Hanging wallpaper in bedrooms with sloped ceilings isn't rocket science; you don't have to be a professional, all you need a bit of patience and sufficient time. A handy trick is to cut the length of wallpaper into two pieces.
Preparing the walls
Preparing the wallpapering surface is the most important basis to ensure a harmonious result. The wall needs to be clean, absorbent, stable, smooth and free of obvious discolouration/colour differences as well as mould or stains.
Putting up lengths of wallpaper on a sloped ceilings in one piece
The main advantage of this method is that no seams will be visible. As lengths (or strips) of wallpaper for sloped ceilings are longer than those for straight walls, it is useful to be able to rely on a helping hand. The mathematical basis for cutting the wallpaper is the total measurement, i.e. from the ceiling edge to the floor edge of the knee wall.
Non-woven wallpaper: Apply wallpaper paste directly to the wall. Now set the length of wallpaper along the plumb line at the top of the wall, pushing it a couple of centimetres above the ceiling/gable area. Please note: The wallpaper should be pressed on gradually from top to bottom. Make sure any air trapped under the wallpaper is gently pushed out towards the sides. If any air bubbles or creases remain, the length must be pulled off carefully up to the affected area and then pressed on and smoothed out again. The bottom part should be held away from the wall by the helping person.
Paper-based wallpaper: The top 1/3 and the bottom 2/3 of the pre-pasted length of wallpaper are folded in. The exact soaking time must be adhered to for each individual length. The top (shorter) end is then pulled out, whilst the longer part remains folded up (held by the second person). Now, the first part can be carefully put up, followed by the second (longer) part. Pressing a broom on the top part can help stabilise this process.
Alternative approach: Putting up lengths of wallpaper on a sloped ceilings in two pieces
Hanging the wallpaper length in two pieces is suitable for heavy wallpapers or those with special surface materials. The first part should be the length of the ceiling edge to the knee wall, the second is the length from the knee wall to the floor (plus a few centimetres each end). In order to make sure the pattern aligns correctly, the exact length of the second strip of wallpaper should be determined by holding the wallpaper roll up against the first strip. After cutting the second strip, it can be aligned so that the pattern continues without any visual irritation. The overlap created this way is than removed with a double-seam cut.