Stucco Application On Painted Exterior Cinder Block Foundation

Stucco is a popular choice for covering exterior cinder block walls, as it offers a classic, uncomplicated finish that is more decorative than concrete. It is also a quick way to change the look of your home. However, the process can be tricky if the wall is painted, as stucco may not adhere properly to the surface. To avoid this, the wall must be prepared correctly, and a bonding agent should be used.

Concrete bonding agents are necessary to ensure the stucco sticks to the surface

Stucco can be applied over painted cinder block walls, but concrete bonding agents are necessary to ensure the stucco sticks to the surface. Painted surfaces are not conducive to this process because they repel water in a manner that inhibits the stucco from bonding to the surface. The plaster will chip or flake off if a bonding agent is not used.

Concrete bonding agents improve the adhesion, life, and performance of stucco and concrete surfaces and their coatings. However, choosing the wrong bonding agent or failing to follow the manufacturer's instructions can lead to ugly surface failures or paint failures. For example, the wrong type of bonding agent (interior vs. exterior) or non-compliant exterior agents can cause issues.

One recommended product is Quikrete 1 Gal. Concrete Bonding Adhesive, which permanently bonds existing concrete, plaster, and stucco to new concrete, plaster, and stucco. It can be used for indoor and outdoor applications and does not require rough surfaces. It can be applied by painting or rolling it on.

Another option is to use a micro cement with added dye and seal it. One user recommends Sure-Crete micro topping with a bonding agent.

Painted surfaces repel water, which inhibits stucco from bonding

Painted surfaces are not ideal for applying stucco because they repel water, which inhibits the stucco from bonding to the surface. This is due to the superhydrophobic properties of paint, which cause an almost imperceptibly thin layer of air to form on top of the painted surface, preventing stucco from adhering properly.

The hydrophobic nature of paint is a result of its composition, which includes materials such as manganese oxide polystyrene (MnO2/PS) nano-composite, zinc oxide polystyrene (ZnO/PS) nano-composite, and fluorinated silanes. These components work together to create a surface that repels water and protects the underlying material from moisture.

When attempting to apply stucco over a painted surface, the stucco will not be able to form a strong bond and is likely to chip or flake off over time. This can result in an uneven and unsightly finish, defeating the purpose of using stucco to enhance the appearance of a home.

To overcome this issue, it is essential to use a concrete bonding agent or a scratch coat before applying stucco. A bonding agent will help the stucco adhere to the surface, ensuring a stronger and more durable finish. Alternatively, a scratch coat involves applying a layer of mortar to the painted surface, providing a textured base for the stucco to hold onto.

By taking these necessary preparatory steps, you can ensure that the stucco will bond successfully to the painted cinder block foundation, resulting in a smooth and long-lasting finish.

The simplest way to cover a cinder block wall is by using surface-bonding cement

Covering Cinder Block Walls

To begin, ensure the cinder blocks are clean and free of any surface contamination. If the wall is painted, you will need to apply a concrete bonding agent to ensure the plaster doesn't chip or flake off. You can then follow these steps:

Step 1: Prepare the Surface

Wet the cinder blocks with water. This will prevent them from sucking moisture from the plaster mix. You can also apply a bonding agent to the wall for better adhesion.

Step 2: Mix the Mortar

Batch a type N or S Mortar with sharp (manufactured) sand, not masonry sand. You can also add a bonding agent to the mortar mix for extra adhesion.

Step 3: Apply the Mortar

Use a hawk and trowel to plaster the mortar onto the wall. You can finish it with a brown coat or hard-trowel it for a smooth surface.

Step 4: Cure and Finish

Allow the plaster to cure for several days. You can then finish the wall by painting it or applying any of the various stucco finishes available.

This method is a straightforward and effective way to cover a cinder block wall, providing insulation and moisture protection while giving you a smooth surface that can be painted or finished as desired.

Stucco is made from a mixture of cement, lime, and silica

Stucco is a mixture of sand, cement, and water. A simple recipe for stucco consists of a 3:1 ratio of sand to cement, with water added until a pudding-like consistency is achieved. This basic recipe can be used to create a scratch coat for stucco, which is the first layer of the material that is applied to a surface.

The process of mixing stucco can be challenging and requires the proper tools and mixing ratios. There are three main mixing methods: the barrel/mortar mixer method, the bucket method, and the wheelbarrow method. The barrel mixer and mortar mixer methods use a machine to mix the stucco, while the bucket method is done by hand with a drill and a paddle attachment. The wheelbarrow method falls between the other two methods in terms of labour and is done by hand with a hoe or shovel.

When mixing stucco, it is important to have all the materials readily available before beginning, as stucco hardens very quickly. The mixing tools should also be wet before use to prevent the stucco from sticking to them. The proper amount of each material should be measured out, with a good rule of thumb being a 3:1 ratio of sand to cement. Water is then added until the desired consistency is achieved. Stucco is easiest to control when it has a thick paste-like consistency.

Stucco can be applied directly to rigid and solid surfaces, as long as the surface is rough and absorbent. If the wall is not absorbent, it may be necessary to wash the surface evenly before applying stucco.

The application process for stucco mixture can vary by manufacturer

The application process for stucco can vary depending on the manufacturer. However, there are some general steps that are typically followed when applying stucco to a wall. Here is a detailed guide on how to apply stucco:

Preparing the Surface

First, ensure that the wall is clean and free from dirt, oils, paint, and old stucco. Use a pressure washer to thoroughly clean the surface and let it dry for 24 hours. If you are applying stucco to a painted cinder block wall, it is important to note that concrete bonding agents are necessary for the stucco to stick to the surface. Painted surfaces tend to repel water, which inhibits the stucco from bonding. Therefore, a bonder or bonding agent is required for the plaster to adhere properly.

Applying the Stucco Mix

Start by mixing the stucco according to the instructions on the package. The mixture should have a consistency similar to thick peanut butter. Begin applying the stucco from the bottom up, spreading it evenly with a trowel. The first layer, also known as the scratch coat, should be approximately 1/4 to 1/2 inch thick.

Scoring the First Coat

Once the first coat starts to harden (after about an hour), use a raking tool to score or scratch it. This process helps the second layer adhere better. Allow the first layer to cure for 48 hours before proceeding to the next step.

Applying the Second Coat

Apply the second coat, also known as the brown coat, following a similar process as the first coat. Maintain the same thickness as the scratch coat to prevent cracking. This layer should also be left to cure for 48 hours.

Applying the Finish Coat

After the second coat has dried, it's time to mix and apply the finish coat. Refer to the manufacturer's instructions for the desired texture and appearance. This layer will create the final texture and look of your wall.

Caring for Your Stucco Wall

Maintaining your stucco wall is relatively easy. Regularly inspect it for cracks and repair them as necessary. Avoid pressure washing stucco, as it can damage the finish. Instead, gently clean it with a garden hose and soft brush.

Additional Considerations

The application of stucco is best done during moderate temperatures, avoiding freezing or excessively hot conditions. It is also important to avoid direct sunlight or strong winds, as these conditions can cause the stucco to dry too quickly and lead to cracking.

Frequently asked questions