Decision support tool
How worried should you be about that crack?
Most concrete cracks. What separates a crack worth acting on from one worth photographing is not how wide it is — it is whether one side has dropped, whether it is still moving, and what water is doing to it.
Seven questions, no contact details, and a monitoring method you can start today.
How this assessment decides
The same two-pass structure as the repair-or-replace tool, and for the same reason. Escalation rules run first: a crack against the house taking on water, a significant height difference, a wide crack that is noticeably still opening, steps that have shifted. Each of those needs the location and at least one other observation to agree, so a single alarming-sounding answer cannot produce an alarming result on its own.
After that, characteristics are scored — width, height difference, nearby settlement, growth, moisture, pattern and location. A crack following a cut joint scores down, because that is the joint doing exactly what it was cut to do. Any real height difference lifts the result to at least a settlement question regardless of the total, because a step across a crack is a movement observation and no quantity of reassuring answers makes it not one.
Where answers are contradictory or incomplete, the result moves toward having somebody look — never toward “this is fine”.
What this is not
It is not a diagnosis and not a safety certification. It cannot tell you whether concrete is safe to walk on, drive on or stand under, and no result here should be read as saying anything is safe. It reads only what is visible from above; reinforcement, slab thickness, the base and the drainage path decide most crack questions and none of them are visible.
If anything about the concrete worries you, have somebody look at it regardless of what this page says.
About this assessment
Is there a crack width that means trouble?
Not one that applies everywhere, and any page that gives you a single number is oversimplifying. Behaviour matters more than width: a narrow crack that is growing, or that has a height difference across it, is more informative than a wide one that has been static for a decade.
The tool says monitor. Is that a way of saying it does not know?
No — it is a real result and often the correct one. Concrete cracks, most flatwork does, and a great deal of it goes on doing its job for decades afterwards. What monitoring gives you is the one piece of information that changes the answer: whether it is still moving.
Why does it ask about a crack against the house separately?
Because location changes what a crack means. An identical crack in the middle of a patio and immediately against the house are different conversations — not because of the concrete, but because of where water goes when it gets into it.
Does using this tool send my answers anywhere?
No. It runs in your browser. If you choose to ask for local help after seeing the result, only which tool you used, its version and the result category go with that request.
If the question is really what to do about the whole slab, start with the repair-or-replace tool →