Price a bathroom, not five square metres of floor
Two 5 m² bathrooms can require very different work. One keeps sound substrates and existing connections; another needs demolition, service alterations and a new shower arrangement. Give bidders a drawing, product schedule and condition record. This independent Warsaw example replaces the finishes and fittings while keeping the main service locations. Structural alterations, a shared riser replacement and a new gas installation are excluded.
Describe the shower, WC frame, basin and storage by model or measurable specification. Record the access panels, valve locations, wall reinforcement, tile layout and finished floor height. Agree who supplies and installs each item. “White installation” or biały montaż should be expanded into an actual list, including sealants, connections, adjustment and testing.
Calculate surfaces and whole packs
Assume a rectangular room 2 m by 2.5 m, tiled to 2.4 m, one 0.8 m by 2 m door and no window. The wall area is 2 × (2 + 2.5) × 2.4 − 1.6 = 20 m². Add the 5 m² floor: 25 m² of finished tiled surface. A teaching cutting allowance of 10% gives 27.5 m² to order before pack rounding; layout and tile format may require a different allowance.
| Calculation | Quantity |
|---|---|
| Net tiled wall area, m² | 20 |
| Floor area, m² | 5 |
| Installed tiled area, m² | 25 |
| Order target with 10% allowance, m² | 27.5 |
| Pack coverage, m² | 1.44 |
| Whole packs required | 20 |
| Purchased tile area, m² | 28.8 |
| Invented gross product price, PLN/m² | 95 |
| Tile purchase, PLN gross | 2 736 |
Twenty packs cover 28.8 m² because 19 packs cover only 27.36 m². The contractor may charge laying labour on the installed area, with separately agreed cuts and details; purchased waste is not automatically extra laid area. Waterproofing has its own specified surfaces and junctions, so its measured quantity need not equal the tile area.
Specify the concealed layers
Ask for substrate assessment, preparation, falls where needed and the selected waterproofing system’s interfaces. Ceresit’s Polish CL51 technical sheet is one manufacturer’s example of a system requiring multiple layers and reinforced junctions and penetrations. The chosen product instructions determine application conditions; this is not a universal drying-time or thickness prescription.
Include inspections before boxing-in pipework and before covering the waterproofing. Ask competent installers to define the appropriate tests and record results. Ventilation must be assessed with the existing building system: a decorative grille or an added fan is not proof of adequate ventilation. PSP guidance also explains why alarms do not replace technical inspection.
Reconcile the whole bathroom budget
All amounts below are invented gross PLN figures with applicable supplier tax included. The tile purchase is the calculation above; laying labour is a separate line. Sanitary fittings include the WC system, basin, tap and shower equipment. Bathroom furniture, heating changes and design changes after approval are excluded.
| Budget line | Amount |
|---|---|
| Removal and substrate preparation | 6 500 |
| Local electrical and plumbing work | 4 800 |
| Waterproofing system and application | 2 200 |
| Tile laying and specified details | 4 800 |
| Tile purchase | 2 736 |
| Adhesive, grout and profiles | 1 100 |
| Sanitary fittings | 7 800 |
| Fitting, sealing and functional checks | 2 500 |
| Waste and carrying | 1 100 |
| Works and purchases subtotal | 33 536 |
| Technical checks outside those packages | 900 |
| Reserve: 10% of works and purchases | 3 353.60 |
| Funding provision | 37 789.60 |
Control changes before ordering
Changing the selected tile from PLN 95 to PLN 115 gross per m² adds PLN 576 to the 28.8 m² purchase, assuming the same packs and no change in laying method. With the reserve preserved, the provision becomes PLN 38,365.60. If the new format needs different cuts, adhesive or preparation, price those changes separately instead of assuming the product difference is the whole change.
Record a discovered substrate defect with photographs, a repair method, a gross price and its schedule effect before approval. An undefined “extra waterproofing” charge is not enough to establish whether the original work was omitted, expanded or corrected.
Accept documented work
- Approve the drawing and fixtures before service alterations.
- Record the condition after removal.
- Inspect concealed services and waterproofing at the agreed points.
- Keep product instructions and photographs of covered work.
- Check drainage, leaks, controls, access and finish with the relevant installers.
- List defects, deadlines and the final account before closing the project.
A tidy bathroom can still lack evidence of its concealed layers. Put the inspection records next to the corresponding stage and payment, so the final review concerns both appearance and the work underneath.
Sources, date and scope
- Henkel / Ceresit Polska — CL51 — polska karta techniczna, 08/2026
- Komenda Główna Państwowej Straży Pożarnej — Czujka na straży Twojego bezpieczeństwa
Checked on 19 October 2026. Local examples concern Warsaw unless stated otherwise. PLN figures are invented calculation examples, not a price list, market average or offer. Each article describes a separate project. Gross figures and VAT apply only under the stated assumptions. Check technical scope, professional qualifications, approvals and support conditions for the individual property.