Foundation crack: what you can observe and who answers what

About this video. The person on screen is an AI-generated avatar in my likeness. The voice is mine, cloned from recordings of my own voice, and the editing adjusts the sound. The image and the voice may therefore differ from my real appearance and delivery. The text is written and approved by me, and I take full responsibility for it. This process lets me publish regularly; it changes nothing about what is said.

Hello. There’s a crack in your basement. You want to know what it means, and you’ve been searching online for twenty minutes.

The question, as people ask it: “how do I know if a foundation crack is serious”

What you observe on a crack

Grab a flashlight and a ruler. There are four things to note on a foundation crack.

Here is what you observe on a foundation crack, concretely, with a flashlight.

Four things can be noted by eye. One: the direction. Vertical, diagonal, horizontal, stair-step in a block wall. You note it. You don’t interpret it.

Two: the width. You measure it. A coin placed next to it gives the scale in a photo. A graduated ruler does better.

Three: whether both sides of the crack have stayed in the same plane, or whether one side is offset from the other. You can feel it by running a finger across.

Four: the length, and how far the line runs.

These four observations, you can make yourself tonight. What I can’t do, and what you can’t do either, is draw a conclusion from them. A direction says nothing on its own. Neither does a width. The assessment belongs to a structural engineer.

Seen once, or followed over time

A photo of your crack shows a state. It doesn’t say whether it’s moving. Here’s how to find out.

There is a difference between a crack you saw once and a crack you followed over time. It’s information an owner can produce themselves, and that no one else will produce for them.

A photo taken today shows a state. It doesn’t say whether that state is changing.

Two simple methods exist. The first: dated photos. Always the same framing, always with a ruler or a coin in the picture, once a season. Write the date in the file name.

The second isn’t something you install yourself: the crack monitor. A small plaster patch across the crack, or a glass slip glued on each side, with a date written on it. You ask the structural engineer for it, and they decide whether to install one and where. You don’t add anything to a crack, or seal it, before you have their written opinion.

I won’t tell you what it means if a monitor changes, or if it doesn’t. That’s not for me to say. But a structural engineer who receives a series of dated observations is working with more than a single visit.

Photograph and date: documenting a crack for the expert

A photo of a crack with no scale and no date is of no use to anyone. Here’s how to do it.

An engineer who arrives in front of a crack with no history is working with much less.

Here is what any owner can do.

Photograph. Straight on, at the height of the crack, with even lighting. Then a second, wider photo that shows where it is on the wall. A close-up on its own doesn’t say where you are.

Give a scale. A coin, a tape measure, a pencil placed next to it. Without a reference, no one can read a dimension on a photo.

Date it. Every photo, with the day. Your phone already does it, but also write it in a separate file.

Repeat. The same photo, taken from the same spot, a few months apart. It’s the comparison that has value, not the image on its own.

And note the context: heavy rain, a thaw, excavation work on the street.

What you produce there isn’t an expert’s finding. It’s material for the person who will make one.

The inside, the outside, and what is buried

There’s one face of a foundation that almost no one looks at. It’s outside, behind the cedars.

A foundation crack has two faces, and people often forget the second one.

Inside, you look at the basement’s concrete wall where it’s bare. Behind the furnace, in the mechanical room, under the stairs, in the storage area. If your basement is finished, a large part of the wall is no longer visible. That’s a fact, not a criticism.

Outside, you look at the portion of concrete that sticks out of the ground. Walk all the way around the house. Look behind the cedars, behind the recycling bin, under the bottom of the siding.

And there’s the buried portion. That one, no one sees. Not you, not me, not an inspector. It would have to be excavated.

When a line shows up in the same place on both sides of a wall, note it as is. The structural engineer will see what to make of it. Photograph both faces.

What it means is for a structural engineer to say. You document.

The garage and the front steps are not the foundation

The crack in your garage slab and the one in your foundation are not the same line in the file.

There’s a confusion I see often. The garage slab, the front porch and the outdoor steps are not the house’s foundation.

A garage slab rests on the ground. So does a poured concrete porch, in many cases. These are separate structures from the foundation wall that carries the house.

So when you document, be precise about the location. Write “foundation wall, north side, basement”. Write “garage slab, near the door”. It’s not the same line in a file, and it’s not the same line in a declaration.

The reverse is true too. When the garage is attached and shares a wall with the house, the distinction takes a trained eye. That eye is a structural engineer’s.

You do three things. Photograph. Name the exact location. Date it. The rest belongs to the expert.

The structural engineer’s written opinion

A structural engineer’s opinion is a dated, signed document. Here’s what it contains.

A structural engineer’s written opinion. Here is what that document changes, concretely.

A structural engineer is a professional regulated by a professional order. They take on responsibility when they sign. Neither I, nor a building inspector, nor a contractor produces that document in their place.

What you receive is a dated document. Observations, a position, and sometimes recommendations. You are free to do what you want with it afterwards.

Without that document, the conversation is about impressions. With it, it’s about a dated document signed by a professional regulated by an order.

And there’s the timeline. An engineer works by appointment. The report arrives after the visit. That delay exists whether you’re selling or not.

Who to call, and for what

I don’t do the inspection. My role is to know where to look and who to call.

• Structural engineer
• Specialized contractor

Frequently asked questions

Get a value report for your property, and a marketing plan

Get a value report for your property, and a marketing plan — comparables, features, opinion of value

Full video transcript

Full transcript of the video above, translated from French. Published October 28, 2026.

Hello. There’s a crack in your basement. You want to know what it means, and you’ve been searching online for twenty minutes.

