How do I compare builders’ quotes that cover different things?
Short answer
Don’t compare the bottom lines. Map every quote onto the same set of build stages, list what each one includes and excludes, pull out provisional sums and prime cost sums, show VAT separately, and fill the gaps with your own estimate of what’s missing. Then compare stage by stage, alongside payment terms and programme. The cheapest total is often the one with the most left out.
Step 1: Put every quote into the same stages
Builders lay out quotes in their own way. One gives a single figure for “shell”, another splits groundworks, drainage and foundations, a third lists materials and labour separately. Before you can compare, translate each quote into one common set of stages, for example: preliminaries (site set-up, scaffolding, welfare, skips), groundworks and foundations, superstructure, roof, windows and doors, first fix, plastering, second fix, kitchen and bathrooms, finishes and decoration, external works.
Take each line in each quote and allocate it to a stage. Where one line covers several stages, split it as sensibly as you can and note that you did.
Step 2: List inclusions and exclusions
For each quote and each stage, write down what is in and what is out. Ask directly about the things that most often get left out: scaffolding, skip hire, drainage and connections, making good, plastering, site clearance, waste disposal, temporary services, decorating.
Gaps are where the money hides. On BuildHub, members describe items that appeared on a materials list but were excluded from the fitting quote, costing around £2,000 extra in one case (BuildHub). For every exclusion, put your own estimate in so each quote covers the same scope.
Step 3: Pull out provisional sums and PC sums
These are allowances, not prices, so they will change.
- A prime cost (PC) sum is used when the quantity is known but the specification isn’t. You know you need ten windows but haven’t picked them. The contractor adds an agreed overheads and profit margin to the supplier’s final invoice (Build It, Tim Doherty).
- A provisional sum is an allowance for work that isn’t defined in enough detail to price, and is replaced by the value of the work actually done, so it can go up or down (Designing Buildings Wiki).
When comparing, check that each builder has used the same allowances. A quote with a £3,000 kitchen allowance will look £7,000 cheaper than one with £10,000, even if the work is the same. Replace low allowances with a realistic figure of your own, and agree the overheads and profit percentage at tender stage, as Build It advises.
Step 4: Show VAT separately
Write each quote as net, VAT and gross. A VAT-registered builder on a new build may zero-rate much of the work, while a non-registered builder won’t charge VAT at all, and some quotes mix the two. If you compare one quote with VAT and one without, you are out by a fifth. This is not VAT advice; check the treatment for your project with a qualified adviser.
Step 5: Check payment terms and programme
Two quotes with the same price can be very different to live with. Note for each: deposit required, how stage payments are triggered, any retention, and how variations are priced (ask for an all-in daily or hourly labour rate). Note the start date, duration and whether the builder can match your lender’s stage releases. A longer programme costs you more in insurance, scaffold hire and living costs.
A comparison table you can copy
| Stage | Builder A | Builder B | Builder C | Notes |
|---|---|---|---|---|
| Preliminaries (scaffold, skips, welfare) | Who includes scaffold? | |||
| Groundworks and foundations | Same foundation design? | |||
| Superstructure | ||||
| Roof | ||||
| Windows and external doors | PC sum or firm price? | |||
| First fix services | ||||
| Plastering | ||||
| Second fix | ||||
| Kitchen and bathrooms | Allowances used | |||
| Finishes and decoration | ||||
| External works | ||||
| Your estimate for exclusions | Fill gaps so scope matches | |||
| Total net of VAT | ||||
| VAT | ||||
| Total including VAT | ||||
| Provisional and PC sums (total) | Higher means less certainty | |||
| Deposit and payment terms | ||||
| Start date and duration |
Red flags
- A single lump sum with no breakdown.
- Lots of provisional sums, or allowances that look too low.
- No mention of scaffolding, skips, drainage or making good.
- A large deposit before any work starts (system builders are different; see our cash flow page).
- No clear way to price variations.
- VAT not shown, or shown inconsistently.
- A price far below the others with no clear reason.
On our build
Our quotes for Highfields covered different things, so comparing their totals told us very little. Setting each quote against the same build stages showed what each one left out, and that’s the comparison we make before accepting anything.
How Self Build Budget helps
In Self Build Budget you can store several quotes for the same work and see them side by side. You can allocate one quote across several budget lines, so a builder’s single “shell” figure is split across groundworks, superstructure and roof. When you accept a quote, you see straight away what it does to the projected total. AI scanning can read a PDF quote and draft the entries for you to confirm. Quotes are part of the Standard plan (£12 a month).
Questions people also ask
How many quotes should I get for a self build? Three is common for main contractors and big packages. More helps only if you have time to normalise them properly.
Should I always choose the cheapest quote? No. Compare like for like first. Once gaps and low allowances are filled, the cheapest headline is often not the cheapest job.
What is the difference between a provisional sum and a PC sum? A PC sum is for known quantities with the product not yet chosen. A provisional sum is for work not yet defined. Both will change.
Can I ask a builder to re-quote on my breakdown? Yes. Sending every builder the same schedule of works and stages makes comparison much easier and is a good test of how they work.