Set the layout and supply boundaries
Give bidders a dimensioned plan and a schedule of the WC, basin, shower, taps, drains and accessories. Describe what stays and what is replaced, including substrate preparation and access to shutoffs. This independent Mexico City example renews a small existing bathroom while retaining the main connection positions. Moving a shared drain, structural work and a new water heater are outside its scope.
A labour-only figure cannot be compared directly with an installed bathroom package. Establish who supplies tile adhesive, grout, waterproofing, sanitary fittings, valves and connection accessories. State whether dismantling includes carrying and lawful disposal. If the owner supplies a fixture, agree who checks compatibility before work makes replacement difficult.
Calculate installed area and whole boxes
Assume a 2 m by 2 m room, tiling to 2.3 m, one 0.8 m by 2 m door and no window. The wall area is 8 × 2.3 − 1.6 = 16.8 m²; adding the 4 m² floor gives 20.8 m². A teaching allowance of 10% gives an order target of 22.88 m² before rounding to boxes. The real layout and format determine the required cutting allowance.
| Item | Quantity |
|---|---|
| Net tiled wall area, m² | 16.80 |
| Floor area, m² | 4 |
| Installed tile area, m² | 20.80 |
| Order target with 10% allowance, m² | 22.88 |
| Box coverage, m² | 1.44 |
| Whole boxes | 16 |
| Purchased tile area, m² | 23.04 |
| Invented price before IVA, MXN/m² | 320 |
| Tile purchase before IVA, MXN | 7 372.80 |
Fifteen boxes cover only 21.6 m²; sixteen cover 23.04 m². Purchased spare/cutting material is not automatically extra laid surface for the labour account. Waterproofing has its own drawing and junctions, so do not infer its quantity from the purchased tile area.
Define the layers that will be concealed
Specify suitable substrate preparation, required falls and a compatible waterproofing, adhesive and finish arrangement. The Mexican SikaTop-107 Seal MX sheet shows that substrate, layers and waiting conditions are product-specific; it does not establish one recipe for every bathroom. Ask the installer to verify the chosen system’s suitability and how drains, corners and penetrations are treated.
Arrange checks of altered pipes and electrical work before covering them. Record the appropriate tests and photographs, including access points. Have ventilation assessed against the actual room and installation; a new grille alone does not demonstrate adequate extraction. CONAVI’s technical-document index provides separate installation and maintenance resources, rather than one finish-only approach to the room.
Reconcile the complete bathroom account
All amounts below are invented. The contractor and product subtotal expressly assumes standard-taxable supplies at 16%. For this calculation, IVA is rounded once on that subtotal to two decimals; actual invoicing must follow the supplier’s applicable rules. Technical fees are already final. Bathroom furniture, heating changes and later design alterations are excluded.
| Line | Amount |
|---|---|
| Removal | 4 500 |
| Local plumbing and electrical work | 9 500 |
| Substrate preparation | 3 800 |
| Waterproofing materials and application | 3 500 |
| Tile installation and agreed details | 6 200 |
| Tile purchase | 7 372.80 |
| Adhesive, grout and profiles | 2 200 |
| Sanitary fittings | 12 500 |
| Fixture installation and checks | 3 200 |
| Specified ventilation work | 2 500 |
| Carrying and waste | 1 600 |
| Subtotal before IVA | 56 872.80 |
| Assumed IVA at 16%, rounded | 9 099.65 |
| Final work and purchase amount | 65 972.45 |
| Independent checks, final | 1 500 |
| Fixed planning reserve | 6 600 |
| Funding provision | 74 072.45 |
Price the whole effect of a change
If the same tile format rises from MXN 320 to MXN 350 per m² before IVA, the 23.04 m² purchase increases by MXN 691.20 net, or MXN 801.79 under the assumed tax treatment. With the fixed reserve unchanged, the provision becomes MXN 74,874.24. Confirm whether a different format also changes cutting, adhesive or preparation; the product difference alone may not describe the variation.
For concealed deterioration, request a location record, proposed method, final price and time effect before approval. Separate a new owner request from correction of work already promised. Replace the old allowance or product line when adopting a new one, and keep any credit for returned items visible.
Finish with an evidence-based handover
- Approve layout and fixture models before altering services.
- Record the condition after removal.
- Inspect concealed services and waterproofing at agreed points.
- Retain product identification and instructions.
- Have competent installers demonstrate operation and complete checks.
- Record defects, responsibilities and the final balance.
The completed bathroom should be usable and maintainable, with accessible controls and a record of what is hidden. Link each inspection to its work stage and payment so completion is assessed against more than the appearance of the new tile.
Sources, date and scope
- Sika México — SikaTop-107 Seal MX — ficha técnica 07/2022
- Comisión Nacional de Vivienda — SIESCO — documentos técnicos de vivienda
Checked on 19 October 2026. Local examples concern Mexico City unless stated otherwise. All MXN amounts are invented calculation examples, not market prices or quotations. Each article describes an independent project. VAT is applied only under the example’s explicit assumptions; final amounts already include the applicable tax. Check diagnosis, design, procedures and contract conditions for the individual property with competent professionals.