side casings 1⁄2 in. long, the head casing will be
spreading, so remove the tacked-up casing, and
that much higher than the head reveal line. But
splice the joints with biscuits, as described earlier
with all casing elements in place, you can see if
in this chapter. Spread glue on all joint surfaces,
the head casing butts squarely to the side casings, and nail up the side casing. (Insert biscuits, if
or if they need to be angle trimmed slightly to
used.) Draw the head casing tight to the side cas-
make a tight fit. Use a utility knife to mark where ing by angle-nailing a single 4d finish nail at each
the head reveal line hits each side casing, and
end. To avoid splits, predrill the two nail holes or
remove the side casings and recut them through
snip the nails’ points. Then remove excess glue
those knife marks. Retack the side casings to the
with a damp cloth.
Finish Carpentry
491
INSTALLING SqUAre-CUT DOOr CASING
Square-cut head casing can easily span ganged windows or, as shown, a double door with windows on both sides. Here,
a carpenter tacked up the door side casings before eyeballing the head casing to be sure the joints were flush.
Use a pin-tacker (brad nailer) to tack the head casing until Slightly back-cut the side casings to ensure a tight fit to you’re sure all joints are tight. When that’s done, secure
the underside of the head casing.
the casing with 6d finish nails.
492 Chapter 17
installing Mitered door Casing
confident you can cut the correct angle on the
first try.) Miter-cut the top of the side casing so it
Before installing the casing, first use a framing
matches the bisecting angle you worked out ear-
square to see if the doorway corners are square.
lier on the scrap. Square-cut the bottom of the
If they aren’t, use an adjustable bevel to record
casing, and tack it to the frame using 18-ga. or
the angles and a protractor to help bisect them.
20-ga. brads.
Then cut the miter joints out of scrap casing until Cut one end of the head casing in the same
their angles exactly match the frame. You can
bisecting angle, leaving the other end long for the
install mitered casing by first cutting the side cas- time being. Fit the mitered casing ends together,
ing and then the head casing, as you would with
and align the bottom edge of the head casing to
square-cut casing. But some carpenters maintain the head reveal line. Then, using a utility knife,
that the best way to match mitered profiles is to
mark the head casing where side and head
work around the opening. That is, start with one
reveals intersect in the second corner. You’ll cut
side casing, cut the head casing ends exactly, and through that mark, using the bisecting angle for
finish with the second side casing.
the second corner (which may be different from
Mark the first piece of the side casing, and
the first corners). Again, there’s no shame in
then cut it. After marking a 1⁄4-in. reveal around
recutting, so you may want that utility-knife
the frame, align a piece of casing stock to a
mark to be 1⁄4 in. proud. When its miter is correct,
reveal line on a side frame. Where head and jamb tack up the head casing, then line up the inside
reveals intersect in the corner, make a mark on
edge of the second side casing to the side reveal
the casing, using a utility knife. (Or make the
line. Use a utility knife to locate its cutline.
utility-knife mark 1⁄4 in. higher if you’re not
Back-cutting miters slightly can make fitting
them easier.
Whether you simply glue mitered joints or
biscuit-join them, remove all three pieces of cas-
ing before securely nailing them. If biscuit join-
SIMPLE BUTT JOINT
zzzzzz Baseboard and side Casings
ing, after slotting each piece, reinstall the leg
Ideal y, door
jambs, apply glue and biscuits, and fit the head
casing will
be thicker
than the
baseboard.
PLINTH-BLOCK JOINT
Plinth block is thicker
than door casing
or baseboard.
If baseboards are the same thickness as
door casings, simply butt them together,
or shape the end of the baseboard slightly
to reduce its thickness.
recutting miters is a normal part of installing casing. To adjust for a slight gap
at the bottom of the joint, this carpenter is marking the amount he needs to
remove from the top of the side casing.
Finish Carpentry
493
casing down onto the biscuits. You can use miter
clamps or 18-ga. brads to draw the joint together
Corner-Block Casing
until the glue dries. Be sure to wipe up the excess
glue immediately.
Casings with corner blocks are a variation of square-cut casing in which you have
seven pieces of trim—two plinth (base) blocks, two cap blocks, two pieces of side
casing, and one head casing—to measure, cut, and fit.
