Wallpaper Inspection

by Nick GromickoCMI® and Kate Tarasenko

Wallpaper is a material used to cover and decorate interior building walls. It is typically sold in rolls and applied using an adhesive. Wallpaper can be plain (so that it can be painted), textured (such as Anaglypta and vinyl), and with patterned graphics. 
InterNACHI inspectors should be aware that wallpaper can be used to mask structural as well as cosmetic defects, and it can also pose a fire hazard, depending on how and where it’s installed. 

A Brief History of Wallpaper

The earliest known form of wallpaper originated during the Renaissance. Depicting exotic landscapes and pastoral subjects, Renaissance-style wallpaper was hand-printed using carved wooden blocks, and either hung loose from the top of a wall or pasted down onto the wall, as it is today. It became popular as an alternative to Middle Age-era tapestries, which were also used to add color to a room as well as to insulate the living space against the cold stone walls, but these were affordable only by the elite. 
The development of steam-powered printing presses in 1813 allowed manufacturers to mass-produce wallpaper, reducing its price and making it affordable to working-class people.

Disadvantages and Defects

While most problems with wallpaper are cosmetic, the following conditions present safety risks:

  • mold. Wallpaper provides excellent conditions for the growth of mold, which is unsightly and hazardous even in small quantities. Airborne mold spores can land on surfaces and will grow in the presence of moisture that may have become trapped between the wall and wallpaper.  The moisture may originate from humid conditions or a leak somewhere in the structure. Mold can eat its way through the wallpaper and appear as widening, dark stains and splotches. Homes that are vacant for long periods or are otherwise neglected can develop wallpaper mold, which can eventually require expensive professional cleanup. Wallpaper has been used to cover electrical wires, which is a serious fire hazard.  (Photo courtesy of InterNACHI member Chris Zimmerman)

Homeowners are advised to consult with an IAC2-Certified InterNACHI inspector before attempting any remediation themselves, as careless removal of mold-laden wallpaper can create a massive release of mold spores into the air; and

  • concealment of electrical conductors. Conductors that run beneath wallpaper pose a fire and safety risk, and a qualified electrician should be consulted for an evaluation. In the photo at right, InterNACHI member Chris Zimmerman documented a bathroom light fixture’s hot and neutral electrical lines running beneath the wallpaper.

Cosmetic defects are more common, however, and they often occur as a result of conditions in the underlying wall. Dust or grease on the wall can weaken the grip between the adhesive and the wall, and every bump, crack and ripple that initially seemed harmless will telegraph through the paper and spoil an otherwise tidy design. That’s why it’s critical that, before installing wallpaper, homeowners and builders need to prepare the walls properly, including cleaning them and sealing any gaps or joints in the drywall.

Other installation cosmetic defects include the following:

  • Bubbles and blisters indicate that air has been trapped between the wallpaper and the drywall or other substrate. This condition may have been caused by the uneven application of adhesive or insufficient smoothing after hanging the paper.
  • Tearing or ripping is caused by the use of blunt tools or poor handling or cutting methods.
  • Wallpaper will rise unevenly where sloppy installation causes it to overlap its neighboring section.
  • If adhesive was mistakenly applied on the front of the wallpaper rather than the side that faces the substrate, it can usually be washed off, if done carefully.
  • Where the adhesive has weakened, the wallpaper will delaminate or peel away from the wall. If this happens, lay new adhesive or replace the wallpaper.
  • Joint shrinkage may result during the drying process where the edges between adjacent wallpaper panels separate.  This can leave unsightly gaps.Mold is growing beneath this wallpaper.  (Photo courtesty of the EPA)

In addition to installation defects, the manufacturing process may result in defects that may not be obvious until the homeowner is underway with his wallpapering project.

Some of these issues include the following:

  • The pattern rises or drops. If the roll was cut on a bias (at an angle), the resulting pattern may drop or rise slightly throughout the length of the roll. The error is difficult to see up close, but it will be obvious after installation.
  • A damaged top or bottom edge is the result when a manufacturing defect causes the edge to weave up and down where it should be straight.  If this is discovered, the roll should be returned. The edge may have been damaged in transit between the factory, supplier and installer, but this defect usually dissipates after the first few rolls of the wallpaper’s manufacturing run.
  • Trimming errors include under-trimming and over-trimming. Under-trimming occurs where patterns mismatch due to a manufacturing error when not enough wallpaper was trimmed away. This problem can usually be solved by carefully cutting the wallpaper to match its neighboring sheet after precise measurement. Over-trimming, however, results in pattern gaps that cannot be remedied.
  • A design may be out-of-register where the coloring of a design exceeds its boundaries or is off-center, such as where the red coloring of an apple expands beyond its outline, or the red section is slightly to the right of the outline.
  • Wallpaper ink may run when made wet by ordinary water if it was not sealed properly or it was manufactured using delicate colorants.
  • If the ink runs low during the manufacturing process, the wallpaper’s patterns or coloring may not fully appear, or they may be shaded unevenly within a single roll (or between rolls in the same batch).
  • Sloppy, dripping ink spots or lines may be created during the manufacturing process and may require replacement of the roll.
In summary, wallpaper is a decorative material used to cover interior building walls. It’s prone to a variety of defects that may be require replacement of the wallpaper to prevent cosmetic and safety issues to the structure.