Bathroom Refit: Full Scope of Work, Materials List, and Regulations

Summary

A bathroom refit is one of the most common jobs for UK plumbers and bathroom fitters, ranging from a straightforward like-for-like suite swap to a full gut-and-rebuild with relocated services. The scope must be clearly defined at the quoting stage because the hidden work -- tanking, first fix pipework, electrical zones, ventilation -- accounts for a significant proportion of both cost and compliance risk. Plumbing typically represents 40-50% of the total project cost, with the remainder split between tiling, electrics, plastering, and materials. Getting the scope right upfront avoids disputes, protects your margins, and ensures the finished bathroom meets all applicable Building Regulations.

Key Facts

• A standard bathroom refit takes 7-14 working days depending on scope and whether services are being relocated
• The average UK bathroom refit costs £6,000-£12,000 for a mid-range finish; budget jobs start around £2,500 and high-end refits exceed £20,000
• Plumbing labour accounts for roughly 40-50% of total project cost
• Like-for-like suite replacement generally does not require building control notification
• Relocated drainage, new bathroom locations, and all bathroom electrical work require building control sign-off or self-certification via a competent person scheme
• BS 5385-1 (2018) requires all substrates in wet areas to be waterproofed before tiling -- this applies to domestic bathrooms, not just wet rooms
• Part F mandates a minimum extract rate of 15 l/s (54 m³/hr) for intermittent bathroom extractor fans
• All bathroom circuits must be protected by a 30mA RCD per BS 7671

Detailed Guidance

What does a full bathroom refit actually involve?

A full refit follows a strict sequence. Getting the order wrong causes costly rework. The stages are:

1. Strip-Out (Day 1-2)

• Disconnect and remove all existing sanitaryware (bath, basin, WC, shower)
• Remove existing tiling, wall panels, and flooring
• Remove old pipework and fittings if relocating services
• Cap off live services (water, waste, gas if applicable)
• Skip hire for waste removal -- budget 1-2 skips for a standard bathroom

2. Structural and Preparatory Work (Day 2-3)

• Repair or replace floor joists and noggins where required
• Install new stud walls or partition walls if changing layout
• Fit bath/shower formers or level access trays
• Install backer boards (e.g. Hardiebacker, Marmox, Wedi) to shower areas and wet zones

3. First Fix Plumbing (Day 3-4)

• Run hot and cold supply pipework to new positions (typically 15mm copper or PEX push-fit)
• Run waste pipework: 40mm for basin and bath/shower, 110mm soil pipe for WC
• Fit concealed cistern frames (e.g. Geberit Duofix) if wall-hung WC
• Install shower valve bodies for concealed thermostatic valves
• Run central heating pipework for towel radiator or underfloor heating manifold
• Pressure test all supply pipework
• Test waste falls (minimum 1:40 gradient for 40mm waste; 1:80 for 110mm soil)

4. First Fix Electrics (Day 3-4, coordinated with plumbing)

• Run cables for lighting circuits, extractor fan, heated towel rail fused spur, shaver socket
• Run cable for electric shower if applicable (typically 10mm² on 40A MCB for 9.5kW; check manufacturer specs)
• Install back boxes for switches and spur outlets (outside bathroom where possible)
• All work must comply with Part P and BS 7671 bathroom zone requirements

5. Waterproofing and Tanking (Day 5)

• Apply tanking membrane (liquid-applied or sheet) to all wet areas
• BS 5385-1 requires waterproofing of all substrates in wet areas before tiling
• Shower areas: tanking must extend minimum 1,200mm up from tray/floor and 300mm beyond the splash zone
• Wet rooms: full floor and wall tanking required with a bonded sheet membrane or liquid system
• Allow proper curing time before tiling (typically 24 hours for liquid systems)
• Tape and seal all joints, corners, pipe penetrations, and floor/wall junctions with waterproof tape or fleece

6. Tiling (Day 5-8)

• Walls first, then floor
• Use flexible adhesive (S1 or S2 rated) on tanked surfaces
• Use flexible, waterproof grout in wet areas
• Seal all perimeter junctions, sanitaryware edges, and movement joints with silicone (not grout)

7. Second Fix Plumbing (Day 8-10)

• Fit and connect bath, basin, WC, shower tray/enclosure
• Connect all waste traps and waste runs
• Fit taps, shower heads, thermostatic valves, and trim kits
• Connect and commission towel radiator
• Fill, flush, and test all connections for leaks
• Check hot water delivery temperature (max 48°C at outlets per Part G)

8. Second Fix Electrics (Day 8-10)

• Fit light fittings, extractor fan, shaver socket
• Connect heated towel rail to fused spur
• Test and commission all circuits
• Issue Minor Electrical Installation Works Certificate (MEIWC) or full EIC as appropriate

9. Finishing and Snagging (Day 10-12)

• Apply silicone sealant to all sanitaryware edges, bath panels, and shower enclosure
• Fit bath panels, access hatches, mirrors, accessories
• Final clean
• Commission and test everything: run taps, flush WC, test shower temperatures, check extractor fan operation
• Hand over to customer with any warranty documentation

What materials do I need for a standard bathroom refit?

