Surface analysis

Surface analysis. Surface properties and related problems

How should the surface be prepared?

For a successful wallpaper application, the substrate must be dry, rigid, at the same time hygroscopic, clean and even. With light-coloured wallpapers, the surface should be a uniform white colour. Accordingly, for the application of such wallpapers, the surface must be even and uniform in tone.

Wet surface

A damp substrate is not suitable for wallpapering or any other type of coating. Mould often forms quickly on damp surfaces and can damage and deteriorate the building material.

If you try to apply wallpaper to a damp wall, this will cause the edges to separate at the folds and will also impair the adhesion of the wallpaper to the surface directly at the folds.

How do I know if the surface is damp and what to do?


Action to be taken

  • Testing using a film (if condensation forms under the film, the wall is too damp).
  • Moisture measuring device (accurate determination of existing moisture).
  • Eliminate the causes of moisture build-up.
  • Allow the surface to dry.
  • Heat and ventilate if necessary.
  • Re-inspect.


During surface delamination (plaster, dispersion paint, chalk dust), the adhesive strength of the wallpaper cannot be guaranteed. Joints or even whole strips may peel away from the surface and damage the overall picture.

How do I know if a surface is unstable and what to do?


Measures to be taken

  • Test for hardness by scratching or denting (if the surface is damaged during compression, it is too soft).
  • Check using adhesive tape (if the old coating sticks to the tape, it should be removed from the wall).
  • Remove weak and unsound parts of the surface.
  • A primer coat (e.g. Metylan for old plaster) can be applied to the surface of slightly worn or dilapidated plaster.

Sticky layers

Sticky layers - accumulation of adhesive substances on the substrate surface which hinders the application of durable wallpaper and other wall coverings.

How do I know if there are adhesive layers on the surface?


Measures to be taken

  • Draw a grid shape on the surface with a sharp object and splash it with water (if the scratch marks become darker, this may indicate adhered layers).
  • The adhered layers must be removed mechanically by sanding.

Ability to absorb moisture

Moisture absorption is a crucial factor for the successful application of wallpaper. If the substrate has too poor an absorption capacity or is no longer able to absorb moisture, the surface in question is not suitable for wallpapering, as this will not ensure adhesion to the substrate.
Problems also arise if the surface has too much moisture absorption. Various difficulties may then arise in the process of adhering the wallpaper, as the adhesive is absorbed too quickly into the substrate and excessive surface tension is generated, which may create gaps at the interfaces.

How do I know if a surface has a high/low moisture absorption capacity?


Measures to be taken

  • Water wetting (if water runs off as droplets, the substrate has a weak moisture absorption capacity; if water is absorbed very quickly, the surface has too strong an absorption capacity).
  • If the surface has no or poor absorption capacity, it is recommended to apply a repair fleece.
  • If the substrate has a high absorption capacity, the primer should be reapplied to the wall.

Rough surface

Rough and uneven surfaces shine through the applied wallpaper, so that the wallpaper does not provide a sufficient surface effect when the repair is complete.

How do I know if the surface is not smooth or clean enough?


Action to be taken

  • Check smoothness and cleanliness using the strong light of a pocket torch.
  • Smooth the uneven surface with a spatula. If necessary, apply repair fleece afterwards.

Alkaline surface

Alkaline surfaces such as new plaster or concrete are not suitable for bonding grass wallpaper, bronze wallpaper or metallic coloured wallpaper. Using other wallpapers may also cause fading which will appear as spots on the wallpaper.

How do I know if the surface is alkaline?


Action to be taken

  • Moisten the surface with distilled water, apply indicator paper, determine the pH level (if the value is 7,8 or more, the substrate is considered alkaline).
  • The surface must dry until the pH reaches 7.
  • Alternatively, you can wash the alkaline surface twice with a multi-component fluorate, followed by washing the wall with clean water.
  • Then apply the repair fleece.

Cracked surface

Cracks on walls and ceilings can adversely affect the process and result of wallpapering.

What if there are cracks on the surface?

Types of cracks

Measures to take

  • Tiny cracks and mesh cracks (become visible when the surface is wet).
  • Cracks and joints caused by settlement (spreading through the entire plaster layer to the joints).
  • Static cracks and tensile cracks (due to the structure of the building).
  • In the case of fine settlement cracks, as well as mesh and joint cracks, repair fleece should be used to cover them.
  • Static cracks require special measures.

Fungal damage

Mould can occur in areas where the environment is favourable for the existence of fungal nutrients and moisture.

What if the surface shows signs of fungal damage?


Action to be taken

  • The room is too humid (the cause of the mould must be identified and eliminated).
  • Preventive measures such as regular ventilation and controlled heating help to reduce humidity.


White salt discolouration on the plaster surface is caused, for example, by increased humidity in the horizontal insulation, loose brickwork or damage caused by exposure to water.

What if faded spots appear on the surface?


Action to be taken

  • As a result of loose brickwork or exposure to water.
  • In this case, the wallpaper should not be applied until remedial measures have been implemented.