What characteristics must the wall surface have?
For successful wallpapering the wall surface must be dry, firm, evenly absorbent, clean and smooth.
Lightly coloured wallpapers need a uniform white background. Therefore, the colour of the surface needs to be adapted accordingly.
A damp substrate is in no case suitable for wallpapering or any other type of coating.
Mould forms very quickly on damp substrates and can endanger the fabric of the building.
If an attempt is made to wallpaper on a damp substrate, the result is that the seams stand up and adhesion is poor, especially in the seam area.
How do I find out if the substrate is damp and what can I do?
- Carry out foil test
If condensation forms behind the film, the wall is too damp.
- Moisture meter
Determination of the exact residual moisture
- Eliminate the cause of the moisture
- Allow the substrate to dry
- If necessary, heat and ventilate
- Carry out inspections
Peeling of the substrate (plaster, emulsion paint, chalky abrasion) does not guarantee adhesive wallpapering.
Seams or entire strips can detach from the substrate and destroy the uniform overall appearance.
How do I find out if the substrate is not load-bearing and what can I do?
- Scratch or compression test
if the surface is damaged by pressure, it is too soft
- Adhesive tape test
If old paint sticks to the adhesive tape, it must be removed.
- Remove loose and non-supporting surfaces
- Slightly chalking or sanding plaster surfaces can be primed with a wallpapering primer (e.g. Metylan wallpapering primer for old plasters).
Sintered layers are accumulations of binder on the surface of the substrate that prevent a firm bond of wallpaper and other wall coverings.
Sintered layers are characterised by a slight surface gloss and low absorbency.
How do I find out if the substrate has sintered layers?
- Score the substrate with a pointed object and wet it with water.
If scratch marks turn darker, they may be sintered layers.
- Sintered layers must be removed mechanically by grinding off
The absorbency of the substrate is a decisive factor for the success of wallpapering. If a substrate is only very slightly absorbent or can no longer absorb moisture, it is unsuitable for wallpapering because no adhesion to the substrate can be achieved.
In the worst case, the wallpaper strips will fall off.
It is equally problematic if the substrate is too absorbent. Here, too, there will be some problems when wallpapering, as the paste is absorbed too quickly by the substrate, resulting in a very high surface tension, which can cause the seams to burst open.
How do I find out if the substrate is too absorbent/non-absorbent?
- Wetting with water
If the water runs off, the substrate is only slightly absorbent; if the water is absorbed very quickly, the substrate is too absorbent.
- For non-absorbent or slightly absorbent substrates, it is advisable to apply maculature fleece.
- For highly absorbent substrates, the wall should be primed again.
Rough and unclean surfaces show through when wallpapering. The processed wallpaper does not show a beautiful surface effect after the renovation.
How do I find out if the substrate is not smooth or clean?
- Check for smoothness and cleanliness with grazing light from a torch.
- Smooth rough substrates with filler and then bond waste fleece if necessary.
Alkaline substrates such as new plaster or concrete are not suitable for wallpapering with grass, bronze or metallic wallpapers.
In individual cases, efflorescence can also occur with other wallpapers, which appears as stains on the wallpaper.
How do I find out if the substrate is alkaline?
- Moisten the substrate with distilled water, apply indicator paper, determine the pH value.
from a value of 7.8, an alkaline substrate is encountered
- Allow the substrate to dry until a pH value of 7 is reached.
- Alternatively, wash the alkaline substrate twice with a multi-fluid and then rinse with clean water.
- then glue down the maculature fleece
Cracks in walls and ceilings can have a significant negative impact on wallpapering.
What can I do if the substrate contains cracks?
- Hair and net cracks
become visible by moistening the surface
- Shrinkage and joint cracks
extend through the entire plaster layer into the joints
- Static cracks and expansion cracks
Due to the construction of the building
- For hairline, net, shrinkage and joint cracks, maculature fleece should be used as a crack bridging material
- Special measures are required for the restoration of static cracks
Mould infestation can occur where fungal nutrients are present and moisture occurs.
What can I do if the substrate has fungal infestation?
- Room air too humid
Cause of mould must be determined and eliminated
- Preventive measures such as regular ventilation and controlled heating leads to a reduction in humidity
White salt efflorescence on the plaster surface is caused, for example, by rising damp from a horizontal barrier that is no longer intact, by leaking masonry or after water damage.
What can I do if the substrate contains efflorescence?
- Leaky masonry or after water damage
- Wallpapering should not be carried out here as long as no suitable remedial measures have been carried out