The following checklist covers a typical family bathroom refit. Adjust quantities based on room dimensions.

Sanitaryware

Plumbing Materials

Waterproofing and Tiling Materials

Electrical Materials

Sundries

How do I quote a bathroom refit accurately?

When scoping a bathroom refit for a quote, systematically work through these areas:

1. Establish the brief -- like-for-like swap or full remodel? Same layout or relocated services?
2. Survey the existing room -- measure dimensions, note existing service positions, check floor construction (timber vs concrete), assess condition of joists, walls, and existing plumbing
3. Identify hidden work -- is the existing plumbing lead or galvanised? Are waste runs adequate? Does the floor need levelling or strengthening?
4. Check ventilation -- is there an existing extractor fan? Does it meet current Part F rates? Is there ducting to an external wall?
5. Confirm electrical scope -- what needs doing? New lighting, new fan, electric shower? All need Part P compliance
6. Waterproofing -- will you tank the shower area only, or the entire room? Wet room vs standard tray?
7. Who does what -- are you subcontracting tiling, electrics, plastering? Or quoting for the full turnkey job?
8. Materials supply -- customer-supplied suite (measure twice) or you sourcing? If you source, add 15-25% markup
9. Access and logistics -- ground floor or upstairs? Can you get a bath up the stairs? Where does the skip go?
10. Contingency -- always include 10-15% contingency for hidden problems (rotten joists, asbestos artex, lead pipework)

Day rate benchmarks (2025-2026):

• Plumber/bathroom fitter: £250-£400/day (regional variation; London at the higher end)
• Electrician: £250-£350/day
• Tiler: £200-£350/day
• Plasterer: £200-£300/day
• Labourer: £120-£180/day

What are the first fix and second fix stages?

First fix is all the work that happens behind the walls and under the floor before surfaces are finished. It includes running supply pipework (hot, cold, heating), waste pipework, fitting concealed valve bodies and cistern frames, and pressure testing.

Second fix is everything that happens after walls and floors are finished (plastered, tiled, painted). It includes fitting visible sanitaryware, connecting taps and wastes, fitting shower enclosures, and commissioning.

The critical coordination point is between first fix and tiling. The plumber and electrician must complete all behind-the-wall work before the tiler starts. Returning to first fix work after tiling is extremely costly and disruptive.

How should shower areas and wet rooms be waterproofed?

BS 5385-1:2018 requires that all substrates in wet areas be waterproofed before tiling. This is not limited to wet rooms -- it applies to standard shower enclosures in domestic bathrooms.

Standard shower enclosure:

• Tanking extends minimum 1,200mm above the shower tray and 300mm beyond the shower enclosure perimeter
• Floor of the shower area must be tanked
• All pipe penetrations sealed with proprietary collars
• All internal corners and wall/floor junctions reinforced with tanking tape or fleece

Wet room (level access / no tray):

• Full room tanking required -- floor and walls to full wet area height
• Floor must have correct falls to the drain (typically 1:60 to 1:80)
• Use a proprietary wet room former or create falls in the screed
• Linear drains need minimum 1:60 fall across the full floor width
• Sheet membrane or multi-coat liquid membrane system
• Must comply with BS 5385-4 for wet room installations

NHBC guidance (November 2024 update):

• Full tanking is mandatory for wet rooms and power showers (flow rate 12 l/s or greater)
• Standard showers with lower flow rates have reduced requirements, but BS 5385 compliance is still best practice

Common tanking products:

• Liquid applied: BAL Tank-it, Mapei Mapelastic AquaDefense, Ardex S7
• Sheet membrane: Schluter DITRA/KERDI, Impey WaterGuard
• Always follow manufacturer instructions for coat thickness, cure times, and number of coats

What ventilation does Part F require?

Approved Document F (2021 edition, current for England) sets minimum extract rates for bathrooms:

Intermittent extract ventilation (standard extractor fan):

• Minimum 15 litres per second (54 m³/hr)
• Fan must have an overrun timer (minimum 15 minutes after the light is switched off)
• If the bathroom has no openable window, the fan must be capable of running continuously or have a humidistat

Continuous mechanical extract ventilation (MEV/MVHR systems):

• Minimum 8 litres per second (29 m³/hr) continuous background rate
• Boost rate of 13 l/s when bathroom is in use

Practical requirements:

• Fan must duct to an external wall or through the roof -- never into a loft space, soffit, or internal void
• Ducting should be as short and straight as possible; each 90-degree bend reduces effective output
• Use rigid ducting where possible (flexible ducting has higher resistance)
• External wall grille with backdraft shutter to prevent draughts
• For internal bathrooms with no external wall, consider inline centrifugal fans with longer duct runs

Building control: Replacing a like-for-like fan to the same spec does not need notification. Installing ventilation where none existed, or as part of a new bathroom, is notifiable.

