A crack in the foundation or the wall is stressful, and a tube of sealant from the hardware store looks like a quick fix. Sometimes it is. Often it is not. The right choice depends on what kind of crack you have and whether it is still moving. This guide separates the cracks you can reasonably handle yourself from the ones that need a professional.
Step One: Watch Before You Seal
Do not seal anything yet. Sealing hides evidence, and a crack that is still moving will reopen. Spend a few weeks, and ideally a wet spell and a dry spell, tracking what the crack does. Clay soil in the Baton Rouge area swells and shrinks with the weather, so a crack can look stable in one season and change in another.
- Measure the width in several places and write it down with the date.
- Mark each end with a pencil line and the date, so growth is easy to see.
- Take photos with a ruler beside the crack from the same angle each time.
- A crack gauge, sold at hardware stores, shows movement more precisely.
- Note whether doors, windows or floors change at the same time.
Cracks You Can Usually Handle Yourself
- Hairline cracks in paint or drywall that are not growing. Patching and repainting is cosmetic, but photograph them first.
- Thin vertical cracks in a poured concrete floor or garage slab that are narrow, stable and have no uneven edge. A concrete crack filler or a flexible sealant made for concrete can keep out water and insects.
- Small shrinkage cracks that appeared soon after concrete was poured and have not changed.
Read the product label and use a material made for the surface. A flexible polyurethane or elastomeric sealant is a common choice for cracks that move slightly, while rigid patching compounds can crack again.
Cracks That Need a Professional
- Cracks wider than about a quarter inch, or any crack that keeps growing
- Horizontal cracks in a foundation or basement-type wall, which can mean pressure from soil or water
- Stair-step cracks in brick or block
- Cracks where one side sits higher than the other
- Cracks with sticking doors or windows, sloping floors or gaps at trim
- Cracks that leak water after rain
- Cracks in crawl space beams, piers or support walls
These can point to movement in the foundation. Sealing them covers the symptom and leaves the cause. See our pages on foundation crack repair and 7 warning signs of foundation problems.
Why Sealing Is Not a Cure
A sealant keeps water or insects out. It does not stop a foundation from settling or soil from shifting. If movement continues, the sealant will tear or pull away. The risk is not only a wasted weekend. A sealed crack can hide the earliest evidence a professional would use to figure out what is happening.
Safety Basics
- Use a stable ladder and a helper for anything above shoulder height.
- Grinding or chiseling concrete creates silica dust, which is harmful to breathe. Wear a properly rated respirator and eye protection, and keep the dust down.
- Follow the ventilation instructions on any sealant or filler.
- Crawl spaces can hold standing water, wiring, mold and animals. Do not go in without protective gear and a plan, and leave it to a professional if you are unsure.
- Turn off nearby electrical circuits if you are working around wet areas.
Do Not Forget the Cause
Even a successful seal only deals with the crack. Look for the reason it formed. Check whether gutters and downspouts empty beside the wall, whether soil slopes toward the house, whether a tree is drying out one side, and whether a leak could be washing soil from under the slab. Fixing these can make a crack stop changing, and it gives a professional a head start if you do need one. Small, inexpensive changes such as extending a downspout often matter more than the sealant itself.
What to Do Instead if You Are Unsure
Photograph the crack, record the measurements and request an inspection. A contractor or an engineer can tell you if the crack is cosmetic, what is causing it, and whether sealing alone is enough. Keep your monitoring notes. They show how long the crack has been changing, which helps any repair decision. Fixing drainage near the crack, covered on our foundation drainage page, can also reduce movement.
Seeing any of this at home? Request a free estimate and a local foundation repair contractor can take a look.
Sources and Further Reading
Written by the Greet Bless editorial team and last reviewed October 2026. This is general information, not engineering, legal, insurance or financial advice. Greet Bless is a referral service and does not inspect homes or perform repairs.
