Where a crack is tells you more than how wide it is.
Nearly every stucco wall in Florida has cracks. Most of them are cosmetic and will still be cosmetic in ten years. A few of them are the wall telling you water is getting behind it. Knowing which is which saves both unnecessary repairs and, more expensively, the ones that get postponed.
Cracks that are almost always cosmetic
Crazing, or map cracking. A fine network of shallow lines across the surface, like the glaze on old pottery. This is shrinkage in the finish coat as it cured, usually from mixing or curing conditions on the day it was applied. It is shallow, it does not go through the system, and it is very common on newer stucco. A coat of quality elastomeric paint covers it and it stays covered.
Hairline cracks in the first year. New stucco shrinks as it cures, and a house settles slightly. Fine cracks appearing in the first twelve months are ordinary. Watch them rather than repair them immediately, because a crack that is still moving will reopen through a patch.
Cracks that follow control joints. Control joints exist so the wall cracks where you want it to. A crack in a joint is the system working.
The rough test: a crack you cannot get a fingernail into, in the middle of a large uninterrupted wall, away from any window, door, or penetration, is nearly always shrinkage.
Cracks worth looking into
Diagonal cracks running off the corners of windows and doors. This is the classic pattern and the most important one to recognize. Window and door openings concentrate stress, and the corners are where a wall relieves it. A short diagonal at one corner can be ordinary settlement. Matching diagonals off several corners, or off both upper corners of the same window, means something is moving, and it also means you now have a crack in the exact place where water most easily gets into a wall.
Window corners are where stucco failure investigations start, because that is where the flashing is.
Horizontal cracks. Less common and less benign. A horizontal crack partway up a wall can follow a floor line where two parts of the structure move differently. One low on the wall at the weep screed can mean the screed is buried or blocked, which means water that gets into the wall cannot drain out of it.
Stair-step cracking, running diagonally in a stepped pattern that follows the block joints underneath. That is the masonry moving, not the stucco, and it points at the foundation.
Any crack wider than roughly an eighth of an inch, regardless of where it is. Width beyond that stops being surface behavior and starts being movement.
Cracks that have opened further since you last looked. A stable crack and a growing crack are different problems, and the only way to know which you have is to mark the ends with a pencil and date it. Two months of that answers a question no amount of looking at a photograph will.
The signs that matter more than the crack
Cracks are the visible part. These are the ones that tell you water has already been getting in, and they change the situation entirely:
- Rust staining bleeding out of a crack. Metal lath or fasteners are corroding, which means they have been wet for a long time.
- Efflorescence, the chalky white deposit around a crack. Water has moved through the wall, dissolved salts, and left them at the surface on the way out.
- Paint bubbling or peeling near a crack rather than fading evenly. Moisture is pushing from behind.
- A soft or spongy feel when you press the wall.
- A musty smell in the room on the other side, particularly after heavy rain.
- Staining that runs in a line below a window or a penetration.
Any of these alongside cracking moves the question from "should I patch this" to "what is behind this wall."
Why location beats width
A quarter-inch crack in the middle of a blank gable wall is an eyesore. A hairline crack at the bottom corner of a window, on the elevation that takes the wind-driven rain, is a path into the wall assembly.
The reason is what the crack is next to. Windows, doors, hose bibs, dryer vents, light fixtures, utility penetrations, and roof-to-wall intersections are all places where the waterproofing behind the stucco has to be interrupted and then made continuous again with flashing. Those transitions are where installation errors live. A crack there gives water an easy route to a detail that may already be imperfect.
So a crack near a penetration deserves attention out of proportion to its size, and a crack in open field usually does not.
What not to do about them
Do not caulk them with silicone. It is the most common homeowner repair and it makes things worse. Silicone will not accept paint or stucco, it stands out permanently, it traps moisture behind it, and it has to be cut out before a proper repair can be made.
Do not just paint over an active crack. Paint bridges a hairline. It will not bridge a crack that is still moving, and it hides the evidence you would want in a year.
Do not seal a weep screed. The gap at the bottom of a stucco wall is there to let water out. Caulking it, burying it in a raised flower bed, or covering it with new hardscape traps water in the wall. This is a genuinely common and genuinely damaging mistake.
Do not patch before you know why it cracked. A patch over a crack caused by movement will crack again, in the same place, usually within a season.
How a proper repair actually goes
For a cosmetic crack: the crack is opened slightly to give the patch material something to hold, cleaned out, filled with a compatible stucco patching material rather than a generic filler, textured to match the surrounding finish, and painted. The texture match is the hard part and it is what separates a repair you cannot find from one you can see from the street.
For a crack with movement: the cause gets addressed first. That might mean adding a control joint where one should have been, addressing a drainage or flashing detail, or, if the movement is structural, getting an answer about the foundation before any stucco work happens at all.
For a crack with any of the water signs listed above: the wall gets moisture tested before anything is patched, because sealing the surface over wet sheathing traps the problem where you cannot see it.
Color matching, since it will come up
Stucco weathers and lightens. A repair painted to the current color of the surrounding wall will match today and drift over time, and a repair painted to the original specification will not match today at all. On a wall with an integral color finish rather than paint, matching is harder still.
The usual answers are to repair and repaint a full elevation to a natural break rather than spot-painting, or to accept a small visible difference in a low-visibility location. Anyone who promises an invisible spot repair on a sun-faded wall is overselling.
The short version
Fine networks and hairlines in open wall: cosmetic, paint them when you next paint.
Diagonals at window and door corners, horizontals, stair-steps, anything over an eighth of an inch, or anything that has grown: get it looked at.
Rust, efflorescence, bubbling paint, soft spots, or musty smells: get the wall moisture tested before anything is repaired.
Stucco Home Repair does free inspections across Jacksonville, Ponte Vedra, St. Augustine, Nocatee, Palm Coast, and Flagler, and we will tell you plainly when a crack is cosmetic rather than sell you a repair you do not need. If you have marked a crack and watched it move, bring that, it is the most useful thing you can hand us.