Tools
Extend out, or build up?
Most people arrive having already decided. The block usually answers it before taste does. Put in the space you need and the yard you have, and see both paths side by side: cost, time on site, the yard you keep and how each gets approved.
- Same space, both ways
- Cost, time and yard compared
- We build both, so the advice is honest
The calculator
Compare the two paths for your block
Change the space you want to add and the size of your backyard. Both options are priced like for like, with one bathroom and a connection back into the house.
Extending out is about $176k less for the same space. Building up keeps all 180 m² of your yard.
Extending would use about 25% of your yard. With room to spare, ground floor work is usually the better value answer.
Ground floor extension
Extend out
Indicative cost
$161,000 to $183,000
- Cost
$161,000 – $183,000
- Time on site
12 to 20 weeks
- Yard you keep
135 of 180 m²
- Approvals
- A CDC takes about 4 to 8 weeks if it fits the standards; a DA can take up to 6 months, depending on council.
- Living at home
- You can often stay living there while it is built.
- Structure
- Avoids the structural question of loading the existing house.
Second storey addition
Build up
Indicative cost
$319,000 to $376,000
- Cost
$319,000 – $376,000
- Time on site
12 to 24 weeks
- Yard you keep
180 of 180 m²
- Approvals
- Heritage areas and tighter blocks usually need a DA, while some additions can use complying development. Usually the longer pathway.
- Living at home
- For part of the structural stage the roof is open, and it is safer to live elsewhere.
- Structure
- An engineer checks footings and frame first. For roughly one house in six the answer is no, or not economically.
Indicative range only. A site visit and an itemised quote confirm the real price. Every Strava Group quote lists inclusions, exclusions and preliminaries separately, with any provisional sums shown openly. Both ranges include about $30,000 in preliminaries. The block plan is illustrative: an extension’s footprint is taken as equal to the space added.
The first decision
Up or out: how we would answer it.
We build both, so there is nothing to sell you either way. We look at your block and tell you which one your home actually wants.
Go up
$3,500 to $5,500 per m²
Choose it if the yard is the reason you bought the place, the block is narrow, or you have already used most of your site coverage.
Going up buys bedrooms without buying land and leaves the garden intact. It costs more per square metre and usually needs a longer approval pathway, but on a tight block it is often the only way to add real space.
Extend out
$2,500 to $4,500 per m²
Choose it if you have real yard to give up and still have some left, the block is wide rather than deep, or the structure cannot carry a floor economically.
Ground floor work is cheaper per square metre, you can often stay living there, and it avoids the structural question entirely. A rear extension is frequently the better value answer.
If the existing house needs work regardless, a full renovation staged alongside the addition costs less than doing them five years apart, because you pay the preliminaries once and open the walls once. Price that with the renovation cost calculator.
Honest numbers
Where the comparison comes from.
| Figure | What it covers | Where it comes from |
|---|---|---|
| $2,500–$4,500 /m²Extending out: ground floor work, with a bathroom and a widened opening into the house. | Extending out: ground floor work, with a bathroom and a widened opening into the house. | Home extensions |
| Package pricesBuilding up: priced from our fixed price second storey packages for the same floor area, with one bathroom. | Building up: priced from our fixed price second storey packages for the same floor area, with one bathroom. | Second storey additions |
| approx. $30,000Preliminaries, included in both ranges. | Preliminaries, included in both ranges. | Home extensions |
| 12–20 vs 12–24 wksTime on site: extension versus second storey. | Time on site: extension versus second storey. | Second storey additions |
| Yard usedAn extension’s footprint is taken as equal to the space it adds. A second storey uses none. | An extension’s footprint is taken as equal to the space it adds. A second storey uses none. | Home extensionsworked out from it |
Keep planning
More tools
- 01
Home Extension Cost Calculator
Size, rooms and finish in, an honest price range out, with what is driving it.
Size · type · kitchen & bathroom · finish
Open the tool - 02
Second Storey Cost Calculator
Price a new upper floor against our fixed price packages, bedroom by bedroom.
Floor size · bedrooms · bathrooms · stair · finish
Open the tool - 03
Renovation Cost Calculator
Pick the rooms, tell us the house, see where a renovation budget really goes.
Rooms · house age · structural walls · finish
Open the tool - 05
Project Timeline Planner
From first call to handover, stage by stage, with the month you could move in.
Project type · approval pathway
Open the tool
Not sure which way your block leans?
Tell us about your property. A builder walks your home and yard with you and tells you honestly whether it wants to go up or out, with real numbers for both. We respond within 24 to 48 business hours.