How to Allocate a Bathroom Renovation Budget Line by Line

The first mental adjustment is accepting the labour share. A full bathroom renovation touches at least six trades, demolition, plumbing, electrical, carpentry, waterproofing and tiling, plus glazing, painting and installation work. Across a typical project, labour and trade services commonly absorb 45% to 60% of the total, before a single tile or tap is purchased.

• Why the labour share is high: Bathrooms are the densest trade environment in the house. Every trade returns at least twice, rough-in and fit-off, and each stage must be sequenced and inspected.
• Why this matters for planning: If your total budget is $32,000, the realistic materials-and-fixtures envelope is roughly $13,000-$17,000, not $25,000. Selections made against the wrong envelope guarantee a mid-project crisis.

Owners comparing quotes should also understand that an abnormally low labour component usually signals missing scope, not efficiency. The trades cost what they cost across Melbourne; quotes diverge mainly on what they include.

The shares overlap because projects differ, but the discipline is the point: every dollar belongs to a category before it is spent, and moving money between categories is a conscious decision rather than a drift.

Blown budgets are rarely caused by the vanity costing more than planned. They are caused by whole categories that never appeared in the plan.

• Old-home rectification: Rotten framing behind a failed shower, non-compliant wiring, corroded galvanised pipework. Common in pre-1980s housing across Melbourne, and the single biggest reason the contingency exists.
• Painting and making good: The ceiling, the door, the architraves and the hallway wall the demolition scuffed.
• Door hardware and accessories: Towel rails, robe hooks, toilet roll holders and door furniture in the matching finish; small items that total $400-$900 in a coherent scheme.
• Delivery, storage and protection: Fixtures arriving weeks before installation need somewhere safe to live.
• Living costs: If it is the only bathroom, gym memberships, temporary arrangements or timing the works around a holiday all have real value.

Add these lines to the budget even if the entry is zero, because a zero written deliberately is a decision, while a line that never existed is a surprise.

When the numbers need trimming, cut in the right order. Some categories forgive economy; others punish it for a decade.

• Never cut: Waterproofing, ventilation, plumbing quality and screed falls. These are the room. Failures here cost multiples of the saving and usually take finished tiling with them.
• Cut carefully: Tiling labour quality. A cheaper tiler laying large-format porcelain badly is visible from the doorway forever. Economise on tile price before tiler price.
• Cut freely: Tile unit price (quality mid-range porcelain at $40-$70 per square metre performs like tiles at three times the price), fixture brand tiers, feature-tile quantity, and accessories that can be added later.
• Defer, do not delete: Underfloor heating cannot be added later, but heated towel rails, better mirrors and paint refreshes can. Distinguish between now-or-never items and upgrade-later items.

A useful discipline is the one-feature rule: choose the single element that will carry the room, a stone benchtop, a fluted vanity, a feature niche wall, fund it properly, and keep everything else calm and mid-range. Rooms designed this way look more expensive than rooms where the budget was spread thin across ten small upgrades.

Contingency is not padding; it is the acknowledgment that no one can see inside a wall before demolition. For post-2000 homes with known plumbing, 8% is usually adequate. For pre-1980s homes, or any bathroom showing water staining, movement cracks or previous amateur work, hold 10-15%.

• Spend it only on discoveries: Hidden damage, non-compliant services, structural surprises. The moment contingency starts funding upgraded tapware, the protection is gone.
• Release it late: If demolition and rough-in pass without surprises, most of the risk has expired. Releasing unspent contingency into finishes at that point is safe; releasing it at selection time is how projects end up unfunded for the real surprises.
• Get variations priced in writing: Victorian domestic building contracts have formal variation processes for good reason. A verbal "we found something, it will be a bit extra" is not a number you can manage a budget against.

Builders read owners quickly. An owner with a managed contingency and a written variation discipline gets treated as a professional client, and the project paperwork tends to rise to match.

When you buy matters nearly as much as what you buy. The allocation survives contact with reality only if selections are locked in the right order.

• Lock before contract: Layout, fixture positions, vanity size and any wall or window changes. These drive the trade scope and therefore the labour half of the budget.
• Lock before rough-in: Every item a pipe or cable serves: tapware (mixers dictate in-wall bodies), toilet type, bath, heated floor decision, lighting plan and shaving cabinet (for recessing and wiring).
• Lock before waterproofing: Niche sizes and positions, screen type and hob decisions.
• Flexible late: Mirrors, accessories, paint colour and hardware, provided finishes were decided as a family early.

Late changes are the silent budget killer because they arrive as variations priced without competition, and they often cascade: a changed mixer needs a different in-wall body, which needs the waterproofed wall reopened, which needs the membrane redone. The allocation table above assumes decisions made once; every reversal taxes it.

Pulling the threads together, a typical full renovation of a 3m x 2.4m family bathroom in a 1970s Melbourne brick veneer home might allocate: $1,800 demolition, $4,200 plumbing, $2,000 electrical and ventilation, $2,400 carpentry and plaster, $1,600 waterproofing, $4,800 tiling labour, $2,400 tiles, $4,000 fixtures and tapware, $2,600 vanity and shaving cabinet, $1,400 glazing, and $3,000 contingency held against a fifty-year-old wall cavity nobody has seen. Total: $30,200 committed, with the contingency completing the envelope.

Notice what that allocation buys: a compliant, certificated, properly ventilated room with mid-range finishes and one funded feature, not a showroom fantasy. That is what real budgets do. They convert a single intimidating number into forty small honest ones, and in doing so they turn every later conversation, with builders, with suppliers, with your own preferences, into a decision you can actually make.