Renovation 4th Edition

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Renovation 4th Edition Page 37

by Michael Litchfield


  lVl trim is available in 1-in. and 11⁄4-in. (5/4) thicknesses and in stan-

  cellular PVC yield slightly different physical attributes: free-form cooling

  dard widths from 4 in. to 12 in., in 2-in. increments. Standard lengths

  PVC is uniform throughout, and veteran carpenters report that its

  are 16 ft. and 20 ft. It’s easy to cut, drill, nail, and handle, and its MDO density, weight, and workability are virtually identical to that of pine, face paints wonderfully. however, lVl is expensive. Clear lam® is one

  whereas celuka-processed PVC has a somewhat harder and more brittle

  well-known brand.

  outer layer that tends to chip. For optimal results, use sharp, carbide-

   Hardboard,fiberboard,orwood-fibercomposite is fash-

  tipped sawblades and drill bits when working either type. the top-

  ioned from wood chips that are steamed, pressed, and glued. there are

  selling cellular PVC trim, Azek®, is a free-form type, as are Fypon®,

  many brands in this category, including MiratEC®, Choicetrim®, and

  kleer®, and Certainteed. In some respects, PVC trim is easier to work

  Protrim®, and product features vary greatly. Composites tend to be

  than wood. You can screw or nail close to the edges and ends of stock

  available in 1-in. and 11⁄4-in. thicknesses, in standard widths of 4 in.

  and not worry about splitting it because, unlike wood, PVC has no

  to 12 in., and in 16-ft. standard lengths. Some are primed on all sides,

  grain. It also lacks knots and won’t cup or warp. there are, however,

  some not; some have MDO-like paper facing, some not—so check with

  several critical differences when working with PVC: (1) It tends to

  your distributor. hardboard sidings have had widespread problems with expand and contract along its length, so when joining long boards, moisture retention, swelling, and degradation, so hardboard-trim mak-bevel-cut their ends so they overlap. (2) Join trim with PVC cement,

  ers have worked hard to improve their products. that noted, however,

  which joins them chemically rather than mechanically, as is the case

  take pains to prime all sides and the cut edges. Drive corrosion-resis-

  with wood joints. (3) PVC doesn’t absorb moisture, so paint takes

  tant nails just flush to the trim surface; nails driven deeper may need

  longer to dry than with wood.

  caulk to keep out moisture. gap butt joints 1⁄8 in. to allow expansion,

  then caulk and paint the trim ASAP.

  warping up) when the sun dries out the exposed

  Prime all faces and edges of exterior

  front face if the back retains moisture. The great-

  trim and siding, including the back.

  er the moisture differential between front and

  Back-priming is especially important

  back faces, the more likely the cupping.

  because moisture trapped between

  back faces and sheathing can lead to

  While cutting trim or siding, keep a can of

  paint or sealer failure, cupping, or—in

  primer and a cheap brush nearby to seal the ends

  extreme cases—rot. After cutting trim

  after every cut; unprimed end grain can absorb a

  or siding, be sure to prime the cut

  lot of moisture. (It’s especially easy to forget to

  edges as well.

  prime cut edges when you’re using preprimed

  trim.) Ideally, apply at least two topcoats of acryl-

  ic latex paint after priming to seal trim and sid-

  ing. If you want stained or clear-finished trim or

  siding, use cedar or heart redwood.

  AttAChIng tRIM

  As a rule, for best attachment secure exterior

  trim to framing. In those rare instances where

  you have only sheathing to nail to, angle the nail

  so that it will be less likely to pull out.

  Exteriors

  159

  a 16-ft. corner board in place while balancing on

  a ladder will appreciate this tool. Nailers also

  ExtEriOr trim tiPs

  drive nails quickly and accurately, reducing splits

   TiP1.Jointrimboardsontheground,

  and eliminating errant hammer blows that mar

  especiallyinthesesituations:Thejointsare

  trim. After setting the trim with finish nails, you

  can always go back and hand-nail with headed

  complex,theheightsaredaunting,thehouse

  nails to secure the trim further. Or you can use

  framingisoutofsquare,and/ortheboardsare

  headed siding nails in the nail gun.

  longandunwieldy.Todothismosteasily,place

  thetrimstockonsawhorsestoshape,assemble,

  Nailing schedules. To face-nail nominal 1-in.

  andprimeit.Theresultingjoinedpieceswillbe

  trim (actual thickness, 3⁄4 in.), use 8d box nails

  alittleheavierthansinglepieces,butthe

  spaced every 16 in. Nail both edges of the trim

  board to prevent cupping, placing nails no closer

  assemblywillbestraightandcrisp,evenifthe

  than 1⁄2 in. to the edge. If the trim goes over sid-

  framingisn’t.Useanexteriorgluesuchas

  ing, say, at corners, use 8d to 10d box nails. To

  GorillaGlueand6dgalvanizedboxnailstodraw

  create a tight joint between corner boards, use

  theboardstight.

