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Seven in ten expect to spend under £10k while one in five think the work can be done in a week.

Many homeowners may be underestimating both the cost and complexity of renovating a bathroom, with new research showing most expect projects to be cheaper and quicker than builders say is realistic.

According to the latest Omnibus Survey from the Federation of Master Builders (FMB), 71% of UK adults expect a bathroom renovation to cost under £10,000, with more than a quarter (26%) believing the work will cost less than £5,000. At the same time, 19% think the project can be completed in a week, while nearly two-thirds expect the work to be finished within a fortnight.

Builders say those expectations rarely match the reality of modern renovation projects, where skilled labour and technical preparation account for a significant share of both the timeline and the budget.

The research also highlights a knowledge gap about where renovation costs typically sit. While 38% of respondents correctly identified labour as the most expensive element of a bathroom renovation, many still assume fittings or fixtures represent the largest expense.

In practice, much of the work involved happens behind the walls. A typical bathroom renovation can require coordination between multiple trades, including plumbers, electricians, tilers and joiners, alongside waterproofing, structural preparation and finishing work. Tasks such as tanking, plumbing installation, electrical checks and adhesive curing times mean most projects take between two and four weeks, and sometimes longer in older homes.

Brian Berry, CEO of the Federation of Master Builders, says, “Too many homeowners start a renovation with an unrealistic picture of how long it will take and what it will cost and that’s where things start to go wrong.”

The FMB adds that misunderstanding the scale of building work can also leave homeowners vulnerable to poor workmanship or rogue traders. Industry estimates suggest £14.3 billion has been lost to rogue traders over the past five years, often in cases where homeowners did not fully understand the work involved before hiring a contractor.

Builders say a large share of a bathroom renovation budget usually goes towards skilled labour. In a typical project, labour can account for around 40–50% of the total cost, followed by fittings such as baths, showers and basins (20–25%), plumbing and electrical work (15–20%), and tiles and finishing materials (10–15%).

Barry explains, “At the show, our members will be on hand to give free, one-to-one guidance on exactly the kind of questions people should be asking before work begins: how to build a realistic timeline and budget, what a proper quote or contract should include, and how to find the right builder for the job. FMB members are held to rigorous standards and independent inspections, so visitors can find out what that means in practice and why it matters. If you’re planning a project, talking to the right people early is the single best thing you can do to protect yourself and your home.” 

Visitors will be able to speak with experienced builders at the FMB Advice Centre, where they can discuss renovation plans and learn what a professionally managed project involves, from early planning and budgeting through to installation and finishing.

Alexandra Powell, of Alexandra Powell Design & Construction, an FMB member, said: “We’re proud to be representing the FMB at the show. It’s a fantastic opportunity to help homeowners understand what makes a well-planned, beautifully delivered project possible and to reinforce why standards matter.” 

Harry Fanshawe at TW Build added: “This is my second year supporting the FMB at the Homebuilding & Renovating Show. It’s brilliant to meet so many engaged homeowners, share insights, and help them move their plans forward with confidence.” 

Charles Okell, another FMB member expert, said: “It’s like project speed dating focused, productive chats where you can quickly help people refine their ideas and expectations. It’s one of the most rewarding events in the calendar.”