mer millwork instead—whose monolithic casting for fancy miter cuts.
molding is also available with a wood veneer,
greatly simplifies installation. Likewise, although
which can be stained and clear finished.
you can build them up by hand, mantels and fire-
place surrounds also are sold as preassembled
CoMBining stoCK eleMents
units and as kits requiring minimal assembly.
Standard molding is often milled from 1-in. stock
You can combine stock moldings with rela-
(actual size, 3⁄4 in.). You’ll find it easy to create
tively inexpensive paneling to make wainscoting
more complex trim by combining 1-in. boards
and frame-over-panel walls. By cutting a piece of
with stock molding caps. For example, with base-
paneling in half, you can use two sections, each
boards, you might start with a 1x8 and add a
4 ft. by 4 ft., topped with a built-up combination
quarter-round shoe at the bottom and a cove-
of moldings to form a cap. Paneling with vertical,
molding cap at the top.
regularly spaced grooves gives the illusion of
Finish Carpentry
483
It’s dusty to cut and shape. Its edges readily suck
up moisture. In fact, MDF can swell from ambi-
ent moisture, so seal it immediately after cutting
or shaping it. Seal cut edges with two coats of
shellac-based primer. Then paint all six sides of
the panels with an oil-based primer. Perhaps
MDF’s most annoying quirk is its tendency to
mushroom around nail heads. MDF is so dense
that it doesn’t compress when you nail it; fiber
near the nail just bulges up. After setting the nail
heads, use a Sandvik carbide scraper to scrape
down bumps, then prime it.
Because of MDF’s tendency to wick moisture,
it’s a poor choice for bathroom trim or window
installations where condensation is common—no
matter how well it’s sealed. In those locations, go
with wood or PVC trim instead.
polyMer Moldings
Although many old-house owners prefer wood
molding, its supply and quality have been dwin-
dling for decades, leading to a run on third-world
forests—now being cut down at an alarming rate.
Alternatively, there are polymer moldings (espe-
cially polyurethane), which are available in most
traditional architectural styles, from simple colo-
nial to elaborate Victorian. Once installed and
painted, polymer moldings are virtually indistin-
Many traditional cornice-molding
guishable from wood trim. The following sec-
types are available in high-density
individual boards. To change the style and create
tions note some of the unique features.
polyurethane. Once filled and
Craftsman-style wainscoting, you could use
painted, they’re indistinguishable
Stability. Unlike wood, polymer molding won’t
1⁄4-in.-thick redwood plywood with the grain run-
from wood molding.
warp, split, rot, or get eaten by termites.
ning vertically and install redwood strips every
Although it does expand slightly (3⁄8 in. for a 12-ft.
foot or two to create detail and cover the seams
piece) in a heated room, special corner pieces
between sheets. For more, see “Wainscoting”
“float” over section ends, allowing them to slide
on p. 503.
freely as they expand. Polymer molding has no
grain, so there is no built-in bias to twist one way
WorKing With MdF
or the other; there are no splits, cracks, or knots.
If you want a cost-effective, easily worked material Quick installation. Synthetic moldings are less
for plain-profile trim, MDF is hard to beat. And
labor intensive. Whereas complex wood mold-
you can add visual interest by installing cove,
ings are built up piece by piece and their joints
bullnose, quarter-round, or other simple molding painstakingly matched, synthetics come out of
along MDF’s plain edges.
the box ready to install. Most polymer moldings
Advantages. MDF cuts and shapes beautifully.
are glued up with a compatible adhesive caulk,
For smooth edge cuts, use a 60-tooth 10-in.
such as polyurethane or latex acrylic, and tacked
blade. Because it has no grain, MDF crosscuts
up with finish nails or trim-head screws, which
and rips equally well, and its edges can be routed are needed for support only until the glue sets.
as well, although most MDF trim is simply butt
Pieces are so light, in fact, that you can install
joined. (No need for biscuits to hold the joints
them single-handedly.
closed.) Use a pneumatic nailer to attach it; MDF easy working and finishing. Most polymers
won’t split. Sand it with 150-grit sandpaper, and
can be trimmed like soft pine, using a 12-tpi to
prime with an oil-based primer (latex roughens
13-tpi saw in a miter box. There’s no need for
the surface). However, MDF does have quirks you fancy joinery because most systems have corner
need to work around.
pieces that cover joints. Touch up holes with
disadvantages. MDF is heavy (a 3⁄4-in. sheet
plastic wood filler, and caulk field joints on long
weighs about 100 lb.); lighter versions cost more. runs. You also may need a bead of caulk where
484 Chapter 17
straight lengths of molding meet existing surfaces
that are irregular.
