How to Price a Wet Room: Tanking, Drainage, Tiling and Labour Costs

Quick Answer: A typical UK wet room installation prices between £8,500 and £18,500 in 2026 for a 4–6 m² space — broken down as £4,500–£8,500 fit-only labour over 12–18 working days, plus £4,000–£10,000 of materials including tanking, linear drain, tiles and fittings. The defining cost line is the tanking system: £400–£900 in materials but £600–£1,200 in skilled labour to apply it correctly. Floor falls (1:80 minimum, 1:40 better near the drain) drive subfloor or screed reconstruction in 7 out of 10 retrofits — that's £600–£1,800 of additional structural work. Disabled-adapted wet rooms qualify for VAT zero-rating under VAT Notice 701/7 if installed for a registered disabled occupant.

Summary

A wet room is not a tile job. It's a waterproofing job that happens to have tile on it. The pricing logic that catches generalist bathroom installers out is that 60% of the wet room labour is below the visible surface — sub-floor preparation, falls construction, tanking, drainage routing — and 40% is the visible tile and fittings. Quote the full waterproofing scope, even where the tile is straightforward, or the snagging on a leaked-through wet floor will eat the margin and the installer's reputation.

The architecture decision is binary at survey: level-access tile-direct-to-screed, or low-profile tray with tanking around it. Tile-direct-to-screed gives the cleanest aesthetic and best accessibility but demands the highest construction tolerance — falls of 22mm per metre achieved in screed laid level enough to plane without ridges. Tray-based wet rooms are forgiving but lose the level-access property. Both need full tanking; both need linear drains specified by load and grate tile-finish.

Tradespeople should not price wet rooms unless they've done at least 3–4. The penalty for getting falls wrong (water tracking back to the entry threshold, pooling against the screen) or tanking wrong (water wicking into adjoining rooms) is a tear-out at the installer's expense. Quote for either no liability beyond commercial good practice, or quote for full waterproofing warranty insured through the tanking manufacturer's installer scheme.

Key Facts

Quick Reference Table

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Job type Floor area Architecture Labour days Total fitted
Small en-suite wet room (no level access) 2–3 m² Low-profile tray + tanking 8–12 £6,500–£10,500
Standard wet room (level access, mid-spec) 4–5 m² Tile-direct-to-screed 12–16 £9,500–£14,000
Family wet room (level access, premium tile) 5–7 m² Tile-direct-to-screed 14–18 £12,500–£18,500
Disabled-adapted wet room 4–6 m² Level access, grab rails, accessible vanity 14–18 £10,500–£16,500
Wet room over timber floor (joist strengthening) 4–6 m² New subfloor + tanking 16–22 £13,500–£20,000
Premium wet room (curbless walk-in, multiple drains) 7–10 m² Tile-direct + ramp 18–25 £18,000–£32,000

Detailed Guidance

Falls construction — the line that kills the budget

Achieving 22mm falls per metre across a 1.5–2m run is more demanding than it sounds. Most retrofits over an existing concrete floor need self-levelling compound (SLC) or rapid-set screed with falls cut in. Most retrofits over timber need a new substrate altogether.

Existing subfloor type?
       │
       ├── CONCRETE (slab or beam-and-block, level) →
       │    SLC application
       │    - Prime existing slab
       │    - Apply SLC, working falls in to drain
       │    - £6–£12/m² materials, £15–£25/m² labour
       │    - Total: £85–£200 over a 5 m² wet room
       │
       ├── CONCRETE (slab, sloping wrong way / out of level) →
       │    Cement screed lay-and-cut
       │    - Lay 50mm screed with falls
       │    - Allow 7–14 days drying before tanking
       │    - £25–£40/m² materials, £35–£55/m² labour
       │    - Total: £300–£475 over 5 m²
       │
       ├── TIMBER (joists 200mm at 400mm centres) →
       │    New plywood subfloor + hardibacker overlay
       │    - 18mm marine ply over joists
       │    - 6mm hardibacker tile backer
       │    - SLC for falls
       │    - £45–£75/m² materials and labour
       │    - Total: £225–£375 over 5 m²
       │
       └── TIMBER (joists undersized or rotten) →
            Joist replacement / sistering
            - Strip floor, replace/sister joists
            - New subfloor + falls construction
            - £600–£1,800 additional
            - May trigger structural calc; allow £200–£400 SE fee

Always survey the floor build-up BEFORE quoting. A "wet room over the existing bathroom" routinely costs £600–£1,200 more than expected because the existing tray/tile build-up has to come out and the floor underneath is not what was assumed.

