03/06/2025
PC Sum vs. Provisional Sum: The Quote Terms That Could Blow Your Budget
If you're planning a home extension or renovation, you'll likely receive several quotes from different builders. But how do you compare them? Beyond the grand total, there are two key terms that can make or break your budget — PC Sum and Provisional Sum.
In this guide, we’ll break them down so you can protect your budget and choose the right contractor with confidence.
🧾 What Is a PC Sum?
PC Sum stands for Prime Cost Sum. It’s a placeholder amount included in your quote for items that you, the client, will choose later. For example:
- Kitchen appliances
- Bathroom fixtures
- Tiles and flooring
- Light fittings
The builder doesn’t know what style, finish, or brand you’ll pick, so they insert a reasonable allowance.
🔍 Example: The quote includes a PC Sum of £1,500 for a bathroom suite. If you later choose one that costs £2,000, you’ll pay the £500 difference — plus any mark-up or installation cost adjustments.
🛠️ What Is a Provisional Sum?
A Provisional Sum is a budget for work that might be needed, but which can’t be confirmed until the project is underway.
This often includes:
- Foundations (when ground conditions are unknown)
- Structural supports revealed during demolition
- Drainage inspection, rerouting
🔍 Example: Your quote includes a Provisional Sum of £3,000 for additional foundation work. Once the builder digs down and confirms the ground is solid, this might drop to £1,500 — or increase to £5,000 if issues are found.
⚠️ Why These Terms Matter to You
When comparing quotes, it’s tempting to look only at the total figure. But here’s what happens if you're not careful:
Builder A
£35,000 Total Quote
PC Sum: £4,000 realistic
Provisional Sum: £3,000 clear
Builder B
£32,000 Total Quote
PC Sum: £1,500 low
Provisional Sum: not listed
Builder B seems cheaper — until you start choosing nicer finishes or hit unexpected structural issues. Then the cost balloons beyond Builder A’s quote.
✅ What to Do:
Ask your builder to explain each PC Sum and whether it reflects your likely choices
Request clarification or backup for Provisional Sums
Don’t be afraid to ask what’s included and what’s not
📄 Pro Tip:
The most detailed and transparent quote isn’t always the cheapest — but it’s often the most honest. That’s what protects your budget.