What does replacing a bath with a shower tray really involve?

Choose the outcome before the product

Decide why the bath is being replaced: easier stepping in, seated washing, space for assistance or simply a different layout. Measure the route from the bathroom door to the shower, the clear entrance when the screen is open and the space beside the WC or basin. A tray advertised as extra-flat can still sit on a raised base after installation.

CEAPAT’s bathing guidance distinguishes the product from the person’s ability to transfer, stand, reach and receive assistance. Check the actual finished threshold, seat position, controls and suitable support locations. For an adaptation, consider an individual home assessment through an appropriate professional or CEAPAT’s accessibility service. Do not promise wheelchair access from the tray’s catalogue dimensions alone.

Ask what is underneath the bath

The installer needs to establish the existing waste location, connection condition and available height for the new trap and route. A flush finish may be impossible without further work, or undesirable if achieving it would interfere with structure or shared services. Ask for the proposed finished floor and tray levels on a simple section drawing before ordering.

The water route must be assessed under the relevant CTE water and drainage provisions, with applicability checked for this intervention. Identify the maintenance access to the trap and connection. A removable screen panel is not a substitute for a serviceable concealed drain. If opening up reveals a damaged communal stack, stop treating the job as a simple product exchange.

Agree the waterproofing and repair boundary

Removing the bath exposes the lower wall and sometimes an unfinished floor. Specify how much old tiling is removed, how the new waterproofing connects with retained construction, which edges are treated and who checks the work before covering it. A narrow decorative tile strip should not conceal an unresolved waterproofing junction.

Ask whether matching tiles are actually available. Price an intentional alternative finish if they are not, rather than promising an invisible patch. Record which existing areas remain outside the work and how damage caused by removal is handled. The electrician should review nearby fittings and outlets after the layout changes: ITC-BT-27 does not treat a shower screen as an electrical-zone barrier.

Compare a complete installed budget

The €150 outside allowance is not a municipal tariff and may not be needed for every job. AEAT’s rules determine whether a particular contractor operation qualifies for 10% rather than 21%. A discounted headline or an old property does not establish the rate.

Check the opening, not only the rectangle

A former 1.7 × 0.7 m bath footprint is 1.19 m². A proposed 1.6 × 0.8 m tray is 1.28 m², yet its extra area says nothing about the clear entrance or safe use. A fixed glass panel, sliding frame, inward-opening door or nearby basin can reduce the useful space. Test the chosen arrangement against the user’s movements before approving the order.

Specify a surface suitable for wet use and cleaning, and request the product information supporting the supplier’s slip-resistance claim. Locate supports on a substrate designed for their loads. A towel rail is not a grab rail. Where seated use or assistance is needed, select the seat, support and screen arrangement as a system; avoid adding them after the clearances have disappeared.

Confirm the local route and the building arrangements

In Madrid, OLDRUAM article 6 exempts certain conservation and replacement work under defined conditions. It does not mean every bathroom alteration is exempt. Tell the professional whether the job changes installation position, affects protected fabric, alters structure or touches shared drainage. A need for street occupation or waste arrangements is a separate question.

Notify the building representative about the intended work and organise water shutdowns, lift protection, carrying routes and noise arrangements. Obtain any necessary approval for common-element intervention before work starts. Ask the installer to price the actual access conditions, including stairs where a lift cannot be used for materials.

Keep changes and downtime visible

Request the sequence for removal, inspection, repairs, installation and commissioning. The installer should specify when the shower can be used under the chosen adhesives, sealants and waterproofing instructions. Do not select solely on an advertised number of hours if the substrate and drain have not been inspected.

If the gross €700 screen selection changes to €950 with unchanged fitting, the increase is €250. Using the €410 reserve leaves €160; preserving the reserve raises total funding from €4,660 to €4,910. A new structural or stack issue is a new scope decision, not automatic permission to spend every euro of reserve.

A short handover checklist

1. Confirm the agreed threshold, entrance and access to controls with the actual user.
2. Have the contractor demonstrate drainage, containment and safe operation through the agreed checks.
3. Check screen movement, fittings, supports and access for maintenance.
4. Obtain cleaning instructions, product documents, invoice and any required installation records.
5. List defects and unfinished repairs in writing, with responsibility and dates.

Keep the before-and-after scope, selections and accepted extras together. Recording costs and payments in Reno Pro can make the small project easier to follow. The best saving is not omitting the waterproofing or screen from the first total; it is buying the intended, usable shower without paying twice for the same work.

Sources, date and scope

• CEAPAT / IMSERSO — Productos de apoyo para la autonomía personal: baño y ducha, pp24–27
• CEAPAT / IMSERSO — Gabinete de Accesibilidad: valoración funcional del domicilio
• Ministerio de Vivienda / Código Técnico de la Edificación — DB-HS Salubridad: HS3, HS4 y HS5
• BOE — Real Decreto 842/2002: REBT e ITC-BT-25/27
• Agencia Tributaria — IVA: obras de renovación o reparación de viviendas
• Ayuntamiento de Madrid — OLDRUAM 6/2022: artículos 6, 7, 8 y anexos I–IV

Sources checked on 19 October 2026. Local procedures and examples concern the city of Madrid unless stated otherwise. IVA explanations concern the territory where that tax applies, rather than the separate tax systems of the Canary Islands, Ceuta or Melilla. Original worked calculations are teaching examples for the stated scope, not market averages or contractor offers.