting the existing space will clearly make sense. In other situations, an extension or different configuration may give you better value for the money you're investing.

Where Should You Start?

Before investing heavily in drawings, establish:

• What the area is currently consented as

• What you actually want to use it for

• Whether the existing construction is suitable

• What upgrades are likely to be required

• Whether structural, plumbing or drainage work is involved

• What Council approvals may be needed

• Whether the likely scope makes financial sense

This is where early investigation can save considerable time and redesign.

A builder, designer and other specialists can then look at the existing building, intended use, compliance requirements and likely construction cost together, rather than designing a conversion first and discovering its constraints later.

Converting Existing Space With Alder Homes

Alder Homes undertakes garage, basement and existing-space conversions across Auckland as part of our residential renovation and alteration work.

We can help assess the existing space, identify potential constraints and work alongside the appropriate designer, engineer and other specialists where required.

Whether you're creating additional rooms for your family or investigating the potential for separate accommodation, the aim isn't simply to make the existing space look like another part of the house.

It's to turn underused space into a part of your home that is properly planned, appropriately approved and built for the way you intend to use it.

If you're considering converting a garage, basement or other non-habitable area, talk to Alder Homes before you begin designing the space.