Casing a Window
start by installing the plinth blocks, which are thicker and wider than the side
Casing windows is essentially the same as casing
and head casing. plinths and cap blocks may line up to reveal lines on door frames,
doors, so review earlier sections about prepping
or they may line up with the inside frame edges; be sure to match the detailing of
frames and installing casing. The main difference
the existing casing.
is that the side casing of windows stands on a
tack up plinths, using 18-ga. brads. then measure from the reveal line on the
window stool, rather than on the floor. Conse-
head frame to the top of the plinth blocks to determine the length of side casings.
quently, most of this section describes measuring
tack up the side casings, aligning them to the reveal lines on the side frames.
and cutting the stool, which covers the inside of
a windowsill, and the apron beneath the stool.
depending on the detailing of the cap blocks, you may need to recut the tops of side
Sills and stools vary, as described in “Window-
casings. recut the side casing as needed, then tack up the cap blocks and place a
sills, Stools, and Aprons” on p. 496. The following
spirit level atop them to see if their top edges align and if they’re level.
text focuses on installing replacement stools
Finally, measure between the cap blocks to determine the length of the head cas-
appropriate to older windows.
ing. (use a rigid folding rule with a slide-out extension for this task.) if the door
frame is slightly out of square, cut the head casing 1⁄16 in. to 1⁄8 in. long, and back-
cut both ends so you can shave them to fit. once the tack-fit is tight, carefully pry
off the tacked-up pieces, cut biscuit slots, glue, insert biscuits, reassemble the pieces,
and finish-nail the assembly. glue all joints even if you don’t use biscuits.
Rough jamb
zzzzzz
Window trim
(trimmer stud)
Frame jamb
Bottom
Side
sash rail
casing
Stool
Pitched
horn
sill
Stool
Apron
Rabbeted underside
of stool
Interior wall
Exterior sheathing
Nail window casing to frame jambs and to the rough
Use 6d or 8d finish nails to attach casing to rough jambs,
opening, spacing finish nails every 16 in. Use a
4d finish nails to attach the inside edge of casing to frame
combination square to line up each pair of nails.
jambs, and 4d nails to tie the stool to the apron edge.
494 Chapter 17
MarKing the WindoW stool
Before you start, decide how far the stool “horns”
will extend beyond the side casings and how far
zzzzzz Cutting a Window stool
TOP VIEW
the interior edge of the stool will protrude into
Interior dim. of window frame
the room. Typically, horns extend 3⁄4 in. beyond
31⁄2-in.-wide side casings, but use the existing cas-
1. After transferring the
ings as your guide.
1
interior dimensions of the
To determine the overall length of the stool,
window frame to the stool
SIDE VIEW
mark 1⁄4-in. reveals along both sides of the frame
stock, cut across the stock til
jambs. Then measure out from those reveals the
the saw blade reaches the
width of side casings plus the amount that the
stool shoulder.
stool horns will extend beyond that casing. Make
Shoulder line
Waste
light pencil marks on the drywall or plaster. Rough-
cut a piece of stool stock slightly longer than the
2. Fol owing the shoulder line,
distance between the outermost pencil marks.
2
cut in from the ends of the
Next, hold the stool stock against the inside
stock to create horns.
edge of the windowsill, centered left to right in
Horn
the window opening. Using a combination
square, transfer the width of the window frame,
from the inside of one jamb to the other, to the
Waste
stool stock. Use a jigsaw to cut along both
squared lines, stopping when the sawblade
3. Rip down the stock so its
reaches the square shoulder in the underside of
3
beveled portion butts the inner
the stool. So you’ll know when you’ve reached
window sash, less 1/16 in.
that shoulder, lightly pencil the width of the
Final bevel
shoulder onto the top of the stool, using a combi-
width
nation square as a marking gauge. Next, cut in
from each end of the stock to create the horns.
Carefully guide your saw along the shoulder
lines, being careful to stay on the waste side of
Waste
the line. Clean up cutlines with a chisel, if needed.
4. Trim the horns of the stool
The cutout section of the stool should now fit
4
so they protrude 3/4 in. beyond
tightly between the jambs. Now, rip down the
side casings.
rabbeted edge of the stool so that it will be snug
against the window sash, and the stool horns will
be flush to the wall (and jamb edges). Push the
arched Window Casing
stool in until it touches the bottom of the sash,
then pull the stool back 1⁄16 in. from the sash to
there’s something inspiring about arched windows. restoration carpenter jim
allow for the thickness of paint to come. Finally,
spaulding (shown on pp. 498–499) offers this advice: “order all the casing from the
measure the distance between the stool horns
same shop so that the same knives cut the arches and the legs (side casing). that
and the wall, which is the amount to reduce the
width of the stool, along the rabbeted edge.
way, all the profiles will sweep continuously around the frame.” arched casings are
Use a tablesaw to rip down the width of the
different from casings for other windows, so installing them takes some flexibility.
stool, then test-fit it again. If it is parallel to (but
after setting the stool and apron, for example, you install its head casing next. side
1⁄
casings are last.
