Understanding Drywall Mud Cracking After Primer: 9 Key Reasons and Solutions

The sight of cracked primer on your freshly mudded drywall can be disheartening. You may wonder, “Why is my drywall mud cracking after primer?” This issue can occur due to a variety of reasons, including large gaps between the drywall and the laminate ceiling, overly thick mud, premature priming before the drywall mud has fully dried, and more. This article aims to explain why joint compounds crack after primer and how to rectify it.

Understanding Drywall Mud Cracking After Primer

1. Types of Drywall Mud Cracks

Primarily, two types of compound cracks can appear on the newly primed area: hairline cracks and spider cracks.

Hairline Cracks: These are single line cracks that appear horizontally or vertically along the tape. They typically occur due to improper taping and issues with drywall joints.

Spider Cracks: These cracks resemble a spider’s web. After these cracks appear, the mud or primer starts peeling. They mainly occur due to issues with the joint compound or primer.

2. Can Drywall Mud be Fixed After Primer?

Once primer is applied on drywall mud, the dry mud is sealed. However, if the drywall mud starts cracking with the primer, the affected area must be cleaned and removed. Then, you need to reapply tape, mud, and paint.

3. Why Shouldn’t Primer be Used on Cracked Mud?

While primer can temporarily hide the crack, the crack will eventually enlarge and reappear. This is because the crack weakens the surface, and the cracking continues under the surface. Therefore, it’s crucial to remove the affected surface area and remud it.

4. Seven Reasons for New Prime Drywall Cracking and How to Fix Them

Large Gaps Between the Drywall and the Laminate Ceiling

This issue arises during the installation of drywall, possibly due to insufficient screws used to attach the drywall. The wall movement then leads to cracks.

Solution: Remove the joint compound on the drywall, drill the edge of the drywall, and add more screws. Then, apply tape and mud again, filling the screw holes with mud. After the mud dries, apply a primer.

Overly Thick Mud

Drywall mud should not be too thick. If the mud is too thick, it takes a long time to dry and can shrink in dry weather, leading to cracks.

Solution: If you’ve applied overly thick mud and it starts cracking, remove the affected area, then apply tape, a thin coat of mud, and primer again.

Premature Priming Before the Joint Compound Dries

Applying primer to the mud before it’s fully dried can lead to cracks.

Solution: If you’ve prematurely applied primer and it’s already cracked, clean the area, tape, mud, and prime it again.

Primer Applied Over Mud Dust

Applying primer over drywall dust can lead to cracks as the primer cannot attach well to the drywall.

Solution: After sanding the surface to make it smooth, clean the dust with a cloth or skim a coat of mud before applying the primer.

Humidity or Wet Weather

In humid weather, the mud may appear dry but can shrink and crack when dry weather comes.

Solution: Avoid applying mud and paint in humid weather.

Mudding Without Tape

Tape is crucial as it connects the gaps. Without tape, even small movements or weather changes can lead to cracks.

Solution: Always use tape when applying drywall mud.

Incorrect Mud or Tape

Using the wrong type of mud or tape can lead to cracks.

Solution: Use the right type of mud and tape. Many professionals suggest using paper tape instead of mesh tape.

5. Caulking: A Temporary Solution

Caulking is indeed a temporary solution for hiding joint compound cracks. It’s an easy and quick fix, but it’s not a permanent solution. Over time, the caulk itself can also crack, especially if it’s exposed to extreme temperatures or moisture. To protect against cracking, it’s recommended to use a high-quality, flexible caulk that can withstand these conditions. Some of the best caulks for this purpose include silicone and acrylic latex caulks, which are known for their flexibility and durability.

6. Hairline Crack in Wall Keeps Coming Back

If hairline cracks keep reappearing after taping and mudding, it could indicate issues with the drywall setting or the methods used for applying mud. This could be due to improper installation of the drywall, using an incorrect type of mud, or not allowing the mud to dry properly before applying another coat. It’s important to follow the manufacturer’s instructions when applying drywall mud and to allow adequate drying time between coats.

7. What are Good Crack Resistant Drywall Muds?

There are several brands that provide crack-resistant drywall mud. For the setting layer, products like Easy Sand 20 or Easy Sand 45 are often recommended. These are lightweight setting-type joint compounds that are easy to mix and provide a strong, durable finish. For the filling layer, again, Easy Sand 20 or Easy Sand 45 can be used for the first and second coats. For the topping layer, plus 3 joint compounds are often recommended. These compounds are designed to be easy to sand and provide a smooth, high-quality finish.

8. Does Primer Prevent Drywall Mud from Cracking?

While a good primer can help protect drywall mud from humidity, water, and different weather conditions, it’s important to note that it only protects the upper side of the mud, not underneath. Therefore, it’s also necessary to ensure that the drywall itself is properly installed and protected to prevent the mud from cracking. This includes using a moisture-resistant drywall in areas with high humidity or potential for water exposure.

9. What is the Best Crack Resistant Primer?

There are several good primers on the market that can help protect against cracking. One such product is Kilz primer, which is known for its excellent adhesion and durability. It’s also resistant to mildew and mold, making it a good choice for areas like bathrooms or basements that are prone to moisture. Other good options include Zinsser Bulls Eye 1-2-3 Primer, which is a water-based primer that’s great for all surfaces, and Rust-Oleum Zinsser B-I-N Primer, which is an oil-based primer that’s excellent for blocking stains.


Cracking in new prime drywall can be unexpected and frustrating. However, by understanding the common reasons for cracking and how to fix them, you can prevent and rectify these issues effectively. Remember, using good products and methods can significantly reduce the chances of new prime wall cracking.

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