Step 1 – Inspect the Surface of Your Wall
Don’t be reductive when thinking about wallpapering. Your wall may appear flat, and your wallpaper may seem smooth, but without making proper preparations to your surface, your final result won’t look good.
The walls must be in good condition before you can hope to take a stab at putting on any wallpaper. This means that any imperfections like holes or cracks must be repaired, and any blemishes like mildew must be removed.
Step 2 – Check the Condition of Any Paint
If the wall that you intend to lay wallpaper on has a preexisting coat of paint on it, you may or may not have a complication. There are two quick tests you can perform to check the condition of painted walls, and the results will either give you the green light to apply wallpaper or indicate that more preliminary work is needed.
To test your paint, hold a damp sponge against the wall for about 15 seconds. Then wipe the area with a cloth vigorously. If very little paint comes off, the painted surface is okay and should be capable of accepting wallpaper. If a lot of paint comes off, the walls should be washed thoroughly – or sanded and washed – to remove the paint before you attempt wallpapering.
The second test involves cutting three small Xs into the wall’s surface. Place a piece of scotch tape over each X shaped incision, and then yank the piece of tape off the wall. Once again, a small amount of paint transfer means that the surface is ready for the following steps, but a lot of paint coming off means you need to sand and wash the walls.
Step 3 – Be Smooth
The ultimate goal in the preparation stage is to provide a smooth finish for materials such as wallpaper to adhere against. Walls painted with gloss or semi-gloss paints should be sanded to dull the surface.
For new drywall, be sure the areas along the joints and over nail heads are thoroughly cured and sanded smooth. New drywall should be primed with an opaque or a white primer.
All sanded surfaces should be primed before hanging wallpaper, and any stains like grease, grime, or adhesive residue from a previous wallpaper should be cleaned and primed with a stain killer or primer.
Wall liners provide some exception to this rule, as they allow wallpaper to be placed over rough surfaces like paneling and masonry block. This is still a risky option and should only be attempted under ideal conditions. Be aware that if you do plan to use wall liners, your choice of primer will be crucial, as you’ll need especially good adhesion between the surface and the wallpaper.
Step 4 – Determine How Much Wallpaper You’ll Need
To determine the amount of paper you’ll need, first measure the height of the wall from the top of the baseboard to the ceiling or bottom of the molding. Next measure the length of each wall.
Add the measurements of the wall lengths together. Find the total number of square feet by multiplying the wall height by the combined length measurements.
If your wallpaper pattern does not repeat, or if it repeats every 0-6 inches, each roll yields approximately 25 square feet. If your pattern repeats every 7-12 inches, each roll yields approximately 22 square feet. This goes on depending on your pattern.
Divide the total number of square feet to be covered by the number that is appropriate for your pattern. This is the total number of single rolls of paper you will need for your wallpaper job.
Wallpaper is usually packaged in single or double rolls. To find the number of double rolls you need, divide the number of single rolls by two. To find the number of triple rolls you need, divide by three.
Ask a store associate for help if you’re unsure how much wallpaper to purchase even after these calculations.
Step 5 – Measure and Mark
Place (but don’t adhere) first strip of wallpaper to the right of a door or window. Using the edge of a door or window frame provides a definitive starting point and makes any break in the pattern of the paper less conspicuous.
Measure the width of the wallpaper and subtract 1/2 inch. This 1/2 inch reduction allows for the paper to overlap the adjoining wall.
Mark the width of the wallpaper less 1/2 inch on the wall to the right of the door or window where you will begin. Line up a level on this mark and draw a pencil line lightly from the ceiling to the floor. You may need to reposition your level several times. Be sure to line it up carefully each time.
Step 6 – Mix the Wallpaper Adhesive
Wallpaper paste or wallpaper adhesive can come in liquid form or as a dry, flake-like product that can be activated with water. Either will act as the bonding material that allows your pattern to stick on the wall.
If you are using paste, read the manufacturer’s instructions carefully and follow them exactly. Always use cold water to mix paste. Mix it thoroughly to be sure it is free of lumps.
TIP: Tie a string across the top of your paste bucket where you can attach a brush. This string will keep your brush clean and also give you an edge to slough off excess paste each time you dip the brush.
Step 7 – Cut the Wallpaper
Cut the first strip of paper 4 inches longer than the wall height. Unroll another section and match the pattern before cutting the second strip.
Study the pattern carefully and always match it before cutting. Your first strip will set the bar for how your pattern looks. All subsequent strips should be matched visually while they are still attached to the roll as once they are cut, a mismatch will stay exactly that.
It is usually wise to cut no more than two or three strips of paper before applying them.
Step 8 – Put Paste on Paper
Unroll the strip of wallpaper on your work surface with the pattern side down. Brush an even layer paste on the non-patterned side so that it covers about 2/3 the length of the strip. Brush the paste out evenly and not too thick.
