Bathroom Renovation Guide: Complete Planning and Cost Breakdown

Understanding the True Cost of Bathroom Renovation in 2026

Bathroom renovations consistently rank as one of the most valuable home improvements in the UK, returning approximately 60-70% of your investment when you sell. But they’re also one of the most complex projects, involving multiple trades working in a confined, moisture-prone environment.

The reality? Most homeowners underestimate both the cost and complexity. In our experience working across Kent, bathroom projects nearly always uncover hidden issues — from dated plumbing that needs replacing to joists weakened by decades of water damage.

Average Bathroom Renovation Costs by Size and Specification

These figures include all labour and materials for a complete renovation: removal of old suite, plastering, tiling, new suite installation, electrical work, plumbing, ventilation, and decoration. They assume you’re working with standard layouts — moving soil pipes or knocking through walls adds £2,000-£5,000 to any project.

The Five Critical Planning Stages

Successful bathroom renovations follow a methodical planning process. Skip stages, and you’ll pay for it — literally — with delays, budget overruns, and substandard results.

Stage 1: Design and Layout (2-3 Weeks)

Start with measurements and photographs. You need accurate dimensions including:

• Floor-to-ceiling height at multiple points (many UK properties have uneven floors)
• Window positions and sizes including sill depth and reveal measurements
• Door swing direction and required clearance
• Exact locations of existing waste pipes, water supply, electrical outlets, and radiator connections
• Structural features like boxing, bulkheads, or sloped ceilings

Professional bathroom designers charge £300-£800 for a full design service, but many retailers like Wickes offer free design consultations when you purchase your bathroom suite through them. This can save money, though you’re limited to their product range.

Stage 2: Building Regulations and Planning (1-2 Weeks)

Most bathroom renovations don’t require planning permission unless you’re extending or converting a loft. However, Building Regulations approval is mandatory for any work involving:

• New or relocated drainage connections
• Electrical work in wet areas (Part P compliance)
• Structural alterations
• Ventilation changes
• Waterproofing in new-build or major alterations

Your local authority building control or an approved inspector will need to inspect the work. Factor in £300-£600 for building control fees, payable in two stages: plan submission and final inspection.

The electrical safety standards introduced in 2020 mean all bathroom electrical work must be completed by a qualified electrician registered with a competent person scheme like NICEIC or NAPIT. They’ll self-certify the work, avoiding separate building control applications for electrics.

Stage 3: Material Selection and Ordering (2-4 Weeks)

Order materials in this sequence to avoid delays:

For plastering specifically, you’ll need moisture-resistant plasterboard (commonly called “green board”) for areas exposed to water splash. British Gypsum’s Glasroc or Gyproc WallBoard are industry standards. Standard plasterboard in a bathroom is a false economy — it’ll fail within 5-10 years even with good ventilation.

Stage 4: Trade Coordination (Critical for Timeline)

A bathroom renovation involves at least five separate trades, often six or seven. The sequence matters enormously:

• Day 1-2: Strip out (general builder or specialist stripper)
• Day 3-5: First fix plumbing and electrical (relocate pipes, install new supply lines, rough in drainage)
• Day 6-7: Carpentry (install plasterboard, boxing, stud walls if needed)
• Day 8-10: Plastering and preparation (skim new boards, render walls if needed)
• Day 11-15: Tiling (walls first, floor second, with 24-48 hour drying between)
• Day 16-18: Second fix plumbing and electrical (install suite, connect taps, fit accessories)
• Day 19-20: Painting, sealing, and finishing touches

In practice, most bathroom renovations take 3-4 weeks because trades aren’t available back-to-back. A good contractor will schedule everyone in advance, but expect 2-3 days between each trade to accommodate drying times and availability.

Plastering Work in Bathroom Renovations

As plastering specialists, we see this aspect overlooked in budget breakdowns, yet it’s fundamental to a long-lasting bathroom. Poor plastering means tiles crack, water penetrates walls, and you’re renovating again in five years.

What Plastering Work Do You Actually Need?

Most bathroom renovations require one or more of these plastering services:

• Plasterboard installation: Replacing old lath and plaster or damaged boards — £250-£400 per bathroom depending on size
• Skim coating: Two-coat finish on new plasterboard or existing walls — £300-£500 for a standard bathroom
• Tanking/waterproofing: Specialist cement-based render systems for wet areas — £400-£700
• Making good: Patching around relocated pipes, filled chases, moved doorways — £150-£300
• Ceiling repair: Often damaged during strip-out when old shower piping is removed — £200-£350

The choice of plaster type matters significantly in bathrooms. Standard gypsum-based finishing plaster (like Multi-Finish) works fine for ceilings and walls that won’t get directly wet, but areas around baths, showers, and basins benefit from cement-based renders or specialist waterproof backing systems.

