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Mistakes to avoid when building
Lahav Meiri, licensed renovation contractor · Published 3 August 2026
Every list of building mistakes is a list of things somebody forgot - an outlet, a closet, a light switch on the wrong wall. Those lists are useful and they can't save you, because the list is infinite. There will always be one more item nobody mentioned. What helps is knowing the few kinds of mistake, because a kind fits your situation and an item doesn't.
There are three moments where a mistake gets made, and only one of them is cheap to prevent.
One thing worth knowing before you start: the most expensive mistakes aren't on anyone's list, because nobody notices them.
Why lists of mistakes don't help
Read three of them and you'll notice they're the same list. Not enough storage. Not enough outlets. Windows too small. Didn't plan for the future. All true, all worth knowing, and none of it is a method.
The problem with an item list is that it only protects you from the items on it. Your house has thousands of decisions in it. A list of twenty-three catches twenty-three.
There's a second problem. Every one of those items is somebody else's regret. They come from other people's houses, other people's habits, other people's lives. The outlet they missed isn't the one you'll miss.
Kinds transfer. Items don't. If you know that late decisions cost more than early ones, you'll apply it to a decision nobody wrote about. If you only know "add more outlets," you'll add outlets.
Kinds transfer. Items don't
The three moments a mistake gets made
Before design.
Deciding what you're building, what it's for, what it can cost. Mistakes here are almost free to fix and enormously expensive to leave. They're also the ones nobody calls mistakes at the time, because nothing has been drawn yet.
During design.
Layout, orientation, structure, where things go. Fixing something here costs a drawing revision and some patience. This is where most people think mistakes happen, and it's the middle of the range.
During construction.
Everything from here costs money, time, and usually both. A change that would have been a pencil line in month two becomes an opened wall in month nine.
The same decision, at two different moments
The pattern is boring and it's the whole game: the same decision gets steadily more expensive the longer it stays open. Not slightly - by orders of magnitude.
And here's the part that catches people. The decisions that lock earliest are the ones that feel least urgent. Nobody feels pressure about which way the house faces. It doesn't have a deadline, nobody's chasing you for it, and it's permanent.
The mistakes you'll never know you made
Every regret list is made of things people noticed. That's a much smaller category than it sounds.
You notice a missing outlet because you go to plug something in and there's nowhere. You notice a small pantry because you can't fit the shopping.
You will never notice the layout you didn't get. If the house works reasonably well, you'll never know that a different arrangement would have given you morning light in the kitchen, or that the hallway eating four square metres could have been part of the room you actually use.
Nobody regrets a plan they never saw.
This is why the regret data undercounts. Surveys measure what people can name. The expensive mistakes are invisible by definition - the house is fine, you live in it, and the better version simply never existed.
And it's the reason the early stage matters so much. Later on, you're choosing between options someone has drawn. At the start, you're deciding which options get drawn at all. The mistakes you'll never see are made there, before anyone picks up a pencil.
Nobody regrets a plan they never saw
The items worth knowing, by kind
The lists aren't wrong. They're just unsorted. Here they are by kind, which is how you use them.
Decided by default
Nobody chose these. They happened because nobody said otherwise: which way the house faces, ceiling height, where the front door is relative to where you actually enter, how sound moves between rooms. Default is a decision. It just isn't yours.
Decided too late
Anything that has to be right before concrete or framing: rough plumbing, structural openings, electrical capacity, drainage. Late here isn't expensive, it's brutal.
Optimised for the wrong thing
Attention goes where the photos go. Kitchens and bathrooms get months; storage, circulation, and where the school bags land get minutes. You'll spend far more of your life in the parts nobody photographs.
Designed for a version of your life
The formal dining room, the guest suite used twice a year, the office nobody sits in. Built sincerely, for a life that didn't turn up.
Assumed rather than agreed
Two people, one of whom stopped putting things forward. It looks settled until month six.
Default is a decision. It just isn't yours
How to catch them before they happen
You can't check a list you don't have. What you can do is ask the questions that surface all five kinds.
Which of these decisions is permanent?
Ask it about everything, early. The answer reorganises your attention immediately.
What am I not deciding?
Go through the plan and find the things nobody has raised. Those are being decided by default right now.
Where do I spend my actual hours?
Then check how much attention those rooms have had compared to the ones that photograph well.
What am I planning for that hasn't happened yet?
Guest rooms, formal dining, a home office. Fine to build - just name it honestly as a bet.
What haven't we discussed?
If there are two of you. Not disagreements - silences.
What would you ask if you did this every day?
The uncomfortable one. You're making decisions you've never made before, and the questions you don't know to ask are where the invisible mistakes live.
The questions above are the ones worth answering early. Nestbrief works through them with you.
See how it works →Most of it is decided before anyone draws
By the time there's a plan to react to, the expensive decisions have already been made. Not badly - just quietly, by whoever was thinking about them, which is usually not you.
The way to avoid the mistakes on every list, and the ones on no list, is the same: know what the house has to do before anyone starts solving it.
Nestbrief asks you those questions one at a time, at home, at your own pace. When you say you want a bigger kitchen, it asks what for. When you're not sure, it helps you think it through instead of moving on. Nothing to prepare, nothing to fill in - you just talk.
This is what comes out of it:
One conversation, and the decisions get made by you.
Common questions
- What's the single most common mistake?
- Starting design before knowing what the house has to do. Everything else is downstream of it.
- Can my builder catch these for me?
- A good one catches a lot, and they should. But they can only catch mistakes against a brief. Without one, there's nothing for them to check your decisions against.
- Is it too late if we've already started?
- Depends where you are. Anything not yet built is still a drawing. Ask your architect which decisions are still open - the answer is usually more than you think.
- How much contingency should I hold?
- Ask your builder for a figure for your specific site and scope. Anyone who gives you a percentage without seeing the site is guessing.