Renovation 4th Edition

by Michael Litchfield

  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-