A crack has appeared in a wall

Mark both ends of the crack with a pencil line, write the date beside it, and photograph it with a ruler or a coin in shot. That takes two minutes and it answers the question that decides everything else, which is whether the wall is still moving.

A crack that has not passed its marks in three months has stopped. One that has is active, and active is a different conversation.

What to record while you are there

Where it is, on which elevation, and at what height. Whether it appears on both faces of the wall, which is worth checking and rarely is. The widest point, measured rather than estimated. The direction it runs, which is the most diagnostic single detail.

Whether anything changed recently: a storm, nearby construction or excavation, a leak, new heavy racking or equipment, or work done in the building. Whether any doors or windows nearby have started sticking or dropping out of square, which is a separate symptom of the same cause and it matters.

The patterns that need an engineer rather than a decorator

Stating this plainly rather than trying to grade severity in prose, because that is not something an article can responsibly do.

Cracks running diagonally from the corners of doors and windows. Stair-stepped cracks following the mortar joints in block or brick. Cracks that continue through more than one story, or that appear in the same place inside and out. Anything wide enough to insert a coin. Cracks accompanied by doors and windows that have started to bind. Any crack in a structural element rather than a partition. Horizontal cracking in a masonry wall.

Any of those is a referral to a structural engineer, and that is a professional assessment rather than a maintenance visit. It is also the cheaper path, because the alternative is repairing something repeatedly while the cause continues.

The ones that are usually just cracks

Fine cracking in drywall at the joints, particularly at the corners of openings, which is normally movement in the board or the tape rather than the structure.

Hairline shrinkage cracking in new plaster or render, which appears in the first months and then stops.

Cracks along the junction between two different materials, or where an extension meets an original wall, which is differential movement between things that were never going to move together.

Settlement cracking in a building that has just been through a first season, which is common and normally stabilizes.

All of those are still worth marking and dating. The point of the mark is that you stop guessing.

Water is the other question

A crack on an external wall is a water path whether or not it is structural, and in this climate that matters within one rainy season. Check inside the same wall for staining, a musty smell or a soft patch.

Where water has already got in, the sequence is seal the outside, let it dry, then make good inside. Our article on drywall repair after a leak covers the drying part, which is the step people skip.

Stucco deserves its own look, because it is what most exteriors here are finished in and it cracks differently. Fine crazing spread across an elevation is usually the render rather than the wall behind it, which makes it a sealing and coating question rather than a structural one.

A single crack running through stucco in a straight line, particularly one that carries on across a control joint, is more likely to be the substrate moving and is worth marking rather than filling. Check the control joints while you are there: stucco is designed with joints so it can move, and where those have been filled, painted over or left out, it cracks somewhere of its own choosing instead.

Who carries this out

Filling, taping, patching, re-stuccoing and repainting a settled non-structural crack are performed directly by our own technicians, along with the caulking and sealing on the outside face. TrionX carries general liability and workers' compensation on that work.

Structural work is coordinated through licensed contractors, and a structural assessment is a licensed professional's job rather than ours. Florida requires a license for structural work at any job size, and we would rather refer you than take a repair that should have been an assessment.

What to do in the meantime

Keep checking the marks monthly and keep the photographs. If a crack is going to be argued about later, whether with an insurer, a landlord or a buyer, that series of dated images is the entire case.

Add external walls to the quarterly property walk and take the same photographs each time from the same positions. After a storm, the first 48 hours article covers recording new damage while it can still be attributed.