If you’re planning a house renovation, you’re probably excited and so you should be!

But before you start choosing paint colours or browsing kitchen taps, there are ten critical steps that will determine whether your project ends in delight or disaster.

I’ve spent thirty years working on country houses and period properties across the UK, and I can tell you: the people who get renovation right are not luckier than the people who get it wrong. They are better prepared.

This isn’t a list of nice-to-haves but the foundations.

Skip any one of them, and you’ll pay for it, usually in time, money, or both.

1. Understand what you’re actually buying before you renovate

You need to know what you own.

This sounds obvious, but you’d be surprised how many people start work before they’ve properly assessed the property.

Get a full structural survey, please!

Not the basic mortgage valuation: a proper survey by a chartered surveyor.

This will flag damp, subsidence, roof condition, wiring issues, asbestos and drainage problems, so all the things that will cost you money once work starts.

If it’s a Listed Building or in a Conservation Area, check what permissions you’ll need.

Listed Building Consent can take months and adds complexity to every decision you make.

2. Set a realistic budget and then add 20%

Please do not ignore this or think you'll make it up on the way: nobody ever does.

Your budget is not what you’d ideally like to spend, it’s what you can actually afford to spend if everything costs more than you thought, which it will.

A mid-range kitchen renovation costs £15,000-£45,000.

A bathroom costs £8,000-£20,000.

An extension?

Budget £2,500-£4,000+ per square metre depending on your part of the country and the specification.

Add 20% contingency on top of your total budget.

That contingency is not optional: it’s the difference between finishing the project and running out of money halfway through.

3. Hire the right professionals in the right order

This is where most people go wrong: they hire a builder first, or they try to manage everything themselves without professional support.

The correct order is:

• An architect or architectural technologist if you need drawings or planning
• A structural engineer (if you’re touching walls, floors or roofing)
• An interior designer or a project management consultant (to specify finishes, coordinate trades, and keep the project on track)
• Builder, via a tender process, once you have drawings and a full, detailed specification

Hiring a builder before you have drawings and a specification means you’re asking them to price work they don’t fully understand; it's asking a lot of a contractor to create something in your head.

If you don't have plans, elevations, electrical and lighting plans you will have vague quotes, hidden extras and arguments later.

4. Specify EVERYTHING before you ask for quotations

Specification comes after function, not before.

Decide what you want the room to do, then specify the materials and finishes that will achieve it.

Don’t browse Instagram for inspiration and hope it all comes together on site: that’s how you end up with mismatched finishes, blow the budget and regret the whole thing.

Write it down! Get it on the drawings and the specification.

• every tap,
• every tile
• every paint colour
• every electrical socket

If it’s not specified, your builder will choose the cheapest, easiest option that gets the job done.

I use a specification document for every project. It can be boring and it takes time but it’s the single most important thing you can do to protect your budget and your sanity.

5. Get three detailed quotations (not estimates which are guesses).

Quotations are commitments.

Ask for itemised quotes from at least three builders.

Every line should be clear:

• materials
• labour
• timescales
• VAT

If it says “kitchen installation: £8,000” with no breakdown, ask for detail.

Compare like with like.

One builder might include plastering, another might list it separately.

Make sure you’re comparing the same scope of work.

And never, ever accept the lowest quote without understanding why it’s low.

Cheap quotes usually mean missing work, cheaper materials or a builder who’s underpriced and will cut corners to stay profitable.

6. Plan for the invisible spend

The things you don’t see: wiring, plumbing, insulation, structural work, will cost as much as the things you do.

Rewiring a house costs £3,000-£8,000 depending on size.

Underfloor heating costs £75-£150 per square metre.

A new boiler is £2,500-£5,000.

Plastering an entire room after the rewiring’s done?

Another £800-£2,000.

These aren’t optional extras, they are the foundation of a functioning home.

Budget for them first, then allocate what’s left to the visible finishes because there's little merit in an expensive paint over poorly plastered walls.

7. Understand PC Sums And Provisional Costs

A PC sum is a Provisional Cost, the placeholder figure your builder has allowed for an item you haven’t specified yet.

For example, your quote might say Bathroom taps: PC sum £500 PC sum

That £500 is not what taps cost. It’s what your builder says they might cost from his merchant up the road.

If you choose taps that cost £800, you pay the difference, but your budget will suffer.

If you choose taps that cost £300, you save £200 so the budget is fiction and you've underplayed another element.

PC sums protect the builder from pricing items they don’t know yet, but they also mean your total quotation isn’t your total cost. Read the small print and understand what’s included and what’s PC.

