Installing Stair Railings
Whoever invented the rail bolt did stair builders a big
favor. It's used for blind fastening of rails to posts, and
also to join two rail sections together as needed (Figure 9).
On one end it's a threaded screw, and on the other end it's a
bolt. The screw end goes into a predrilled hole on the post or
on one railing section; the bolt end goes into a hole in the
other rail. But first we predrill a 1-inch hole under the
railing, just big enough to get a nut through. We insert the
nut from underneath and tighten it onto the bolt to bring the
9. Where two rails meet at a post, only one side
can be screwed. The other side is attached with a rail
bolt. One end of the bolt has screw threads for
attaching to the post; the other end is
machine-threaded to accept a nut. A pilot hole for the
bolt in the end of the rail and a 1 inch hole for the
nut under the rail are prebored at the shop. In the
field, the installer has to drill a pilot hole in the
post, attach the bolt, and then tighten the nut on from
beneath the railing. A plug hides the hole in the
With an over-the-post rail system, we preset all the rail
bolts. Where there's a joint, we attach the rail bolt to one
railing and predrill the 1-inch hole in the matching piece's
butt end. We preassemble the whole railing in the shop to make
sure it's right, then dismantle it and ship it. All the
installer has to do on site is put it back together and tighten
Balusters. The treads and the rail have been
predrilled in the shop to receive the balusters. The bases of
the balusters are level with the rails, but the upper turnings
are rail-oriented — the profile follows the pitch of the
In the field, I install the center baluster first, then
sight the railing to make sure it's straight (Figure 10). In
fact, I like to put a slight crown to it, on the assumption
that it might sag over time.
10. The author slides a baluster into the
predrilled hole in the railing, then lowers the pin
into the hole in the tread. He sights the rail: It
should have a very slight crown.
I also double-check the railing height. The rake rail height
should be measured plumb from the top of the tread at its tip
to the top of the rail (Figure 11). Our local code calls for a
34-inch rail height, but that varies from place to place. I
marked my level at the 34-inch height so I can make a quick
measurement perfectly plumb without having to use my tape.
11. Railing height should be measured from the
front and top of the step, straight up to the top of
the railing. The author uses his level, which is marked
for 34 inches, the code-prescribed rail height in his
If the railing is at the correct height, I proceed to
install all the rake balusters. I first measure and cut each
baluster to length. Then I take the baluster, line it up with
the hole in the rake rail, push it up, slip the pin over the
hole in the tread (which we have first squeezed a little glue
into), then drop the baluster back down (Figure 12). At the
top, I predrill a hole and put in a 4d finish nail. At the
bottom, we send in one 6d nail to keep the baluster from
spinning. The nail goes about 3/8 inch from the top of the
tread, on a 30-degree angle going into the baluster, so it goes
right through the pin and connects into the tread.
12. The author fastens the top of the baluster
with a 4d finish nail and the bottom with a 6d finish
Level balusters. Unlike
the rake rail and the stair treads, the level rails and the
upper landing treads are not drilled in the shop. Again, the
contractor on site may have his own preference for laying out
and attaching these elements, or a discrepancy on site could
affect the spacing between the post and the wall. So before I
can install those balusters, I have to mark and drill the
landing tread and railings (Figure 13).
13. The author marks his hole centers with
dividers (above left), drills the holes, and transfers
the hole centers to a story pole (above right), then
transfers the same layout onto the underside of the
I use dividers to mark the landing tread, but first I have
to figure the spacing. I look first at the spacing of the
balusters on the stair treads; I want the landing balusters to
be in that vicinity. Say it's 4 1/2 inches: I measure the
distance between the landing posts (which happens to be just
under 4 feet) and divide that number by 4 1/2 inches to see how
many spaces I need to mark off. The answer is 10 spaces so I
divide the total distance by 10 to get the interval, which is
close to 4 1/2 inches. I set that distance on my dividers and
step it off to mark the centers of the holes.
I drill the bottom holes first, then transfer the centers to
a story pole that's cut to the length of the rail. I use the
story pole to transfer the marks to the underside of the rail,
and then drill the upper holes.
Once the balusters are in, all that's left is a few trim
pieces. At the mid-landing, I install a couple of pieces of
baseboard. I place the baseboard on two scraps of the actual
flooring material to elevate it, so that the flooring
contractor can slide his material under there later. Base cap
molding goes on above the baseboard. I also apply base cap
below the fascia around the upper landing, using 8d gun nails.
Here, the base cap is flipped upside down (Figure 14).
14. Using 8d nails, the author applies base cap
molding around the stringers and landing baseboards. He
uses the same material flipped upside down below the
stringers on the open side of the stairs, and below the
fascia around the open landing.
Cove molding covers the joint where the fascia butts up
under the landing tread. Cove molding under the stair treads
was already applied at the shop in the same way; but on site I
still need to place a couple of final pieces of cove under the
landing treads at the top of each run of stairs.
To finish up, I plug all the 3/8-inch countersunk screw
holes with wood plugs and sand them flush.
coordinator at Cooper Stairworks in Somerset, Mass.