Frequently Asked Questions

Do I need building control sign-off for a bathroom refit?

It depends on the scope. A straightforward like-for-like suite replacement with no changes to drainage layout or electrics generally does not require building control notification. However, you will need sign-off if you are: installing a bathroom in a new location; relocating the WC or changing the drainage layout; carrying out any electrical work (Part P) unless self-certified through a competent person scheme (NICEIC, NAPIT, ELECSA); or making structural changes such as removing walls. If your electrician is registered with a competent person scheme, they can self-certify the electrical work and issue the certificate directly without involving building control. Always clarify this at the quoting stage so the customer knows what certificates they will receive.

How long does a full bathroom refit take?

A like-for-like suite swap with no tiling changes takes 2-3 days. A full strip-out and refit with new tiling, relocated services, and new electrics takes 7-14 working days depending on room size, complexity, and how many trades are involved. Allow extra time if you discover rotten joists, lead pipework, or asbestos materials during strip-out. Build realistic timescales into your quote -- rushed bathroom jobs lead to leaks, callbacks, and unhappy customers.

What is the maximum hot water temperature allowed at bathroom outlets?

Part G of the Building Regulations requires that hot water to baths is delivered at no more than 48°C to prevent scalding. This is typically achieved with thermostatic mixing valves (TMVs) fitted to bath taps. Basin and shower outlets should also be thermostatically controlled. TMV2 valves are the standard for domestic bathrooms; TMV3 is required for healthcare and care home settings.

Can I install a socket in a bathroom?

Standard 13A sockets are not permitted inside a bathroom. The only socket permitted is a shaver socket complying with BS EN 61558, which contains an isolating transformer. This must be installed outside Zone 2 (more than 0.6m from the bath/shower perimeter and above 2.25m, or outside the room entirely). Fused spurs for towel rails should ideally be located outside the bathroom. If they must be inside, they must be outside Zone 2 and RCD protected.

Regulations & Standards

• Approved Document F (Ventilation) -- Minimum extract rates: 15 l/s intermittent or 8 l/s continuous for bathrooms. Fan overrun timers required. Ducting must terminate externally. [2021 edition, current for England]

• Approved Document P (Electrical Safety) -- All bathroom electrical work is notifiable to building control unless self-certified by a registered competent person. Covers design, installation, inspection, and testing of electrical installations

• Approved Document G (Sanitation, Hot Water Safety) -- Maximum 48°C at bath outlets. Requirements for unvented hot water systems, adequate drainage, and sanitary provision. [Updated 2024]

• Approved Document M (Access to and Use of Buildings) -- Relevant for new-build and accessible bathroom installations. Category 2 dwellings require level access showers (minimum 1200x1200mm) and wheelchair turning circles (1500mm diameter)

• BS 7671:2018 (IET Wiring Regulations, 18th Edition) -- Defines bathroom zones (Zone 0, 1, 2) and IP rating requirements. Zone 0: SELV max 12V, IPX7. Zone 1: IPX4 minimum, up to 2.25m above bath/shower. Zone 2: IP44 minimum, 0.6m beyond Zone 1. All bathroom circuits require 30mA RCD protection (Regulation 411.3.3)

• BS 5385-1:2018 (Wall and Floor Tiling) -- All substrates in wet areas must be waterproofed before tiling. Tanking must extend 1,200mm above shower base and 300mm beyond splash zone

• BS 5385-4 (Wet Room Installations) -- Full tanking requirements for wet rooms including floor falls and drainage

• NHBC Standards Chapter 9.2 (Tiling Showers and Bathrooms) -- Updated November 2024. Full tanking mandatory for wet rooms and power showers (12+ l/s flow rate)

• Water Supply (Water Fittings) Regulations 1999 -- Requirements for backflow prevention, air gaps, and compliance of fittings in contact with drinking water (WRAS approved)

• Planning Portal - Kitchen and Bathroom Building Regulations

• Approved Document G: Sanitation, Hot Water Safety (2024 amendments)

• Approved Document F: Ventilation (2021 edition)

• LABC - When does a replacement bathroom need building regulations approval?

• BS 5385-1 Waterproofing Regulations - The Wetroom Store

• NHBC Technical Guidance 9.2: Tiling Showers and Bathrooms

• BS 7671 Bathroom Zones - ProCerts Software

• Selco - First Fix vs Second Fix Electrics in a Bathroom

• MyBuilder - New Bathroom Cost Guide 2026

• FMB - Bathroom Renovation Costs Breakdown

• MML Plumbing - First Fix and Second Fix Plumbing Explained

• GOV.UK - Building Regulations Approval

• waste pipes — Waste pipe sizing for bathroom installations

• bathroom zones — Electrical zones in bathrooms (BS 7671)

• building control — When building control sign-off is needed

• wet rooms — Wet room tanking and drainage requirements

• hot water safety — TMVs, Part G compliance, and scalding prevention

• extractor fans — Bathroom ventilation and Part F compliance