Hanging over a painted surface
If the painted surface is glossy or painted in a flat paint you will need to prime the surface with a wall covering primer. Use a primer that will adhere to glossy surfaces and will also seal a flat surface. Priming is important to ensure proper adhesion and removal of the border when it comes time for removal down the road. If you are hanging the border at the top of the wall at the ceiling line, you will need to measure down from the ceiling ¼” short of the width of the border and draw a line with a pencil parallel with the ceiling at this measurement. You will apply the wall covering primer from the pencil line up to the ceiling. Be sure that you are less than the width of the border on this measurement or you may have primer showing below your border once installed.
Hanging over wallpaper
The best way (and some will argue the only way) to install border over wallpaper is to cut the border into place and inset it into the wallpaper.
Hang your wallpaper as usual, and once you reach the end of the wall you will need to install the border over the wallpaper as you go. Position the border in place, and with a new razor, cut the border into place through the wall covering so that it may be inset into place. Lift up the border and remove the wall covering from underneath and lay the border back down.
If the wallpaper is already dry and installed and you later decide you want to install a border over the wallpaper, you will have to install the border on top of the wallpaper using VOV ( vinyl on vinyl ) glue as opposed to insetting the border as previously described.
Start at an inconspicuous place. If hanging the border at the top of the wall at the ceiling line, start in the inside corner above the door that you enter the room. This will be the starting and ending point where you will get a mismatch at the end once you have circled the room. There are techniques for making this mismatch less noticeable which is a topic for another article at another time, but if you put you mismatch in this corner it should not be too noticeable.
Holding the border up. One challenge you will need to overcome is how to hold the border in place at the ceiling as you work your way around the room. The best solution I have come across for this is to hold the border to the wall with a thumb tack, which allows you to come down the ladder to re-position the ladder as you work your way across the wall. The hole left by the thumb tack can be smoothed out with a smoother and shouldn’t be noticeable once the border is installed.
Turning the corner. As a rule you will cut your corners as you turn them. The method used by most paper hangers is to turn the corner onto the next wall about ¼” and cut the border there, this creates a ¼” “buffer”. Next you overlap the border over this ¼” buffer and realign your border to level as begin down the next wall. I like to dab this overlap with a bit of VOV (vinyl on vinyl) paste to be sure the overlap holds.
Smoothing and cleaning. Smooth down the border with a smoother to remove air bubbles and to lay the border down onto the wall. Keep a small bucket of clean, warm water and using a sponge, wipe down the ceiling, wall below and above the border, and the border itself to keep it clean from paste. Clean everything as you go, don’t let the glue dry on anything thinking that you can remove it later- it may not come off later at all or without damage and / or a struggle after it dries.
Change blades often. Probably the number one error that many DIYers make is using a dull razor blade. If the blade snags or tears your paper as you cut, you will not get a clean and neat job – so change blades often.