Stucco Repair in St. Louis: Cracks, Patches, and When to Call a Pro
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Most stucco repair in St. Louis starts with cracks. Hairline cracks thinner than a credit card are usually cosmetic and can be filled and coated. Cracks wider than about 1/8 inch, cracks that keep growing, or cracks with one side offset from the other point to movement or moisture, and those need a professional diagnosis before any patching.
Stucco shows up all over the metro, from Tudor-style homes in Webster Groves and Kirkwood to newer houses with stucco accents out in Chesterfield. Our freeze-thaw winters work on it hard, and by early summer people start noticing the cracks that opened over the winter. Here's how to read them and what a good repair involves.
Which stucco cracks are normal and which are serious?
Fine, spidery cracks are normal. Stucco is a cement-based plaster, and it shrinks a little as it cures and moves a little with temperature. Wide, long or displaced cracks aren't normal, and they tell you something behind the wall is moving or getting wet.
Here's a rough way to sort what you're seeing:
| What you see | Likely cause | What it usually needs |
|---|---|---|
| Hairline web or map cracks across a wall | Normal shrinkage as the stucco cured | Cleaning, a crack filler that stays flexible, and a coating |
| Short diagonal cracks at window and door corners | Stress concentrating at openings | Routing out and filling; check the flashing around the opening |
| Cracks wider than about 1/8 inch | Settlement, framing movement, or freeze-thaw damage | Professional inspection before patching |
| Cracks with one edge sticking out past the other | Structural movement or loose lath | Inspection of the framing and foundation |
| Stains, bulges or soft, hollow-sounding areas | Water behind the stucco | Moisture investigation and removal of damaged sections |
Mark the ends of a suspicious crack with a pencil and date it. Check again in a month. If it's grown past your marks, it's active, and filling it won't stop it.
How do you check stucco for moisture damage?
Look for staining, then press and tap. Dark streaks running down from window corners, rust-colored stains, bulging, and areas that sound hollow or feel soft when you push on them are all warning signs. Water trapped behind stucco can rot sheathing and framing long before you see it from outside.
The usual entry points are around windows and doors where flashing failed, where a roof line meets a wall, at the bottom edge near grade, and around fixtures and vents. Check the inside of those same walls for stains, too.
If you suspect water, a contractor can probe or moisture-test the wall. Patching over wet stucco only hides the damage while it gets worse. For readers who like the technical side, the Journal of Light Construction covers stucco assemblies and moisture management in real depth.
One note before you test anything: make sure you actually have traditional stucco and not EIFS, a foam-backed system that looks similar and is repaired differently. If you're not sure, ask before you poke holes in it.
How is stucco patched?
Small cracks get cleaned out and filled. Larger damage gets cut out to sound material and rebuilt in layers. Either way, the repair is only as good as the prep around it.
For hairline cracks, the usual approach is to clean the crack, open it slightly so filler can grip, and fill it with a flexible patching compound made for stucco. Rigid fillers tend to crack again along the same line as the wall moves through another Missouri winter.
Bigger repairs are a different job. A contractor cuts the damaged area back to solid stucco, replaces any rusted lath or rotten sheathing, and fixes the water source. New stucco then goes on in coats, each allowed to cure, before a finish layer matched to the wall around it.
Can you match stucco texture on a patch?
Yes, but it takes skill, and the patch almost always shows to some degree. Stucco finishes vary a lot, from smooth trowel to sand float to heavier dash and lace textures. A skilled hand can get close. Getting it invisible is harder.
Color is the bigger giveaway. New stucco and old stucco take paint differently, and even a perfect texture match can look like a patch once the light hits it at an angle. That's why many homeowners coat the whole wall, or the whole house, after repairs. A uniform finish hides the transitions far better than touching up the patches.
What affects the cost of stucco repair?
Cost depends far more on what's behind the cracks than on the cracks themselves. Two houses with similar-looking cracks can end up with very different bills once someone opens up the wall.
The main cost drivers:
- Number and width of cracks. Hairline filling is quick. Wide cracks need routing and rebuilding.
- Hidden damage. Rusted lath, rotted sheathing or framing adds carpentry to the job.
- Fixing the water source. Flashing, sealant and gutter corrections around the damaged area.
- Texture matching. Specialty finishes take more time to blend.
- Access and height. Second-story walls and steep grades mean ladders, staging or lifts.
- What happens after. A spot repair costs less up front than repairing and coating the full house, but it's the coating that ties the repairs together.
An honest estimate breaks those pieces out. Be skeptical of a single number with no detail behind it.
When should you call a pro for stucco repair?
Handle a few hairline cracks yourself if you're comfortable on a ladder. Call a professional for anything wider, anything growing, anything stained or soft, or any wall you can't reach safely. Those are the cases where the real problem is usually behind the surface.
At Rhino Shield of Missouri, repairs are built into every job. Our application process runs cleaning, then repairs, caulking and sealing, a primer matched to the surface, and multiple coats of ceramic topcoat. On stucco homes we coat, the ceramic elastomeric coating goes on at 8 to 10 mils, flexible enough to bridge hairline cracks and even out the look of patched areas. The homeowner reviews we hear most often mention the crew as much as the finish:
"If you want to use a company who is professional and 5 star from sales to service, use Darrin & his teams. The team of Ram, Randy & George was exceptional!! Our home looks amazing!!"
— Arthur B.
Crews like that are the reason repairs disappear under the finished coat instead of showing through it. You can see finished stucco and masonry work in our gallery of applications.
Related reading: Stucco Paint Repair
Frequently Asked Questions
Can I repair stucco cracks myself?
Hairline cracks, yes. Clean them, open them slightly, and fill with a flexible stucco patch. Leave wide, growing or displaced cracks to a professional, because they usually mean movement or moisture behind the wall that a surface patch won't fix.
How long does a stucco patch need before painting?
It depends on the product and the depth of the repair. Thin crack fillers may be ready in a day or so, while new stucco built up in layers needs much longer to cure. Follow the patch manufacturer's directions and let the area dry completely before any primer or coating goes on.
Why does my stucco keep cracking in the same spot?
Repeat cracking means the cause is still active. The wall may be moving at a window or door opening, the framing or foundation may be settling, or water may be getting in and freezing. A rigid filler can also crack again along the old line. Find the cause before you patch it a third time.
Does coating stucco stop cracks?
A thick elastomeric coating expands and contracts with the wall, bridges hairline cracks, and helps keep water out of them. It won't stop structural movement or fix cracks caused by settling or water damage. Those need to be repaired properly before the wall is coated.
Have someone look at your stucco
If you've got cracks you're not sure about, we're glad to take a look and tell you what we see. Request a free estimate or call 314-239-7947.
