Can you wall paper over a wall that has been painted over the original paper
You can as long as its in reasonable condition although it would be better to steam the old paper off.
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It would all depend what type of paper the original paper was, if it is just lining paper, you can (although ideally you should always completely strip walls and begin again).
To get a better finish and eliminate any risk of it going wrong it would be best to remove old wallpaper first
Its not a good idea to paper over any existing wallpaper let alone a painted wallpaper as the finish and seems can never be tidy and will quite easily attract air bubbles and the old paper my become saturated with the new paste it begins to lift.
You can, and can make the wall paper behind bubble or lift. Ideally would be more suitable and recommend taking the wall paper off and cross lining first and then putting your main wall paper on top.
FOR A BEST FINISH YOU NEED TO TAKE OF THE OLD WALL PAPER .
BUT IF THE PAPER IS LINED PAPER AND IN GOOD SURFACE IS POSSIBLE.
If the paint is in good condition thats ok
depends on the type of paint, i would sugest a watered down thin layer of pva glue first
Not recommended. Strip old paper first.
It can be papered but you cannot guarantee you won't get any bubbles from original paper.
You can but it wouldn't last long it would start peeling away unless u put an oil based primer on first
Your better off removing old paper, as once new paper is put up it may raise due to the moisture from paste and the end result may not look great