  6d nails spaced every 12 in., and drive them in

   TiP2.ifyourtrimrunislongerthan

  a slight angle. If you’ll be painting the trim, also

  individualboards,jointheboardswithbevel

  caulk this joint or glue it using an exterior ure-

  joints,whichwon’tshowwoodshrinkageas

  thane glue, such as Gorilla Glue or Titebond

  obviouslyasbuttjoints.Whenusingbeveled

  III (which is less expensive and won’t stain

  jointsonverticalboards—say,cornerboards—

  your hands).

  makethetopbevelslantdown,awayfromthe

  About nail heads. Taking the time to line up nail

  building,sowaterwon’trunintothejoint.

  heads makes the job look neater. For example,

  Staggertrimjointsbyatleast32in.sothey’ll

  when nailing up jamb casing, use a combination

  belessobvious.

  square to align nail pairs. If you’re putting up a

  long piece of trim that runs perpendicular to

  studs, snap chalklines onto the building paper

  beforehand so that you’ll know stud positions for

  Choosing fasteners. Pick a nail meant for exte-

  nailing. If the trim will be painted, take the time

  riors. If you’ll be using a transparent finish, mak-

  to set the nail heads slightly below the surface,

  ing nail heads visible, stainless-steel nails are the

  using a flathead punch. Then use exterior wood

  premier choice; though expensive, they won’t

  filler to fill the holes. If you don’t set the heads

  rust. Aluminum nails won’t stain but are some-

  slightly, they may later protrude as the wood

  what brittle and more likely to bend. Galvanized

  shrinks, compromising the paint membrane and

  nails are the most popular because they’re eco-

  admitting water. On larger jobs, carpenters are

  P R O T I P

  nomical, stain minimally, and grip well. Many

  usually expected to set nail heads. Painters fill

  nail types (including stainless steel) also come in

 
; and paint them.

  If trim paint is a different color

  colors matched to different wood types—cedar,

  than the siding, paint the trim

  redwood, and so on. Ring-shank nails hold best.

  EAVES tRIM

  edges—especially hard-to-reach

  For stained exteriors, some contractors prefer Because eaves trim is often complex and can

  eaves and rake trim—before

  galvanized finish or casing nails because their

  impact framing, roofing, ventilation, and the

  installing the siding. using a

  heads are smaller and less visible. Box nails are a house’s aesthetic integrity, draw a cross section of

  minimal number of staples, tack-

  good compromise. Their larger heads hold better it as early as possible.

  staple a 4-in.-wide strip of plas-

  than finish nails, yet their shanks are smaller

  There is no single correct way to construct the

  tic to the painted trim edges,

  than those of common nails, making box nails

  then install and paint the siding.

  eaves, but the boxed eaves on the facing page are

  less likely to split wood. There are also “splitless”

  Finally, rip the plastic out, and—

  a good place to start. First, a fascia board that

  siding nails that come with preblunted points to

  voilá—perfect edges! Even if you

  overhangs a soffit by 3⁄8 in. to 1⁄2 in. enables you to

  minimize splits. (The blunt point smashes through

  forego the plastic and need to

  hide rafter irregularities—rafters are rarely per-

  wood fibers, rather than wedging them apart.)

  touch up trim edges, you’ll save

  fectly straight or cut equally long. Second, that

  Where you want maximum grip, use stainless-

  tons of time.

  overhang accommodates a rabbeted fascia–soffit

  steel trim-head screws instead of nails.

  joint, which protects the outer soffit edge, even if

  Pneumatic nailers. Most pros use pneumatic

  the wood shrinks slightly. Third, if you rabbet the

  nailers to attach exterior trim. Using a finish nail- back edge of a frieze board or build it out using

  er with galvanized nails allows you to tack up

  blocks, the frieze will conceal the top edge of the

  trim exactly where you want it. Anyone who has

  siding. A frieze also creates an inconspicuous

  spent time trying to simultaneously hold and nail space to install an eave vent.

  160 Chapter 7

  Ventilation channels at eaves allow air to flow

  up under the roof and exit at ridge or gable-end

  vents. This airflow is beneficial because it lowers

  attic temperatures and helps remove excess mois-

  ture from the house, thus mitigating mold, ice

  dams, and a host of other problems. To keep

  insects out, soffits need screening. In a wide sof-

  fit, there’s plenty of room for screened vents in

  the middle. In a narrower soffit, you may need to

  leave a 3⁄4-in. space at the front of the soffit or at

  the back hidden behind a built-out frieze board.

  If the house has exposed rafter tails rather

  than soffits, you have fewer ventilation options

  that will look good. Consider leaving the eaves

  sealed and adding rooftop intake vents, as

  described on pp. 90–91.

  WAtER tABlE

  Water-table trim often

  finishes off the bottom of a

  A water table is horizontal trim running around

  wall and provides a level

  the base of a building below the siding. Not all

  base for the first course of

  houses have it. Depending mostly on regional

  siding. To forestall rot, cap

  preferences, the water table takes several forms.

  the water table with metal

  In the West, it typically looks like windowsill ears

  or vinyl flashing before

  installing the siding.

