We have produced a "How To" video which explains the factors that affect wallcoverings and also has a masterclass on how to hang wallcoverings click here.

We also have a section in our Product Support Manual on how to successfully hang wallpaper.

Here are some of the main points covered:

Removing old wallpapers

Most wallpapers have a protective waterproof coating on their face that makes them serviceable (spongeable, washable). For this reason it can be difficult to remove a well coated paper without scratching its surface with a wire brush or decorator’s tool. This allows the adhesive beneath the coating to soften and facilitate easy removal of the paper.
Following the scouring process apply a steam stripper to the wall.
Once the paper is soaked scrape it off using a stripping knife, ensuring walls and paintwork are washed down afterwards with clean water.
Vinyl wallcoverings are made up of a backing sheet with a PVC layer laid on top. This top PVC layer can be peeled off by pulling at it from the bottom. The exposed backing layer can be easily removed by wetting and scraping it. It will come off either in a complete length, or in large sections. 

Ensure that the bare walls are sound and that any holes or cracks are suitably filled and rubbed smooth when dry. New plaster, or any other particularly absorbent surface, should be sized with a weakened solution of wallpaper adhesive, or preferably a primer/sealer. Damp walls, or walls with any history of damp or mould problems, should be made good and treated with a fungicidal wash prior to decoration beginning.
Lining paper 
Hang the lining paper horizontally. This ensures the join of the lining paper does not coincide with the join from the wallpaper.
To Hang Lining paper
A Cut the lining paper the length of the wall plus 50-100mm (2-4 inches) for going around the corner to the next wall.
B For accurate results, use a long spirit level to draw a horizontal line, however, using the ceiling or coving line will be acceptable for the lining.
C Paste the length generously, concertina fold it and allow it to soak out for 4-5 minutes.
D Working from a corner at the top of the wall, gradually open up the folds and smooth the paper from the centre out, removing bubbles and creasing as you go. Ensure that the edges are well bonded, applying a little extra paste if deemed necessary. Once the paper is smoothed down tightly against the wall, cut the lining paper into the corner and remove the small piece that was turned on to the next wall. This will prevent any visual ‘ridging’ underneath the wallpaper created by the lining paper being overlapped.
E Successive lengths should be initially very lightly butt joined and then just slightly pulled apart, leaving a small gap of circa. 1 mm. This is to ensure that the lining paper, should it expand again when the wallpaper is hung on top, does not create a buckled join that will show through from underneath the wallpaper as a horizontal line around the room.
F Allow the lining to fully dry (normally 24 hours) before hanging top wallcovering.

Getting the wallpaper vertical
There are very few walls, if any, that are truly square or absolutely vertical. Therefore, if you were to hang your wallpaper starting in a corner the chances are that the design on the paper would run askew, probably giving the appearance of it running up or down hill. To overcome this it is necessary to create a true vertical line as a starting point for hanging.
The best way of achieving this is by way of a spirit level, preferably a 2 metre one. Place it on the wall and mark lightly with a pencil every 150mm (6 inches) from the top of the wall to the bottom. 
An alternative option is to use a ‘plumb line’. This is a piece of string with a weight on the bottom, that is attached to the top of the wall with a pin or nail. 
Once fixed at the top of the wall, allow it to swing freely until it rests. Mark the wall with a pencil both underneath the weight and at the top where the nail is. Then mark the wall behind the string, every 300-600mm (12-24 inches), before joining them all up with a long straight edge. Plumb lines are readily available from any DIY shop.
Starting point
For best optical results start the hanging on a focal point, such as chimney 
breast. If there is no focal point, then hang the first drop in the middle of the wall and work out towards the corners .
For wallpapers with a big pattern or motif, cut the first length ensuring that when the paper is finally trimmed, that there is a complete motif at the top of the 
wall. Cutting through a motif will highlight any deviation in the trueness of the ceiling. Always try and finish where any bad pattern match will be least visible, such as into a corner or above a door.

A. Position the wallpaper face down with one edge ‘square on’ with the very edge of the pasting table.
B. Apply the adhesive generously down the centre of the sheet and then brush out towards the edge that’s lined-up with the edge of the board. Use outward strokes only, as drawing the brush back towards you may result in paste being pulled onto the face of the paper. Once this is done, pull the whole length back towards you, lining up the other edge with the other side of the paste board, and then paste outwards from the centre again. This method will ensure a minimum amount of paste contaminating the paste table and finding its way on to the face of the next length to be pasted.
C. Once pasted, fold the adhesive surfaces together, top to middle and bottom to middle. This ensures that the moisture stays in the sheet, reducing the risk of drying out of the edges. Allow the paper to soak for the recommended time as per the wallpaper label. 

