House Extensions Perth · Second-storey, rear & side
House
Extensions
Perth.
House extensions Perth-wide since 2023 — second-storey additions, rear extensions, structural refurbishments. Recent flagship: a $320K Elliot extension in Coolbinia. WA Builder BC104702, fixed-price contracts, statutory home-warranty under the WA Home Building Act, twelve months direct aftercare on every job.
2023
Trading since — WA construction company
BC104702
WA Builder Licence — current
$7.5K–$300K+
Project range delivered to date
12mo
Direct aftercare on every job
What we build
Four paths to a house extension Perth-wide.
House extensions Perth fall into four delivery types — each suits a different block, footprint and budget. Add the floor area without the demolition cost. Often the smarter spend than a knock-down rebuild.
01 · Second-storey
Build up.
Add bedrooms, ensuite or living upstairs without losing yard. Highest cost per m² but unbeatable on narrow blocks where extending out isn’t possible.
02 · Rear
Build back.
Open-plan living, kitchen, master suite to the back of the dwelling. Most popular path Perth-wide — single storey, easier engineering, best value per m².
03 · Side
Build out.
Lateral extension into side setback where block allows. Suits homes with generous side yards or wider blocks. Council rules decide the envelope.
04 · Structural
Major refurb.
Extension plus major internal restructure — load-bearing walls moved, structural integration, near-new-build complexity within an existing dwelling.
What we build
Four paths to a house extension Perth-wide.
House extensions Perth fall into four delivery types — each suits a different block, footprint and budget. Add the floor area without the demolition cost. Often the smarter spend than a knock-down rebuild.
House extensions Perth fall into four delivery types — each suits a different block, footprint and budget. Add the floor area without the demolition cost. Often the smarter spend than a knock-down rebuild.
01 · Second-storey
Build up.
Add bedrooms, ensuite or living upstairs without losing yard. Highest cost per m² but unbeatable on narrow blocks where extending out isn’t possible.
02 · Rear
Build back.
Open-plan living, kitchen, master suite to the back of the dwelling. Most popular path Perth-wide — single storey, easier engineering, best value per m².
03 · Side
Build out.
Lateral extension into side setback where block allows. Suits homes with generous side yards or wider blocks. Council rules decide the envelope.
04 · Structural
Major refurb.
Extension plus major internal restructure — load-bearing walls moved, structural integration, near-new-build complexity within an existing dwelling.
Featured extension
A $320K extension
in Coolbinia.
A house extension Perth project delivered for the Elliot family in Coolbinia — major residential structural work, near-new-build complexity within an existing dwelling envelope. Reference contact available on request.
Elliot · Coolbinia · Major extension
Elliot — Coolbinia extension.
A $320,000 major residential extension delivered for the Elliot family in Coolbinia. Full structural integration with the existing dwelling, near-new-build complexity, council-approved and lodged in our name as the licensed builder. Twelve months direct aftercare on handover.
Value
$320,000
YEAR
2023
Role
Head builder
Status
Delivered
Featured extension
A $320K extension
in Coolbinia.
A house extension Perth project delivered for the Elliot family in Coolbinia — major residential structural work, near-new-build complexity within an existing dwelling envelope. Reference contact available on request.
Elliot · Coolbinia · Major extension
Elliot — Coolbinia extension.
A $320,000 major residential extension delivered for the Elliot family in Coolbinia. Full structural integration with the existing dwelling, near-new-build complexity, council-approved and lodged in our name as the licensed builder. Twelve months direct aftercare on handover.
Value
$320,000
YEAR
2023
Role
Head builder
Status
Delivered
Why us
Why Perth
homeowners
brief us for house extensions.
Four practical reasons clients pick GPD as the licensed builder for an extension. The unglamorous things that decide whether structural integration with the existing house lasts thirty years — or starts to crack at year five.
01
A WA licensed builder.
BC104702 since 2023. Statutory home-warranty under the WA Home Building Act applies on residential builds over $20,000. Liability flows with the licence.
02
Real extension delivered.
Recent $320K extension delivered in Coolbinia — full structural integration, near-new-build complexity. Reference contact available on request.
03
Direct line to the builder.
Owner-operated. The builder reads every brief, signs every contract, runs every site meeting. No project-manager intermediary, no head-office bottleneck on decisions.
04
Twelve months aftercare.
Direct aftercare line for twelve months from handover, every job. Statutory warranty under the WA Home Building Act applies on top of that for the warranty period.
Investment & timeline
What a Perth
house extension
actually costs.
Three honest price bands — single-room single-storey through to second-storey or major structural. Real Perth market economics 2026, anchored by recent delivery (Coolbinia $320K).
Single-room
$80k–$180k
3–4 months · single-storey rear
Single-room rear or side extension — bedroom, ensuite, study addition. 15–30m² typical. Council-approved, integrated services and finishes.
