People often ask us questions about the stucco process, so we are providing you with a general outline of the steps we take to replace a wall that has been destroyed due to initial construction defects. In this example, we use a three-coat stucco process on a wood-framed second floor of a Florida home that is concrete block on first floor. It is, unfortunately, rather common for the stucco on wood-framed second floors on Florida homes to have been poorly installed, which, over time, causes cracks and leaks. Conversely, first floors in Florida homes are uniformly constructed of concrete block, and stucco problems are much more rare due to the extreme strength and rigidity of the concrete-filled block wall underneath the stucco.
Engineers will determine whether the entire wall’s stucco need to be replaced due to initial construction defects, and once that is established, we begin the 3-coat stucco process. First, we completely remove all existing stucco, lathe and paper to reveal the wood sheathing that forms the base of the outside of the wall. This sheathing is what many homeowners call plywood, but today the more frequently used substrate is Oriented Strand Board (OSB). We remove all extraneous nails, construction staples and any little bits of stucco that cling to the sheathing to create a clean and clear base prepared for proper installation of the three-coat stucco wall system.
Using a staple gun, we attach a water resistive barrier (WRB) to the wood. This is a thin paper membrane impregnated with a tar-like resin that is designed to provide a water barrier and drainage plane for any water that gets through the stucco layers.
Next, we attach the lathe, a metal netting, by stapling it to the wall. This metal mesh somewhat resembles chicken wire but is much stronger and designed specifically for quality stucco work. The stucco is then securely fastened every 8 inches, through the WRB to the sheathing. The lathe supports the weight of the stucco and holds it very tightly to the wall sheathing and WRB. It’s important that the lathe be as tight as possible so that the stucco is not permitted any movement.
The scratch coat is the base layer of the stucco that is directly applied to the lathe. It is trowel applied and then the wet surface is scratched up with a scratcher before fully setting up to allow for a strong physical bond of the scratch coat to the brown coat that will be applied next. The scratch coat is applied as a thin layer and its primary role is to engage the lathe and create a stronger wall base for the brown coat.
The brown coat is the thickest and strongest coat of stucco in the system. It provides the strength and rigidity of the wall coating that is why stucco is such a popular option. This layer needs to be very flat and uniform as it is the base for the finish coat and thus has much to do with the final appearance, especially for simpler finishes. To achieve this smooth layer a long tool called a “Darby” is used to apply the brown coat.
The finish coat is what you see and the reason why stucco exteriors are loved by so many people. There are a wide range of finish textures available. Some are fast and easy to apply ranging up to others that require decades of experience and artisanal skill to achieve a perfect result. In Florida, the most common finish is what we call a “dash” which is a rough, yet flattened effect formed by applying a very thin layer of stucco and then slinging small stucco blobs at the wall using a special type of brush. After these little blobs cure slightly and are become firm, they are troweled down to have the high points at a consistent level on the wall. The advantage of the dash texture is not only is it easy and inexpensive to apply, it is attractive and easy to repair should damage happen to the wall and require patching.
Painted stucco has its own water protective qualities inherently but a modern and high-quality stucco wall always includes a complete sealant layer. First, the entire wall is sprayed with a water based, penetrating sealer usually with a silane or siloxane base that provides the stucco with a nearly permanent water repellent surface. A final step in the sealant step is the use of elastomeric caulking around the edges of stucco where they interact with doors, windows and penetrations for wires, pipes and vents of various types. This step ensures there is not an easy path for water to penetrate the wall system.
With rare exception, all finished stucco work is painted with a high quality paint designed to be used over stucco. These are elastomeric coatings, a masonry paints or an acrylic coating. We typically just need to know the specific color you want and we will purchase a coating matched to the color you select.
Every Aptitude Associates crew member is expertly trained and led by a very experienced stucco foreman. In addition to closely supervising all steps in the process, our foreman carefully inspects the finished work to ensure all elements meet our high standards of quality and in alignment with local codes and national ASTM standards.