Split level homes get quoted at somewhere around ten to fifteen per cent above the same house built flat. I've used that figure myself in early conversations because it's roughly right and people want a number. It's also close to useless, because on the block where a split level makes sense, the flat version of that house doesn't exist at a sensible price. To build it flat you'd be cutting into the high side, retaining what you cut, importing fill for the low side and retaining that too. Price both properly and the split is often the cheaper house, not the dearer one.
So the real question isn't what a split costs. It's how many levels, how far apart, and where the stairs land, because those three decisions set the budget and they get made in about twenty minutes of the first design meeting.
I've written separately about building on a sloping block in the Illawarra, which covers the choice between cut and fill, split level and pole construction, and what slope adds to site costs generally. This one assumes you've landed on a split and picks up from there.
Half a level, not a whole one
The thing that separates a split level from an ordinary two storey is the size of the step. A two storey house stacks a full floor above another, so you climb a full flight, usually thirteen to sixteen risers, and the upstairs is a separate world. A split steps by half that, seven or eight risers, and it changes how the house feels more than the drawings suggest.
At half a level you can see and hear between zones. Someone in the kitchen can talk to someone in the lounge three steps down. The house reads as one connected space with definition, rather than two floors joined by a staircase nobody uses socially. That's the actual reason to split, and it's worth saying out loud, because plenty of people arrive assuming a split is purely a slope workaround.
The step height should follow the land. If your block falls about 1.5 metres across the building footprint, one split at roughly that height means you barely move dirt. If it falls three metres, you're either splitting twice or accepting more excavation on one side. Designing the split to match the fall is the whole trick, and a design bought off a plan website was drawn for someone else's fall.
Where the garage goes decides the ground floor
On most Illawarra split levels the garage sits at the lowest point, at street level, because that's where the driveway can meet the kerb without a stupid gradient. Everything else in the plan hangs off that.
Driveway grade is the constraint people underestimate. Council has rules about how steeply a driveway can rise from the kerb and how quickly the grade can change, and a driveway that's legal on paper can still scrape the underside of a car at the transition. On a steep block the garage placement is fixed for you before you've thought about a single room.
Once the garage is set, the entry usually lands on the same level or half a step above it, and the living zone goes on the next level up where the outlook is. Bedrooms take the top. That's the standard arrangement and it works, though it means the front door often opens into a stair landing rather than a room, which some people hate. The fix is a small entry level with a study or a guest room on it, which costs you floor area and buys you a house that doesn't greet visitors with a staircase.
The stairs are not free
Every split you add costs floor area. A half flight with a landing eats roughly four to five square metres by the time you've allowed for the run, the landing and the approach at both ends, and you pay for that twice: once in build cost, once in the useful space you didn't get.
Two splits in a house of about 200 square metres is usually the sensible ceiling. Three starts to feel like a car park ramp, and I've walked through a couple of four-level designs where the owners had stopped using the top zone entirely within a year.
The stairs also have to comply. The National Construction Code sets limits on riser and going dimensions so that steps are consistent and safe, and it requires a barrier wherever you can fall more than a metre, which on a split level includes the edges of the upper floor looking down into the lower one. Volume Two of the NCC is the one that applies to houses. This matters at design stage because a designer who hasn't checked the riser dimensions against the actual floor-to-floor height ends up with an awkward extra step at the bottom, and you live with it forever.
One more thing about short flights: they're the ones people fall on. A seven-riser flight doesn't read as a staircase from a distance the way a full one does. Good lighting at the top and bottom, a consistent tread, and a handrail that people actually reach for. It's not a code question, it's a design one.
What the structure is doing underneath
A split level slab is not one slab. Most of the ones we build are stepped slabs on ground, with the drop between levels handled by a deepened edge beam and retaining, or by a small block retaining wall that the upper slab bears onto. That detail is engineered per site off the geotechnical report, and it's the item that moves most between a gentle fall and a steep one.
Where the drop is bigger, or where the lower level has to be enclosed, you're into a suspended floor over the lower zone, either a suspended slab or a timber floor on a bearer and joist frame. Suspended costs more per square metre than a slab on ground, and it's the point where a lot of split level budgets get away from people. Ask early which of these your design assumes, because the answer changes the number by a meaningful margin. The general shape of new build pricing is in what it costs to build a house in NSW.
Plumbing is the quieter cost. Waste has to fall to a discharge point, and on a split the discharge point is usually at the low end, which means the upper wet areas have longer runs and less fall to work with than they would on a flat floor. Stack the bathrooms and the laundry vertically, or at least keep them on the same level, and you avoid the whole problem.
Living with the levels
Two things are genuinely better on a split, and one is genuinely worse.
Better: zoning. Noise doesn't travel between levels the way it does across an open flat plan, so a media room half a level down from the kitchen is quiet without needing a door. And heating and cooling work more sensibly, because you can condition the living level properly without pushing air through bedrooms you're not using. Warm air still climbs, so the top level runs warmer, which is either a feature or a problem depending on which way your block faces.
Worse: accessibility. Half flights are still stairs, and a house with three of them is a house that doesn't age with you. If ageing in place is on your list, or someone in the household has mobility issues now, put a bathroom and a bedroom on the entry level. It costs area. It's the difference between a house you keep and a house you sell in fifteen years.
Storage is the other one. Splits generate leftover space under the upper floors, and if it isn't drawn in as storage at plan stage, it gets sealed up and lost. I've cut access hatches into finished houses to reclaim those voids more than once, and it's always messier than drawing a door in the first place.
Approval, briefly
Split levels get more attention from council than a flat-pad house does, because the things that make a split work — cut and fill depths, retaining near boundaries, overshadowing from an upper level, wall height measured from natural ground — are exactly what the planning controls limit. That pushes plenty of split level projects onto a full development application rather than the complying development fast path, and the fork is set out in CDC vs DA in NSW. The NSW planning department is where the state controls sit, and your council's own development control plan is where the height and cut-and-fill numbers usually bite.
Narrow blocks are a related but separate constraint, and plenty of blocks around here are both. That's covered in narrow block house designs.
The three conditions
Here's how I'd decide, in order.
Does the fall roughly match one or two half-levels? A block that drops between about one and three metres across the footprint is the sweet spot. Under a metre and you're adding stairs and cost for no structural reason, and a flat design with a single step down to the living area gets you most of the character. Over about four metres and a split stops absorbing the fall on its own, so you're back to serious retaining or a suspended structure, and the economics change.
Is there a view or an aspect worth chasing? The second reason to split is to put the living areas where the light and the outlook are, half a level away from everything else. If your block has no meaningful outlook and the good sun is on the same side as the entry, a well-planned single level on a cut pad is a better house and a cheaper one.
Who's living there in fifteen years? If the answer is you, and you'd rather not be negotiating stairs to reach a toilet, design the entry level to work as a complete small home before you commit to the split. If the answer is that you'll have moved on, this one drops away and the first two conditions decide it.
If the first two both say yes, split it. If only one does, price both and let the numbers argue.
We design and build new homes on split, sloping and awkward blocks across Wollongong, the Illawarra and the Southern Highlands, and you can see how we run those jobs on our new homes page. If you've got a block with a fall on it and a plan you're not sure suits it, send the survey and the drawings through the contact page or call 0434 037 851 and I'll tell you where the levels want to sit.
Want a hand with this at your place? Get a free quote or call 0434 037 851.