What are structural cracks and their causes

What to do if there are cracks in the plaster

In most cases, cracks in the plaster are minor visual defects that can be easily repaired. All you have to do is apply a new layer of plaster and everything is as it was before. However, cracks can also indicate deeper damage to the facade. Here's how to distinguish different types of defects and what to do about them.

Different types of cracks

Cracks differ mainly in their width, length and depth. While smaller cracks only allow some moisture to penetrate, larger cracks can indicate serious structural defects. Basically, a distinction is made between two types, plaster-related and dynamic cracks.

1. Cracks caused by plaster

These are surface cracks that only affect the plaster, but not the structure. As a rule, they are only a few millimeters deep and spread out flat. That is why they are also known as hairline or network cracks. But there are also cracks that penetrate all plaster layers. Moisture can penetrate these areas and cause permanent damage.

There are five types of plaster-related cracks.

Shrinkage cracks:

These types of cracks are the most common. It mainly occurs when layers of plaster dry out too quickly. This is especially the case during the hot season.

Shrinkage cracks / stress cracks:

Shrinkage cracks usually appear a few months after plastering. The main cause is the tension between the different layers of plaster. These can also cause the plaster to peel off the substrate along the crack. You can recognize this type of crack by its reticulate structure (craquelure).


Notches have their origin mainly at the corners of wall openings. Window and door areas are particularly at risk. They are caused by tension in the plaster and have a diagonal course. The masonry is still intact.

Sack cracks:

If too thickly applied when plastering unevenness, this type of crack can occur. The excess plaster sags and the plaster above tears open.

Age damage:

Last but not least, there are the cracks that can be traced back to the signs of age. Over time, the plaster loses its adhesion and cavities form. Flaking plaster that becomes porous also belongs to this category.

Note: Regardless of the type of crack, the Association of Private Builders e. V. to consult an expert. In this way, the causes of the cracks can be determined without a doubt and risks can be excluded.

Be careful with dynamic cracks

In the case of dynamic cracks, the situation is a little more complex. They are mostly caused by unwanted movements in the masonry. Typical reasons are:

  • Too large joints in the masonry

  • Inadequate preparation of the plaster base or substrate

  • Neglect of the service life of the materials used

  • Subsidence in the subsoil

  • Large deviations in dimensions that are simply plastered over

There are a number of features that even laypeople can use to identify dynamic cracks. The location can provide the first clues. Places susceptible to cracking are primarily wall openings, additions and wall gables.

The shape and course of the cracks can also provide clues. Typical are:

  • Noticeably straight course

  • Gradual course

  • The crack is significantly wider than conventional hairline cracks

  • The crack is located at the corners of wall openings and runs diagonally from there

Since dynamic cracks are complex problems that can have serious effects, a specialist should be commissioned. If you live in a tenement house, you should inform the property management.

Note: If it is a condominium, the condominium manager will be responsible for carrying out the work. If you are not satisfied with the results, a change can be an option. This is possible e.g. B. at www.hausverwalter-wechsel.de.

So you can treat smaller cracks in the plaster yourself

There is no one-size-fits-all approach to the variety of cracks. Basically you have three options. Either cover the cracks found, fill them in or plaster them.

Covering the cracks:

Covering is the easiest method. You simply apply a new layer of plaster over the crack. This method is used when only superficial cracks of small width are involved. In addition, the old plaster must adhere firmly and must not be sanded off.

Filling the cracks:

The second approach is a little more complex. Here, the affected areas must first be cleaned and freed from dirt. It is best to wet the areas around the cracks beforehand. The cracks are then filled.

Various ready-made fillers can be found in hardware stores. There is also a large selection of pasty leveling compounds for shrinkage and shrinkage cracks.


Plastering is the classic method of repairing more pronounced cracks. First of all, the cracks are enlarged in a V-shape with a power cutter or with a hammer and chisel. This gives the edges a larger adhesive surface. Then you paint the widened cracks with a deep primer and plaster them. Depending on your needs, you can apply a top coat and a base coat.

Tip: Do you also need help with other topics relating to renovation, conversion and refurbishment? Then take a look at our advice section. You will find a lot of additional information here.

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