Second storey or ground-floor extension?

Updated 19 Aug 2026/8 min read/By Manttan Construction · QBCC 15030266

Comparison for typical Brisbane and Redlands houses

Cost / m²	Ground floor $2,500–$4,500; second storey $3,500–$5,500 — the gap is structure, access and staging.
Land	Extending out consumes yard and counts toward site cover. Going up consumes none.
Structure	A second storey depends on existing footings and frame; an extension needs new footings and slab.
Stairs	A second storey costs you roughly 8–10 m² of usable floor area for the stair.
Living in it	Ground-floor work is usually liveable. Second-storey work means the roof comes off — plan to move out.
Program	Ground floor typically 3–5 months on site; second storey 4–8 months, plus approvals.
Approvals	Both are assessable building work. Character and demolition controls bite harder on the street elevation when you go up.

01 — The block

The block decides more than the budget

Before comparing prices, five site facts usually settle the question. We check all five on the first visit:

• Site cover and setbacks. If you are already near the limit of what can be built on the block, out is not an option.
• Slope. A steep fall makes ground-floor work expensive (retaining, earthworks) and build-under attractive.
• Existing footings and frame. Whether they can carry another floor, and what it costs to upgrade them if not.
• Roof form. A simple gable or hip takes a second storey far more easily than a complex cut roof.
• Overlays. Character, demolition control, flood and coastal overlays all restrict what can change, especially at the front.
• ,

On a pre-1946 house in a character area, the answer is often "out, or up at the rear" — our approvals guide explains why the street elevation matters so much.

02 — Going up

What a second storey actually involves

A second storey is a structural project first and a renovation second. The order of work is what makes it more expensive per square metre, not the finishes.

• Assessment. Engineer reviews the existing footings, frame and slab, and specifies any upgrades required.
• Roof off. The existing roof is removed or lifted, which means weather protection and a program that respects it.
• New floor and frame. Floor structure, walls and a new roof, often craned in — as in our own recent beam lifts.
• Stair. A compliant stair has to come out of the existing floor plan, which sometimes reshapes rooms below.
• Services extended. Plumbing, electrical and often a switchboard upgrade to serve the new level.

03 — Going out

What a ground-floor extension involves

Why it is usually cheaper

Simpler structure, no roof removal, no stair, and you can normally keep living in the house. The new work sits on its own footings and slab, so it does not depend on what is already there.

What you give up

Yard, and sometimes light. A rear extension can darken the rooms it attaches to unless you design for glazing and roof form — and it counts toward site cover, which may limit future work.

When it is the obvious answer

Generous block, single-level living that suits you, a ground floor that already relates to the garden, or a house whose footings and roof make going up expensive.

If you want more room and the yard can spare it, out is almost always the faster, cheaper and less disruptive project. See extensions and second storeys for how we run both.

04 — Compared

Cost, time and disruption compared

On cost, out wins per square metre almost every time. On value, up often wins where land is scarce or the outlook is worth capturing — a second storey that buys a bay view in Manly or Wynnum is not competing with a ground-floor room, it is competing with moving suburb.

On time and disruption, out wins clearly: shorter program, you stay in the house, and the weather risk is smaller. Balance that against what you lose permanently — yard is the one thing a builder cannot give back.

05 — Deciding

How to make the call

• Get the engineer in early. What the existing structure can carry is a fact, not an opinion, and it often decides the project.
• Check the overlays before you sketch. Character and flood controls change what is possible, not just what it costs.
• Value the yard honestly. If the garden is why you bought the place, out is expensive in a way no quote shows.
• Price both properly once. A real comparison beats a year of guessing; we quote both where the site allows it.

There is no universally right answer — but there is usually a clearly right answer for your block, and it takes one site visit and an engineer to find it.

Questions

Up or out FAQ

Not sure which way your house should go? Call 0402 847 873 and we will tell you straight.

Can every house take a second storey?+

No. It depends on the existing footings, frame and slab, the roof form and the overlays that apply. An engineer's assessment answers it, and where the structure cannot carry another floor, upgrading it can cost more than extending out.

Is a second storey worth the extra cost per square metre?+

Where land is scarce or the outlook is upstairs, usually yes — you keep the yard and gain a view. On a generous block with an ordinary outlook, a ground-floor extension gives you the same room for less.

Do I have to move out during a second-storey build?+

For most of it, yes. Once the roof comes off the house is not weathertight, so plan on four to eight weeks elsewhere. Ground-floor extensions are normally liveable throughout.

Which one adds more value?+

In a tight-land suburb, a well-designed second storey that captures a view. On a large block, a ground-floor extension that connects living areas to the garden. Both add more when the design looks original rather than bolted on.

Extensions & second storeys→ What an extension costs→ Structural changes→ All guides→

Get advice & a quote → 0402 847 873