Structo-Lite Cracking (Common Causes And How To Prevent)

Structo-Lite, manufactured by USG, is one of the best basecoat plasters in the market. DIYers and professional contractors love using Structo-Lite because of its lightweight and high thermal conductivity.

Structo-Lite basecoat plaster is also quite durable and conforms easily to different shapes. It can be applied on many surfaces, such as concrete, gypsum, clay, and metal lath.

Even though Structo-Lite has many impressive features, like every other plaster, it is vulnerable to cracking.

This article will identify the common causes of Structo-Lite cracking and share expert tips on how you can prevent this problem.


Common Causes of Structo-Lite Cracking

1. Structo-Lite Drying Too Fast

This isn’t a problem that affects nearly all types of plaster. If Structo-Lite is left to dry too fast, there is a good chance that it will crack prematurely.

This often happens when the Structo-Lite is applied on a surface like brick or concrete that sucks out the moisture in the plaster.

When installing Structo-Lite, there are several measures you can take to prevent it from drying too fast. You can start by wetting the surface.

If you are plastering a brick wall, when you water the surface, you prevent it from sucking the moisture in the Structo-Lite, which leads to the development of cracks.

The other step you can take to prevent the Structo-Lite from cracking because of drying too fast is to use a bonding agent.

This bonding agent will promote better adhesion. When you use a bonding agent and wet the walls before installation, you can be 100% guaranteed that the Structo-Lite won’t dry too fast.

2. Cracks on the Substrate

If you are plastering an old home, there is a good chance that the walls have cracks. Unfortunately, cracks on a wall are easily transferred to the next surface, which in this case is the Structo-Lite basecoat plaster.

If you find yourself plastering an old wall filled with cracks, you must fix them before applying the plaster. Start by removing any loose materials on the cracks.

Ensure that you rough up the area before filling it with caulk. In case the cracks are too big and deep, adding some reinforcements such as a metal lath and then caulk is a good idea.

With such a foundation, you can prevent the cracks on your wall from being transferred to the surface of your Structo-Lite basecoat plaster.

3. Using Too Much Water

Another mistake that can lead to the development of cracks in Structo-Lite is mixing it with too much water. A lot of water weakens the molecular strength of Structo-Lite. Once applied, it starts to crack.

USG recommends mixing a 50-pound bag of Structo-Lite with 3 to 3.75 gallons of water. When you start mixing, you should aim for a stiff viscosity and not one that runs too easily.

Using a lot of water may be tempting as it makes the paste easier to spread. But doing so lowers the adhesive strength, and the Structo-Lite can develop cracks.

To prevent this problem, kindly stick to the recommended mixture ratios.

4. Applying Thick Layers of Structo-Lite

The ideal thickness of Structo-Lite basecoat plaster should be from 12mm to around 20mm. Even though it is a lightweight plaster, Structo-Lite, when applied in extremely thick layers, it starts to develop cracks as it dries.

During installation, refrain from applying thick layers of Structo-Lite. Even if you intend to apply several coats, ensure you don’t overdo it.

5. Using Expired Structo-Lite

Another reason why Structo-Lite may be cracking is that you are using an expired product. Most people don’t know this, but Structo-Lite has an extremely short shelf life of around one to two years.

If you had stored some Structo-Lite for a long time and want to use it to plaster your walls, be mindful of the dates indicated on the bag.

When you use an expired Structo-Lite, a couple of things may happen. First, the Structo-Lite won’t set. Secondly, the dried Structo-Lite may develop cracks due to poor adhesion.

You may want to save a few bucks by using an old bag of Structo-Lite, but it may land you in deeper trouble. It’s safe to always buy a new bag every time you have a plastering job.

Make sure that you use all the amount. If some remains, you can always give it to a friend or family member with an urgent project.

6. Movements within the Foundation

Cracks on Structo-Lite don’t always occur when it’s drying. Sometimes it can happen months or years later. One of the common culprits for Structo-Lite cracking a few months or years after installation is a movement within the foundation.

Sometimes, masonry units such as roofs and ceilings are vulnerable to movement. Structo-Lite may conform easily to various shapes and designs during installation, but it stops being flexible once it dries. Therefore, these movements cause stress within the plaster, leading to cracks.

When it comes to movements within the foundation, there isn’t much you can do rather than repair the cracks.

7. Shrinkage of the Structo-Lite Plaster

Despite being a high-end plaster, Structo-Lite is also susceptible to shrinking. And when that happens, cracks can quickly form within the plaster.

Shrinking in Structo-Lite is more severe when you mix it with a lot of water. The drier Structo-Lite is, the lesser it will shrink. That is why you should always strive to achieve a thicker consistency when mixing it with water.

What are the Different Types of Structo-Lite Cracks?

Now that you are familiar with the common causes of Structo-Lite cracking, let us examine the different types of cracks you may find on Structo-Lite plaster;

• Hairline cracks – These are the tiniest cracks that can occur on Structo-Lite. They are often less than 0.1mm.

• Fine cracks – These are slightly bigger and can have a width of up to 1mm.

• Easy-filled cracks – These refer to cracks with a width of up to 5mm. Easy-filled cracks are the most common type you can find in Structo-Lite plaster.

• Door and window frame cracks – As the name suggests, these cracks occur on plaster located near the window and door frames. They are often bigger and can have a width of around 20mm.

• Structural Cracks – These are cracks bigger than 25mm in width. Most of the time, structural cracks are often caused by movements within the foundation.

The bigger the crack on your Structo-Lite plaster, the more difficult it will be to fix or repair.

Can Weather Cause Structo-Lite Cracking?

How well your Structo-Lite plaster sets depend heavily on the weather. According to USG, Structo-Lite should be dried at around 55 degrees F. Anything more or less may cause failure. The weather can cause Structo-Lite to crack in the following ways.

If the plastered wall or ceiling is exposed to direct sunlight, the excess heat will speed up the drying process. When the moisture dissipates prematurely, cracks will develop on the surface.

In case you install Structo-Lite when it’s windy, there is a good chance that the excess aeration will cause premature drying and eventually cracking.

Finally, if the Structo-Lite is exposed to moisture from rain or high humidity levels, that will extend the setting time. Fine cracks may start to occur.

How to Repair Structo-Lite Cracks?

Should you install Structo-Lite and spot some cracks on the finish, there is a way you can fill and repair them. However, not all cracks are repairable. The likes of structural cracks are often more significant, and you may have to re-install a new Structo-Lite plaster.

As for hairline and easy-filled cracks on Structo-Lite, you can repair them by filling in some adhesive and caulk. Make sure you clean off the dust particles first and add some caulk with a bonding agent.

You can then smoothen the finish and let it dry. Before repairing Structo-Lite cracks, you must identify the underlying problem. This is the best way to prevent the problem from re-occurring.

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