# Provisional Sums & PC Sums in a Builder’s Quote — Plain English

> PC sum vs provisional sum in a UK builder's quote, in plain English: what each means, how homeowners get caught out and how to compare tenders fairly.

Author: Ben Murrell, Homeowners Project Manager · Published: 2026-09-22 · Category: Quoting · Areas: Wandsworth, Fulham
Canonical: https://www.homeownersprojectmanager.co.uk/blog/provisional-sums-pc-sums-builder-quotes-explained

Three quotes. Three totals. One feels reassuringly cheap. Then you notice the phrase **provisional sum** — or **PC sum** — scattered through the schedule, and nobody has explained whether that money is real.

Search threads and comparison blogs often wave at the problem in a bullet list. Useful as a reminder; not enough when you are about to appoint a contractor on a Wandsworth side-return or a Fulham loft-plus-extension.

Here is the blunt version: **a provisional sum is usually a placeholder, not a fixed price.** A **PC / prime-cost sum** is usually an allowance for a defined *supply* item before you pick the final product — a different animal, still not a free lunch. Until those lines are firm, your “quote” is partly a forecast.

This article is education first. It deepens the short PS/PC/contingency bullets already on [how to compare builder quotes](https://www.homeownersprojectmanager.co.uk/blog/how-to-compare-builder-quotes) into a dedicated plain-English pillar — so that post can keep pointing here instead of growing into a textbook.

Homeowners Project Manager is a **client-side** renovation project manager for SW / West / Central London homeowners. We do not sell SaaS, we do not invent tender figures, and we do not pretend every PS is a scam. Many are honest markers of incomplete information. The burn happens when nobody forces them into the open before you sign.

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## Provisional sum (PS) in plain English

A **provisional sum** is money included in the tender for work (or work-plus-supply) where the **scope, quantity or method is not yet firm enough** for a fixed price.

Typical homeowner examples on SW London jobs:

- Kitchen electrics “to be confirmed once layout is final”  
- Drainage connection “subject to survey / council / existing run”  
- Making-good / decoration “where the extension meets the existing house”  
- Structural steel “allowance pending engineer’s final schedule”  
- Temporary works, temporary kitchen, or unknown opening-up repairs  

**What it is good for:** keeping the tender moving when information is genuinely incomplete.  
**What it is dangerous for:** making the headline total look competitive while parking risk in small print.

Treat every PS as **risk until converted**. Ask, in writing:

1. What exactly does this line cover (and what does it exclude)?  
2. What information turns it into a firm price?  
3. Who owns overrun if the firm price exceeds the allowance?  
4. Is the figure “works only,” or does it include prelims, overhead and profit?

If the answer is vague, the number is not a price. It is a hope with a pound sign.

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## PC sum / prime cost in plain English

A **PC sum** (prime cost) is commonly an **allowance for the supply cost of a specified type of goods** — sanitaryware, tiles, ironmongery, appliances, sometimes specialist fittings — before the final product is chosen.

It is **not** automatically the same as a vague provisional sum dumping ground.

Still check:

- Is labour to *fit* the item included separately and firmly?  
- Are overhead, profit and delivery inside or outside the PC?  
- What happens if you choose a product above the allowance — variation process?  
- Are you comparing the same PC description across builders (same quality band)?

A tidy PC for “sanitaryware £X” can still burn you if fitting labour was optimistic, the quality band was fantasy, or two tenders used different assumptions for the same bathroom.

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## PS vs PC vs contingency (keep these separate)

| Term | Whose money / where it sits | What it usually means | Homeowner trap |
|------|-----------------------------|------------------------|----------------|
| **Provisional sum (PS)** | Inside the tender | Placeholder for incomplete *scope* | Headline looks cheap; risk not firm |
| **PC / prime cost** | Inside the tender | Allowance for *supply* before final choice | Labour/margin around it ignored |
| **Contingency** | Client-held buffer (should be visible to you) | Buffer against unknowns / decisions | Assuming leftover PS = contingency |

Contingency is covered in depth in [how much contingency for a UK renovation or extension](https://www.homeownersprojectmanager.co.uk/blog/how-much-contingency-renovation-extension-uk). Overrun *causes* that eat buffers live on [common renovation budget overruns](https://www.homeownersprojectmanager.co.uk/blog/common-renovation-budget-overruns). Do not collapse the three terms into one vague “extras” feeling.

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## How homeowners get burned (predictable patterns)

None of these require a cartoon villain builder. They require incomplete information and soft comparison:

1. **Headline shopping** — appointing on the lowest total before PS/PC rows match.  
2. **Undefined PS** — “allowance for electrics” with no circuit count, no consumer-unit assumption, no temporary works.  
3. **PS used as a dumping ground** — anything awkward parked as provisional so the fixed part looks keen.  
4. **PC without fitting clarity** — supply allowance looks generous; labour quietly thin.  
5. **Unequal assumptions across tenders** — Builder A’s PS includes scaffold; Builder B excludes it and looks cheaper.  
6. **Late client choices** — finishes decided after the roof is open; PC overrun becomes a variation under programme pressure.  
7. **Contingency confusion** — homeowner thinks the PS *is* the contingency, then both get spent.