8. Lock-in lead times early

Supply chains are unpredictable! I think we can be pretty sure of that now given global volatility over the last few years!

A bespoke kitchen can take 12-16 weeks minimum after the drawings have been signed off, so this needs planning six months out.

Natural stone tiles might be 8 weeks.

A custom-made bath could be 10 - 12 weeks.

If your builder is booked to start in six weeks and you haven’t ordered the kitchen, you’ll either delay the project or work around gaps in the schedule, both of which cost money.

Order long-lead items as soon as your specification is locked. Even if that feels early, even if it’s before building work starts.

The lead time starts when you place the order, not when you need the item on site.

9. Plan for disruption

Renovation is disruptive:

• Dust, noise, builders arriving at 7:30am, no kitchen for three months..
• How well will your family tolerate life with a microwave and a kettle for cooking facilities?

If you’re staying in the property during work, plan how you’ll manage.

Can you live upstairs while the downstairs is gutted? The stairs will need to be sealed completely to avoid dust EVERYWHERE! You need every single possession boxed up and in storage.

• Do you need a temporary kitchen setup?
• Where will you store displaced furniture?

If the disruption is too much, factor in rental costs while the work happens.

A three-month rental might cost £3,000-£10,000 depending on location, but it might also save your sanity and your relationship.

10. Accept that things will go wrong, so build slack into the timeline

Renovations seldom run exactly to plan.

• You’ll find something hidden in the walls
• A delivery will be delayed
• A trade will be double-booked
• The weather will be terrible for four weeks in a row

Please, add buffer time into your schedule.

If your builder says eight weeks, plan for ten.

If the kitchen company says twelve weeks, assume fourteen.

The projects that finish on time are the ones where the timeline had breathing room built in from the start.

Key takeaways before you start

1. Get a full survey
2. Set a realistic budget plus 20% contingency
3. Hire professionals in the right order
4. Specify everything in writing
5. Get three detailed quotes
6. Budget for the invisible spend
7. Understand PC sums
8. Order long-lead items early
9. Plan for disruption
10. Build slack into the timeline

Do these ten things, and you’ll avoid the most common renovation disasters.

Frequently Asked Questions

Q: Do I really need a 20% contingency, or is 10% enough?

A: Start with 20%. On a £50,000 renovation, that’s £10,000 set aside for unknowns. Period properties, structural work and listed buildings often hit contingency hard: hidden damp, asbestos, failed lintels. If you finish under budget, you’ve saved money!

If you don’t have contingency and something goes wrong, you’re borrowing or stopping work halfway through: sub-optimal.

Q: Can I hire a builder without an architect if I’m not changing the structure?

A: Yes, if the work is straightforward i.e. a new kitchen, a bathroom refit, rewiring, redecorating.

But if you’re moving walls, adding windows or changing room layouts, you will need drawings.

A builder can’t price structural changes from a sketch on the back of an envelope.

Even non-structural work benefits from a detailed specification document, which an interior designer or project management consultant can provide.

Q: What’s the difference between a quotation and an estimate?

A: An estimate is a rough figure ”I think this will cost around £20,000.”

A quote is a fixed commitment: ”I will do this work for £20,000 plus VAT.”

Estimates can drift or 'recollections may differ'.

Quotations lock in the price, assuming the scope doesn’t change.

Always ask for quotations, not estimates.

Q: How do I know if a builder’s quote is fair?

A: Get three quotes for the same scope of work and compare.

If one is significantly lower, ask why: it’s usually missing work, cheaper materials or an underpriced job that will cause problems later.

If one is significantly higher, ask what’s included: this might uncover items others listed as extras.

A fair quote comes with clear breakdowns.

Q: Should I stay in the house during renovation or move out?

A: It depends on the scale.

A kitchen refit while living upstairs is potentially manageable, depending on who is having to manage and for how long.

A whole-house renovation with structural work, rewiring, and plastering is brutal to live through.

If you have young children, pets, or health issues affected by dust, moving out will be worth the cost. Budget at least £1,000-2,000 per month for a rental depending on location and size.

Full Video Transcript

[00:00:00] 10 mistakes to avoid when renovating your home. After 30 years designing renovations for financially sophisticated clients, I can tell you the same 10 mistakes destroy every project. Most people make at least seven of them. Every one of them is predictable and everyone is avoidable. Here is mistake number one:

[00:00:17] starting with shopping instead of scope.

[00:00:19] You start by booking a builder and buying things before you've worked out what you are actually trying to achieve.

