If many of the balusters are loose, check the rail­ing and the newel post: They may not be firmly attached. Or if the upper end of the railing dead ends into a wall on the floor above, the railing may be anchored with a bracket beneath. Make sure this bracket is tight.

If the newel post is shaky, try shimming underneath its base or screwing the post down

Anatomy of a Hollow Newel Post

Unlike modern newel posts, older ones are often hollow and attach to railings in various ways. One common way is a star nut centered in the end of a railing, which is accessed by removing a plug on the underside. The bottom of the post may be screwed to a stringer or held fast by an adjustable rod-and-plate assembly running down the middle of the post.

with predrilled 3-in. Torx screws. If this easy repair doesn’t suffice, see if the internal hardware needs tightening. Quite often newel posts are hol­low, with a long, threaded rod inside, as shown in "Anatomy of a Hollow Newel Post,” on p. 173.

You may be able to tighten the upper end of this rod, concealed by the post cap, by turning a nut against a restraining plate. Because you may have difficulty finding the cap joint under many years of polish and grime, loosen the cap by rapping the side of it with a rubber mallet. The bottom end of the threaded rod often emerges on the underside of the subflooring—if it’s exposed, have a look.

On occasion, newel posts also connect to another plate-and-rod assembly on the inside of the nearest stair carriage. About the only way to get at that assembly (if it exists at all) is to pull up the first tread. Where the railing meets the newel, the railing is held tight by wood joinery or by a double-ended hanger bolt accessible through a plug on the underside of the railing.

REPLACING STAIR TREADS

Treads crack because they aren’t supported cor­rectly or they weren’t made from good stock. To replace them, you’ll need to pry or cut them out. Prying is preferable but rarely possible, especially if the treads are rabbeted to risers or housed in stringers.

To cut a tread out, first remove the balusters from the step’s open end, saving that end as a template for the new tread. Drill into the middle of the tread and, driving a chisel with the wood grain, split out the old tread. Clean up any old glue or wood fragments. After fabricating the new tread and testing its fit, apply glue to its edges and to the tops of the carriages on which it will sit. To each carriage, screw down the tread with two or three trim-head screws, predrilled to prevent splitting. Reinsert and glue balusters and nosing.

Whether structural damage is caused by insects or rot fungi, excess water is usually the heart of the problem. Thus, before treating the specific agent causing the deterioration, reduce excess water by maintaining gutters, improving drainage, grading the soil away from the building, eliminating wood-soil contact, improving ventilation, and so on.

The fungi that rot wood reproduce by airborne spores, so they’re virtually every­where. But they can’t establish colonies on wood with a moisture content (MC) less than 28 percent; and they go dormant if the MC drops below 20 percent or the air temperature drops below 40°F. Household molds, also caused by fungi, thrive in a similar moisture and temperature range. So if moisture-meter readings in your basement or crawl space are too high, reducing excess moisture may solve both wood rot and mold problems.

How you reduce moisture, however, is something experts can’t agree on (see Chapter 14 for more on mitigating moisture and mold). Many building codes recom­mend covering dirt floors in crawl spaces or basements with sheet plastic and installing screened vents to circulate air and disperse moisture: 1 sq. ft. of vent per 100 sq. ft. of floor space is the standard formula. Whereas another group of builders argues that it makes more sense—especially in the humid South—to close vents, insulate crawl space or basement walls, seal air leaks, and install a dehumidifier. That, they argue, will stop mold from colonizing and migrating to living spaces. Best bet: See which approach builders in your region favor.

Stair Repairs

Stairs are complicated to build, and problems can be tricky to diagnose. For example, it may be possible to repair squeaky stairs with glue and a few screws. But if squeaking is widespread, stairs tilt to one side, and there’s a gap along a stairwell wall, the diagonal supports beneath the staircase may be failing. In that case, you’ll probably need to expose those supports to find out.

SQUEAKY STEPS

If the underside of your staircase is covered and you have only a few squeaks, try fixing them without tearing out finish materials. Many peo­ple mistakenly attempt to fix squeaks by nailing down offending treads with finish nails, but nails alone won’t work. The nails may split the nosing, and they’ll almost certainly pull loose. It’s far bet­ter to predrill and countersink Torx screws

through the tread into a riser or center carriage beneath.

If stairs can be painted or carpeted over, caulk the squeaky joint with subflooring adhesive. This doesn’t bind the pieces together as well as screws do, but the adhesive cushions them, in effect. Keep people off the stairs until the compound has cured. If that doesn’t eliminate squeaking, expose the underside of the staircase to examine its underpinnings.

What you do next depends on the construc­tion of the stairs. If there are blocks glued along the riser-tread joint, it’s likely the glue has failed. First, eliminate tread movement by nailing through the back side of risers into treads: predrill, and use two or three 6d finish nails per tread. Then reglue errant blocks with white glue or, better yet, with construction adhesive.

REPLACING BALUSTERS

Broken balusters can usually be doweled, glued, and filled. But if you’re disappointed with the repair, see if your lumberyard can order a replacement in the same pattern. Stair parts have been mass-produced for a century or more, so there are catalogs full of stock balusters. Custom mills can create new balusters to match old ones, but the process is labor intensive and costly.

Thus, if you have many damaged or missing balusters and can’t find stock replacements, con­sider replacing all with another pattern.

If balusters are intact but shaky, remove and reglue them; simply nailing them won’t do much good. To get at balusters, pry free the return molding at the end of the tread by inserting a putty knife or small chisel into the nosing seam. Once you start prying, you’ll see small finish nails holding the nosing in place; remove these nails. Then gently tap out the bottom of the baluster, which is usually joined to the tread by a dovetail joint or a dowel. The top of the baluster is held in place by fillet strips that fit tightly between balus­ter tops and are toenailed with tiny finish nails to the plow (routed channel) in the underside of the railing. Pry out the fillets first, shown in the photo on the facing page.

To fit the baluster back in place tightly, lightly coat both ends with white glue and replace the tenoned or doweled end first. Replace fillets to evenly space the tops of the balusters. Replace the return molding and wipe off the excess glue. To prevent marring during this operation, cush­ion blows with a rubber mallet or scrap wood.