Mistakes 1–5: budgeting and planning
1. Comparing quotes by total only. The cheapest quote is often the one that's missing things. Always compare line-item breakdowns.
2. Not allowing a contingency. Add 10–15% to your budget for what's behind the tiles. Period and 1930s properties: 20%.
3. Picking the suite before the layout. Decide what fits where first, then choose models that fit those positions.
4. Skipping the survey. A 30-minute survey identifies issues that turn into £2,000 surprises mid-job.
5. Letting the fitter bring random tradespeople. Insist on knowing who's doing the electrics (Part P) and gas work (Gas Safe). Get the certs after.
Mistakes 6–10: spec and finish
6. Cheap silicone. The £4 tube fails in 18 months. Spend £12 on a sanitary-grade tube and you forget about it for a decade.
7. Wrong extractor. An undersized extractor causes mould that the £80 saving never recovers. Size to room volume + shower factor.
8. Cheap shower valve. The valve is the part that fails. Brand-name thermostatic valves cost £150–£300 and last 15+ years. £40 valves last 2–3.
9. Mosaic floors. They look great in showrooms and they're a nightmare to clean and seal in real life. Use a single large tile if you can.
10. No isolation valves. Every appliance should have one. Adding them later means cutting open your finished walls.