Contingency fund FAQ: what to know about your construction or renovation budget

A contingency fund is an envelope of cash you set aside during the budgeting process to cover cost overruns or changes in scope, materials, or finish. It’s your “break glass in case of emergency” slush fund and should live outside of your actual construction budget.

This matters because no matter how well you plan your home build or renovation, the construction process has a way of throwing you a curveball — usually at the worst possible moment.

Building a contingency fund into your construction or renovation budget protects you from those curveballs. But I get a lot of questions from clients about what that looks like in different scenarios and projects, so that’s what we’re covering in this article.

Why do I need a contingency fund? 

Contingency funds matter because the construction process is long and expensive, and it’s very hard to plan for every eventuality in advance. 

Your contingency gives you an emergency fund to draw on when things change or unexpected costs come up — and they will come up. 

It gives you extra runway and flexibility that often makes all the difference in getting to the end of your project with your budget intact. If you don't have a contingency, you may have to make significant sacrifices or even stop the project midstream. 

How much should I set aside for my contingency fund? 

How much to set aside as your contingency depends on a number of things, including:

• The size and complexity of your project. Bigger projects and unique or custom features mean more room for changes in labour, materials, and timelines.

• Your home's age and condition (if you’re renovating). Older homes tend to hide more expensive surprises behind the walls.

• How detailed your planning is. The more specifics you lock down in advance — from detailed blueprints to selecting your finishes and appliances — the fewer budget surprises you'll face.

• Market conditions and material choices. Supply chain issues and material costs vary by region and can change quickly, especially with high-end finishes.

That said, as a very rough rule of thumb, I suggest setting a contingency in the range of 15-30% of your total budget — 15% for new builds and 30% for renos, because with renos there’s a greater chance of unknowns. The smaller your project, or the newer your home, the more you can slide to the lower end of that scale.

More than any one number, though, my advice is to set aside as much of a buffer as you possibly can. It will make decision-making and managing stress much easier once you’re in the thick of your project.

When should I create my contingency fund? 

At the very beginning of your project, when you’re setting your initial budget. You should start your budgeting process by figuring out what you can afford to spend on your project. 

Once you have that high-level number in mind, set your contingency budget. Put it off to the side and don’t touch it or earmark it for anything other than, “we’ll use this to cover emergencies”.

Once you’ve determined your contingency budget, the rest becomes your actual planning budget. This is the number that you’ll give to contractors, designers, trades, and anyone else who asks “what is your budget for this project”?

So to do some simple math: 

Your construction budget (what you plan to spend) = the maximum amount you want to spend (what you can afford) - your contingency (your emergency fund)

Why do I need a higher contingency for a renovation vs. a new build? 

Because renovations come with more unknowns. (More on the difference between building new vs. renovating here.)

With a renovation, you're building out a budget on a project you can't fully see yet — which means more risk, more surprises, and more possibility for unexpected expenses to come up. For example: 

• Old wiring that hasn't been touched since the '60s

• Black mold or water damage that might need abatement or structural repairs

• Copper pipes that are wearing a little thin

• Newspapers that make a great time capsule but awful insulation

While a good contractor can make an educated guess on what to expect behind the walls based on clues like the era of your home, at the end of the day it’s still just a guessing game until demo begins and you actually start pulling things down. No matter how experienced your contractor is or how detailed your estimates, there will be things you didn't account for. 

Who controls the contingency fund — me or my contractor?

You do, full stop.

Your contingency is your money, and it sits outside of your construction budget. Every draw against it should be authorized by you — in writing! A good contractor will flag when something unexpected comes up, explain what it will cost, and ask for your approval before proceeding. That's how it should work.

If your contractor is spending against your contingency without your sign-off, that's a problem. Make sure this is spelled out clearly in your contract before construction begins.

Can I use my contingency for upgrades I want to make mid-project?

You could, but I’d be very careful.

Contingency funds are typically used up during demo and the reconstruction of your building envelope or shell. That includes things related to electrical, plumbing, heating, windows, insulation, roof, and doors — all of the systems inside the walls that make your home functional. 

If you’re still in the part of your project where the walls are open and you’re working on these systems, you might want to hold your horses. 

But if you’re at the point where you’re getting close to the drywall stage or you don’t think you’re going to expose any more surprises, then by all means, upgrade your tile!

What happens to my contingency if I don't use it all?

Simple: You keep it! It stays in your bank account and you can celebrate the fact that you managed your budget more successfully than pretty much every other homeowner out there. 

The bottom line

A contingency fund isn't optional! It's one of the smartest budget decisions you'll make before construction begins. Set it aside early, protect it fiercely, and hope you don't need all of it.

Ready to build out the rest of your construction budget? Here's everything you need to know to get started.