It depends on the type style, and condition of your existing wallpaper. If it is non-coated wallpaper, then this is the only wallpaper that can guarantee success. If it's vinyl-coated wallpaper, then you must make every effort to remove the wallpaper first. The reason for this is based on the principle of adhesion.
yes, but i think that would be difficult and kinda weird. my walpaper is kinda bulgy and if i put another one over it, my wall will probably look like a ton of pillows in my wall xD but yea its very possible
Any flaws or seams will show through under the new wallpaper. Especially if you don't know how many layers of wallpapers or other surface are under there, the best situation is to strip the old wallpaper off. Renting a steamer for this purpose is your best bet.
It is not advisable, but sometimes I get a customer who insists - therefore 1. make sure that the old paper is tight - not loose on the wall 2. prime the walls with a good primer - shields is good 3. make sure the new paper does not line up on the same seam line as the old paper. last notes-- you will probably see some of the lines from the old paper and.. as your new paper is drying - it will most likely bubble up - this is caused from the moisture lifting the old paper off the wall - the bubbles should suck down after 24 hours.