Mixing and Patching Exterior Stucco

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To repair damaged and crumbling stucco, make a compound of 1 part portland cement, 3 parts fine sand and enough water to make a thick paste. If you need to match the natural color of your existing stucco because it's not painted, look for a sand color that's comes close and vary the ratio slightly until you mix the color you want. To see the final color of your stucco mix you will have to let it dry completely which will take 24 hours or more, so you may want to mix a small amount of paste to start and let it dry before deciding on the right ratio of sand to cement to achieve the desired color.

Mix your stucco paste thick enough to stay on a vertical surface without sagging. If you make a mistake and make the paste too thin, mix more portland cement and sand together and then add it to the paste to thicken it. Once it is mixed the paste will be workable for about an hour.

Patching Stucco

To make stucco repairs remove all loose material from the damaged area using a putty knife or similar tool. Then use a stiff brush or broom to remove dust and wet the surface with a spray bottle or compression sprayer of water. Apply the stucco paste while the surface is wet and shape it to match the existing finish. As the new patch sets and cures keep it wet with the water sprayer soaking it 3 or 4 times a day for three days. This will prevent cracks from forming as the stucco drys.