The Moisture-Resistant Plasterboard Specification

When we install plasterboard in bathrooms, we use 12.5mm moisture-resistant board as standard. This contains additives that resist moisture absorption — they’re not waterproof, but they significantly outperform standard board in humid environments.

For shower areas specifically, many plasterers now install cement-based backer board (like Wedi, Marmox, or Jackoboard) instead of plasterboard. These are genuinely waterproof and provide a superior substrate for tiling. The cost difference is minimal:

• Standard moisture-resistant plasterboard: £8-£12 per sheet (2400mm × 1200mm)
• Cement backer board: £25-£45 per sheet (same size)
• Installation labour: Similar for both (£150-£250 for a typical shower enclosure)

The additional £100-£150 for backer board in a shower area is money well spent. We’ve replastered countless bathrooms where standard board has failed behind tiles within 3-5 years.

Tanking Systems: Are They Necessary?

Tanking refers to waterproofing systems applied over plasterboard or render before tiling. Products like BAL Tank-It or Mapei Mapegum WPS create a waterproof membrane that protects the substrate even if tile grout cracks or sealant fails.

Under BS 5385-1:2018 (the British Standard for wall and floor tiling), tanking is recommended (though not mandatory) for:

• Shower enclosures and wet rooms
• Bath surrounds
• Areas above baths with wall-mounted showers

Professional tilers typically include tanking in their quotes for shower areas. If your tiler isn’t proposing it, ask why. The additional cost is £150-£300 for materials and application in a standard shower enclosure.

Detailed Cost Breakdown by Trade

Understanding where your money goes helps identify areas to economise without compromising quality. Here’s how a typical £8,000 bathroom renovation breaks down:

This breakdown assumes you’re using a main contractor who coordinates trades. If you project-manage yourself, you can save the contractor’s markup (typically 15-20%) but you’ll spend considerable time scheduling, resolving issues, and ensuring quality standards.

Common Hidden Costs That Blow Budgets

In fifteen years of working on bathroom renovations across Kent, we’ve identified these recurring unexpected expenses that homeowners rarely budget for:

Structural Issues Discovered During Strip-Out

• Rotten floor joists: £500-£1,500 to repair or replace affected sections
• Inadequate joist spacing: £400-£800 to install additional noggins and reinforcement for tile floors
• Poor lintel installation: £300-£700 to install proper lintels above windows
• Damp walls requiring treatment: £600-£1,200 for damp-proofing and re-plastering

Plumbing Complications

• Lead pipe replacement: Now mandatory if discovered — £800-£1,500 for full replacement to boundary
• Incompatible pipe fittings: £200-£400 to upgrade or adapt old imperial pipework
• Poor water pressure: £600-£1,200 to install a pump system for power showers
• Soil pipe relocation: £1,000-£2,500 if you want to move the toilet position significantly

Electrical Upgrades

• Consumer unit upgrade: £400-£800 if your existing fuse box doesn’t have RCD protection (required for bathroom circuits)
• Supplementary bonding: £200-£400 if your property requires additional earthing (common in pre-2008 properties)
• Extractor fan ducting: £150-£300 if existing route is blocked or inadequate

Money-Saving Strategies That Don’t Compromise Quality

Having worked on hundreds of bathroom renovations, we’ve identified these legitimate ways to reduce costs without cutting corners on critical elements:

Smart Specifications

• Keep the existing layout: Moving soil pipes costs £1,500-£3,000. A redesign that keeps toilets in the same position saves substantially.
• Choose mid-range taps and fittings: The difference between budget and mid-range taps is significant (lifespan and reliability), but mid-range to premium is largely aesthetic. Quality brands like Grohe, Hansgrohe, or Bristan offer excellent mid-range products at £80-£150 versus £300+ for premium lines.
• Use larger format tiles: 600mm × 300mm tiles cost slightly more per square metre than 300mm × 300mm, but installation is faster (fewer cuts, less grouting), saving 20-30% on tiling labour.
• Tile half-height only: Full-height tiling looks premium but isn’t necessary except in shower enclosures. Tiling to 1.2-1.5m height and plastering/painting above saves £400-£700 in materials and labour.

Timing and Sourcing

• January sales: Most bathroom retailers heavily discount in January. Planning for a February/March start date lets you access 30-40% discounts on suites.
• Trade accounts: If you’re project-managing, open trade accounts at Screwfix, Plumb Center, and CTD Tiles. Trade pricing saves 15-25% versus retail on materials.
• Consider ex-display suites: Victoria Plum and similar retailers sell ex-display items at 40-60% off. Check carefully for damage, but most are perfect condition.

