7 Reasons Your Renovation Budget Overruns (and How to Avoid It)
Ask anyone who has just finished renovating whether it cost exactly what they budgeted, and you will rarely hear yes. That is not a coincidence. Across bathrooms, kitchens and smaller facelifts, the same cost traps show up again and again, and most of them are entirely foreseeable. Here are the seven most common reasons renovation budgets overrun, and what you can actually do about each one.
1. You move the drain, sink or hob
This is the single decision that adds the most cost to a project, on both bathrooms and kitchens. Keeping pipework and drainage where they already are saves you the most expensive plumbing work there is. Move the drain in a bathroom, and the plumber's bill alone can more than double. Same story in the kitchen: the sink and hob cost little to leave in place, and a lot to move.
How to avoid it: Decide whether the layout genuinely needs to change, or whether you just assume it should. See our bathroom price guide and kitchen price guide for real figures on what moving pipework costs in practice, and how much of a full renovation budget the plumber and electrician typically take up.
2. You skip the contingency in the budget
Every price guide in this series lands on the same number: build in a contingency of 10 to 15 per cent, more in older homes. Yet this is often the first thing cut when the budget gets tight before a project even starts, which is exactly backwards, since this is where the surprises turn up.
How to avoid it: Set the contingency aside as its own line in the budget from day one, not as something you add if there is room. Treat it as a fixed cost, not a reserve you hope not to touch.
3. You change your mind mid-project
Switching your tile choice after the tiler has started, or adding an extra socket once the wall is already closed up, is the most expensive way to make decisions. Changes mid-project usually mean something has to be redone, the tradesperson has to stop and come back, or materials already ordered sit unused.
How to avoid it: Lock every choice, from tiles to doors to lighting, before anyone starts work. If you are not sure how something will look, test it digitally before you decide for real.
4. Tiles or waterproofing were worse than expected
A "quick refresh" assumes the tiles, waterproofing and pipework are all in good condition. The trouble is, it is often impossible to know for certain until someone actually opens the wall. Even trade bodies admit there is little solid research on exactly how long bathroom waterproofing lasts in practice, which is why "check the grout and feel for damp" is about as close as you get to a guarantee beforehand.
How to avoid it: Look for signs of damp, cracked grout and loose tiles before you commit to a cosmetic refresh over a full renovation. See our bathroom refresh price guide for exactly what to check, and build in extra contingency if the bathroom is old and has never been renovated.
5. You pick the cheapest quote without checking scope
A low quote is often low for a reason: it includes less. Maybe it leaves out strip-out, waste removal, or the finishing work other quotes have priced in. If you are only comparing the bottom line, you are often comparing apples with pears.
How to avoid it: Ask for an itemised description of what is actually included in each quote, not just a price. Always get at least three quotes, and ask every tradesperson the same questions.
6. You underestimate the electrician and plumber
Kitchen and bathroom retailers advertise the price of units and tiles. What is not in the advert is the electrician and plumber's bill, which is usually the biggest surprise. New circuits, an electric shower, leak protection and moved sockets all sit on top of the price of what you can actually see.
How to avoid it: Expect the electrician and plumber combined to make up roughly a quarter to a third of the total price on a bathroom, a bit less on a kitchen where cabinetry eats a bigger share of the budget. See the detailed cost breakdowns in our kitchen guide and bathroom guide for real figures, and remember both trades' work is notifiable under Part P and needs proper certification.
7. Materials cost more, or you upgraded along the way
It is easy to budget for the cheapest option during the research phase, then change your mind in the showroom. A £100 tap can quickly become a £400 one once you see it in person, and a premium range can cost three times what you first pictured.
How to avoid it: Decide on the standard you actually want before you budget, not after. If you want room to stretch on certain items, build that into the budget from the start instead of discovering it later as an overrun. If you are weighing a full replacement against just swapping doors, our kitchen facelift guide shows how much upgrading the doors, worktop or handles alone can add.
Frequently asked questions
How big a contingency should I build in?
10 to 15 per cent is the standard recommendation for most projects. If the home is older than 20 to 25 years and has never been renovated, 20 to 25 per cent is a safer contingency, since the odds of hidden surprises behind walls and floors rise with the age of the property.
Is it normal for renovations to cost more than budgeted?
It is certainly very common. A 2022 UK Houzz & Home Renovation Trends Study, one of the largest UK surveys of residential renovation activity, found that while 70 per cent of homeowners set an initial budget, only around half of them managed to stick to it. That is exactly why the contingency is not an optional extra caution, it is part of the budget itself.
Which single decision affects the budget most?
Whether pipework and drainage are moved or not. This applies to both bathrooms and kitchens, and it is the one factor that most often decides whether a project lands at the cheap or expensive end of a price range.
Should I choose the cheapest quote?
Not without checking what is included first. A lower quote that leaves out strip-out, waste removal or finishing work can end up costing more than a seemingly higher quote that covers everything.
How do I keep track of the budget while the project is running?
By logging receipts and invoices as they come in, not collecting them in a shoebox until the end. That way you see a budget overrun while you can still do something about it, not after the money is already spent.
Keep the budget under control from the first receipt
This is exactly why Pilt exists. You set the budget, log receipts and invoices as they arrive, and see immediately if a project is heading over budget, instead of finding out once the bills are paid. Combined with tasks and photos in the same place, you get a full picture of the whole project, not just the numbers.
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