Most steps in older homes creak and squeak underfoot because the wood has dried and shrunk over time. Squeaks in stairs are usually caused by a loose tread rubbing against a riser or a stringer when the stair is stepped on.

Treads can become loose when wood shrinks or when supporting blocks or nails work loose. This is usually not a problem unless the parts become very loose or the creaking indicates that a section of the stairway is nearing the breaking point.

There are two approaches to fixing squeaky stairs—from below the stairs or from above. It’s preferable if you can fix them from below because your repair is less likely to show.

Once you find the source of the noise, you can usually fix it relatively easily. If the noise comes from the spot where your foot meets the tread, concentrate your repair efforts there. If the noise comes from one side when you step in the center or if it comes from the rear of the tread when you step at the front, the chances are pretty good the entire tread is moving or deflecting.

If you’re concerned about the noises, start by investigating the source of the sound. Stairs with open undersides (such as when basement stairs or closets are built below) make this job easier. Where the underside is not accessible, you may have to pull down a finished ceiling underneath to get a good look.

Before making any repairs, try lubricating the parts with talcum powder or powdered graphite to reduce the friction where the parts rub together. Forcefully blow the powder into the joints, especially where the backs of the treads meet the risers. If this doesn’t help, you’ll need to take on a little carpentry work.

Check that the wood wedges, used to lock the treads into their mortised slots, haven’t worked loose or fallen out. If they have, glue them back in place and tap them tightly home. Blocks under the treads where they meet each riser also can fall away. If so, nail and reglue them as well. Look for longitudinal splitting or cracks across the width of the stringers, which carry the treads. Also check the vertical plumb and horizontal level of the major parts to determine if the stairs are leaning in any particular direction—the noises you hear could indicate that the structure is moving or in danger of collapsing.

If you can get at the stairs from underneath, you can use wedges, brackets, or wood blocks to secure the treads to the risers. (Wear eye protection to keep sawdust and other debris from getting into your eyes.) Glue and screw wood blocks under the tread and against the riser. Be sure not to drive the screws through the tread’s surface.

If you don't have access from below, you’ll have to work from above. To prevent the wood from splitting, drill pilot holes before inserting nails or screws; counterbore the holes if you plan to fill them with dowel plugs. Otherwise, set the heads slightly below the surface and cover the holes with matching wood putty.