i personally would not paper over any kind of shiny finish that many modern vinyls can have. if flat and sound it should be fine, though you might end up with more bubbles that won't go away if the existing paper has spots where it is not properly adhered to the wall. the glue will make the paper wet, it will expand and with lamination effect of the new paper on top the bubbles may not disappear.
Iam not lazy,its because my walls are bumpy and uneven with old glue etc,Last time I papered we put special lining underneath,And I don't want to plaster the walls,because the I would rather have wallpaper not paint!
Hi Jackie, have to agree with JRS on this one. Unless you have put on lining paper then it will always be best to strip the walls completely. If you have bits of glue etc on the walls then you didn't prepare them properly the last time they were done. If you want a good job that you are really happy with then strip them back to the bare plaster, get all the little bits of glue and paper off, rub them down to make sure they are flat then fill in all holes and cracks. After this size them and if they are not reasonably flat put up a lining paper first horizontally then put up the new paper. I know it's a long job but if you want it to look good then you have to put in the work on the preparation. Good luck. Shed.
Man speaks the truth. :wink: As above says give the bare wall a right good sand fill any massive holes and sand and size then line walls as above then when dry face fill and thing that shows through sand lightly then tough up filler with size then hang paper as required.