What NOT to Economise On

Some areas are false economies. Saving here costs more in the long run:

• Waterproofing systems: The £200-£300 saved by skipping tanking costs £3,000-£5,000 when you’re replacing failed tiles and damaged plasterboard in five years.
• Extractor fan quality: A £25 basic fan versus a £80 quality humidity-sensing model seems like a saving, but poor ventilation causes mould, damaged plaster, and health issues.
• Shower valve quality: Thermostatic shower valves from reputable manufacturers (Grohe, Aqualisa, Mira) cost £150-£300. Budget valves at £50-£80 fail within 2-3 years and can scald users when they fail.
• Professional tiling: Bathroom tiling looks deceptively simple but requires precision, especially around outlets and fixtures. DIY tiling rarely matches professional standards and affects the entire room’s appearance.

For context on broader renovation planning, our guide on why renovation projects fail explores common pitfalls that apply equally to bathroom projects.

The Essential Bathroom Renovation Timeline

A realistic timeline prevents the stress of an unusable bathroom for longer than necessary. Here’s how a well-managed project progresses:

This 11-week timeline from initial planning to completion is realistic for most standard bathroom renovations. It includes proper drying times and realistic trade availability. Compressed timelines inevitably lead to compromise — usually in drying times, which causes problems later.

Choosing Between Main Contractor and Project Management

You have two main options for managing your bathroom renovation:

Option 1: Main Contractor (Recommended for Most Homeowners)

Advantages:

• Single point of contact and accountability
• Contractor coordinates all trades and manages the schedule
• Professional dispute resolution if issues arise between trades
• Usually includes warranty on workmanship (typically 12 months)
• Less stress and time commitment for you

Disadvantages:

• 15-20% markup on labour costs for project management
• Less direct control over trade selection
• May use subcontractors you wouldn’t have chosen independently

Cost impact: Adds £1,200-£1,800 to a £7,000 base cost, but saves 30-50 hours of your time coordinating trades.

Option 2: Self-Project Management

Advantages:

• Direct relationships with each trade
• No contractor markup — save 15-20% on labour
• Complete control over quality standards and material choices
• Flexibility to adjust timeline and specification

Disadvantages:

• Significant time commitment (expect 2-4 hours daily during the build)
• You’re responsible for scheduling coordination
• No warranty unless you arrange separately with each trade
• Risk of trades blaming each other if problems arise
• You handle Building Control liaison and inspections

Who this suits: Experienced renovators, retired people with time flexibility, or those with building industry contacts.

Ventilation: The Most Overlooked Critical Element

Inadequate ventilation causes more bathroom plastering failures than any other factor. We replaster bathrooms with mould-damaged walls weekly, and poor ventilation is almost always the root cause.

Building Regulations Requirements

Under Approved Document F (Ventilation), bathrooms require:

• Continuous background ventilation: Minimum 4,000mm² equivalent area (typically provided by trickle vents in windows)
• Mechanical extract: Minimum 15 litres/second (54m³/hour) for bathrooms without windows, or supplementary extraction if windows present
• Overrun timer: Extract fans must run for at least 15 minutes after light switch-off or humidity drops

Don’t be tempted to install the minimum. For a typical 6m² bathroom, we recommend:

• Humidity-sensing fan: Automatically activates when humidity exceeds 60-65% (models like Envirovent Silent-100H or Manrose MG100H cost £70-£120)
• 100mm ducting: Provides better airflow than standard 4-inch ducting
• External venting: Ducting must terminate outside, not into loft space (surprisingly common building control failure)
• Shortest duct run possible: Each 90° bend reduces efficiency by approximately 15%

Quality ventilation protects your plastering investment. The £150-£250 for a proper installation versus a basic fan saves thousands in replastering and remedial work.

The Plastering Drying Time Controversy

The single biggest cause of tiling failures and customer disputes in bathroom renovations is insufficient plaster drying time. Let’s settle this once and for all with proper technical guidance.

Actual Drying Times for Different Plaster Types

These times are minimums assuming good conditions. In winter, with limited heating and ventilation, double these times. A moisture meter reading below 0.5% is the only reliable confirmation that plaster is dry enough for tiling.

For comprehensive detail on drying times and conditions, see our complete guide to plaster drying times.

Frequently Asked Questions

How long does a typical bathroom renovation take from start to finish?

A standard bathroom renovation takes 3-4 weeks of actual work, but you should plan for 10-12 weeks from initial planning to completion. This includes 2-3 weeks design and material ordering, 3-4 weeks actual construction (including necessary drying times between trades), and allows buffer time for trade availability.

The critical path is usually plaster drying time before tiling can commence. New skim coat requires 10-14 days minimum to dry sufficiently for tiling, and this can’t be rushed without risking tile adhesive failure. Projects that compress this timeline to “get it done faster” invariably face problems 6-18 months later when tiles start debonding.

Do I need Building Regulations approval for a bathroom renovation?