  (the beveled parts that stick out) and is often

  zzzzzz Boxed Eave: Detail 1

  zzzzzz Boxed Eave: Detail 2

  Insulation

  Air rising

  baffle

  Rafter

  Insulation

  baffle

  Rabbeted

  fascia

  Rafter

  Fascia

  Insulation

  Insulation

  Air rising

  Soffit

  Spacer blocks

  Screened

  Soffit

  16 in. o.c.

  soffit vent

  Rabbeted

  frieze

  Frieze

  Screen or

  corrugated

  vent strip

  Siding

  Siding

  A strip of continuous screen in the soffit allows

  air to circulate into the attic. The rabbeted frieze

  You can create ventilation channels behind the frieze by

  conceals and protects the top of the siding.

  spacing it out 3/4 in., using blocks spaced every 16 in. on center.

  This also conceals the top of the siding.

  Exteriors

  161

  used to separate different types of siding materi-

  CORnER BOARDS

  als, such as shiplap siding from wood shingles

  Corner boards are usually 1-in. boards butted

  above. Typically, 11⁄2 in. by 11⁄2 in., this type of

  together. Siding is then butted against them,

  water table runs continuously around the build-

  making an attractive and weathertight corner.

  ing and is mitered at the corners. It often has a

  Not all buildings have horizontal trim below

  rabbeted heel, which fits over the top of the wood the bottom of the siding. For example, the first

  siding below, and a beveled top, which is overlain (bottom) course of shingles is often doubled and

  with shingles or clapboards.

  overhangs the sheathing slightly. In that case, run

  In the East, water tables are also called splash- corner boards 2 in. to 3 in. below the bottom

  boards; they usually are 1-in. boards 8 in. to

  edge of the sheathing; then, after you nail up the

  12 in. wide and may be capped to shed water.

  first course of shingles, trim the corner-board

  Splashboards are most common in wet regions,

  ends level to the shingles’ butts. If the house has

  where roof runoff often splashes back along the

  a water table or splashboard, measure from its

  base of a house. (Some primal carpenter may

  top edge up to the underside of the soffit to deter-

  have reasoned it would be easier to replace a sin-

  mine the length of the corner boards.

  gle rotted board than to disturb several courses

  If you’re installing shingles, whose overlap-

  of siding, or that a thicker board would simply

  ping courses have a higher profile than clap-

  last longer.)

  boards, use 5/4 corner boards, which are a full

  Whatever the shape of the water table, flash

  1 in. thick. To give the illusion that corner

  the top with a metal drip-edge that extends at

  boards are the same width at each side, rip down

  least 1⁄2 in. beyond the face of the board. The sec-

  the overlapped board by the thickness of the

/>   tion where corner boards sit atop the water table

  stock. And for a crisp, straight corner, preassem-

  is especially prone to rot. Prime and paint the

  ble corner boards before installing them, as

  boards thoroughly.

  shown in the photo below.

  Occasionally, corner boards are nailed over

  siding. This can be a problem because nails driv-

  en through the trim may split the siding under-

  neath. Besides, corner boards can’t seal well if

  zzzzzz Corners

  5/4 square stock

  1x4

  INSIDE CORNER

  1x4 ripped down

  OUTSIDE CORNER

  Butt siding to the corner boards to avoid complex miter cuts. In

  Preassemble corner boards, soffit and fascia boards, and

  outside corners, rip down the overlapped board by the thickness

  other exterior trim on the ground whenever possible. The

  of the stock, and both boards will look equally wide.

  joined pieces will be tight and square, even if the framing

  and sheathing behind them isn’t.

  162 Chapter 7

  P R O T I P

  Epoxy filler can be applied

  with a putty knife. But the filler

  is easier to shape to match exist-

  ing contours by hand—hands

  protected by latex gloves, that

  is. Restorationist tom O’Brien

  suggests donning three or four

  pairs of disposable latex gloves

  at the start of the job and peel-

  After wire-brushing away loose material, inject liquid

  Use a taping knife to compress and smooth the filler. The

  ing them off as they become

  consolidant into the wood until saturated. After allowing

  galvanized metal tacked to the sill keeps the filler in place

  gunked up.

  the consolidant to set, apply the pastelike filler to build up until it dries and doubles as a screed strip to which you the damaged area.

  can level the filler.

  nailed over an irregular surface. It’s an awkward

  original trim. To join the new section to the old,

  way to resolve a corner, but this method was

  use a biscuit joiner (see p. 480) to cut a biscuit

  commonly used on Victorian homes with flat,

  slot in both board ends. Dry-fit everything, prime

  shiplap siding. Careful nailing and liberal doses

  all surfaces with epoxy primer, and allow the

  of caulk will help ensure a weathertight seal. To

  primer to dry well. Then epoxy the pieces togeth-

  minimize splits, predrill the board nails.

  er. Hold the boards in place with a piece of scrap

 

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