Polymer molding is typically primed white in
zzzzzz Back-Cutting trim
the factory and could be installed as is, but most
homeowners paint it. You paint smooth-surfaced
Saw blade
Back-cut angle greater
urethanes just like standard wood trim. Some
than 90°
products can be stained, but that gets into the iffy
Miter box/saw bed
territory of making plastic look like wood.
Shim
Waste
Basic Skil s
Using quality tools and materials matters, but
not as much as the skill and judgment of the ren-
ovator. This section of tips will help hone your
skills in measuring, cutting, and attaching trim.
After back-cut,
surface edge meets
adjacent trim first.
Measuring
Accurate measurements are crucial because trim
is pricey, and even small discrepancies will stand
out. In the following paragraphs, you’ll find a few
new twists on the old chestnut, “Measure twice
and cut once.”
P R O T I P
Use a sharp point to mark stock. A stubby
lumberyard pencil is fine for marking framing
For odd-shaped or compli-
lumber. But because the margin of error is small
cated pieces, such as winding
By raising the board’s end and keeping the
stair treads, make a template
on trim, use a sharp pencil to mark precisely. A
sawblade plumb, you create a back-cut
; using heavy paper, cardboard, or
utility knife leaves an even thinner line, although
strips of 1⁄8-in. plywood hot-
it’s more difficult to see.
joint whose surface edges can easily be
glued together. “the Beauty of
shaved to create tight joints.
Mark trim in place, if possible. It’s almost
templates” on p. 372 has more
always more accurate than taking a tape reading
about templates.
and transferring it to stock, especially if your
memory’s bad.
Change directions. If you normally measure left
to right, double-check your figures by changing
direction and measuring right to left.
Use templates instead of remeasuring. When
you need to cut many pieces the same length,
carefully cut one, check it in position to make
sure it’s accurate, and use that piece to mark the
cutline on others. You can also clamp a template
to a bench or saw table to act as a stop block. As
you cut successive pieces, simply butt a square-
cut end against the block, and the blade will cut
each in exactly the same place.
When in doubt, go long. If you’re not quite sure
of the exact measurement and don’t want to climb
back up the ladder to recheck, cut the piece a lit-
tle long. You can always make a long board
shorter, but reversing the process is quite a trick.
X marks the scrap. As you mark cutlines, pencil
a prominent X on the scrap ends of boards. This
habit will sooner or later help you avoid wasting
trim because you mistook the scrap end for the
measured end.
When mitering or coping corner joints, make sure a joint fits well before cutting the other end to
final length. Whenever possible, mark the trim in place—that’s easier and more accurate than
transferring tape-measure readings.
Finish Carpentry
485
general Cutting
Clamp that stock. If your hands are big enough,
it’s possible to hold stock against a miter-saw
Tight trim joints require accurate layouts, sharp
fence with one hand and operate the saw with
saws, and consistent methods.
the other, but it’s far easier—and safer—to clamp
Recuts are a fact of life. If you’re filling and
the stock, using a spring clamp or a quick-release
painting trim, slight gaps are acceptable. But if
clamp (see the center photo on p. 53). Newer
you’re using a clear finish, joints must be tight.
models of compound miter saws have flip-up
Before you start cutting trim, always check the
stops that hold molding against the fence. Finally,
accuracy of power-saw miter-stop settings by
use an outfeed roller or a sawhorse to support the
cutting a few joints from scrap. Then cut stock
far end of long pieces so they don’t bow or flap as
a hair long so that you can recut joints until
you try to cut them.
they’re right.
Cutting Miter joints
Cut lines consistently. It doesn’t matter whether
your sawblade cuts through the middle of a cut-
A miter splits a 90º corner in half, with a 45º cut
P R O T I P
line or just past it. What matters is that your
on each board. With the sawblade set perpendic-
method is consistent. For example, moving the
ular to the stock (0º bevel), cut a 45º angle across
to erase pencil marks on clear
width of a sawkerf to one side of the line or the
the face of the trim. When the cut edges are
wood surfaces, try rubbing the
other can make the difference between tight and
closed together, the boards should form a right
marks with a rag dipped in
open joints. Some pros prefer to just “kiss” the
angle. Of course, if door or window frames aren’t
denatured alcohol.
inside of the cutline with the sawkerf so that the
square, corners may be 89º or 91º, requiring that
line stays on the board.
each miter be slightly more or less than 45º,
though equal. That is, miter joints should bisect
Keep tools sharp. This applies to saws, chisels,
whatever angle is there.
