Home Extensions Brisbane Northside
You’ve outgrown your home, but you don’t want to give up your street, school zone or neighbours. That’s where we come in. James Marsden Builders specialises in home extensions, major internal renovations and bathrooms on Brisbane’s northside, typically on projects between $100,000 and $1,000,000.
We’re a small builder–carpenter team: two builders on the tools and one apprentice. No salespeople, no handballing. Just the people who quote your job, build your job.
More space, better layout, without leaving the suburb you love.
The kinds of extensions we build
We focus on extensions that add real living space and value:
Ground‑floor extensions for larger kitchens, living and dining areas
Second‑storey additions for extra bedrooms, bathrooms and parents’ retreats
Under‑house / downstairs conversions where structure allows
Decks and outdoor living spaces that tie into the main house
From new foundations and framing through to final paint and handover, we take care of the lot under a fixed‑price contract.
Why extend instead of move?
For many northside families, extending makes more sense than selling and buying again:
Stay in the same school catchment and community
Avoid stamp duty, agent fees and moving costs
Customise the layout to how your family actually lives
Add significant value to a home you already like
Our job is to help you work out what’s possible on your block, what it’s likely to cost, and how long it will take.
Our Extension Design & Costing Pathway
To price an extension properly we need a set of scaled plans. So we break the process into two clear stages to save you from spending thousands too early in the wrong direction.
1. Get your plans done with the right people
If you don’t already have plans:
We’ll introduce you to building draftsmen and architects we trust who specialise in extensions.
You work directly with them to design your extension and get a set of plans that suit your home, budget and block.
At this stage you’re only paying for plans, not full engineering and certification. Those later stages can easily add $6,000+ depending on project size, so it makes sense to get the layout right first.
We can’t provide a detailed costing until there are proper plans to work from.
2. Pre‑Construction Costing Package
Once you have plans, we offer a paid pre‑construction package where we:
Complete a detailed take‑off and fixed‑price quote for your extension
Review buildability and flag any obvious cost or complexity issues
Provide an outline program / timeline for the works
Clarify inclusions, exclusions and allowances so there are no surprises
Fee: typically $750–$1,500 depending on project size and complexity
Credit: 100% of this fee is credited back to you if you proceed to build with us.
This way, before you commit to engineering, approvals and construction, you’ve paid for:
A set of plans from a designer we trust
A detailed costing package from us
And you know what your extension is likely to cost before you spend the big money on the next steps.
Why homeowners choose us for extensions
Owner‑led, low volume: We only take on a limited number of projects at a time so we can stay across every detail.
Clear communication: Straight answers on budget, timelines and what’s included. No sugar‑coating.
Quality over shortcuts: We build as if we’re going to live in it – from structure through to finishes.
Waterproofing peace of mind: For bathrooms and wet areas within your extension we use the Wedi waterproofing system, flood‑test showers (and floors where applicable), and back it with a 10‑year manufacturer guarantee.
Kedron Project
Our team extended off the existing rear deck to create a new wellness room and walk‑in robe, tying the addition seamlessly into the original roofline and floor levels. Inside, we completely updated the main bathroom and separate toilet, including new fixtures, tiling and waterproofing using our Wedi system with full flood testing. The result is a much more functional master suite and upgraded wet areas, without the clients needing to move or change the character of their Kedron home.
Timeframe
10 Weeks
Year
2025
How The Process Works
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You contact us through the website or by phone with a brief outline of your project and location.
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We send you a short online questionnaire to get the key details: what you want to do, rough budget, timing and who’s living in the home during works. This helps us see if the project is likely to be a good fit.
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Once we’ve reviewed your answers, we book a phone call to talk through your project in more detail, answer initial questions and explain how we work. If it’s not the right fit, we’ll tell you straight and point you in a better direction.
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If you already have plans:
We enter into our paid Pre‑Construction Costing Package.
We complete a detailed take‑off and fixed‑price quote for your project.
This typically takes 4–6 weeks, depending on size and complexity.
If you don’t have plans yet:
We’ll introduce you to our draftsmen and architects we trust.
Once your plans are complete, we move into the same Pre‑Construction Costing Package.
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When the costing work is done, we sit down together and walk you through:
The fixed‑price construction proposal
What’s included and excluded
Provisional sums & prime cost and allowances
The proposed schedule for your project
You’ll have time to ask questions and make any final tweaks before moving to contracts and approvals.
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Once you approve the proposal:
We prepare and sign the building contract.
Your pre‑construction fee is credited back to you with cash into your bank account
We lock your project into our schedule and outline the next steps for approvals and site start.