[00:00:25] This is the equivalent of booking a flight before you've decided where you want to go on holiday. You wouldn't plan a holiday that way, and you shouldn't plan a renovation that way, either. The correct sequence is to define the outcome first, then build the plan to get there. What does the end state look like? A new kitchen, another bedroom, more space, a contemporary feel throughout a complete redecoration.

[00:00:47] Work that out first and then work backwards from there. The mistake most people make is starting with Pinterest boards and Instagram saves, choosing tiles and taps and furniture before they've even defined the use. You see a table you like, fine, but have you worked out the size of the table that will fit ..the finish ...the shape?

[00:01:06] How many people you need to seat regularly or occasionally at Christmas? Where does it go? Specification comes after function, not before. Start with the vision, not the shopping list.

[00:01:18] Mistake two: the budget conversation you are avoiding.

[00:01:21] You haven't had an honest conversation about money. The conversation begins with yourself and involves anyone else involved with the project from a financial perspective.

[00:01:31] How much money do you actually have? I'm not talking about aspirational money, not 'when the bonus comes through' money. Liquid capital that you can deploy when the project starts. If the money is in a bond maturing in a year, that affects the timeline. If it's an inheritance that hasn't materialised yet, the project has to wait.

[00:01:48] You need to know when the capital appears, because that determines when the work starts. What's the maximum you're willing to spend? I'm talking to the nearest £1000. What's the figure that if you exceed it, your lifestyle changes?

[00:02:03] I'm not talking about genuine hardship. I'm talking about the point where you can't go to the cinema or take a weekend away. You can't do the things you normally do. This figure is your maximum spending, and it includes the contingency. The contingency isn't the buffer that takes you into hardship. The contingency is the maximum ceiling then you've got to plan for breaks, build holiday into the budget. Build in a weekend away per month. if you are living with family during the work and at least one week per quarter, if it's a long-term project, this isn't indulgence, it's sanity and survival. You need breathing space.

[00:02:41] Budget for it now, or pay for it later in stress and mistakes.

[00:02:45] Mistake three: skipping the survey. You don't commission a proper survey.

[00:02:49] If you are buying the property, you will need a full structural survey, not a valuation, not a home buyer's report. A structural survey will tell you what's actually wrong with the building. If you already own the property and you're planning major works the same applies. Commission a survey to find out what you are actually working with before you start.

[00:03:08] Surveys can cost maybe £500 or up to £2000 pounds, it obviously depends on the size of the property. That's cheap insurance against discovering structural problems halfway through a £200,000 pound renovation. The survey will tell you whether the walls are solid, whether the roof needs replacing, whether there's damp, whether there's subsidence, drainage issues, problems with the electrics,

[00:03:31] it will tell you whether you need another survey, perhaps like an asbestos survey. Wouldn't you rather know this in advance? You need to know all of this before you price the works. Otherwise, your budget is fiction.

[00:03:42] Mistake four: appointing professionals in the wrong order. You appoint professionals in the wrong sequence, or you skip professionals, you actually need.

[00:03:49] The correct sequence depends on what you are doing. But here's the framework For major structural work planning applications or listed buildings and complex projects with multiple trades, hire your project manager first. They coordinate trades. They manage the budget and schedule, and they make sure the whole project runs to time and to plan If they're also an interior designer like me you will end up with an exceptionally beautiful project. They design the scope and specification in tandem with your architect or designer and create the tender documents for submission to interested contractors.

[00:04:20] They coordinate trades, they manage the schedule. They make sure the project runs to plan. The architect comes next. They design the project within your budget and constraints. They handle the planning consent, and they produce the tender documents your builder needs to quote accurately within your budget.

[00:04:36] On large projects, you may want to involve a quantity surveyor. If you employ the architect first, you'll have a beautiful design that you can't afford to build, so don't do that.

[00:04:44] You don't need an architect to replace a kitchen or redecorate though, but you do need someone who understands specification, finishes and furniture.

[00:04:52] This is where your interior designer comes in and provides valuable input and designs within your scope. The standard mistake is to appoint a builder before you've appointed the designer or appointing a designer who can't actually deliver what you need, work on what you're trying to achieve, then appoint the right professional to deliver it.

[00:05:09] Mistake number five: going to tender without a complete specification.

[00:05:13] You ask your builders to quote before you've specified everything in granular detail.

[00:05:17] This is where PC sums destroy your budget. A PC sum, 'a provisional cost sum' is a builder's allowance for something you haven't specified yet.

