Class 1a Buildings vs Class 10a Buildings

Sheds and Compliance with Australian Building Codes

Navigating the Building Code of Australia can be challenging. It's crucial to know what you need in a shed or garage and how to achieve it. For example, the BCA classifies a non-habitable shed, carport, or private garage as Class 10a. This classification is vital since building codes vary for habitable and non-habitable structures.

Whether your shed is a single room or has multiple rooms, it may be subject to classification if it includes any of the following types of rooms:

·       Bedrooms

·       Living Rooms

·       Dining Rooms

·       Sewing Rooms

·       Kitchens

·       Lounges

·       Studies

·       Playrooms

·       Television Rooms

·       Music Rooms

·       Sunrooms

·       Family Rooms

Any shed that includes one of these rooms listed above will be classified as a Class 1a building, which requires the appropriate building permit.

The BCA specifies certain rooms that can exist in a shed without making it "habitable" and subject to Class 1a limits. These rules ensure that sheds or garages are not used as permanent dwellings without meeting safety standards.

Here's what you can include in your shed without affecting its Class 10a status:

·       Bathrooms

·       Laundry rooms

·       Clothes-drying rooms

·       Photographic darkrooms

·       Water closets

·       Pantries

·       Walk-in robes

·       Lobbies

·       Corridors

·       Hallways

This also encompasses dedicated storage solutions, such as garages designed for motor vehicles or storage sheds intended to protect personal belongings from the elements.

There is a misconception in some circles that converting a basic shed into a house or granny flat is an inexpensive way to build. However, this is not accurate.

To clarify, it is indeed possible to purchase a "Class 10" shed building and subsequently convert it into a house or habitable dwelling, classified as "Class 1" or "Class 1a". Nevertheless, it is crucial to seek proper advice before proceeding with such a project.

What is your goal?

The primary consideration is to determine your objective. If you are seeking a weekend retreat or a modest dwelling in the countryside without requiring elaborate features, then a shed may suffice. However, if your intention is to fully equip the interior to resemble a conventional house, it would be more practical to construct a traditional home.

Not only is it likely to be more cost-effective over time, but it will also offer significantly better resale value. For instance, if you invest $150,000 in constructing a shed and converting it into a house, a potential buyer might perceive it as a budget conversion, valuing it at approximately $120,000. Conversely, if you spend the same amount on building a standard home, the prospective buyer could appreciate it as a well-constructed residence, potentially valuing it at no less than $200,000.

This illustrates the clear advantage in terms of perceived value and investment return by opting for a traditional construction approach.

Comparison Between a Class 1a Home and a Class 10 Shed

The differences between a Class 1a “home” and a Class 10 “shed” are more than external features.  Let’s look at a couple.

Engineering

A Class 10 shed is designed to withstand wind storms without structural damage, allowing some frame flex since it's not internally lined. Conversely, a Class 1 building must prevent any frame movement during storms to protect its internal lining from cracking or damage.

The concrete slab

Many "habitable sheds" are built on inadequate standard shed slabs. Class 10 buildings can handle slight slab settlements, as they aren't lined and can accommodate movement. However, Class 1 buildings cannot tolerate any settlement without developing large cracks in the linings. Therefore, Class 1 buildings need a much stronger slab with substantial footings.

There are numerous other differences to consider, including requirements for vermin proofing, termite control, and energy efficiency, among others. While these differences can be addressed, the time, effort, and financial resources required may outweigh the potential benefits. It is essential to thoroughly research and evaluate these factors.

Class 1 vs Class 10 Building Structural Design Differences

Now let’s move onto the actual structural design. A Class 10 portal frame building can be constructed to a weatherproof lock-up stage at a lower cost compared to a Class 1 stud frame and truss building. However, the costs increase significantly during the fitting-out phase.

Class 10 buildings are not designed for lining. Even if wall girts are replaced with stud frames, lining the roof area remains challenging because plasterboard cannot be fixed to the bottom of the roof purlins as they will flex when walked on.

If an interior stud frame is built within the shed frame for attaching lining, a separate shed frame is unnecessary since any exterior cladding, such as Colorbond Steel, can be easily attached to the stud wall frame.

With the wall frame in place, trusses can be added on top, simplifying ceiling lining by fixing it directly to the bottom cord of the truss. Subsequent tasks will also be more cost-effective and straightforward with the stud frame and trusses, including window reveals.

In a shed with an internal stud frame for lining, larger custom-made reveals are required, making them more expensive. In contrast, a Class 1 stud wall frame design uses standard components familiar to builders, resulting in quicker and easier installation of architraves and skirtings.

Builder

You don't have to use a full builder. Many companies can help design and sell you frames and trusses directly. After building the house, hire a renovation company or kitchen designer for the interior.

Some companies build standard houses in factories and deliver them fully finished or in segments that bolt together on-site. These homes are well-appointed and offer great value.