Regardless of how you use stucco, to perform the work perfectly you would need bonding agents. Bonding agents are mostly natural or synthetic materials. They are mainly used to join the new concrete surface with the old one. They are also used to connect the successive concrete surfaces/layers, for example to join the stucco coating with the brown coating. Because of these bonding agents different concrete surfaces act as a single unit.

When to apply a bonding agent on stucco?

Most of the time there are specified instructions from the manufacturer on how to and when to apply bonding agents on stucco. But the most commonly specified recommendation is to cure the existing layer for at least 24 hours and then apply the bonding agents and the successive layer. However, all bonding agents are not equally effective on stucco. Let’s see how the adhesives work and how to apply them.

Use of Bonding Agents in Stucco Applications:

Bonding agents improve the adhesion, performance and longevity of all concrete surfaces, stucco and their coatings. Whether you are using the right bonding agents or not is dependent upon the type of specific stucco product you are using on your home. But it is very important to choose the proper bonding agents to finish the stucco work accurately; for instance, indoor agents for indoor use.

Very often a wrong bonding agent leads to revolting stucco, stucco coated surface disappointments and overall paint failures in no time. Neglecting to adhere to the manufacturer’s directions while applying may result in the same.

So, it is essential to accept the manufacturer’s opinion while installing stucco on your home. Every manufacturer usually has an idea about whether to apply a binding agent or not in the first place. They also instruct about how and when to apply the bonding agents. ASTM C932 specifies what type of bonding agents to use to paint onto a surface, on Portland-cement based stucco, and onto a transitional or intermediate coat.

Functions of Stucco Bonding Agent:

Usually there is no separate bonding agent present in the cement of the concrete mix. So, when you apply the stucco coat over the brown coat, it becomes two separate layers, but there is no bond. So, it is essential to apply a bonding agent on the brown coat and apply the stucco coat later.

A bonding agent increases the strength and performance of stucco in many ways and because of the bonding agent, different stucco layers can act like a single unit.

Usually when a bonding agent is applied over the existing layer, the successive fresh layer can easily adhere to that existing layer. There are two major factors, which affect the bonding between the existing layer, and the successive fresh layer:

·         Cleanliness of the old surface and surface preparation.

·         Integrity and overall strength of the existing surface.

What are the characteristics of Bonding Agents?

·         These bonding agents are very straightforward and effortless to apply.

·         Most of the bonding agents are chemical action and frost-resistant.

·         They enhance the adhesion between the successive layers of stucco.

·         Bonding agents can easily reduce the cracks that are formed in shrinkage.

·         They also reduce the permeability of the stucco very effectively.

·         They also increase the mortar, bond strength, flexural and the tensile of the concreate.

So, if you apply a traditional layer of stucco and plan to apply the acrylic stucco (the finishing layer) before applying the bonding agent, you have to wait at least 24 hours to cure the traditional stucco layer.

According to the industry experts, the only coat that is bonded to the substrate on a two-coat work is the base coat. It needs to be about 3/8″ thick at the least and needs to be dried for a minimum period of 24 hours. If you apply the second coat without giving at the specified time to cure properly, the moisture is very likely to enter into the scratch coat and wet the yet-to-dry bonding agent, which eventually results in a delamination.

Some bonding agent manufacturers also set a time-frame for applying the binding agent and successive layer of stucco. Take Bull-Bond™, a premium grade bonding agent, for instance, warns its users to cure the existing layer to ‘industry standards’ which is very often 24 hours. Then you can apply the bonding agent on the existing layer. But yet you cannot apply the top layer of stucco until the binding agent itself is perfectly cured. So, you have to wait until the bonding agent feels dry to touch before applying the successive layer.

If you check the instructions provided by the stucco manufacturer and bonding agent, you will get a more specific answer as to the application of bonding agent while applying the specific type of stucco you are using.

Types of bonding agents used on stucco:

There are a few types of bonding agents or adhesive that are used on stucco for various purposes. Not all of them are suitable for every purpose. So, no one shall use them neglecting the manufacturer’s instructions.

Cement Bonding Agents:

Cement bonding agents are mainly used on stucco and other cement-based materials. This type of bonding agent works by bonding the cement within the material. As cements form the biggest percentage of stucco, these bonding work perfectly on stucco by bonding the cement within the stucco.

But the biggest draw-back of the cement bonding agents are that they do not work effectively on the materials that are cement-based. The main function of these bonding agents is to bond the new cement or successive layer to the old cement. They are good only for this purpose but they are hardly usable for other attachment purposes.

Masonry Sealants:

We use bonding agents on stucco to apply a patch so that it can prevent a hole or crack from any leaking. To be more specific, applying a patch on a hole or crack is one of the main reasons we use stucco adhesive. This is where the masonry sealants work perfectly. They are like the other stucco adhesives. They are just used on stucco to apply a patch on the existing hole or cracks to prevent subsequent leaking.

When these sealants are applied, holes or cracks harden and prevent water from leaking. Basically, all the sealants specified for cement, concrete and masonry work fine on stucco.

Super Glue:

Super glue works fine on most surfaces. Stucco is usually no different from most of the surfaces in this case. But super glue is neither like the other type of adhesive as mentioned above, nor can it be applied in all situations as it doesn’t work effectively.

To clarify, we can take a masonry sealant that is best used for applying a patch on the existing holes and cracks on stucco. So super glue is not the ideal option here. But there are situations when neither of the above two options works well, such as attaching plastic stars to a stucco ceiling. In such situation, super glue is the ideal option.

Regardless of the type of bonding agents you are applying, make sure the concrete surface is properly cleaned before you apply the bonding agent. Shake the bonding agents well and go through the manufacturer’s instruction word by word and apply the bonding agents following the application procedures stated therein

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