What Are Preliminaries in a Builder's Quote? A Builder Explains

You've got a quote for your extension or renovation, and near the top there's a line that says "Preliminaries" with a figure next to it. Sometimes it's a few hundred pounds, sometimes it's several thousand. Sometimes it's not there at all.

It's one of the lines homeowners ask me about most, and it's easy to see why. It doesn't sound like building work, because it isn't building work. But it is a real cost, every job has it, and how a builder handles it tells you a lot about how carefully they've priced your job.

Quick answer: what are preliminaries?

Preliminaries (or "prelims") are the costs of setting up, running and clearing a building site, rather than the cost of the building work itself. They usually cover things like:

• Scaffolding and access equipment
• Skips and waste removal
• Welfare facilities (toilet, washing, somewhere to take a break)
• Site setup, protection and security
• Temporary power, water and lighting
• Insurance for the works
• Supervision and management of the job
• Health and safety measures
• Permits and licences (for example a skip or scaffold on the road)
• Cleaning up and handing over at the end

The building's professional cost body, BCIS, describes prelims as the costed items that "establish, manage and support" the building works and that don't form part of the finished structure (BCIS). In plain English, it's everything the job needs to happen that you won't see once it's finished.

Why are preliminaries in a quote at all?

Because the job can't happen without them. You can't build a first-floor wall without a scaffold, and you can't strip out a kitchen without somewhere to put the rubbish. A builder who leaves these out hasn't made them disappear. They've just not told you about them yet.

There are three common ways a builder deals with prelims on a domestic quote:

1. A separate prelims line or section. This is the clearest. You can see what you're paying to run the site and compare it between builders.
2. Spread through the other prices. The scaffold is hidden inside the "roof" price, the skips are inside "demolition", and so on. That's not dishonest, and on small jobs it's very common. But it makes quotes much harder to compare.
3. Left out or listed as an exclusion. "Scaffolding by others" or "skips not included". This is the one to watch. Those costs will still land on you, either as an extra later or as something you have to arrange yourself.

On a small job, like a bathroom refit, I wouldn't expect a separate prelims section. On an extension, loft conversion or a big refurbishment, I'd want to see one, or at least see each prelims item clearly written somewhere in the quote.

What's normally included in preliminaries?

Here's what I'd expect to find in prelims on a typical extension or major renovation, and what each one is for.

Scaffolding and access

Scaffold for any work at height: walls, roofs, chimneys, gutters. The quote should say whether the price covers putting it up, the hire period and taking it down, and what happens if it's needed for longer. If the scaffold goes onto the pavement or road, your council will usually need to grant a licence. Ask who's applying for it and who's paying.

Skips and waste removal

Strip-out, demolition and groundworks make a lot of waste. Look for how many skips are allowed (or "waste removal as required"), and whether a skip permit is included if the skip sits on the road. Muck-away from digging foundations is often priced separately from general skips, so check it's covered somewhere.

Welfare facilities

Workers need a toilet, somewhere to wash their hands, drinking water and somewhere to take a break. On many home jobs that's agreed with you, for example the team uses a downstairs loo. On bigger jobs, or if you're moving out, the builder may hire a site toilet. Either way it's a cost, and it's better to agree it at the start than argue about it in week three.

Site setup and protection

Getting the site ready and keeping your home safe while it's a building site. That means dust sheets and floor protection, temporary walls or dust screens between the works and the rooms you're living in, hoarding or fencing where needed, protecting the drive and garden, and making the site secure at night.

Temporary services

Temporary power, lighting and water for the trades, and sometimes a temporary kitchen if yours is being ripped out. Check whether the builder expects to use your electricity and water. That's normal on home jobs, but it's worth knowing.

Insurance

The builder should have public liability insurance, and employers' liability insurance if they employ anyone. That's a legal requirement where they have employees (Citizens Advice). On bigger jobs, there should also be contract works or "contractors' all-risk" cover, which protects the work in progress if it's damaged before it's finished. Some builders show part of this cost in prelims. Whatever the quote says, ask to see the certificates and check the expiry dates. You should also tell your own home insurer about the work.

Supervision and management

Someone has to run the job: order materials, book the trades in the right order, meet building control and deal with your questions. On a small job that's the builder themselves. On a bigger one it might be a site manager or foreman. This is a real cost, and a builder who prices it is usually a builder who plans to turn up and manage the job properly.

Health and safety

On home building work, the health and safety duties that would normally sit with the client usually pass to the builder under the CDM 2015 regulations (HSE). In practice that means things like a plan for the work, safe access, fencing off dangerous areas, and first aid. It's part of running the site, so it often sits in prelims.

Cleaning and handover

The final clean, removing the scaffold and skips, and leaving the site tidy. If the quote doesn't mention a final clean, ask.