Hanging the first piece
A. Measure out the first length of wallpaper carefully, adding on 75-100mm for trimming top and bottom, ensuring a full motif starts at the top of the wall.
B. Subsequent lengths will need trim waste adding plus the pattern repeat, to ensure that it will be long enough to pattern match the previous length from top to bottom.
C. Check that the pattern is the correct way up, never assume that it comes off the roll the correct way up. Hang the first length vertically to the plumb line drawn on the wall. Holding at the top, gently open the paper and allow it to fall down the wall. 
D. Position the top half and smooth it gently down the centre with a good quality paperhanger’s brush, working out towards the edges as you go. 
E. Ensure that any air bubbles are fully brushed out. If this proves difficult, then gently pull the paper away from the wall and brush it down again.
F. Open the bottom fold and continue to smooth the paper down to the skirting. 
G. Brush the paper tight into the top of the skirting and wall join before gently running a pencil along it to create a line for cutting. Carefully pull the wallpaper away from the wall and cut along the line with a pair of long decorators shears or scissors.
Another option is to brush the paper into the skirting and wall join, then holding the paper tight against the wall using a long ‘steel’, such as a wide width scraper or steel ruler. Trim the paper by firmly drawing a sharp trimming blade (keeping it a shallow angle) along the edge of the steel. (It is important that the blade is kept at a shallow angle to reduce the risk of tearing.)
TIP: Always cut paper into the angle between the wall and the skirting (or ceiling), with the aid of something to hold the paper tight against the wall. Otherwise the paper may snag and tear, resulting in a poor finish.
H Dilute off any surplus paste that contaminates the face of the paper, skirting board and ceiling with a damp soft sponge. Do not rub with a dry cloth, as this will smear the adhesive into the paper.
I Precisely position subsequent lengths using butt-joins. Do not overlap unless instructed to do so for double cutting purposes. See opposite for double cutting procedure.

Hanging into corners
As previously mentioned, corners are rarely, if ever, truly vertical. Never attempt to hang papers around them. Always hang them into two parts, decorating first into the corner before going onto the next wall and decorating back into the same corner.
A. To do this, first measure the distance in 2 or 3 places, from the last drop into the corner. Add 5-10mm to the longest of the distances measured and cut the length dry to that width. 
B. Paste in the normal way and hang the paper. Fold the excess around the corner and brush tight in using a paperhangers brush.
C. On the next wall, measure the width of the piece cut off from the last drop and make a new vertical plumb line at that width for the corner. 
D. Using the plumb line as a vertical guide, paste and hang the cut-off piece back into the corner, slightly overlapping the piece turned around from the previous wall.
E. Use an overlap or border adhesive for overlapping into the corners. This is particularly important when hanging vinyls.
F. On thick or heavily embossed papers it may be necessary to overlap and double cut. See below.
G. On external corners, particularly if using heavily embossed papers, double cutting may also be required.

Double cutting
Double cutting is often a good way of achieving a perfect, invisible butt-join. It is particularly useful when using thick or heavily embossed papers where an overlap would clearly show.
A. To achieve this it is necessary, having overlapped the papers, to use a sharp trimming knife and metal straight edge. Holding the straight edge down the middle of the overlap and pressing just hard enough to go through both layers of paper, draw the trimming knife from top to bottom. 
B. Remove the outer trimmed excess, then lift the top layer clear and remove the underneath trimmed excess. Brush the two layers flat to the wall. Wipe off excess adhesive that will be on the face of one edge with a clean damp sponge.

Light switches and plug sockets
There are three ways of cutting around sockets. Full removal guarantees the best result, though some decorators prefer to save time through part or even non-removal.
In all cases the electricity will require turning off at the mains.
Full removal of switch plate
Remove the screws from the switch, undo the wires from the back and completely remove the plate, ensuring that the procedure for putting them back has been recorded. Then hang the paper over the hole and identify its location. Gently trim or cut around the inside of the hole leaving approximately 5-6 mm overlapping inside. Allow the paper to dry for a little while and then put the light switch back on.
Part removal of switch plate
Undo the switch plate screws just enough for the plate to be pulled away from the wall by about 5-10mm, without completely removing it.
Hang the paper over the top of the switchplate and identify (by gently creasing the paper around it) the switch location. Make a small hole in the middle of where the switch is and cut diagonally out towards the corners, using single clean cuts.
Cut past the corner of the switch by about 5-10 mm. This will allow the switch to be pulled through without tearing the paper. Once pulled through, trim the flapsleaving about 5-6 mm for tucking under the switch plate. Brush the flaps under the plate and re-tighten the screws.
Non-removal of switch plate
Leaving the switch plate in situ, hang the paper over the top and identify its position by gently creasing. Make a small hole in the middle of where the switch will go and cut diagonally out towards the corners using single clean cuts.
Cut past the switch by about 5-10 mm and then brush the paper down tight in against the angle between the plate and wall. (The flaps will stick up.)
Using a steel blade, such as a 4 inch scraper, hold the paper into the join where the switch and wall meet. Trim off the excess using a sharp trimming knife.

Hanging into recessed windows
Hanging into a recessed window is not as daunting as it may at first seem, so long as you accept that almost inevitably there is going to be some patching in. The important thing about patching in is that you identify, before starting, the place it will be best hidden. With conventional curtains this may be on the side wall recess, whereas if you’re using a deep valance or swags, it may be more appropriate to put it on the underside of the top recess.
To paper around a recess window follow these steps:
Hang the length that will go into the recess and cut horizontal cuts, top and bottom, to allow the spare piece to be brushed into the recess.
Butt join the next piece above the window and turn under the recess and trim-up.
Butt join the next piece below the window and trim. Continue with this sequence until the other side of the window is reached.
Hanging the final length for the other side of the window is as piece 1.
Cut the fill in pieces, slightly over-sized, to allow for underlapping the paper already hung. Firstly, peel back the edges of the full drops and then paste, position and trim the pieces, ensuring that any pattern match is accounted for, before brushing back down the edges of the full drops. If need be, use double cut technique as illustrated above.