All tools have their advantages but a right tool can greatly speed up the application process and provide ease in installation. For example, a stucco sprayer can be many times faster than the traditional old hawk & trowel application of traditional hardcoat stucco.
Application of exterior stucco is not science rather it is a skill gained from hands on practice. The correct mixture and consistency of stucco allows for much easier application and overall appeal. Numerous contractors place their newest employees in charge of preparation of the stucco mix. However, keep in mind that a stucco application crew will perform better and more efficiently if an experienced employee prepares the right mix with the right consistency. The secret is the consistency.
There are various ways that stucco can be applied. It can be either applied with a hawk and a trowel or a more advance pneumatic system. After the initial application of the mix to the substrate (wall) the stucco coat needs to be densified which means that a mechanic needs to smooth out the coat with a trowel. The purpose of this smoothing or floating method is to allow the all the voids to be removed from the mix and in turn force the mix to be in a tight and even contact with the substrate
Tip 1. If you notice that stucco mix is sagging after the smoothing is performed then the mix has too much water content or the mix is applied too thick. Correct the problem by adding more dry stucco mix to the mixture. Keep in mind that if it is necessary to apply a thick coat to even out the surface or achieve a desired look that the stucco can be applied in a number of layers ranging from ¼ in to ¾ in.
Tip 2. When applying the stucco with a hawk and trowel start by placing approximately a trowel or two of material on the hawk and then applying it to the wall. It allows you to have more room for maneuvering with the hawk. As you get better you can add more to the hawk but keep in mind that while you don’t have to reach for the bucket so often you will experience fatigue the more materials you handle with the hawk.
The actual application of the stucco mix is done when you place the hawk next to the wall and scoop the mix upward from the hawk with the trowel while holding the towel’s upper edge approximately 2 inches away from the wall. The reason for keep the trowel at the angle is to allow ease in spreading the material and at the same time to allow for constant pressure where the material is pushed onto the substrate. Additionally, once you reach the end of stucco mix from the trowel that you’re spreading flip the trowel and pull the float the material down toward the hawk. This allows the air to escape and prevents hollow pockets from forming in the mix.
*** Always start your full trowel full at the bottom of the panel or while going over existing stucco. This prevents voids in the lath.
*** For traditional three-coat application start by applying a coat which is ½ in thick.
Applying stucco with a stucco sprayer greatly improves the speed of application because the stucco mix is thrown onto the wall by compressed air. Inadvertently there will be some bouncing back of the materials and that is why a correct stucco mix is important because if the mix has the right consistency the majority of the materials will remain on the wall. If necessary correct it by removing excess water from the mix. This process is a two stop process because once the man with the sprayer moves thru another mechanic trowels or smoothes the stucco out and ensures it is keyed into the lath.
After the first coat is applied, a straight rod (Darby or browning rod) should be used to ensure that the stucco does not extend out beyond the casing bead and weep screed placed around the window or door openings. The first coat is traditionally scratched horizontally to assist the second coat to bond to the first coat, thus the first coat is often called the scratch coat.
The first coat needs to cure for 48 hours. It is important to keep the coat lightly misted thus preventing rapid water evaporation and allowing for the mix to cure properly. Done correctly, the mix will remain dark gray-green color during curing process. Allowing for the coat to cure for 48 hours limits the cracking and settling on the second coat.
The second coat is applied in the same manner as the first coat. Keep in mind the when you apply the second coat the coat cannot extend past the casing beads and the weep screed edges, another words work the mix lighly in between the scratch coat. After the second coat is applied, a straight rod is used to skim any excess stucco off and leave a wall that can receive a finish coat of stucco.
*** Do not polish the stucco surface it reduces bonding.
Back-dragging with the trowel provides a better surface for the finish coat to be applied. After the second coat has been moist-cured for 48 hours and ambient-cured for 5 to 26 more days then the finish coat can be applied. Acrylic or elastomeric finish coat is a very popular final finish.