[00:05:26] He puts in a standard rate for white plastic sockets or builder grade taps or basic appliances. If you actually want brass sockets or mounted taps and a Wolf range cooker, the difference between his allowance and your actual choice becomes an extra. The extras accumulate your fi. Your £50,000 pound kitchen quote becomes an 80,000 pound kitchen by the time you specified what you actually want.

[00:05:48] The fix is simple. Just specify everything in advance before anyone quotes. Make sure it's within your budget. Are your taps wall mounted or deck mounted? The plumber's quote will differ quite a bit. What make and model; a double vanity or a single? What size? What finish? Are your switch plates white plastic or unlacquered brass? How many per room? What configuration, how many gangs and ways, what appliances? What's the exact make and the exact model, not a fridge, which Sub-Zero Fridge? Which Fisher and Paykel fridge?

[00:06:20] Specify first, quote second. Never the other way round.

[00:06:24] Specify everything at the design stage, check lead times, and order before the work starts.

[00:06:29] Long lead time items get ordered first, short lead time items come later. You are coordinating 14 trades and hundreds of line items. The order really matters.

[00:06:39] Mistake seven. Underestimating the accommodation cost. You don't budget for living elsewhere during major works. If you are doing significant kitchen or bathroom work and you don't have another kitchen or bathroom to use, you're moving out. Six months of rental accommodation in the southeast of England might be 12 or maybe 18,000 pounds.

[00:06:58] Nobody puts this in the budget. Then they're surprised when the project goes over the fix budget for accommodation from the start. If you're living with family budget for weekends away and holidays to maintain your sanity, this isn't optional. It's a line item.

[00:07:13] Mistake eight. Forgetting about storage, waste, and insurance.

[00:07:17] You don't plan for storage or update your insurance if your possessions are out of the house. They need to be insured under your contents policy whilst in storage. If your house is empty and having work done, your buildings insurance rate changes.

[00:07:31] You need to tell your insurer or you're not covered. Other risks appear when the house is empty. Flooding, break-ins, damage from trades, they need to be insured against. Storage for six months, a thousand or maybe 5,000 pounds depending on the volume insurance. Premium increase for empty properties under renovation.

[00:07:49] This varies, but budget for it. Ask your insurer and put it in under a line item. Add both to the budget at the outset. Don't forget the cost of waste. Skips can add up to many thousands of pounds, and if you're doing a landscaping project, they'll be muckaway too, and it's really expensive.

[00:08:06] Mistake nine. Skipping the granular detail.

[00:08:09] If you think that 'new kitchen' is enough detail to price and build, it isn't. A new kitchen has at least 14 line items. Heating, flooring, cabinetry, architectural hardware, that's taps and handles and hinges. Open shelving, taps and sinks, worktops, appliances, extraction, lighting, that's wall lights and down lights and table lamps and lighting perhaps under a counter, so LED and cob strips, paint and wallpaper, kitchen furniture plus structural work, plumbing, electrical work, decoration, making good, and VAT on top of all of that each line item has multiple decisions. The finish, the specification level, the make, the model, the lead time, the installation sequence.

[00:08:59] If you haven't thought through the detail, your builder price is what he thinks you want, then you tell him what you actually want and the gap between becomes extras and delay. Think through the detail before anyone quotes. Put it in writing. Make sure everyone's pricing the same scope.

[00:09:15] And the last mistake, believing it can't go to plan.

[00:09:17] Mistake number 10: you assume renovation projects always go wrong, always run over budget, always overrun on time.

[00:09:25] Well, they don't. I've been doing this for 30 years. The projects that finish on time and on budget with no stress are ones where everything was planned correctly at the start.

[00:09:35] If the mistakes are predictable, you can anticipate them, you can prevent them, then they don't happen. Can you imagine a building project that just went according to plan? No surprises, no overruns, no budget blowouts.

[00:09:48] That's what's supposed to happen, and if you plan correctly, that's what will happen. The projects that go wrong are the ones where someone skipped these 10 steps, 10 mistakes, all predictable, all avoidable. The only question is whether you'll make them before you know how to prevent them or whether you'll prevent them and finish on time, on budget, and with your sanity intact.

[00:10:10] However, there's more to it than this. There's a link in the description for the full framework. Every step, every detail, every line item. If you've got questions about your project, then leave them in the comments below. I've been doing this for 30 years, so I've probably seen your question before, and I'll reply and perhaps do a video about your specific query.

[00:10:30] Thank you.

About This Newsletter

These articles are part of the Ministry of the Interior newsletter, published every Wednesday and Saturday. Each article is a companion to a YouTube video covering the same topic; you can watch, read or do both!

Download the guide: How Not To Get It Wrong: 23 Steps Before You Renovate

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