My name is Ernso Cléus. I’m a residential and commercial real estate broker with RE/MAX Crystal. Before becoming a broker, I earned a diploma in building inspection technology. I’ve walked into hundreds of basements with a flashlight.

Let me tell you right away what this video won’t do. I’m not going to tell you whether your crack is serious. No one can say before a structural engineer has looked at it.

What it will do is show you what can be observed, how to document it, and who answers what.

What all this changes when it’s time to sell is, or will be, the subject of a separate video on my channel.

What you observe on a crack

Here is what you observe on a foundation crack, concretely, with a flashlight.

Four things can be noted by eye. One: the direction. Vertical, diagonal, horizontal, stair-step in a block wall. You note it. You don’t interpret it.

Two: the width. You measure it. A coin placed next to it gives the scale in a photo. A graduated ruler does better.

Three: whether both sides of the crack have stayed in the same plane, or whether one side is offset from the other. You can feel it by running a finger across.

Four: the length, and how far the line runs.

These four observations, you can make yourself tonight. What I can’t do, and what you can’t do either, is draw a conclusion from them. A direction says nothing on its own. Neither does a width. The assessment belongs to a structural engineer.

Seen once, or followed over time

There is a difference between a crack you saw once and a crack you followed over time. It’s information an owner can produce themselves, and that no one else will produce for them.

A photo taken today shows a state. It doesn’t say whether that state is changing.

Two simple methods exist. The first: dated photos. Always the same framing, always with a ruler or a coin in the picture, once a season. Write the date in the file name.

The second isn’t something you install yourself: the crack monitor. A small plaster patch across the crack, or a glass slip glued on each side, with a date written on it. You ask the structural engineer for it, and they decide whether to install one and where. You don’t add anything to a crack, or seal it, before you have their written opinion.

I won’t tell you what it means if a monitor changes, or if it doesn’t. That’s not for me to say. But a structural engineer who receives a series of dated observations is working with more than a single visit.

Photograph and date: documenting a crack for the expert

An engineer who arrives in front of a crack with no history is working with much less.

Here is what any owner can do.

Photograph. Straight on, at the height of the crack, with even lighting. Then a second, wider photo that shows where it is on the wall. A close-up on its own doesn’t say where you are.

Give a scale. A coin, a tape measure, a pencil placed next to it. Without a reference, no one can read a dimension on a photo.

Date it. Every photo, with the day. Your phone already does it, but also write it in a separate file.

Repeat. The same photo, taken from the same spot, a few months apart. It’s the comparison that has value, not the image on its own.

And note the context: heavy rain, a thaw, excavation work on the street.

What you produce there isn’t an expert’s finding. It’s material for the person who will make one.

The inside, the outside, and what is buried

A foundation crack has two faces, and people often forget the second one.

Inside, you look at the basement’s concrete wall where it’s bare. Behind the furnace, in the mechanical room, under the stairs, in the storage area. If your basement is finished, a large part of the wall is no longer visible. That’s a fact, not a criticism.

Outside, you look at the portion of concrete that sticks out of the ground. Walk all the way around the house. Look behind the cedars, behind the recycling bin, under the bottom of the siding.

And there’s the buried portion. That one, no one sees. Not you, not me, not an inspector. It would have to be excavated.

When a line shows up in the same place on both sides of a wall, note it as is. The structural engineer will see what to make of it. Photograph both faces.

What it means is for a structural engineer to say. You document.

The garage and the front steps are not the foundation

There’s a confusion I see often. The garage slab, the front porch and the outdoor steps are not the house’s foundation.

A garage slab rests on the ground. So does a poured concrete porch, in many cases. These are separate structures from the foundation wall that carries the house.

So when you document, be precise about the location. Write “foundation wall, north side, basement”. Write “garage slab, near the door”. It’s not the same line in a file, and it’s not the same line in a declaration.

The reverse is true too. When the garage is attached and shares a wall with the house, the distinction takes a trained eye. That eye is a structural engineer’s.

You do three things. Photograph. Name the exact location. Date it. The rest belongs to the expert.

The structural engineer’s written opinion

A structural engineer’s written opinion. Here is what that document changes, concretely.

A structural engineer is a professional regulated by a professional order. They take on responsibility when they sign. Neither I, nor a building inspector, nor a contractor produces that document in their place.

What you receive is a dated document. Observations, a position, and sometimes recommendations. You are free to do what you want with it afterwards.

Without that document, the conversation is about impressions. With it, it’s about a dated document signed by a professional regulated by an order.

And there’s the timeline. An engineer works by appointment. The report arrives after the visit. That delay exists whether you’re selling or not.

A crack is observed; it isn’t read. It gets assessed, and it’s a structural engineer’s written opinion that answers. The specialized contractor carries out the work.

What has value is the comparison over time. Photograph with a scale and a date.

A seller’s first question is still the value of their property. I produce a value report and a marketing plan. You can request it through the links below the video.

If you’re already bound by a brokerage contract with another broker, this invitation isn’t meant for you.

I don’t pass verdicts, I don’t put a price on work, and I don’t act as an inspector in any transaction. I observe, and I tell you which expert to call.

Ernso Cléus, residential and commercial real estate broker, RE/MAX Crystal. Your broker who knows buildings.

Read also: selling a house with a foundation crack · do I have to declare a repaired crack · what not to repair before getting a written opinion · get in touch

Ernso Cléus, residential and commercial real estate broker — RE/MAX Crystal. Your broker who knows buildings.