You can apply new wallpaper over an existing layer, but this is only possible under a specific condition related to the old wallpaper's surface finish.
Key Considerations for Wallpapering Over Existing
According to the provided information, you can successfully install certain types of new wallpaper over existing wallpaper. Specifically, you can put peel-and-stick wallpaper or pre-pasted wallpaper over existing wallpaper.
However, the success of this method critically depends on the characteristics of the old wallpaper.
The Crucial Condition: Avoiding Vinyl
The fundamental requirement for wallpapering over an existing layer is that the old wallpaper must not have a vinyl coating on top to protect it from moisture.
Attempting to apply peel-and-stick or pre-pasted wallpaper over a vinyl-coated surface will likely lead to adhesion problems.
Adhesion Factors
The reason for this limitation is directly related to how the old wallpaper's surface interacts with the new wallpaper's adhesive backing.
| Old Wallpaper Surface Type | New Wallpaper Type (from reference) | Adhesion Likelihood | Reason for Adhesion Outcome (from reference) |
|---|---|---|---|
| Existing wallpaper (no vinyl) | Peel-and-stick or Pre-pasted | Likely Good | Surface is typically porous enough for adhesive to bond. |
| Existing wallpaper (with vinyl) | Peel-and-stick or Pre-pasted | Poor | The vinyl coating is designed to be non-porous and won't allow the peel-and-stick backing to adhere properly. |
Therefore, before attempting to wallpaper over old wallpaper, it is essential to confirm that the existing layer does not have a non-porous vinyl coating.