Yes, for most bathroom renovations you’ll need Building Regulations approval, though not planning permission (unless you’re extending the property). Building Regs apply to:

• Any new or relocated drainage connections
• Electrical work in wet areas (Part P compliance)
• Structural alterations like removing walls
• New or relocated ventilation systems
• Installation of new heating systems or radiators

Your electrician and plumber should be registered with competent person schemes (NICEIC/NAPIT for electrical, Gas Safe for heating), allowing them to self-certify most work. You’ll still need a building control inspection for drainage and structural work. Fees typically range from £300-£600 depending on your local authority.

What’s the most cost-effective way to renovate a bathroom without compromising quality?

The most effective cost-saving strategy is to maintain the existing bathroom layout — specifically keeping the toilet in the same position. Moving soil pipes costs £1,500-£3,000 and provides minimal functional benefit in most cases.

Other smart economies include:

• Using larger format tiles (600mm × 300mm) which reduce installation time by 20-30%
• Choosing mid-range fixtures from quality manufacturers rather than premium lines — the durability difference is minimal
• Tiling to half-height (1.2-1.5m) except in shower areas, then plastering and painting above
• Shopping during January sales when bathroom retailers discount heavily (30-40% off)

Never economise on waterproofing systems, extractor fan quality, or shower valve quality — these false economies cost far more in repairs within 3-5 years.

Can I tile directly onto new plasterboard or does it need plastering first?

You can tile directly onto moisture-resistant plasterboard in shower areas and other locations that will be fully tiled, but the board joints must be properly taped and the surface primed with appropriate tile primer. Most professional tilers prefer this approach for shower enclosures as it eliminates the plaster drying time bottleneck.

However, for walls that will be partially tiled (common in bathrooms where you tile to dado height), plastering first provides a better finish for the painted sections above. The junction between tiles and paint looks more professional when both meet plaster rather than having tiles against plasterboard and paint above.

In either case, you must use moisture-resistant plasterboard (green or blue board) in bathrooms. Standard ivory board will fail within 5-10 years even with good ventilation. For shower areas specifically, cement backer board provides superior moisture resistance and is worth the additional £100-£150 cost.

What plastering work is typically needed in a bathroom renovation?

Most bathroom renovations require several plastering services. The typical scope includes:

• Plasterboard installation: Replacing old lath and plaster or damaged boards with moisture-resistant specification (£250-£400 labour)
• Skim coating: Two-coat gypsum finish on new boards or prepared walls (£300-£500 for standard bathroom)
• Making good: Patching around relocated pipes, filled chases for new wiring, and areas disturbed during strip-out (£150-£300)
• Ceiling repair: Often damaged during removal of old shower piping or ventilation systems (£200-£350)

Some plasterers also offer tanking/waterproofing services, though this is more commonly handled by the tiler. Budget £500-£750 total for plastering work in a standard family bathroom.

The key specification is ensuring moisture-resistant plasterboard throughout. Our types of plaster guide explains which materials suit different bathroom applications.

How much contingency budget should I include for a bathroom renovation?

Budget a 15-20% contingency beyond your planned spend for bathroom renovations. Unlike other home improvements, bathrooms always hide problems behind tiles and boxing that only become apparent during strip-out.

Common unexpected costs we encounter regularly include:

• Rotten floor joists from decades of water exposure (£500-£1,500 to repair)
• Lead pipes requiring replacement under current regulations (£800-£1,500)
• Inadequate joist spacing for tile floors (£400-£800 for additional reinforcement)
• Damaged lintels or inadequate support above windows (£300-£700)
• Damp walls requiring treatment before re-plastering (£600-£1,200)

On a £7,000-£8,000 bathroom renovation, keep £1,200-£1,500 in reserve. If you don’t need it, excellent — but you’ll likely use at least half. Projects without contingency either compromise on fixes (storing up problems) or cause significant stress when unexpected issues arise.

Should I install underfloor heating in my bathroom renovation?

Electric underfloor heating is an excellent addition to bathroom renovations, providing even warmth and eliminating cold feet on tile floors. The installation cost is relatively modest when you’re already lifting floors and tiling:

• Materials: £200-£400 for a typical 4-6m² bathroom (systems like Warmup or ProWarm)
• Installation: £150-£300 additional tiling labour (adds approximately half a day)
• Electrical connection: £100-£200 if a dedicated circuit is needed

Total additional cost of £450-£900 for a feature that adds genuine comfort and potentially 2-3% to property value. Running costs are minimal — approximately £0.50-£1.00 per day during winter months if used for 2-3 hours daily.

The system must be installed on proper insulation boards (6mm or 10mm tile backer boards with insulation) to prevent heat loss downward. Without insulation, you’re heating the floor structure rather than the room — wasting 40-50% of the heat generated.