The Paint Facts

Why Is Drywall Mud Cracking After Primer? 7 Main Reasons

You already finished mud and prime on drywall, but very soon you see the prime start cracking. It isn’t very pleasant. You may wonder why drywall mud cracks after primer.

This crack happens for many reasons. The major reasons are large gaps between the drywall and the laminate ceiling, mud too thick, before drywall mud completely dry use primer, apply primer over joint compound dust, wrong mud or tape, humidity or wet weather, etc.

In this article, I will explain why joint compounds crack after primer and how to fix it.

Type of cracks drywall mud

Mainly you can see 2 types of compound cracks on the new primer area. Those are hairline cracks and spider cracks. 

Hairline cracks: it is a single line crack that is seen horizontally or vertically on the following tape. This crack commonly happens for wrong taping and drywall joint issues.

Spider crack: this crack looks like a spider net. After this crack, the mud or primer starts peeling. This crack mainly happens for joint compound or primer issues.

Can you fix drywall mud after primer?

Using a primer on drywall mud means dry mud is already sealed. So you do not need to use mud on the primer. But if drywall mud starts cracking with primer, you have to remove and clean the crack mud and primer. And then again tape, mud and paint on it.

A similar article where I explain what should you do if mud starts peeling after being painted.

Why should not use primer on crack mud?

Primer seals over mud, but mud cracking also occurs under the surface. Crack makes the surface weak. When it starts to crack, it never ends until you remove the affected surface area and remud it. However, the primer can hide the crack for a short time, but very soon, the crack will be bigger, and the cracking will come back.

Most 7 reasons for cracking new prime drywall and guide to fix

New prime drywall cracking is very unexpected. Below I will explain common reasons for cracking. 

Large gaps between the drywall and the laminate ceiling

This issue is created when you install drywall. Maybe you do not use enough screws on edge to attach drywall. And now the wall is moving, and it creates cracks.

You must remove the joint compound on the drywall to fix this issue. Then drill the edge of the drywall and add more screws. Then apply tape and mud again. Also, fill the screws hole with mud. After dry mud, as a final step, use a primer.

You can often deal with crack issues if drywall is attached to the wall properly.

Mud is too thick

Mud does not have a specific thickness. However, drywall mud should not be too thick. Topping coat mud should not be more than ½ inch, and ¼ inch is recommended.

In this article, I explain estimate value of mud thickness.

If mud is too thick, it takes a lot of time to dry. Also, the thick compound can shrink in dry weather, creating cracks.

If you apply too thick mud and it starts cracking, you should remove the affected area, then apply tape, thin coat mud, and primer again.

The joint compound does not dry properly before applying primer

Sometimes you may think the drywall is almost dry, and you must hurry. And apply primer to the mud!! Don’t do that.

If you did this and the primer is already cracked, you have to clean the area, tape, mud, and prime on it.

Applied premier over mud dust

Drywall dust is very loose, and it doesn’t have any adhesive ability. After applying mud, you might sand the surface to make it smooth. And after sand creates a lot of dust. It would be best if you cleaned it with a cloth, or you can skim a coat of mud. 

Without cleaning the mud surface, the primer can not attach well on drywall if you apply primer on it. It makes cracks on the primer.

Humidity or wet weather

In wet weather, you may apply joint compound mud, and your eyes the mud is dry. But the truth is when the dry weather comes, mud almost dries up. It creates cracks.

This is why experts prohibit applying mud and paint in humid weather.

Without tape mudding

Tape is a very important part. It is connected between gaps. It will crack if you do not use tape on drywall for small moving or weather reasons.

The wrong mud or tape

Many pros suggest using paper tape instead of mash. However, mash tape is not bad, but it has more crack issues than paper tape.

You should use a good joint compound product. Apply the right mud in the right layer. For Example, you should not use hot mud on the top layer. 

Caulking: a fast but temporary solution

Caulk is made to fill small gaps and cracks. Caulk also can do a good job of hiding joint compound cracks. However, this is not a permanent solution. After applying caulk, it also can crack. To protect against cracking, you should use a good flexible caulk.

In this article, I compared mudding vs caulking.

Caulking is not a hard task. Apply caulk on the crack area, then use your finger to plan it. And then clean the edge of the caulk with a cloth. Remember the crack edge dry fast and stick hard. After drying, you can not clean the area, and sanding is impossible.

Hairline crack in wall keeps coming back

Hairline cracks coming back again and again after tape and mud means your drywall setting with the wall has issues or wrong methods you used for applying mud. 

Above the article, I explained why crack happens. If you take care of these, I hope you will not be affected by crack issues again.

What are good crack resistant drywall muds?

In the market, different brands provide drywall mud. 

Mudding projects need different layers to apply. So you can choose the following products which can protect from cracking. 

Setting layer: use Easy Sand 20 or Easy Sand 45. Then apply tape on it.

Filling layer: For the first and second coats, use Easy Sand 20 or Easy Sand 45. And wait for it to dry.

Topping layer: Use plus 3 joint compounds. 

Does primer prevent drywall mud from cracking?

Primer is applied on top of the joint compound, and it seals the mud. Good primer protects mud from humidity, water, different weather, etc., which is why mud cracks.

However, the primer only can protect the upper side, not under the mud. You should also ensure protection under the mud surface to prevent drywall mud from cracking completely. 

What is the best crack resistant primer?

There is no substitute for using a good primer in drywall. In the market, top brands already make this type of primer. However, I personally like Kilz premier. It provides great protection from any bad weather, mold, wet areas like bathrooms, etc. 

It is a little expensive product, but it is worth the money. Without this, I did not find any bad that I could share.


If you are careful about your task, there is a very low chance of new prime wall cracking. Try to use good products and methods from your side.  

I hope you got your answer. If you think this article is helpful, share it with your friends and family. 

About the Author

Shojib Hoq

My name is Shojib, and painting has been my passion since childhood, and it still holds a special place in my heart. I absolutely adore the process of painting, pouring, and creating crafts.