Why 4 m² does not determine the price
Two bathrooms with the same floor area may need very different work. One keeps its connection points and a sound substrate; another needs demolition, new services and a redesigned shower. The equipment and room condition determine the trades and installation operations, not floor area alone.
Define the result before requesting an estimate: bath or shower, floor-standing or wall-hung toilet, washing machine, water heater, furniture and ventilation. Choose a model or agree clear installation requirements for each fixture. Postponing the choice of a concealed mixer until tiling can mean opening a finished wall again.
Six checks before demolition
- Actual dimensions, height, geometry and door swing.
- Risers, isolation valves, branches and maintenance access.
- Signs of moisture and wall/floor condition: what can remain after inspection?
- Ventilation duct, replacement-air route and future equipment.
- Electrical requirements, lighting, appliances and connection locations: a brief for a qualified specialist.
- Waste removal, protection of common areas and temporary use of another bathroom.
Ask which assumptions cannot be verified until the substrate is exposed. Agree a pause, photographs and separate approval if demolition disproves them. Keep unknowns visible instead of hiding them in “other work”.
Compare the same scope
| Category | Questions to resolve |
|---|---|
| Demolition | Finishes, fixtures, substrate layers, carrying out and disposal |
| Water and drainage | Routes, materials, points, valves, checks and access |
| Electrical work and ventilation | Equipment, routes, connections and specialist trades |
| Substrates and waterproofing | Preparation, system, junctions, penetrations and checks |
| Tiling | Areas, layout, format, cuts, holes, corners and grout |
| Fixtures and furniture | Specific models and a separate installation list |
| Completion | Sealants, small fittings, protection, cleaning and handover |
A waterproofing system needs an agreed specification, not just the name on a bucket. Ceresit documentation separately describes substrates and junctions. The contractor must confirm suitability and checks for your situation; visually even tiling does not prove the quality of the concealed layer.
Tile area: a simple unit check
An illustrative 2 × 2 m room tiled to a height of 2.6 m has an 8 m perimeter. Wall area before openings is 8 × 2.6 = 20.8 m². Subtracting a 1.6 m² doorway leaves 19.2 m² of walls. Adding the 4 m² floor gives 23.2 m² of finishes. This geometry excludes niches, boxing and separate finish types.
Purchase quantity also depends on layout and pack sizes. An illustrative agreed 8% allowance gives 25.056 m² before rounding to whole boxes. This is not a universal wastage standard: diagonal layouts, large formats and complex corners change the result. Waterproofing area and tiling labour use their own agreed measurement boundaries, not automatically the quantity of tiles purchased.
A worked budget with explicit boundaries
| Category | Amount |
|---|---|
| Demolition and waste | 8 000 |
| Pipes and plumbing labour | 14 000 |
| Electrical work | 6 000 |
| Preparation and waterproofing | 4 500 |
| Tiles and tiling | 18 000 |
| Fixtures, furniture and agreed installation | 26 000 |
| Ceiling and ventilation | 6 000 |
| Delivery, fittings and completion | 6 500 |
| Subtotal | 89 000 |
| Illustrative 10% contingency | 8 900 |
| Example limit including contingency | 97 900 |
Each installation belongs in one category only. If the plumber charges fixture installation separately, move that amount out of the equipment category instead of adding it twice. A bespoke shower enclosure, changed opening or expensive mixers can alter the budget. “Fixtures” without a specification leaves that cost unresolved.
Decisions worth checking now
On the layout, check door and drawer openings, whether the washing machine can be removed for repair, and access to traps and mixers. Agree servicing access for concealed cisterns and fittings using manufacturer documentation. Concealing equipment and retaining access are separate requirements.
Ask for the difference between two options, such as keeping the bath and relocating a shower. Compare the whole change: services, substrate, waterproofing, enclosure, tiling and programme. The price of a shower tray or drain alone does not show the full cost of the decision.
Accept stages as well as the finished room
- Before covering services: agreed specialist checks, route photographs and records of accessible connections.
- Before tiling: confirmation that substrates and contracted concealed work are ready.
- Before ordering an enclosure or furniture: final measurements at the required room condition.
- After installation: check fixtures in use with the contractor, maintenance access, doors and supplied parts.
- At completion: defects, equipment documents, warranty terms and final reconciliation with the estimate.
Track scope, cost and payments separately. Tiles you purchase yourself must not remain charged within the crew’s materials as well. Keep approvals with the corresponding stage; the fields guide explains organising work and payments in Reno Pro.
Sources
- Ceresit CL 51: technical sheet — requirements of a particular system, not universal instructions for all materials
- Geberit: spare parts and servicing — the importance of model identification and professional servicing
- Profirem: itemised price-list structure — preparation, tiling and installation are distinct items; not a source for the illustrative figures
Editorial source review: 18 October 2026. The numerical examples were created for teaching; they are not a contractor’s personal quotation. English translation reviewed on 18 October 2026.