If you need to repair wallpaper, particularly wallpaper seams that have become loose, you will be encouraged to know that repairing loose wallpaper seams isn’t as difficult as it might seem. Vertical seams on wallpaper may come loose for several reasons. One reason is that when the wallpaper was initially installed and when the seam was rolled, too much glue may have inadvertently been squeezed out from beneath the wallpaper by pressure from the roller, leaving the wallpaper without paste. If you have a pre-pasted vinyl wallpaper, the loosening of the seams may have happened because the paste applied at the factory didn’t adhere well to the vinyl paper.

Although the cause of your loose wallpaper seam problem may vary,the solutions to all these problems will be the same. If you prefer to keep the wallpaper that is attached to your wall, and if you'd like to repair seams that have begun to separate, the following steps will help you:

Materials needed

Damp sponge
Seam adhesive (4-oz container)
Wallpaper roller
Putty knife
Paint brush
Step 1 – Dampen Seam

Purchase a 4-oz tube of seam adhesive from your local hardware or wall covering store. With a damp sponge, moisten the loose edge of the seam with hot water. Run the moist sponge up and down the surface of the seam until the wallpaper becomes soft and flexible.

Lift the edge of the seam with the edge of a putty knife or other flat implement such as a drywall knife. This will help prevent the seam from tearing as it's lifted.

Step 2 – Spread the Adhesive

The seam adhesive you use should be in a tube with a pointed nozzle. To spread the adhesive under the loose wallpaper seam, place the nozzle of the adhesive tube under the loose edge of the seam and squeeze just enough adhesive to lightly coat the wall surface. Using the edge of your putty knife, spread the adhesive evenly. Apply enough adhesive to moisten the entire surface on which you want your wallpaper to stick, but not so much that when you put pressure on the wallpaper the adhesive doesn't ooze out from the edge of the seam.

If you use an adhesive that should be applied with a paint brush, work the adhesive carefully onto the back surface of the wallpaper with the brush, so that the surface is completely covered.

Step 3 – Flatten the Seam

With your wallpaper roller, roll over the top of the seam several times until it appears smooth and flat. Make sure the seams edges meet with no spaces between.

If you find small, horizontal tears in your loose seam, make certain you roll the wallpaper flaps flat against the wall surface and into the same position they were in before they became loose.

Step 4 – Clean Off Excess Paste

With a damp sponge or clean damp cloth, wipe off any excess adhesive from the seam's surface. Then, wipe the area with a dry towel and dry it with a blow dryer.