How to Repair Wall Cracks

 

Summary

– Wall cracks: superficial or through?

– Repairing cracks in interior walls

– Wall cracks: inexpensive repair

 

Whether the building is new or old, sooner or later, cracks appear in the walls.

With walls, you can be faced with different types of problems:

– a crack in the wall,

– filling a hole in the wall,

– moisture problems.

In the vast majority of cases, these cracks are treated well, but before any repair, it is necessary to determine the cause of the damage as best as possible.

Before repairing the wall cracks, it is advisable to fill the holes and check for moisture in the walls.

Wall cracks: superficial or through?

 

We distinguish:

– the crack that is inside the building, on a partition,

– the crack which is located on an external wall or load-bearing wall.

These cracks can be:

– superficial: completely through the plaster and/or part of the wall,

– through crossing the wall in all its thickness.

Here is a summary table of the different types of cracks:

Different Types of Wall Cracks

TYPE OF CRACK	DESCRIPTION	POSSIBLE CAUSES
Micro crack	< 0,2 mm: very fine and superficial mesh	Gentle infiltration of water into and under the rendering can cause problems of humidity over time or even detachment of the rendering.
Fine crack	Between 1 and 2 mm	It is necessary to check the stability of the cracks over time: – if the cracks do not evolve after the installation of a witness, you can repair them according to the nature of the wall, – if the cracks evolve, you must look for the causes and stabilize the propagation.
Big crack or cracking	> 2 mm	The causes are often structural. It is necessary to call in a professional and consider repair work.

Repairing cracks in interior walls

Before applying a new finish, it is necessary to repair the cracks in the walls to prevent them from reappearing.

The most common cracks are in plastering, plasterboard, and plaster tiles: they are not dangerous for your home but are unsightly.

Wall cracks: choosing a filling plaster

There are a lot of fillers available, but the choice is difficult. Read the labels carefully:

– powdered coatings: they must be mixed with water to obtain a malleable paste,

– ready-to-use” fillers: in tubes for small, quick repairs or in pots.

Mastics and resins for wall cracks

There are also sealants and resins intended for specific works:

– repairs in humid environments or outdoors,

– cracks on wood,

– cracks that require “flexibility”, etc.

Good to know: If the crack is intended to be painted and you are using a filler, it must be acrylic. Check the label to make sure it can be painted over and what type.

Which repair for which type of wall cracks?

Here are the different cases of cracks you may be confronted with:

FISSURES MURS : SOLUTIONS

TYPE OF CRACK	REPAIR
Small crack	– Open the crack with a triangle. – Lightly sand the edges of the crack. – Dust carefully and brush wet inside and outside the crack. – Fill the crack by overflowing a little and let the coating make a small bead, do not smooth it. It retracts a little while drying. – Once it’s dry, run an American knife over it to remove the sardines and excess plaster. – It is often unnecessary to sand, but you can give it a quick sandpaper stroke to finish it off. – You can paint the surface by applying an undercoat or your thinned finishing paint to the repaired areas.
Medium crack	– For a slightly deeper and wider crack, the preparation is the same as for a small crack. Open the crack, dust, and dampen. – Apply a coating that can be applied in thickness. Check the label. – Because the amount of coating is larger, you have more shrinkage when drying. – Once dry, you can apply a new coat of coating after scraping off the existing one to help with adhesion and remove sardines. – Overflow a little more to get a uniform surface.
Large crack	– Open the crack with the triangle by making a small bevel on the lips of the crack. The triangle allows it. – Sand the edges of the crack to thin the lips of the crack, making a slight “hollow”. – Moisten the inside of the crack with a brush and apply the plaster. – Place a calico or crack strip on the coating. It will stabilize the crack. – Drown the strip in the plaster by passing the plaster knife and covering it with a thin layer of plaster. – Let dry before sanding carefully, dust off, and apply the finish, not forgetting the undercoat.
Crack between connections: wall/wall, wall/ceiling, doorframes/plasterboard/plasterboard. Door frames in general and wall and/or ceiling.	– A soft acrylic filler is recommended. – Lightly sand the lips of the crack and clean it thoroughly. – Apply the filler and smooth it out. – When dry, you can paint. – For wall/wall and wall/ceiling junctions, patch the cracks with a calico.

Wall cracks: the different types of calico

Calico is a coarse cotton strip.

There are three types of calico:

– fine: for very fine to fine cracks

◦ it is applied over a layer of vinyl paint,

◦ it is smoothed with a brush so as not to distort it,

◦ once dry, you coat it to mask it,

– adhesive: ideal for frame/wall junctions, it is glued directly to the clean crack before being coated to mask the frame,

– adhesive and bridged: apply the calico to the crack and apply the coating with a coating knife.

Note: depending on the depth of the crack, you may want to apply plaster before applying the calico, especially for adhesive and bridged adhesive calico.

Wall cracks: inexpensive repair

The price range of the filler depends on the brands and the retailers.

Check the prices per kg. We generally find that the larger the container, the lower the price per kg:

WALL CRACKS: PRICE

TYPE OF FILLER	PRICE
Ready to use in 1 kg pots.	From $3 to $16.
In powder, in a 1 kg bag or package.	From $1 to $11.
In 200 ml tubes.	From $1 to $8.

Read more:

– How Do You Fix Cracks in Concrete?

– Facade Microcracking: Types, Causes, and Repairs.