Scope of Works in Construction: Why Every Contractor Must Price the Same Tender Pack

What a scope of works in construction is

A scope of works is a written, line-by-line list of the exact works. It says what the contractor builds, what it supplies and what it leaves out. Good scopes go down to the number of sockets and lights, and the specification of each one.

That detail matters more than it sounds. A cheap white plastic socket and a better metal one are both "a socket" on a drawing. Priced across a whole floor, the difference is real money.

The term itself is loose. Designing Buildings calls it "a very general, and sometimes ambiguous term". It also notes that clashes between the scope and other contract documents are often cited as a cause of disputes.

So think of the scope as one step in a chain. First the brief, then the scope, then the tender pack, then the contract. If you have not written the brief yet, start with the brief.

A bill of quantities is measured to the RICS rules, NRM2. RICS says it "provides a consistent basis for obtaining competitive bids". A good scope of works aims for the same thing on a smaller budget.

Why every contractor must price the same documents

One contractor gets the drawings and the specification. Another gets a site walk and a phone call with you. A third prices revision B, because revision C only went to the others.

Three prices come back. They are prices for three different jobs. Only one of them is the job you want.

In our experience, quotes for the same job can differ by 30% to 40% this way. We have watched clients lose a week working out why one price was £20,000 and another £45,000. Usually, neither contractor was wrong. They were pricing different things.

Think of a recipe. Without the exact ingredients and steps, every cook makes the dish their own way. The result and the cost both change. "Can you build this for me?" plus a few drawings is not a recipe.

If the prices are already back, read how to level quotes like for like. This guide is about the stage before that.

How a gap in the scope becomes an extra

When the scope is silent, each bidder prices its own cheapest reading. The one that read least usually comes in lowest, and wins.

Then work starts. The missing item turns up on site. "We didn't know you wanted that. That's another £3,000." Then another £4,000. In our experience, that is how extras usually begin.

You pay for missing detail one way or another. At the start, in a proper scope. In the middle, as extras. Or at the end, in the final bill. That is why the cheapest quote often turns out to be the most expensive. Our cost plus contract guide explains why the lowest tender so often costs more.

Catch-all wording does not fix it. A line like "contractor to allow for everything necessary" does not create a shared scope. Each bidder still prices its own version, and the argument comes later.

After you sign, a missing item is a change to the contract. It is priced with no competition. Our guide to variations in construction contracts explains how they are valued. If you are already there, read what to do when a builder asks for more money.

What to include in a scope of works

A useful scope answers every question a bidder would otherwise guess. These are the parts that make the biggest difference to price.

Quantities and specification

List every item with a number and a specification. Sockets, switches, light fittings, doors, sanitaryware. "Lighting to designer's layout" is not a quantity.

Finish level, area by area

Say where money matters and where it doesn't. A staff toilet or a back-of-house ceiling just needs to work. The front of house that customers see needs the best finish you can afford. Without this, bidders pick one finish level for everything.

Named products for key finishes

Name the supplier or product for flooring, tiles and lighting. Designers often show beautiful visuals without saying where anything comes from. Each bidder then picks its own product, and you pay for that gap later.

Built to last

In a commercial space, specify flooring and lighting that last years, not months. Cheap bulbs mean a maintenance visit every six months, in our experience. That cost never appears in the tender.

Allowances you set

Some items are not designed yet. Put your own figure in the pack as a provisional sum, so every bidder carries the same number. Our guide to provisional sums in construction covers how they work.

Keep your own contingency on top. We usually advise 5% to 10% of construction cost, depending on complexity. See how much contingency to allow.

What goes in a tender pack

The scope sits inside a tender pack. The pack is everything a bidder needs to price the same job, by the same date. Designing Buildings notes that tender documents vary with the nature, size and complexity of the contract.

The responsibility matrix closes the gaps between parties. One page, one line per item. The rows below are an example to show the format, not a rule.

Under CDM 2015, the pre-construction information is your duty as the client.

Run the tender so the prices stay comparable

A good scope only works if every bidder gets it in the same way. This is the order we suggest.

1. Build one scope. Sit down with your designer and write it together. If useful, ask one contractor to check it can be built as drawn.
2. Send the same pack to every bidder. Same documents, same revisions, same day.
3. Set one return date. One date and time for everyone, with no private extensions.
4. Offer every bidder a site visit. If one walks the site, all of them can.
5. Answer every question to all bidders. In writing, numbered, sent to everyone. Designing Buildings says clarifications are circulated to all tenderers to keep a level playing field.
6. Issue drawing changes to all. A new revision goes to every bidder, with the register updated.
7. Ask for a compliant price first: a price for exactly what the pack asks for. Alternatives and savings come as a separate list.
8. Ask for qualifications in writing (conditions a bidder attaches to its price). Any reservation must be listed, not hidden in a covering letter.

Ask every bidder to fill in the same pricing schedule. A blank line tells you nothing. "Excluded" written in tells you exactly where the gap is.

Allow time for pricing and procurement

A proper price takes time. Rushed tenders get rushed prices, with more assumptions and more exclusions.

Build both into the programme before you set a start date. Designing Buildings makes the same point: it is better to allow enough time in the tender to clarify problems.

Tender on finished design, not on a sketch

The RIBA Plan of Work 2020 splits design into stages. Stage 3 is Spatial Coordination. Stage 4, Technical Design, ends with all the design information needed to construct the project.

RIBA lists tendering on Stage 3 information as a common misapplication. It says that information "is unlikely to contain sufficient detail to allow robust tenders". Unfinished design means bidders guess. Guesses become provisional sums, then variations.

If the design is not finished, say so in the pack. Use provisional sums with the same figure for every bidder. Or bring a contractor in early on a pre-construction services agreement. Our guide to design and build vs traditional procurement compares the routes.

Unfinished design at tender is one of the reasons construction projects go over budget.

Your legal duty to share information

Under CDM 2015, regulation 4(4), a client must provide pre-construction information as soon as is practicable. That duty covers every designer and contractor "appointed, or being considered for appointment". So it applies to every bidder, not just the winner.

In England, the Building Regulations add a similar duty. Regulation 11A(4) says a client must provide building information to every designer and contractor on the project.

Our guide to CDM 2015 client duties sets out the rest.

How we price a tender

When a clear scope reaches us, we price it unit by unit before we give a total. Around 60% of our labour is our own, in-house team.

Every price we send has one section for qualifications, assumptions and exclusions. If the scope is silent on something, we write down what we assumed. That makes our price easy to compare with the others.

We take on construction projects from £100,000.

One line-by-line scope, the same pack to every bidder. A clear scope of works costs a few days at the start. A vague one costs you at the start, in the middle or at the end. Before you send your drawings out, book a site visit and we will walk the job with you.