How to Patch Up a Stucco Ceiling

Climb up a ladder and examine the crack. If it's small enough (1/8-inch or less), you can just patch it with siliconized acrylic caulk.

Brush dust and debris out of the crack with a stiff wire brush.

Apply a bead of siliconized acrylic caulk over the crack and allow it to set for the time specified on the packaging. If the crack is larger than an 1/8-inch, you'll need to apply stucco to patch the crack.

Scrape away loose stucco around the crack with a 4-inch drywall knife, then brush it again with a stiff wire brush to remove any debris.

Mix a batch of stucco consisting of three parts sand, one part Portland cement and 1/4-part lime, along with a pigment to match your ceiling color (if the ceiling isn't painted). You may want to mix small test batches and apply them to a piece of scrap wood and then compare the test batches to the ceiling to see which mixture comes closest to matching the ceiling. Mix the stucco until it has the consistency of peanut butter.

Dampen the area of the ceiling around the crack with a sponge or spray bottle. This prevents the moisture from being drawn out of the stucco as it sets, which can cause it to crack.

Apply the stucco to the crack with a trowel or small putty knife, depending on the size of the crack.

Blend the edges of the patched area into the surrounding stucco with a rubber float. If the patched area is larger than an inch, use the float to create textures in the patch. Allow the stucco to dry overnight.

Apply masonry primer to the patch, then paint the patched area (if the ceiling is painted).