Going up instead of out lets you add bedrooms and living space without losing your backyard. A second storey extension, also called a first floor addition, is one of the biggest renovations you can do, so it pays to understand the process before you design.
Step 1: Can the house take it?
Your existing footings, walls and frame were designed for a single storey. A structural engineer checks whether they can carry the extra load. Many homes need some strengthening, such as new steel beams, posts, footings or, in some cases, underpinning.
Step 2: Approvals
Some second storey additions can be approved as complying development if they meet the standards for height, setbacks, overshadowing and privacy. Others, including homes in heritage conservation areas or on constrained sites, need a development application. A planning check early saves redesigning later.
Step 3: Design
- Stairs: where the new staircase goes affects the downstairs layout more than anything else.
- Services: plumbing, electrical and air conditioning need to reach the new level.
- Roof form and light: what the street and neighbours see, and how much light the new rooms get.
- Energy: BASIX requirements for insulation, glazing and water.
Step 4: Construction
The roof is removed and the house is protected from weather, the floor structure and any strengthening are installed, then the new level is framed, closed in, and fitted out. Good weather protection during the roof-off stage is critical.
Can you live there during the build?
Sometimes, but many families move out during the roof-off and structural stages because of noise, dust, disconnected services and safety. Plan for this in your budget.
What drives the cost
- Size and complexity of the new level.
- Structural strengthening needed downstairs.
- Bathrooms and kitchenettes upstairs.
- Access for cranes, scaffolding and materials.
- Finishes and fixtures.
- Approvals, engineering and design fees.
Compare going up with going out in our guide to renovation vs extension costs.
Second storey additions in Sydney
See our first floor additions service or book a free site assessment on 0415 840 500.
Frequently asked questions
Can my house support a second storey?
Often, but an engineer must check the footings, walls and frame. Some strengthening is common.
Do I need a DA for a second storey extension in NSW?
Not always. Some additions can be approved as complying development, while heritage areas and constrained sites usually need a DA.
Can we stay in the house during a second storey build?
Sometimes, but many families move out during the roof-off and structural stages.
