Need more space but love where you live? MSJ Building Services designs and builds home extensions across Sydney, from single-storey rear additions to full second storey builds and new wings. Managing Director Modest Jablonski has more than 35 years in the building industry and is personally on site for every project. We work throughout the Hills District and North-East Sydney, including Castle Hill, Baulkham Hills, Kellyville, the Inner West and the Lower North Shore, managing the design, council approval and construction from first call to final handover.
A home extension adds floor area to the house you already own instead of replacing it, so you keep the address, the garden and the character while gaining the rooms you need. In Sydney, there are three common approaches:
Every option starts the same way: a structural assessment of what your home can safely carry, and a check of what your block and council will allow.
Extending is usually the smarter move when the house is right but too small:
Approvals are where most Sydney extension projects stall. There are two pathways, and we manage both for you.
One more protection: residential building work in NSW over $20,000 including GST requires Home Building Compensation Fund (HBCF) insurance before work starts or a deposit is accepted. You receive that certificate with your contract.
Modest visits your home, listens to your vision and gives honest advice about what is possible for your budget and timeframe.
You receive a clear, itemised fixed-price quote with design guidance. No vague estimates and no hidden costs that appear later.
A clear contract price with the scope written down, not an estimate that grows later.
Where council approval or a CDC is required, we handle the entire application process so you never have to navigate it alone.
Your project is built to the highest standard with regular updates from Modest throughout every stage. You always know where things stand.
A thorough walkthrough with Modest to ensure you are 100% satisfied before we consider the job done.
Typical timeframe is four to nine months: roughly two to five months for design and approvals, then ten to twenty weeks on site.
We build home extensions across Sydney including the Hills District, Castle Hill, Baulkham Hills, Kellyville, the Eastern Suburbs, Inner West, Lower North Shore, North West Sydney, Northern Beaches, South West Sydney and Western Sydney.
A track record on Federation, art deco and Californian bungalow homes as well as modern builds.
Bricklaying, plastering, plumbing, electrical, tiling, carpentry and painting are handled by the team, so the program never waits on outside trades.
You deal directly with the Managing Director from first consult to handover.
CDC and DA applications prepared and lodged on your behalf.
Five-star reviews from Sydney homeowners, including repeat clients across four renovations.
No obligation and no sales team. Modest replies personally, usually within hours.
Sydney extension pricing is driven by whether you build out or up, and by the level of finish. As a 2026 guide, single-storey ground-floor extensions generally run about $2,500 to $3,800 per square metre for mid-range finishes, with budget work starting nearer $1,800 and premium finishes above $3,800. Second storey additions typically sit between $3,200 and $5,500 per square metre because footings, walls and roof structure all need work. So a 40 square metre rear extension commonly lands between $100,000 and $152,000 before approvals, engineering and site costs.
Allow four to nine months end to end. Approvals take two to five months depending on the CDC or DA route, and construction runs ten to twenty weeks. A single-storey rear extension sits at the short end.
Yes, in some form. Many single-storey extensions can be approved as Complying Development by a private certifier, which is far faster. Second-storey additions, heritage properties and flood-prone land need a Development Application through council. We manage either pathway.
Usually yes for a ground floor extension, because the new work happens outside the existing walls until we break through. For a second storey addition, the roof comes off, so most families relocate for that stage. Modest will tell you at quoting stage which weeks are affected.
Not always, but the existing footings and walls must be assessed by an engineer before the design is locked in. Many older Sydney homes need targeted underpinning or steel beams rather than a full rebuild, and that assessment happens early so the cost is known upfront.
We work across the Hills District and North-East Sydney including Castle Hill, Baulkham Hills and Kellyville, plus the Eastern Suburbs, Inner West, Lower North Shore, North West Sydney, Northern Beaches, South West Sydney and Western Sydney.
Contact Modest directly. He will give you an honest answer and point you in the right direction.