On period houses in Wandsworth and Fulham, the burn is often quiet: steels, drainage, making-good and party-wall-adjacent works — not a single dramatic disaster.

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## How to compare quotes when PS/PC lines exist

Do not compare totals first. Compare **rows**.

### Step-by-step

1. **List every PS and PC** from each tender into one sheet (description, £, assumptions).  
2. **Normalise language** — same item, same unit, same inclusion of OHP.  
3. **Mark firm vs provisional** — colour-code if it helps.  
4. **Force clarifications in writing** before you rank builders.  
5. **Add missing exclusions** (drainage, steels supply, scaffold, skips, building control, making-good) as explicit lines — see the compare-quotes post.  
6. **Only then** look at adjusted totals.  
7. **Hold client contingency separately** — do not treat matching PS rows as “risk solved.”

Printable structure: use the [builder quote comparison checklist](https://www.homeownersprojectmanager.co.uk/resources/builder-quote-comparison-checklist) (Sheet / printable) and line up PS, PC, steels, drainage, scaffold and making-good **before** totals. Method overview: [how to compare builder quotes](https://www.homeownersprojectmanager.co.uk/blog/how-to-compare-builder-quotes). Budget structure (works + fees + contingency): [extension / loft budget planner](https://www.homeownersprojectmanager.co.uk/resources/extension-loft-budget-planner).

### What “like-for-like” means here

Like-for-like is not identical fonts on a PDF. It is the same **scope**, same **exclusions made explicit**, same **PS/PC assumptions**, and the same **contingency treatment on your side**. Until that is true, you do not have three prices. You have three different jobs wearing price tags.

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## Questions to ask every builder (copy/paste)

Use these in email — not only on a site visit:

1. Please list every provisional sum and PC sum with a one-line scope and what converts it to a firm price.  
2. For each PS/PC, confirm whether overhead and profit are included.  
3. What is excluded entirely from your tender (attach a full exclusions list)?  
4. If a PS overruns, what is the valuation / variation process under the proposed contract?  
5. Which lines can be firmed before we appoint if we supply X information by date Y?  
6. Are steels, drainage, scaffold, skips and making-good firm, provisional, or excluded?  
7. How do you treat client-supplied items against any PC allowances?

If answers stay oral only, you do not have tender clarity. You have a conversation.

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## Soft path to HOPM quote review (honest, not bait-and-switch)

You can run the checklist yourself. Many homeowners should.

A **client-side** quote review earns its keep when:

- PS/PC density is high and clarifications still bounce  
- Totals look close but assumptions do not  
- You are time-poor and living in  
- You want someone on *your* side reading commercial risk before appointment — not instead of your architect  

That is quote literacy and commercial protection. It is not “skip the builder” theatre and not a replacement for design. If the outcome is “appoint Builder B after firming three PS lines” or “go back for better drawings before retender,” that is a successful conversation. For how client-side fees work when you need more than a one-off review, see [renovation project manager cost](https://www.homeownersprojectmanager.co.uk/project-manager-cost).

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## Practical checklist before you appoint

1. Extract every PS and PC into one comparison sheet.  
2. Demand written scope and conversion triggers.  
3. Align exclusions across tenders.  
4. Firm what can be firmed *before* appointment.  
5. Hold client contingency separately ([contingency guide](https://www.homeownersprojectmanager.co.uk/blog/how-much-contingency-renovation-extension-uk)).  
6. Know the contract’s variation / valuation path.  
7. If money risk still sits in opaque allowances, get a client-side read — or do not pretend the cheapest total is the safest.

When a provisional sum is spent and the figure moves, the difference is a variation. How to get one priced and agreed in writing is in [builder variations: what an extra should cost](https://www.homeownersprojectmanager.co.uk/blog/builder-variations-what-an-extra-should-cost).

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## Soft close — enquire / phone

If you are in SW, West or Central London with two or three builder quotes in hand and you want a straight, like-for-like read on provisional sums, PC allowances and exclusions — [enquire](https://www.homeownersprojectmanager.co.uk/contact) or phone. There is no fee for the first conversation. Bring the PDFs. If you mainly need clearer drawings, firmer PC selections, or a different tender process, that is a valid outcome. This is not a pitch to skip your design team or appoint HOPM by default.

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Homeowners Project Manager — independent client-side project management for homeowners in South West London. Contact: 07525 474 849 · https://www.homeownersprojectmanager.co.uk/contact