Major
$180k–$320k
5–8 months · most popular
Major rear or side extension — open-plan living, kitchen, master suite. Recent Elliot Coolbinia extension landed at the top of this band ($320K).
Second-storey
$320k–$500k+
8–12 months · second-storey
Second-storey addition or major structural refurbishment — load-bearing structural work, full integration, near-new-build complexity.
Investment & timeline
What a Perth
house extension
actually costs.
Three honest price bands — single-room single-storey through to second-storey or major structural. Real Perth market economics 2026, anchored by recent delivery (Coolbinia $320K).
Three honest price bands — single-room single-storey through to second-storey or major structural. Real Perth market economics 2026, anchored by recent delivery (Coolbinia $320K).
Single-room
$80k–$180k
3–4 months · single-storey rear
Single-room rear or side extension — bedroom, ensuite, study addition. 15–30m² typical. Council-approved, integrated services and finishes.
Major
$180k–$320k
5–8 months · most popular
Major rear or side extension — open-plan living, kitchen, master suite. Recent Elliot Coolbinia extension landed at the top of this band ($320K).
Second-storey
$320k–$500k+
8–12 months · second-storey
Second-storey addition or major structural refurbishment — load-bearing structural work, full integration, near-new-build complexity.
How we work
Five steps from brief to handover.
House extensions have one defining characteristic: structural integration with the existing dwelling decides whether the build feels like one house or two stuck together. Our process loads the design and engineering work upfront — not as nasty surprises mid-build.
How we work
Five steps from brief to handover.
House extensions have one defining characteristic: structural integration with the existing dwelling decides whether the build feels like one house or two stuck together. Our process loads the design and engineering work upfront — not as nasty surprises mid-build.
Quality criteria
What separates a
good
Perth house
extension.
The unglamorous things that decide whether an extension feels like part of the house — or like a bolted-on box that always reads “added later.” None of these show in finished photos. All of them matter.
Footings
Tied to existing slab.
New footings engineered to the existing slab and soil profile. Inadequate tie-in is the most common reason cracks appear at the junction within five years.
Roofline
Tied to existing eave.
Roof profile integrated with the existing dwelling — pitch, eave height, fascia line. Mismatched roofline is what makes extensions read as “added later” from the street.
Services
Sized for the whole house.
Power, water, hot water, sewer sized for the new total floor area — not just the extension. Existing services upgraded where capacity is the bottleneck.
Junction
Where new meets old.
Wall, floor, ceiling junctions detailed for movement and waterproofing. Done right, invisible for thirty years. Done cheap, the first failure point — every time.
Energy
7-star NatHERS standard.
National Construction Code 7-star energy rating applies to extensions over 50m². Insulation, glazing, orientation specified at design — not value-engineered out at quote.
Live-in
Managed for occupied builds.
Most extension clients live in the house during construction. Site management plans dust, noise, services interruptions, family impact — not “you’ll just have to deal with it.”
Quality criteria
What separates a
good
Perth house
extension.
The unglamorous things that decide whether an extension feels like part of the house — or like a bolted-on box that always reads “added later.” None of these show in finished photos. All of them matter.
The unglamorous things that decide whether an extension feels like part of the house — or like a bolted-on box that always reads “added later.” None of these show in finished photos. All of them matter.
Footings
Tied to existing slab.
New footings engineered to the existing slab and soil profile. Inadequate tie-in is the most common reason cracks appear at the junction within five years.
Roofline
Tied to existing eave.
Roof profile integrated with the existing dwelling — pitch, eave height, fascia line. Mismatched roofline is what makes extensions read as “added later” from the street.
Services
Sized for the whole house.
Power, water, hot water, sewer sized for the new total floor area — not just the extension. Existing services upgraded where capacity is the bottleneck.
Junction
Where new meets old.
Wall, floor, ceiling junctions detailed for movement and waterproofing. Done right, invisible for thirty years. Done cheap, the first failure point — every time.
Energy
7-star NatHERS standard.
National Construction Code 7-star energy rating applies to extensions over 50m². Insulation, glazing, orientation specified at design — not value-engineered out at quote.
Live-in
Managed for occupied builds.
Most extension clients live in the house during construction. Site management plans dust, noise, services interruptions, family impact — not “you’ll just have to deal with it.”
More residential work
Other recent
residential
work at scale.
A spread of recent residential projects from the GPD register — extensions, renovations and government residential housing. Reference contacts available on request.
A spread of recent residential projects from the GPD register — extensions, renovations and government residential housing. Reference contacts available on request.
Common questions
House extensions
Perth —
the questions we get.
The questions Perth homeowners ask before briefing an extension. Plain answers, plain English, no salesy hedge.
Brief us on an extension
Tell us about your Perth house extension.
A short brief so we can come back with an informed first call. The builder reads every brief personally — replies within one business day. No commitment beyond an honest conversation.