From taking the proper measurements and affixing the tackless strips and padding to correctly scoring and cutting the carpet, there is plenty of room for error when you install carpet on stairs. In order to avoid any major mistakes, it is best to go into the process with a few helpful techniques. Carpet stair installation may be either a runner or full carpeting. Either way it requires tackless strips, padding and the carpet. Each element may be incorrectly affixed, so it’s best to avoid the common problems.
Tackless Strip Mistakes
The first thing you will install are the tackless strips. Make sure you nail them to the wood about 1/2-inch from the crotch or corner between the tread and riser. Don't place them right up against the corner. Also, be sure they are completely parallel to the crotch of the stairs. A common mistake is installing the tackless strips with the upward-facing pins pointed away from the crotch. Make sure they point towards it. Don't forget to place one strip on the tread and one on the riser bordering each crotch. If installing a carpet runner, the tackless strips should be cut and placed so that the runner will extend an 1 inch to either side of the strip.
After the tackless strips are in place, the padding is up next. Don't make the mistake of cutting one long piece of padding for the entire staircase. Cut individual lengths of padding for each riser/tread combination for each stair. Also, make sure you do not cut each length of padding so short that you have to stretch it too tightly. It should rest somewhat slackly over the nosing. Staple one end of the padding directly against the tackless strip, fold it over the nosing and mark where it meets the next strip. Don't overlap the tackless strip. Cut it so it rests right up against each strip.
If you are installing a runner, don't forget to add 4 inches to the runner's final width. A common mistake is neglecting to fold each long edge over on itself by scoring along the backside of the carpet. Doing this allows the frayed edges of the carpet to be invisible. While each pieces of padding only runs from strip to strip, the carpeting extends the full length of the stairs.
If you precut the carpet lengthwise, be sure you accurately measure the total length including the risers, treads and around the nosing. What commonly happens is that the carpet is cut too short which creates a noticeable seam when fixed. If possible, precut the carpet widthwise but not lengthwise. Don't neglect to cut it 2 inches wider than it needs to be. This allows you to snugly fit the carpet into place. If too wide, it can be corrected as you install it. Avoid stapling the carpet to the tread behind the tackless strip until it is pulled tight and packed into the corner over the tackless strip. The first set of staple should be on the riser just under the nosing. When stapling, be sure to set the staples deep in the carpet webbing or else they might be visible.
Make sure the stairway is clean and clear of any debris that might hinder your progress. Probably the biggest mistakes that happens when installing carpeting on stairs is the appearance of seams and a carpet not stretched tightly enough. Carpet cut too short requires an extension piece to cover the stairs while loosely-installed carpeting will flap beneath your feet.