01Mount Lawley · 2025
Rear extension and open-plan kitchen
Double-storey rear addition to a 1930s brick-and-tile — new kitchen, family room and two bedrooms above.
- Added
- 78 m²
- On site
- 14 weeks
- Contract
- Fixed price, held
01What we build
Home extensions and second-storey additions
Ground-floor and upstairs additions that match the original house rather than argue with it.
AWhy people ring
You have outgrown the house, not the street
Almost every extension enquiry we take starts the same way. The house is too small now, but the block is good, the neighbours are decent and nobody wants to start again in an outer suburb with a forty-minute commute.
The hesitation is rarely about money on its own. It is about not knowing whether the addition will look bolted on, whether the council will allow it, and whether the number quoted in March will still be the number in September.
BThe work
What an extension with us involves
We start at the house, not at a plan. What the existing structure can carry, where the light comes from, which walls are load-bearing and what the roof line is doing all decide what is sensible before anything is drawn.
From there we produce concept drawings, get the engineering done, lodge with your local government and hand you a fixed-price contract. The design is deliberately conservative about matching the original house — brick selection, roof pitch, eave depth and window proportion are the details that decide whether an addition reads as original or as an afterthought.
Most of our extension clients stay in the house while we build. Where that is possible we seal the work zone, keep the kitchen or bathroom running as long as we can, and give you a written weekly plan so you are never guessing what happens on Monday.
- 01Concept drawings
- Two rounds of plan and elevation drawings, revised with you before anything is lodged.
- 02Structural engineering
- Independent engineer's design for footings, beams and any new load paths through the existing house.
- 03Council and shire approvals
- Building permit lodged and chased by us, including planning conditions and any heritage or R-code issues.
- 04Fixed-price contract
- One number covering the trade schedule, materials and site costs. Variations are quoted and signed before work begins on them.
- 05Live-in staging
- Dust sealing, temporary services and a work sequence that keeps you in the house wherever the structure allows it.
- 06Handover and six-month check
- Defect walk-through, full clean, documented warranty, then a return visit at six months to look over the lot.
How it runs
Five stages, and you know where you are in them.
Every home extensions job runs the same way. The stage you are in, and what you get at the end of it, is written down before you sign anything.
- 01
Site visit and feasibility
We walk the block, look at the existing structure and tell you what will and will not work. Free, and you get an honest read even if the answer is no.
- 02
Concept and fixed price
Drawings, engineering and a fixed-price contract. You see the final number before you commit to anything beyond the design fee.
- 03
Approvals
Building permit lodged with your local government. We handle the back-and-forth and keep you posted on where it sits.
- 04
Build
One supervisor, one point of contact, photo updates every Friday. Typically ten to sixteen weeks on site for a standard addition.
- 05
Handover
Walk-through, defects closed out, keys back and the warranty documented. Six-month check booked in on the day.
CCost
What extensions cost in Perth
Nobody enjoys reading 'prices on application', so here is the honest version. Cost is driven by three things: floor area, whether you are going up or out, and how much of the existing house has to be opened up to connect the two.
Ground-floor additions generally start around $250,000. Second-storey work sits higher because of the structural upgrade to what is already there.
Indicative
From $250k
You get a real number after the site visit and concept stage — not a range, and not a figure that moves once the slab is down.
Proof
One we built, documented in full.
Mount Lawley, 2025. Suburb, time on site, whether the price held and whether the owners stayed in the house — the four things people actually check.
“We had three builders quote the extension. Karri were the only ones who told us what would not work and why. They finished a week early and the price never moved.”
Questions
What people ask about home extensions.
How much does a home extension cost?
It depends on size, site access and how much of the existing house has to change. As a rough guide, ground-floor additions in Perth start around $250,000, and second-storey work sits higher because the existing structure usually needs upgrading. We give you a real number after the site visit and concept drawings rather than a range you cannot plan around.
Can we stay in the house during the build?
Usually yes for extensions, because we can seal the work area off from the rest of the house. Second-storey additions are harder during the roof-off stage, which is generally a two to three week window. We tell you at the site visit rather than letting you find out halfway through.
Do you handle council approvals?
Yes. Drawings, engineering, the building permit submission and any planning conditions are all managed by us. You sign, we lodge, we chase it.
How long does an extension take?
Ten to sixteen weeks on site for a standard addition, plus roughly eight to twelve weeks beforehand for design, engineering and approvals. We give you a dated program with the contract.
Will the addition match the original house?
That is the whole point of how we design them. Brick selection, roof pitch, eave depth and window proportion are chosen against the original, and where a match is genuinely impossible we will tell you and suggest a deliberate contrast instead of a near miss.
We build across Inner north, Western suburbs, River south, Coastal north, Fremantle and around — see the full list on the service areas page.
The next step
Have us out to look at your home extensions.
Free to have us out, about an hour on site, and you leave with a written summary of what is feasible and a realistic budget band.