Before starting to wallpaper, make sure that:
The ceiling has been finished.
Any coving, picture or dado rails has been fitted and finished.
Check to find out if the paint is both non-water soluble and soundly bonded to the wall surface. In olden days, whitewash or distemper was often used as the decorative finish and these are unsuitable for wallpapering onto, pay special attention to areas around the tops of the walls; these areas may have been above a picture rail and this areas was often distempered.
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West Coast Fine Art