Hire a bathroom fitter when…
- The room stays the same size
- You are re-tiling, re-plumbing and swapping sanitaryware
- You want a wet room within the existing space
- You need it done fast (1–3 weeks)
- No walls are being moved or removed
Compare Guide · Updated July 2026
Bathroom Fitter vs Extension Builder: Which Should You Hire in 2026?
The rule of thumb is simple: hire a bathroom fitter if you are refurbishing within your existing walls, and hire an extension builder if you are adding new floor space. A bathroom fitter is a finishing specialist (£4,000–£12,000 for a typical refit); an extension builder is a structural contractor who can add a downstairs WC, en-suite or bathroom extension (£15,000–£40,000+). This guide compares scope, cost, timeline and the exact scenarios where each trade wins.
Scope & skill comparison Cost & timeline side-by-side Decision checklist
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Reviewed by the BestBuilders editorial team on 2 July 2026. Cost ranges and trade scopes verified against current Q3 2026 UK market data. Editorial standards: /editorial-standards.
⚡ Quick Answer
Bathroom fitter or extension builder — which do I need?
Choose a bathroom fitter when the room already exists and you are re-tiling, re-plumbing and re-fitting within the same footprint. Choose an extension builder when you are creating new space — a bathroom extension, a knock-through, or adding an en-suite where there is currently no room.
For a hybrid job (extend, then fit out) an extension builder usually project-manages the shell and brings in a bathroom fitter for the final fit — or you hire both and coordinate the handover yourself.
Bathroom Fitter vs Extension Builder: Head to Head
Two different trades for two different jobs. Here is how they compare across the factors that matter.
| Factor | Bathroom Fitter | Extension Builder |
|---|---|---|
| Core job | Refit within existing walls | Add new structural floor space |
| Typical scope | Strip out, plumbing, tiling, sanitaryware, electrics | Foundations, walls, roof, glazing, then fit-out |
| Typical cost | £4,000–£12,000 | £15,000–£40,000+ |
| Timeline | 1–3 weeks | 8–16 weeks |
| Planning / Building Regs | Building Regs for drainage & electrics only | Full Building Regs; often planning or PD |
| Best for | Same-size bathroom upgrade or wet room | New bathroom, downstairs WC, or larger footprint |
Hire an extension builder when…
- You are adding a new bathroom or en-suite
- You need a bathroom or utility extension
- Structural walls are being removed
- The project needs foundations and a roof
- You want one contractor to manage the whole build
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Bathroom Fitter vs Builder FAQ
Can a bathroom fitter build an extension?+
No. A bathroom fitter is a finishing specialist covering plumbing, tiling, sanitaryware and second-fix electrics. Adding floor space needs foundations, structural walls and a roof, which is the domain of an extension builder. If your project involves any new structure, hire a builder and let them bring in a fitter for the final fit-out.
Is a bathroom fitter cheaper than a builder?+
Yes, for a like-for-like refit. A bathroom fitter charges £4,000–£12,000 for a full refurbishment within existing walls. An extension builder starts around £15,000 because you are paying for structure, not just finishes. They are not really competing on price — they do different jobs.
Who do I hire to add a downstairs toilet?+
It depends on the location. Converting an existing understairs cupboard or utility space is often a job a bathroom fitter or general builder can handle. Adding a WC that needs a small extension or moving a load-bearing wall needs an extension builder. Get quotes from both and compare scope.
Do I need planning permission either way?+
A same-footprint bathroom refit needs no planning — only Building Regulations for drainage and electrics. A bathroom extension may fall under permitted development or need full planning depending on size and location. Your extension builder can advise on the right route.
Can I hire both on the same project?+
Yes, and it is common. The extension builder constructs the watertight shell and first-fix, then a specialist bathroom fitter completes the tiling and sanitaryware. Agree the handover point in writing so both parties know who is responsible for what.