What to Sort Out Before Starting a Home Extension

Extensions look simple on paper. Knock out a back wall, push the house another few metres into the garden, and suddenly you've got the kitchen you always wanted. In practice, the projects that go smoothly almost always have the same thing in common: the homeowners did a lot of thinking before the first trade showed up.

The messy ones? They usually skipped that part.

Start with the problem, not the plan

Before you sketch anything, get honest about what's actually wrong with the house. "We need more space" isn't really the problem. The problem is that you're tripping over each other in the kitchen at breakfast, or the kids don't have anywhere to do homework, or you work from home and there's nowhere quiet enough to take a call.

If you skip straight to blueprints without naming the real issue, you can spend six figures and still not fix it. A bigger lounge doesn't solve a storage problem. A second living area doesn't solve a lack of natural light. Nail the underlying issue first, and let the design follow.

Set a budget you can actually live with

Everyone knows extensions cost money. Fewer people plan properly for how much, or where it tends to leak.

The obvious costs

Design fees, council approvals, structural work, materials, labour, and finishes. This is the part most people price up first, and it's usually the smallest source of surprise.

The less obvious costs

Site preparation, connecting services, patching sections of roof or floor that don't line up with the new build, temporary accommodation if you can't live in the house during work, and the inevitable "while we're at it" items. A dated bathroom next to your shiny new kitchen tends to bug you within a month.

Then add a contingency of at least 15 percent on top of the total. Old houses hide things. Once walls come down, you find out what was really behind them, and it's rarely good news.

Get the approvals question answered early

Do you actually need council approval? Sometimes yes, sometimes no, and the rules shift depending on your council, zone, heritage status, and how close you're pushing to boundary lines.

This isn't the sort of thing to guess at. A quick conversation with a private certifier or your local council can tell you whether you're looking at complying development, a full development application, or something more involved because of overlay rules. It affects your timeline, your fees, and sometimes the design itself.

Assume nothing. People who assume "it's my own backyard" have been made to pull down finished work.

Choose the right people, not just the cheapest ones

Three quotes is the standard advice. Three quotes with wildly different scopes is what actually happens. Comparing them ends up feeling like comparing meals at three restaurants where the menus don't overlap.

Ask each builder for a detailed inclusions list. What kind of insulation? What grade of window? Who handles the electrical certification? Who pays for the skip bin? Cheap quotes usually leave things out that the other two included, and those things quietly reappear as variations halfway through the build.

You want to work with trusted home extension specialists who can walk you through the whole scope in plain language and put every assumption in writing. If a builder can't tell you what's included and what isn't, they don't know their own quote, and you don't want to find that out in month three.

Also: talk to their past clients. Not the two glowing references they hand you. Ask to see a job that's twelve months old, and ask that owner what they'd do differently.

Plan how you're going to live during the build

This is the part almost nobody thinks about until week two.

Extensions take months. Sometimes many months. Depending on the scope, you might lose the use of your kitchen, your main bathroom, or a whole side of the house. Dust travels. Tradies start early. You lose your driveway to a skip and a scaffold.

Options generally look like:

• Stay put and set up a small temporary kitchen somewhere else

• Move in with family for a stretch

• Rent short-term nearby

Each option has a cost, both financial and emotional, and none of them are as fun as they sound on week eight. Pick the one you can actually stomach, and factor it into the budget from day one.

Think ten years out, not two

An extension shapes how the house works for decades. Design for the life you'll have, not just the one you have now.

If the kids are little, they'll be teenagers before the extension pays itself off. If you're planning to age in place, does the new layout still work when stairs get harder? If you might sell one day, does adding a fifth bedroom actually match what buyers in your area want?

None of that means overbuilding. It means designing with the next decade in mind, so the space still fits you as your life changes.

The short version

The best time to solve extension problems is on paper, before anyone picks up a hammer. Get clear on what you're really fixing. Budget with your eyes open, contingency included. Sort out the approvals. Choose builders you can trust, and get everything in writing. Have a real plan for the months of disruption. And design for the version of your family that will be living in the house five or ten years from now.

Do the thinking upfront and the build itself starts to feel almost boring, which, when it comes to construction, is exactly what you want.