How to Repair Stucco. Stucco looks great - unless it has a long, ugly crack running through it. Here's how to get it back into tip-top shape.
Note the direction of the crack. Vertical cracks from base to window or roof to door sometimes indicate a problem with the foundation. Before fixing the crack, call a foundation specialist to determine the condition of the foundation.
Fix very small cracks by filling them with a high-quality caulk - preferably one that can be painted over. Use your fingers to press it in well and a damp cloth to clean up.
Use a cold chisel or an old screwdriver to clean out wider cracks.
Soak the area thoroughly with a hose so that the stucco won't leach the water from the new mortar and cause it to crumble.
Mix your mortar in a shallow bucket: one part portland cement, four parts builders' sand and a little bit of water to make the mortar workable but not runny.
Cover the area to be patched with a polyvinyl acetate (PVA) bonding agent made for masonry.
When the bond is slightly sticky, fill the crack with the mortar mix.
Cover the patched area with a piece of bitumen-coated fiberglass. (Bitumen is a tarlike substance.)
Use a paint roller to press it into place, and apply a coat of bitumen over the patch.
Let the bitumen dry and then apply another coat, stippling it with a soft-bristled brush to match the rest of the wall.
Paint over the area with a primer made for stucco or bitumen patching. Allow the primer to dry.
Repaint the area - but be aware that you may have to repaint the entire wall so that the patch won't stand out.