16 in. back from) the sash rail, you are ready to
cut each horn to its final length. If your stool is
although modern window makers offer a limited selection of prefab casing for
flat stock, that’s the last step. But if the stool is
the arched windows they sell, plan on custom-ordering casing for older arched win-
molded (has a shaped profile), miter returns to
dows. Correctly determining the radius of the arch is challenging: one method is to
hide the end grain of the horns, as shown in the
tack 1⁄8-in.-thick plywood (also called doorskin) to the inside edge of the arched
top photo on p. 487.
frame head—run it about 1 ft. below the “spring line” of the arch, where the frame
becomes straight. go outside and trace the arch, tracing lightly so you don’t bow the
attaChing the stool and apron
plywood. Make templates for each arched window, and take them to a local shop
Lightly sand and prime the stool, including its
that mills trim.
underside and ends, so it won’t absorb any mois-
Note: the inside edge of arched casing must be revealed (set back) from the arch
ture from condensation or driving rains. After the
you traced of the frame’s inside edge.
paint is thoroughly dry, apply waterproof glue to
the underside of the stool, level it, and nail it to
Finish Carpentry
495
the rough sill using two or three 6d galvanized
INSTALLING A WINDOW STOOL AND APrON
finish nails. Try not to lean on the only partially
supported stool until it’s nailed to the top of the
apron, which will steady the stool.
Next, cut the apron, which is generally the
same casing used for side and head casing. Its
thicker edge is butted to the underside of the
stool. The apron should be as long as the head
casing so that it lines up visually with the outside
edges of the side casing. If the apron is molded,
cope each end to accentuate its profile or miter-
cut it and glue on a return. If you’ll be painting
the casing, caulk along the underside of the stool
to prevent drafts. Then butt the apron to the
underside of the stool. Nail up the apron, driving
6d finish nails into framing beneath the sill.
Start casing a window by installing
Typically, the apron is as wide as the casing above the
Finally, nail the stool to the top of the apron,
its stool. Use a combination-square
window stool; the stool horns project 3⁄4 in. beyond both.
using three or four 6d galvanized finish nails.
>
level or a torpedo level to level it,
Set and fill those nails.
then 8d finish nails to secure it to the
rough sill underneath. However, the
install the side and head casing in the same
stool won’t be stable until it is also
order that you would case a door: side casing,
nailed and glued to an apron under
head casing, and second side casing. The main
its inside edge.
difference is that window side casing sits on the
stool horns. If you’re casing side-by-side windows
with flat trim, you can run a single piece of head
casing over both windows and butt the middle
Windowsil s, STOOLS, And ApROnS and side casings to the underside of the head cas-
ing, as shown in the top photo on p. 492.
Windowsills have both an inner and outer life—one half is interior, and the other is
exterior. it makes sense to pitch the outer portion of a sill so it can shed water. but in
the old days, windowsills were pitched all the way, front to back, which created a use-
Baseboard and
lessly pitched interior section that had to be covered with a stool piece, as shown in
Crown Molding
“Window trim” on p. 494. to fit a pitched sill, usually set at 14º to 20º, the underside
As noted in “The Case for Not Leveling Trim” on
of a stool must be partially rabbeted at the same angle so that when the stool is
p. 488, baseboard and crown molding should fol-
nailed on top of the sill, the top face of the stool will be level. it’s an archaic design,
low floors and ceilings, rather than level lines
but, surprisingly, it survives in some new window designs.
projected across the walls. If floors and ceilings
Many modern windows, however, have a sill whose interior portion is flat on top and
are level, fine. Otherwise, leveled trim next to
flush to the insides of the window frame. consequently, there’s no need for a stool or
out-of-level surfaces is glaringly obvious.
an apron. such windows may be “picture framed.” that is, the casing can be mitered
around all four sides of the window frame.
installing BaseBoards
if your windows have traditional stools and aprons, the trickiest part of casing the
Install the finish floors first, with a slight gap,
windows will be fitting the stools. typically, a stool’s outer edge almost abuts the
typically 1⁄2 in., between the wood flooring and
inside of the lower window sash (allow a 1⁄16-in. space for the thickness of paint), and
Renovation 4th Edition Page 115
