What Is the Procedure When Working With Stucco?

Temperature

• Working on a cool, overcast day prevents the stucco from prematurely drying out and cracking. Alternatively, a cold day can leave the stucco too stiff for a trowel and stop the ingredients from binding together. Installers should never work with stucco when outside temperatures drop below 40 degrees Fahrenheit or exceed 120 degrees Fahrenheit, cautions the Portland Cement Association.

Preparation

• A stucco installer nails or screws a steel mesh onto the walls of a house to provide a backing onto which the stucco will stick. If the house already has a stucco exterior, the new stucco goes directly on top of the old layer, after the removal of damaged pieces. Mixing fresh stucco requires an appropriate balance between wetness and dryness in the mortar: Stucco should be damp enough to spread easy with a trowel, but not so wet that it drips off the steel mesh.

Process

• A trowel or sprayer spreads up to three layers of stucco on the sides of a house. The first coat usually measures 3/8-inch thick and is scratched in long, even rows before drying, to provide a backing for the second coat, which the installer will usually apply with the same thickness, explains Russ Flynn in the October 1990 issue of "Construction Dimensions." For a finer finish or to create texture, the installer lightly scratches the second coat and applies a final, thin layer.

Time Frame

• Each layer of stucco must dry before the installer adds additional coats, because wet stucco shrinks when the water in it evaporates. While time frames for drying vary depending upon geography and professional opinion, MortarSprayer.com, for example, recommends installers wait two days before applying a second coat and between five and 26 days after that for a third coat.

Techniques

• Stucco installers use consistent pressure when applying stucco with a trowel create an even surface, and smooth out high spots and fill in low spots before the material dries. They usually install the first coat in a circular motion and then work the trowel across a wall horizontally in even rows with a slight overlap before spreading and smoothing additional coats in horizontal rows.