Tanking systems — choose one and follow the spec

Three options dominate the UK retrofit market:

System Application Cost (5 m² wet room) Pros Cons
Cementitious slurry (e.g. Mapelastic, Aquafin) 2-coat slurry brushed/rollered onto primed substrate; tape internal corners £180–£300 materials, £400–£700 labour Tile-bonds directly without primer; flexible enough for timber subfloor Slow application — 2 coats with 6-hour cure between
Polyurethane liquid (e.g. Mapegum WPS, Schluter Kerdi liquid) Single-coat liquid with reinforcing fabric tape at junctions £200–£400 materials, £350–£600 labour Very fast turnaround; full waterproofing in 24 hours Material cost premium; needs specific primer for substrate
Sheet membrane (e.g. Schluter Kerdi, Wedi, Marmox) Glued/bonded sheets with overlapping seams and corner pre-formed pieces £400–£900 materials, £450–£800 labour Best for problem subfloors; most consistent thickness; long warranty Highest material cost; corner detail labour-intensive

Manufacturer installer schemes matter. A Schluter-trained installer can offer a 25-year manufacturer-backed warranty on the tanking; a generalist tiler applying the same products has personal liability only.

Linear drain selection and installation

The linear drain is the single most-visible technical fitting. Specification considerations:

Installation labour: 0.5–1 day for the drain; 1 day for the soil pipe routing if it's not already in place.

Acoustic and waterproofing details

Two pinch points where shortcuts cost money:

  1. Wet room over a bedroom or living room — water on a ceramic floor is loud. Add 8–12mm acoustic underlay (Regupol, Maxitile) under the tanking; £8–£15/m² + 0.5 day. Without this, the homeowner gets every footstep transmitted.
  2. Wet room threshold — a level-access wet room must NOT have water tracking to the doorway. A back-fall toward the drain plus a 50mm wide silicone bead at the threshold is the standard detail.

Disabled-adapted wet rooms — VAT and grants

The single biggest pricing-sensitivity for disabled wet rooms is the VAT zero-rating. VAT Notice 701/7 zero-rates the supply of goods and services to a registered disabled occupant for the purpose of accessibility adaptation. The installer needs:

This is a 20% saving on the gross — £1,500–£3,500 typical on a £7,500–£17,500 install.

The Disabled Facilities Grant (DFG) administered by the local authority adds means-tested grant funding up to £30,000. The DFG application timeline is 6–14 weeks; the installer must be approved by the council before the grant is released.

Premium specification choices

For high-spec wet rooms, the materials line dominates the labour line:

Frequently Asked Questions

Is a wet room better than a walk-in shower?

For accessibility, yes — level access removes the trip risk of a tray lip. For waterproofing risk, the walk-in shower with a low-profile tray is more forgiving because the tray pre-defines the falls. The pricing reflects this: walk-in shower with low-profile tray runs £4,500–£8,500; full wet room £8,500–£18,500.

Why is my quote so much higher than the £4,000 wet rooms I've seen advertised?

£4,000 advertised prices typically refer to the kit (tanking + drain + tray + screen) and assume you're a self-installer with a perfect substrate and no plastering, plumbing reroute or tile work needed. A real-world wet room install includes 12–18 days of skilled labour, full waterproofing, drainage reroute, plastering and tiling — that's why the gross runs £8,500–£18,500.

Can I do a wet room over a timber floor in a 1930s house?

Yes, but the joists need surveying. Joists at 200mm depth or less, especially if undersized or notched, often fail the deflection check for ceramic-tiled floors (max L/360 deflection per BS 5385-3). Sistering the joists or installing a new structural floor is £600–£1,800 of additional work.

How long does a wet room take to install?

Plan for 12–18 working days site time, plus 7–14 days of cure/dry time built into the schedule (screed dry, tanking cure, tile adhesive cure). Total calendar time from strip-out to completion: 4–6 weeks.

Will my wet room leak?

A correctly tanked wet room with linear drain, falls and movement joints does not leak. Leaks happen when (in order of frequency): the tanking is incompletely applied at internal corners or pipe penetrations; the falls run the wrong way or are insufficient; movement-joint silicone fails over time. A 5-year tanking warranty is the minimum the homeowner should be quoted; 25-year manufacturer-backed warranty is achievable with a registered installer.

Regulations & Standards