planes, and utility knives. Whenever a blade
If you’ll be painting the joints and the trim
becomes fouled with resin or glue, wipe it clean
stock is relatively narrow (3 in. wide), you can
immediately with solvent. A sharp tool is easier
fudge the joints and fill any gaps with spackling.
to push and thus less likely to move the stock
But if you’re installing stain-grade molding, espe-
you’re cutting. Likewise, a clean power-saw blade cially if it’s 5 in. or 6 in. wide, faking a miter joint
is less likely to bind or scorch wood.
will look terrible. So if a frame is out of square,
Handsaws usually cut on the push stroke.
take the time to cut and recut joints as necessary
Start handsaw cuts with gentle pull strokes, but
so that they bisect the frame’s angle.
once the kerf is established along the cutline,
There are two good reasons to use miters.
emphasize push strokes. (Western-saw teeth are
First, mitering aligns the profiles of moldings so
set so that they cut on the push stroke, whereas
that bead lines and other details join neatly along
Japanese saws cut on the pull stroke.) As you
the joint and sweep uninterrupted around the
continue the cut, keep your elbow behind the
corner. Second, although flat trim allows you to
saw, which will help you push the saw straight
butt or miter joints at corners, with butt joints
and follow the cutline.
you would see the rough end grain of one of the
adjoining boards. Even if you sand down the
roughness, end grain soaks up extra paint or
stain so it often looks noticeably different from
adjacent surfaces.
spliCing triM
When a wall is too long for a single piece of trim,
you can splice pieces by beveling their ends at a
60º angle and overlapping them (called a scarf
joint) or by butt joining them and using a biscuit
to hold the joint together. If boards shrink, gaps
will be less noticeable in a scarf joint because
you’ll see wood, rather than space, as the overlap
separates. In general, scarf joints are better suited
to flat stock, whereas shaped molding will dis-
play a shorter joint line if butted together.
(Viewed head on, the joint is a thin, straight line.)
Mitered casing joints look dressy and conceal the end grain of
intersecting pieces.
486 Chapter 17
Back-Cutting Miters
ideally, miter cuts will meet perfectly, creating a tight joint. But back-cutting
(also called undercutting) can improve the odds that joints will be tight even if cor-
ners aren’t perfectly square and frame jambs aren’t flush to the surrounding walls. in
other words, the front faces
of back-cut boards make contact before the backs, so the
front edges can be finely shaved to fit. it’s far less work to shave the leading edge of
a back-cut board with a block plane than it is to recut the joint.
the easiest way to back-cut trim is to shim under it slightly in the miter box or
on the saw bed, as shown in the drawing on p. 485. the sawblade is still set at 90°
(0° bevel), but the shimmed boards receive a slight bevel because they aren’t lying
flat. even a 1⁄16-in.-thick sliver under the board is enough to give you a decent back cut.
Glued biscuit joints will keep butt joints or miter joints
Fussing over a miter joint is probably not worthwhile if you plan to paint the trim
from spreading due to seasonal expansion and
contraction. Here, a biscuit joins a mitered window-
because slight gaps can be filled with wood filler. But open joints are difficult to dis-
stool return. Biscuits can also join straight runs of
guise when wood is to be stained and almost impossible when it is clear-sealed.
crown molding or baseboard when a wall is too long
for a single board.
zzzzzz two Ways to splice trim
Biscuit
zzzzzz Coping a joint
Square-cut molding
butts to corner wall.
Scarf joint
Butt joint
When it’s necessary to use several trim boards
to span a distance, center end joints over stud
centers so you can nail board ends securely to
Coped molding,
prevent cupping. Where that’s not possible, say,
slightly back-cut
To cope a joint, first use a tablesaw or
where a baseboard butts to door casing, nail the
a miter saw to cut the trim at a 45°
bottom of the baseboard to the wall sole plate,
bevel. Use a jigsaw to cut the straight
part of the trim profile, then use a
and angle-nail the top of the baseboard to the
A coped joint is first mitered, then back-cut
coping saw to back-cut along the
edge of the casing. Predrill the trim or snip the
along the profile left by the miter so that
shaped part, as shown.
nail points to minimize splits.
the leading edge of the trim hits the adjacent
trim first. That thinner, leading edge can be
Coping a joint
easily shaved to fit tightly.
All wood trim shrinks somewhat. Where beveled
boards overlap, gaps aren’t as noticeable, but
board carefully cut to fit the profile of the mold-
Renovation 4th Edition Page 113
