How to patch cracks and small holes in stucco

How a cement stucco wall is built

Traditional stucco is a cement plaster made of Portland cement, sand, lime and water. On a wood-framed house it usually goes on in three coats over a layer of black building paper and a metal mesh called lath. The paper sheds any water that gets through. The lath is nailed or stapled to the wall and gives the wet cement something to grab. The first coat, the scratch coat, locks into the lath. The thin finish coat on top carries the color and texture you see.

Cement shrinks a little as it dries, and the house frame swells and shrinks with heat and humidity. That's why fine hairline cracks show up in a lot of stucco, often around the corners of windows and doors. Stucco makers describe fine surface cracking as normal. What isn't normal is a crack that keeps getting wider, cracks shaped like stair steps, stucco that bulges or feels soft, or water stains inside. Those point to water getting behind the stucco or the structure moving, and a surface patch won't fix either one.

Why stucco cracks or breaks

Let's fix it

1. Decide if the crack is safe to patchLook closely along the whole crack in good daylight. A hairline crack is about as thin as a sheet of paper or a credit card edge, and the stucco on both sides sits flat and even. Those are usually surface cracks and safe to seal. Now look for warning signs. Watch for a crack wider than about 1/8 inch, one side sitting higher than the other, cracks that step up the wall like stairs, or bulging stucco. Check inside for water stains too. If you see any of these, stop here and call a stucco contractor. A patch would hide the problem while water keeps doing damage.
   Done

   Something went wrong?

   • Not sure if the crack is growing Put a pencil mark at each end of the crack and write the date next to it. Check it after a few weeks and again after a season. If it runs past the marks or gets wider, have a pro look before patching.

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2. Rule out synthetic stucco and hidden waterTap the wall near the damage with the handle of a screwdriver. Traditional cement stucco feels hard and sounds solid, a bit like tapping a sidewalk. Synthetic stucco, called EIFS, is a thin coating over foam board. It often sounds hollow, and a firm thumb press may dent it. If a hole shows white or gray foam behind the finish, it's EIFS. Don't use cement patch on it, since it won't bond or flex the same way. Call an EIFS contractor instead. On cement stucco, also tap for patches that sound hollow or crumble. Stucco that comes away in your hand or shows rusty lath often has water behind it, so stop and call a pro.
   Done

   Something went wrong?

   • The whole area around the hole sounds hollow The stucco has likely separated from the lath over a large area. Don't keep chipping, because more will fall off. A stucco contractor needs to cut out and rebuild that section.

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3. Seal hairline cracks with stucco crack fillerUse a textured acrylic crack filler made for stucco, sold in caulk tubes. Pick a day above the label's minimum temperature with no rain expected for about 12 hours. Brush the crack with a stiff nylon or steel brush to remove dust, dirt and flaking paint. Cut the tube tip so the bead just covers the crack, and squeeze a thin bead along it. Smooth it into the crack with a gloved finger or a damp brush. Then dab the bead with a damp sponge or stiff brush so it picks up the wall's texture. Let it dry as the label says, usually about 24 hours, before painting.
   Done

   Something went wrong?

   • The filler looks smooth and shiny Dab it again while it's still soft, using a stiff brush or a wadded rag. Once it's dry, painting the wall color usually blends it in.
   • Filler shrank into the crack Let it dry, then add a second thin bead and texture it the same way.

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4. Clean out and prepare a small holePut on gloves, safety glasses and a dust mask. Tap around the hole with a hammer and a cold chisel or an old flat screwdriver, and remove any stucco that's loose or crumbly. Keep going until the edges are solid. Then angle the chisel to cut the edges slightly wider at the back than at the front. Brush out all dust. If metal lath shows and it's solid, leave it. If the lath is missing or torn, staple or screw a piece of galvanized metal lath over the gap so it sits a little below the surface. If the lath is badly rusted or the paper behind is torn and soggy, stop and call a pro.
   Done

   Something went wrong?

   • The hole keeps getting bigger If solid edges never show up and the hole passes about the size of your palm, stop chipping. That much loose stucco usually means water damage, and a contractor should open and rebuild it.

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5. Fill the hole in thin layersMist the edges and back of the hole with a spray bottle so the old stucco is damp but has no standing water. Stir premixed stucco patch well, or mix a bagged stucco patch with water as the bag says. Press the first layer in hard with a putty knife or margin trowel, working it into the lath and the undercut edges. Keep each layer no thicker than the label allows. For one common premixed patch that's 1/4 inch, with 24 hours between layers. Scratch the surface of each layer except the last with the knife tip so the next one grabs. Leave the last layer just level with the wall.
   Done

   Something went wrong?

   • The patch sags or slides out The layer was too thick or the mix too wet. Scrape it out, let what's left firm up, and put it back in thinner layers.
   • Cracks appear as the patch dries It likely dried too fast in sun or wind. Mist it lightly and shade it, and fill the cracks with the next layer.

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6. Match the texture, cure it and paintShape the texture on the last layer while it's still soft, usually within the first half hour or so. A damp sponge or rubber float worked in small circles gives a sand finish. A stiff brush dabbed straight in gives a rougher look. For a skip-trowel finish, flick small dabs of patch on and flatten them lightly with the trowel. If the label calls for it, mist the patch lightly a few times a day while it cures. Protect it from rain for at least 12 hours. Paint with exterior latex paint only after the label's wait time, often 24 hours or more.
   Done

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Watch it done

How to Repair Cracks and Holes in StuccoBy QUIKRETE on YouTube. Their method may vary a little from ours.

Watch on YouTube

If it comes back

A fine hairline crack that reopens in the same spot every year is usually seasonal movement. Seal it again with crack filler, which stays more flexible than hard patch. For tips on prep and paint, see the guide to fixing peeling paint.

If cracks keep growing, form stair steps, or show up along with sticking doors, treat it as movement, not a surface problem. Check drainage first. See the guide for water pooling around the foundation and the guide to cleaning gutters.

If the cracks are in a concrete patio, walk or foundation wall rather than the stucco, the products and steps are different. See the guide to patching a concrete crack.