Tightening or replacing balusters

As a companion piece to the prior post, I thought I'd include how to tighten or replace loose or broken balusters.

Tightening Loose Balusters
Sometimes the settling of the house causes a staircase to sag or twist, which in addition to causing squeaky treads, can loosen the balusters as well. This can easily be repaired with glue and shims. It's best to schedule this project either late in the evening, or prior to leaving the house for an extended period so that the stairs won't be used and the glue has ample time to set.
You can easily buy or make your own wood shims. To make your own shims, cut a strip of wood with the grain running the length of the strip. Make it slightly thicker than the widest gap between the top of the baluster and the handrail. Cut the strip into shims and sand or plane them into wedges. Coat the shims with glue and insert it at the top upstairs side of the baluster. Lightly tap it into position using a mallet or hammer and a block of scrap wood. Once the glue is dry, trim the excess shim flush with the baluster.
Alternatively, you can drill a countersunk hole at an angle through the baluster and into the handrail, using a carpenter screw to tie the baluster and handrail together.

Replacing Damaged Balusters
If the baluster is doweled (peg in hole) start by sawing it in half. Twist sharply to break the glue bond holding the baluster in place, and remove the two halves. Cut the new baluster to the desired length and coat the tread hole with glue. Insert the top end of the new baluster into the handrail, then slide the bottom end across the tread and into the tread hole.
If the baluster is dovetailed, remove the outside tread trim, being careful not to damage it. Saw the baluster flush with the tread, and use a chisel to remove the old dovetail. Cut the new baluster to length, put top into the handrail, and bottom into the now empty dovetail socket. Drill a pilot hole through dovetail and into tread, and attach the two with a nail. Finish by replacing the outside tread trim.
If the baluster is filleted, chisel out fillet on the upstairs side of the baluster being replaced. Tap the baluster loose from nails and remove. Clean old glue from the groove. On the new baluster mark the angles using either the old baluster or a T-bevel, and cut to fit. Set the new baluster against the existing downstairs fillet, and toenail into place. Glue and nail new fillet into the handrail behind the new baluster.

How To Fix a Squeaky Stair

Squeaky wood stairs are caused by friction against the nail shanks. Because stairs get a lot of traffic, it is almost inevitable that nails will start to drop from the wood.

How Not to Fix Squeaky Stairs!
If you are familiar with the process of fixing squeaky floors, this is substantially the same. Maybe you already know that hammering down loose nails is only a temporary fix as the nail will soon be lose again - or worse, back out to where someone might get hurt. Hammering in a second nail, next to the squeaky nail is a little better, but not much. If you decide to go this route, be careful that the new nail doesn't split the tread - a very real possibility, especially with older homes and stairs.

Screw 'Em!
The best solution is to pre-drill a hole next to the squeaky nail and secure the board with a screw into the underlying riser.

If you have access directly to the tread (the stair treads are not covered with carpet), you can apply some caulking into the squeaky riser-tread joints or into any cracks. Caulk isn't glue, it serves as a kind of cushion letting the objects still move some.

To really do the job right, it helps if you have access to the underside of the stairs. The fix then is similar to the fix that you would take to fix a squeaky floor board. With this method, you can investigate and see if there are blocks that were attached to the joints between the risers and treads. It is possible the blocks have fallen out or broken. In this case, you reattach or replace the wooden block of with construction grade wood glue and finishing nails. Alternatively, beneath the stairs you may find wedges at the riser-tread joint. In this case you can lightly tap in new wedges to which you applied a light layer of construction grade wood glue.

That's all there is to it!