Things that sometimes appear in prelims (and sometimes don't)

Building control fees, structural engineer's calculations, party wall costs and planning fees are professional and approval fees, not site running costs. Some builders put them in prelims, most leave them for you. The important thing is that you know who's paying for each one. If nobody has mentioned them, assume they're yours until the builder confirms otherwise in writing.

How much should preliminaries be?

This is the question everyone asks, and the honest answer is that it depends on the job. Prelims are driven mostly by how long the job takes, how hard the site is to get to, and how much needs to be set up. A job with rear access through a side gate costs less to run than a mid-terrace where every barrow of rubbish goes through the house.

The industry normally expresses prelims as a percentage of the building work. BCIS, for example, measures them as a percentage of the contract sum excluding the prelims themselves and any contingency (BCIS). Bear in mind that most published prelims figures come from commercial projects, which run very differently from a house extension.

On typical UK home jobs, published figures from firms that share their numbers put prelims roughly in the 8–14% range of contract value. One London firm reported 9.5–14% on recent tenders (Mount St Projects); an extension specialist quotes 8–12% (The Extension Company). These are other businesses' published figures, not independent national data, and your site may sit outside that band if access is tight, the programme is long, or a lot of scaffold is needed.

A few things are worth knowing whatever the percentage:

• Prelims are often time-related. Scaffold hire, site toilets and supervision are paid by the week. If the job runs over, this is the part of the price that grows. Who pays for that depends on why it ran over and what your contract says, so get it agreed up front.
• A low prelims figure isn't automatically good news. The costs are either hidden elsewhere in the quote or missing.
• A high prelims figure isn't automatically bad either. A tight site, a long programme or a lot of scaffold all cost money. What matters is that the builder can explain what's in it.

Red flags in the preliminaries line

Ask more questions if you see any of these:

• No prelims, and no mention of scaffold, skips or waste anywhere in the quote. On an extension or loft that almost always means they're missing, not free.
• "Scaffolding by others" or "skips by client". You'll be arranging and paying for them yourself. Add the cost to this quote before you compare it with the others.
• One lump sum with no breakdown, especially if it's large. You can't tell what you're paying for, and you can't tell what happens if the job takes longer.
• Prelims that don't match the job. A two-storey extension with no scaffold, or a full strip-out with only one skip.
• No mention of who applies for and pays for scaffold or skip licences when they'll be on the road.
• Professional fees quietly assumed. The quote doesn't say who's paying for building control or the engineer, and the builder says "don't worry about that" when you ask.
• Big differences between builders that nobody can explain. If one builder's prelims are several times another's, ask both what's included. One of them has probably misunderstood the job, and it isn't always the expensive one.

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What to ask your builder about preliminaries

Copy these into an email. A good builder will be happy to answer them, and having the answers in writing protects you both.

1. What exactly is included in the preliminaries figure?
2. Is scaffolding included? For how many weeks? What happens if it's needed for longer?
3. How many skips, or how much waste removal, have you allowed? Does that include muck-away from the foundations?
4. Who is applying and paying for any scaffold or skip licences?
5. What welfare arrangements are you planning? Do you need to use our toilet, electricity or water?
6. What protection will you put in place for the parts of the house we're living in?
7. Who will be managing the job day to day, and how often will they be on site?
8. Can I see your public liability (and employers' liability, if you have staff) insurance certificates? Is the work in progress covered?
9. Are any of the prelims time-related? If the job overruns, how is that handled?
10. Who is paying for building control, the structural engineer and any party wall costs?

How to compare prelims between quotes

When you've got more than one quote:

1. Find the prelims in each quote, even if they're spread through other lines. Look for scaffold, skips, protection, welfare and supervision.
2. Make a simple table with each prelims item down the side and each builder across the top. Mark each one as included, excluded or not mentioned.
3. Put a price on the gaps. If one builder excludes scaffold, ask a scaffolder for a rough figure and add it to that quote before you compare totals.
4. Check the programme. A builder who has priced eight weeks of scaffold for a job another builder says will take sixteen weeks is pricing a different job.

Our free builder quote checker will help you score a single quote, and the builder quote comparison tool puts up to three quotes side by side. The full guide to checking a builder's quote covers everything else a good quote should include. If the totals are wildly different, read why builder quotes are so different.

The short version

Preliminaries are the cost of running the site. Every job has them, whether the quote shows them or not. A clear quote either lists them or shows each item somewhere you can find it. If they're missing, they'll come back as extras or as jobs you have to sort out yourself. Ask what's included, check whether it's time-related, and make sure every quote you compare covers the same things.

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Try the free preliminaries sense-check tool (uses commonly cited 8-14% industry bands as a guide).