Measure the total length of stair carpet required by adding the height of a riser (the upright portion of a step) to the front-to-back width of a tread (the horizontal portion that is trodden on). Multiply by the number of risers and then add the height of one more riser.
Now add about half a metre (18 in) extra to allow for moving the carpet up or down once a year to distribute wear. Never cut to exact length, relying on turning top to bottom, because when you make such a turn there will be excessive wear. The carpet shop will tell you which is the correct way up.
Use grippers of length slightly less than the width of the carpet — provided that the carpet does not have a rubber or foam backing. Such backings do not offer a hold for the spikes of the grippers, and clips or stair rods will have to be substituted. Nail or screw the grippers on to the treads near to the junction with the risers.
Neither can grippers be used where stairs turn half-way up in the form of a spiral instead of in a square half-landing.
Use grippers for securing to all the remainder of the stairs first, leaving the bend until afterwards. Stretch the part of the carpet (the outside of the arc) over the outside wider part of the turn of the stairs. Use tacks at the turned portion and fold the surplus at the narrow part (inside the arc) upwards and underneath. Folding the other way round will leave a dust trap and could cause anyone using the stairs to trip.
Before starting work measure the width of the carpet and transfer this with chalk to the stair treads, so that there will be an equal amount of surround at each side.
Using this mark as a guide, start at the top by securing the surplus half metre (18 in) of carpet under the landing carpet with tacks. Pull on the carpet tightly and secure over the first lot of grippers by banging into the junction of tread and riser with the edge of a piece of plywood or hardboard. Carry on stretching and securing over each gripper as you descend, unrolling the carpet behind you.
Removal of the carpet at a future date for cleaning is carried out by working from the bottom up and easing the carpet away from the grippers with a lifting motion and in the direction of the slope of the metal spikes.
An open stairway cannot be carpeted by this method. The cnly way is to buy small pieces to fit the treads and either tack or stick them on. A good hardwood may, of course, be stained; but if you attempt to protect the surface with varnish it will wear very quickly under scuffing of feet. This same stricture applies to even the hardest-wearing of paints. Such materials can, however, be used at the sides of stairs where there is no wear.
To ensure long life, all stair carpets that are not already backed should have good thick underlays in the form of pads tacked securely over the nosing of each tread, for this is where the wear will be.