Understanding Construction Allowances: Provisional Sums Explained Simply

If you’ve ever looked at a building quote and felt confused by terms like “Provisional Sum”, you’re not alone. Many homeowners sign contracts without fully understanding these allowances, and that’s often where budgets start going wrong.

Let’s break it down simply, without technical language.

What Is a Provisional Sum?

A Provisional Sum (PS) is an estimated allowance included in a building quote for work or materials that haven’t been fully defined yet.

In plain terms:

It’s a best guess, not a fixed price.

Builders use provisional sums when they don’t yet have enough detail to give an exact cost.

Common Examples of Provisional Sums

You’ll often see provisional sums for things like:

• Excavation and earthworks

• Electrical and plumbing work

• Tiling and finishes

• Kitchen or bathroom fittings

• Landscaping

These items depend on factors that may only become clear once construction starts.

Why Provisional Sums Can Be Risky

Provisional sums are not bad by themselves, but they carry risk if they’re unrealistic.

Here’s why:

• If the actual cost is higher than the allowance, you pay the difference

• Multiple provisional sums can quickly push a project over budget

• Low provisional sums can make a quote look cheaper than it really is

This is why two quotes can look very different on paper, even if they’re for the same project.

Provisional Sums vs Fixed Costs

Fixed Cost	Provisional Sum
Known and agreed upfront	Estimated only
Low risk	Higher risk
Rarely changes	Often changes

A quote with many provisional sums is usually less certain than one with well-defined, fixed costs.

How Provisional Sums Affect Your Final Price

Let’s say your quote includes:

• Provisional Sum for electrical work: R60,000

• Actual cost after installation: R85,000

That extra R25,000 comes out of your pocket.

Now imagine this happening across several items, that’s how projects quietly exceed budgets.

How to Protect Yourself as a Homeowner

You don’t need to be a construction expert, but you do need clarity.

Here’s what helps:

• Ask what each provisional sum covers

• Check if allowances are realistic for your expectations

• Reduce provisional sums by finalising finishes early

• Get a detailed cost estimate before construction starts

The more detail upfront, the fewer surprises later.

Why Accurate Estimating Matters

Professional building estimators aim to:

• Minimise provisional sums

• Base allowances on real market rates

• Help homeowners plan with confidence

Good estimating doesn’t eliminate uncertainty, but it controls it.

Final Thoughts

Provisional sums are a normal part of construction, but they shouldn’t be ignored or misunderstood.

Understanding them helps you:

• Compare quotes properly

• Avoid unexpected costs

• Make informed decisions before building starts

If you’re planning a new build or renovation, getting clarity on allowances early can save you money, stress, and disputes later on.