Surface Preparation when Hanging a Wallcovering

When hanging a wallcovering, the surface should be clean, dry and as flat as possible. Cracks and holes should be filled and the surface made smooth. Screw or nail heads should be sealed with a blob of oil-based paint before tilling over them. Where shelves or other fittings are removed, put matchsticks in the screw holes so they can be found.

Papered surfaces
Walls which have a wallcovering on them should preferably be stripped before another wallcovering is hung. But this is not essential when the original wallcovering is in good condition, clean and firmly stuck as long as it is neither embossed nor has a plastic surface. If a few odd patches of wallcovering have lifted these should be torn away and the rough edges left should be gently abraded smooth with a medium-grade abrasive. If the original surface is in poor condition, do not attempt to hang wallcovering on lop of it - it may come off.

Stripping wallcoverings
A few washable wallcoverings and foamed polyethylene ones are dry strippablc and can be simply peeled off the wall to leave the original surface beneath. With vinyls, the top layer of plastic can with care be peeled away, leaving its backing paper on the wall.

Stripping old wallcoverings often means a lot of hard work. The success of the operation depends on getting water to the original adhesive beneath the wallcovering so that it begins to dissolve and lose its grip. The wallcovering then has to be removed. Sometimes some wallcovering can be removed without welting it first. With ordinary wallpapers there is relatively little problem soak the wallpaper with warm water containing a little washing-up liquid or with a special-purpose wallpaper stripper (usually dissolved in water too). Leave it for a short while to soak through the paper and then scrape off the wallpaper with a flat scraper. This is a messy job lay polythene sheeting over the floor to catch soggy scrapings as they fall. Stripping is tedious - allow plenty of lime to complete the task and keep the wallpaper well soaked. Once all the paper is off, allow the surface to dry and then abrade off any small nibs of paper left and wash down the whole surface with a detergent solution. A steam stripper which can be hired will speed up the process but it is hard work to use.

Stripping washables and papers which have been painted is much more difficult
the surface on these is water-resistant and so the diluted washing-up liquid or wallpaper stripper will not be able to do its job until the surface has been removed or broken up. A special-purpose stripping tool with serrated edges can be used to score the surface, or a wire brush or a coarse abrasive waterproof silicon carbide paper used wet, for example. If the wallpaper has a particularly stubborn painted finish then it may be necessary to use a chemical paint stripper. In all these cases take care to avoid damaging the surface beneath.
Painted surfaces
If the old paintwork has a matt finish -probably emulsion paint - and is in good condition, it should be washed down with a detergent solution or a paint cleaner, to make sure that all grease is removed. The wallcovering can then be hung when the surface is dry. Sound gloss-painted areas should be washed down too but in addition follow this up by thoroughly rubbing down the whole surface with a coarse grade abrasive. Make good any damaged areas with a filler and when this is dry seal it with wallpaper paste, size or emulsion paint.

Any paint that washes off fairly easily, such as old whitewash or distemper, should be removed completely.

Where textured paint has been used on a wall or ceiling, this can be particularly difficult to remove. There are special gel-like strippers that will soften the coaling, allowing it to be stripped off, or you could try using a steam wallpaper stripper.

Bare surfaces
Bare surfaces should be treated as if they were to be painted over using the appropriate primer or sealer for the surface. New plaster or render which is in sound condition and dry should be painted with a coat of emulsion paint diluted with water. Painting is not essential size can be used instead but painting will make it easier to strip the wallcovering at some future dale. The wallcovering can be hung as soon as the paint is dry.

Sizing
On very absorbent surfaces, the adhesive applied to a wallcovering may soak into the surface, making it difficult to slide the wallcovering into place and producing a less good bond between the wallcovering and the surface beneath.

To stop this happening, the surface can be sealed with a coat of the adhesive before the wallcovering is hung. This is known as sizing.

Very absorbent surfaces bare plaster and plasterboard should be scaled and it is also sensible to size a surface before hanging a very heavy or embossed wallcovering. It is not necessary, however, to size painted surfaces or surfaces which have just been stripped. The size should be applied by a brush or a roller and allowed to dry thoroughly before hanging the wallcovering.

A few wallcovering adhesives recommend an animal glue size before using the wallcovering adhesive. But this is rapidly being superseded by using a coal of the wallcovering adhesive itself as a size applied at half the strength recommended for hanging wallcoverings.

When using ready-pasted vinyl wallcoverings use an adhesive containing a fungicide as a size.

Lining paper
Wallcoverings hung straight over uneven walls may crease and stretch; on non-absorbent surfaces such as gloss paint, the adhesive may lake a long lime to dry and so either stain the new wallpaper or cause it to lift. A lining paper can be used to solve these problems and should also prevent shrinkage.

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