Covering stairs with carpet can be a challenging task. Hidden bulges or slipping carpet can lead to accidents on the stairs. If you lay it improperly, the carpet can loosen and pull free over time. This doesn't mean that you need to hire an expensive carpet installer to do the job for you, though. With attention to detail, some basic tools in your garage and a few you can rent at many shops where you buy your carpet, you can handle this project yourself.
Remove all old carpet. Take up the tack strips, padding and any nails or staples. You need a clean surface for your new carpet. Any old material has the potential of either not holding properly or creating bumps underneath the new carpet.
Calculate how much new carpeting you will need. Measure the height of the riser, the distance around the edge of the stair and across the stair. If you use carpet padding, add 7.5 cm (3 inches) to each stair's total measurement. Multiply this by the number of stairs you will be carpeting.
Apply the tack strips. Cut the tack strip to fit the length of the wall where it meets the stair, where the stair and riser meet and where the wall meets the riser. Nail the strips to the stair and riser about 3 mm (1/8 inch) from the wall.
Lay the carpet on the stairs so that it hooks on the tack strip. Use a knee kicker to tuck in the carpeting in the crotch of the stair. Slide your stair tool along the stair crotch to compress the pins in the tack strip so that it holds the carpet. Do the same thing for the side of the stair where it meets the wall.
Trim the carpeting as needed. Use your utility knife to cut off any excess carpet. Smooth out the carpeting before moving onto the next stair.
Staple along the stair lip and along the riser every 5 cm (2 inches) to help hold the carpeting in place.
Some people prefer to install each stair with a separate piece of carpet, tucking the bottom edge of the higher stair behind the upper end of the lower stair. You may want to wear knee pads when using the knee kicker.