How to Patch Exterior Stucco Cracks in a Soffit


Stucco is almost as old as architecture itself. Various mixes of cement, plaster, sand and other materials work together to form a hard, long-lasting surface that sheds rain and resists rot. House settling and seasonal expansion and contraction, however, can open up cracks that let in the elements and mar your home's beauty. Many of these flaws are not hard to repair. If you have stucco cracks on the underside of a soffit, for example, you'll find the repair a fairly straightforward afternoon project.

Things You'll Need

  • Scrub brush
  • Caulk gun
  • Exterior latex caulk
  • Utility knife
  • Small container of water
  • Clean cloth
  • Backer rod (optional)
  • Latex exterior primer (optional)
  • Exterior latex topcoat (optional)
  • Paintbrush (optional)
  • Remove debris and loose bits from the crack with a dry, stiff cleaning brush or a toothbrush. Don't enlarge or further damage the crack with anything too big or hard. Brush the dust away from the crack with a clean cloth or an old paintbrush.

  • Insert the caulk tube into the caulk gun and slide the gun's rod forward until its end just touches the bottom of the tube. Cut off the tip of the applicator so it extrudes a bead of caulk about as wide as the crack. Follow the slanted guidelines on the plastic tip. If you're not sure, start at 1/8 inch and enlarge it later if needed. Use a utility knife or the built-in cutter that is part of many caulk guns.

  • Set the tip at one end of the crack and squeeze the gun's trigger to extrude and push a bead of caulk into the crack. Move the tip along the crack while squeezing the trigger. When the trigger hits a stop, let it go and squeeze again. Fill 2 or 3 feet of the crack.

  • Dip a finger in water, then use it to push the caulk into the crack and smooth it out. If you did a good job and applied just enough caulk, you won't have a lot of excess caulk left on the surface of the stucco. Carefully wipe away excess caulk with your finger or a dampened cloth.

  • Move to the next section until the entire crack is filled. Let the caulk cure for 24 hours before painting. If your caulk bead is 3/16 inch or greater, let it cure for at least 48 hours.

Tips & Warnings

  • If the crack expands and contracts seasonally, fill the gap during cool weather when the crack is near its widest. Check the temperature allowances on your caulk's label. Most exterior caulk products can be applied between 40 degrees and 100 degrees Fahrenheit.
  • Hairlines that close up completely in summer or are 1/8 inch or smaller are superficial. There's no need to fill them unless you find them unsightly.
  • Fill cracks wider than 1/4 inch with fiber or latex backer rod before applying the caulk. This minimizes caulk shrinkage and cracking. Backer rod will be near the caulk at the hardware store.
  • Your soffit's stucco repair is protected from the elements by the eaves, so leave it alone if it's discreet. If it shows, prime the crack with exterior latex primer, then touch it up with exterior latex topcoat.
  • Don't take on repairs to artificial stucco products, such as exterior insulation and finish systems. Repair methods for EIFS are different from those for genuine stucco, and you could possibly void your product warranty. Consult your contractor or the manufacturer for guidance.

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