Why small building projects can produce surprisingly large quotes

This week I found myself doing something I’ve done dozens of times before.

A family had received a quote for a very small addition to their home. They looked at the number, looked at the size of the room, and assumed something must be wrong.

I did the same.

The room was only a few square metres.

The quote had not received that memo.

Most people instinctively think about building costs the same way they think about buying land, carpet or tiles.

More square metres equals more money.

Fewer square metres equals less money.

It feels logical. Unfortunately, building has a habit of taking logic outside and asking it to wait in the car.

In this case, I went away and estimated the project line by line. What emerged wasn’t really a story about an expensive builder, or a quote that had got carried away with itself. It was a reminder of something I see repeatedly.

Small projects can be some of the most expensive projects you can undertake on a square metre basis.

The reason is fairly simple.

When people picture a small extension, they usually picture the room.

Builders are pricing three things.

First, the room itself.

Second, the structure required to create it: footings, framing, roofing, cladding and weatherproofing.

Third, the connection back into the existing house: plumbing, drainage, electrical work, structural alterations, roof tie-ins, and making good everything disturbed along the way.

That third part is often where the quiet money lives.

The room might be small, but it still needs most of the same trades as a project two or three times the size. The plumber still needs to turn up. The electrician still needs to turn up. The roofer still needs to make the junction work. The builder still needs to manage the job, carry insurance, set up the site, coordinate the work and take responsibility for the outcome.

No one gives you a half-sized building permit. 

This is why I get nervous when small projects are discussed entirely in dollars per square metre. Square metre rates can be useful on larger projects, where the fixed costs are spread across a decent amount of floor area. On small projects, they can be actively misleading.

Using a rate is not wrong because the maths is wrong.

It is wrong because it is being asked to describe the wrong thing.

And that is often where people get into trouble. Because they made a reasonable decision based on an assumption that did not apply.

Most projects don’t run into difficulty because of one catastrophic mistake. They drift off course through a series of assumptions that were never properly tested.

A small extension sounds simple.

Then it needs a footing.

Then the roof has to connect.

Then the drainage needs somewhere to go.

Then the existing wall turns out to be less cooperative than hoped.

Then everyone is standing around wondering how a few square metres became a proper building project with boots on.

The earlier those assumptions are tested, the more options remain available.

Sometimes the answer is still to build the small extension.

Sometimes it is to make it larger, because the extra area costs less than people expect once the fixed costs are already there.

Sometimes it is to renovate differently.

And occasionally, the best answer is to leave the existing house alone and spend the money somewhere it will work harder.

The important thing is understanding what you are actually buying before the design begins and the decisions become expensive to change.

That is usually where the best savings are found.

Not by squeezing the builder at the end.

By asking better questions at the beginning.

If you're trying to work out whether you're planning a contained renovation, a major transformation or something that may be pushing towards a rebuild, start with our Renovate or Rebuild Assessment.