TIP: Add a few drops of food coloring to the paste to tint it slightly. This will make it easier to judge the thickness of the paste and detect any missed spots.
Step 9 – Fold the Pasted Paper
Fold the pasted end of the paper back about 2/3 of the length of the piece so that you put the pasted side to the pasted side, avoiding any creases.
Slide the paper forward on the work surface and apply paste to the remaining 1/3 of the piece. Fold it back over in the same manner. This process where you glue each end of the wallpaper and then fold it back in toward the middle is known as “booking” the wallpaper.
Once you book the wallpaper, allow about five minutes before using the piece. If you have to stop or will not be using the strip right away, place it in a plastic bag to keep it moist.
Pre-pasted wallpaper already has an adhesive applied on its backing. The bonding properties of this product are activated when you run the pre-pasted paper through clear water. Plastic and metal dip troughs for pre-pasted paper are available. Cut a piece of pipe or dowel rod an inch shorter than the trough. Lay it in the bottom of the trough over the paper. It will hold the paper under water as you pull it out.
Step 10 – Create a Butt Joint
Carry your long strip of pasted wallpaper from your work surface over to the wall. Drape the folded paper over your arm like a coat. Never open the paper until it is in position to hang.
Use extreme care when placing the first strip of paper on the wall, since all other strips of paper will be aligned to this first one.
Most manufacturers recommend the butt joint. It leaves no ridges at all, but requires a little extra care to make. The edge of one strip is butted up against the edge of an adjoining strip. If you force the two edges together too tightly, it will form a ridge. If they are not placed together tightly enough, you will leave a gap between the two edges. Use the palms of your hands when positioning the paper. Try not to pull on the edges.
It may be necessary to trim the edge of the paper to ensure a proper fit. You can trim the paper with a razor knife and a straightedge.
Step 11 – Position the Paper on the Wall
When the paper is in position for hanging, unfold the top half of the pasted sheet. Overlap the top edge of the pasted paper at the top by about 2 inches. You’ll cut away this overlap in the trimming process.
Hold the edge of the paper with one hand and pull the pasted fold apart. The pasted side of the paper should be held firmly against the wall. Reposition the strip as necessary so that the right edge of the paper lines up with the pencil line you made previously.
Step 12 – Smoothing
Use a smoothing brush to smooth out the top and bottom. Allow the bottom of the paper to fall of its own weight. Brush it out evenly. If you trap some air behind the paper, smooth it out with the brush. If this does not work, pull the paper away from the wall.
Continue to apply each sheet of paper in this same manner. Use care to align the design in each succeeding sheet.
Step 13 – Trimming
Trim off the surplus paper at the bottom and top of each strip. Use a metal paint edger or broad knife and a razor knife to get a clean edge. Change the blade on your knife every strip for better results.
Step 14 – Wash Away Excess Paste
Use clean water to rinse all baseboards, casings, etc., with a damp sponge before the paste dries.
Step 15 – Wallpaper Rolling
Let the paper dry about 15 or 20 minutes, then roll all seams. Use a regular wallpaper roller and roll thoroughly for a neat job. Do not apply too much pressure; you may form paste ridges under the paper or force the paste out through the seam.
Step 16 – Do Your Corners
At the corners, measure from the last full strip of wallpaper to the corner and add 1/2 inch. This 1/2 inch will allow the strip to go into the corner and onto the adjoining wall by 1/2 inch. If your walls are not running straight up and down, you may want to use 1 inch instead of 1/2 inch.
A small slit at the top and bottom of the piece in the corner will make it easier to go around the corner.
For the next piece, measure out the width of the wallpaper from the corner and make a pencil mark. Use your level and make another perfectly straight line from the floor to ceiling as before. This piece will overlap the 1/2 inch strip on the wall from the previous piece installed. For vinyl wallpaper, use a vinyl-to-vinyl adhesive on these corner seams.
Odd and Ends
Be especially careful when trimming paper along the edges around fireplaces, windows, mantelpieces, etc. Sometimes the weight of the paper causes it to tear at its narrowest point.
For outside corners, measure the distance from the last full strip to the corner. Add 1 inch to this measurement. Measure the width of the paper and add 1/2 inch. Measure out from the corner the width of the paper and add 1/2 inch. Make a pencil mark on the wall. Using your level, again draw a light pencil line from the floor to the ceiling. Align your wallpaper with this line and match the pattern as closely as possible. This piece will overlap the last piece by 1/2 inch.
For doors and windows, hang the paper over the edge. Using your razor knife cut away the excess wallpaper. Making small cuts from the corners of the doors and windows toward the center will help you position the wallpaper around these obstacles. After the paper is smoothed, use your edger and razor knife to trim around the doors and windows.
Since all the switch-plates, outlet plates, etc. were removed before papering, you can apply the wallpaper right over these openings. The wallpaper can then be cut with the razor knife and straightedge. Replace the fixture plates for a finished job.
Credit – http://www.doityourself.com/stry/h2wallpaper