Renovation 4th Edition

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Renovation 4th Edition Page 24

by Michael Litchfield


  If the old roof was once covered with wood

  out or missing flashing. Or, in some cases, it’s

  shingles, they were likely nailed to skip-sheathing,

  necessary to disturb shingles to install a roof vent which consists of widely spaced 1-in. boards

  or a vent pipe.

  that allow air to circulate under the shingles and

  When removing a shingle or a course of shin-

  dry them. These days, most roofers cover skip-

  gles, disturb surrounding shingles as little as pos-

  sheathing with plywood because it stiffens the

  sible. First, break the adhesive seal between

  roof and is safer to walk on. But nailing shingles

  courses by sliding a mason’s trowel or a shingle

  directly to plywood or building paper impedes air

  98

  Chapter 5

  Wood shingle Basics

  If the old wood shingle roof was attached to

  zzzzzz Wood shingle details

  no matter how wide the wood shingle, use only

  skip-sheathing, cover it with plywood for safety

  two nails—placed 3⁄

  and stability. A layer of synthetic mesh allows

  Solid plywood

  4 in. in from the edge and

  the underside of the wood shingles to dry out.

  sheathing

  11⁄2 in. above the exposure line. To allow for

  expansion, leave a 1⁄4-in. gap between shingles,

  Old skip-sheathing

  unless they are wet, in which case you can place

  Two nails per shingle,

  them snugly against each other. Offset joints

  in 3/4 in. from edges

  Felt paper

  between successive courses at least 11⁄2 in.

  Shingle joints that line up must be separated by

  Mesh allows

  shingles to breathe.

  two courses—in other words, shingle joints can

  line up every fourth course but not sooner.

  Finally, nail heads should touch but not crush

  shingle surfaces; any deeper and they may split

  the wood.

  1/4-in.

  circulation and may lead to cupping (shingles’

  gap

  undersides will dry much more slowly than the

  tops), rotting, and shortened shingle life.

  Double first course

  One answer to this dilemma is a layer of

  of shingles along

  Fascia board

  1⁄4-in.-thick synthetic mesh between the building

  eaves.

  paper and the shingles. Cedar Breather is one

  Offset shingle joints

  brand, which comes in 39-in.-wide rolls. Roll the

  11/2 in. minimum.

  Shingles overhang

  mesh out over 30-lb. building paper, tack or staple

  1 in. at eaves and rake.

  it down, and you’re ready to shingle. The mesh

  retains enough loft to allow air to circulate freely

  under the shingles so they can dry fully. To attach

  shingles over the mesh, you’ll need longer nails:

  Alternate direction

  zzzzzz Ventilating a Wood shingle Ridge of shingle-cap

  6d shingle nails should do, but check the product’s

  overlaps.

  literature to be sure.

  Flash a wood shingle roof as you would an

  Ridge vent

  asphalt roof, including WSU along the eaves,

  rakes, and valleys and metal drip-edge along the

  Cut back sheathing

  eaves and rakes.

  from ridgeboard by

  1 in. minimum.

  estimating mateRiaLs

  Urethane

  caulk

  Use only No. 1 (blue-label) shingles on roofs

  because they’re free of sapwood and knots.

  Lesser grades are fine for siding but may leak on

  a roof. Shingles come 16 in., 18 in., and 24 in.

  long, with recommended exposures of 5 in.,

  51⁄2 in., and 71⁄2 in., respectively, on roofs with a

  4-in-12 slope or steeper. Ultimately, slope deter-

  mines exposure and thus the number of bundles

  per square (100 sq. ft.).

  In general, four bundles will cover a square.

  To calculate the number of squares you’ll need,

  Felt paper

  Cedar Breather

  calculate the square footage of the roof and

  (synthetic mesh)

  divide by 100. Because shingles are doubled

  Solid sheathing

  along eaves and rakes, add an extra bundle for

  each 60 lin. ft. of eaves or rake. For valleys, add

  Use a pneumatic nailer to attach

  an extra bundle for each 25 lin. ft. For ridges and

  preassembled ridge caps over the ridge vents

  roof hips, buy preassembled ridge caps, sold in

  because hand nailing the caps could split them.

  Roofs

  99

  GoT moss?

  Moss-covered shingles and shakes are common

  in moist, shaded areas. Hand-scrape or use a

  wire brush to take the moss off. keep it off by

  stapling 10-gauge or 12-gauge copper wire to

  a course of shingle butts all the way across the

  roof. run one wire along the ridge and another

  halfway down. during rains, a dilute copper

  solution will wash down the shingles, discourag-

  ing moss. It’s a nice alternative to toxic

  chemical treatments.

  You could snap chalklines to indicate expo-

  sures for successive courses, but chalk can be

  unsightly and slow to fade on wood shingles.

  After installing drip-edge flashing,

  Instead, get a straight board as wide as the shin-

  double the first course of wood

  gle exposure (5 in., for example), place its bottom

  shingles along the eaves. Along eaves bundles that cover 16 lin. ft. One Canadian sup-

  edge flush to the bottom of the last shingle

  and rakes, the drip-edge overhangs

  plier, WoodRoof (www.woodroof.com), has an

  course, and position the next course of shingles

  sheathing or trim boards by 1⁄2 in. to

  especially informative website about hip and

  by simply placing them atop the board. Move

  3⁄4 in., and shingles extend at least

  ridge caps, precut “fancy butt” shingles, specialty loose shingles around until all their joints are

  1 in. beyond the drip-edge.

  tools, and more.

  correctly offset to the courses below, then nail

  You’ll need 2 lb. of 4d or 5d galvanized shingle them down. A single shingle nail at either end of

  nails per square of shingles. For shingle caps

  the “nailing board” will tack it in place.

  along ridges and hips, use 6d shingle nails to

  When you must stretch to install courses

  accommodate the greater thickness of materials.

  above, install roof jacks as described on p. 95.

  Have your supplier deliver the materials in a lift-

  Because wood shingles have random widths

  bed truck so that you can unload the shingles

  (unlike the fixed lengths of asphalt shingles),

  directly onto the roof.

  several people can work on a course at the same

  time. As you get within 6 ft. of the top, measure

  instaLLing Wood shingLes

  up to the ridge. If the ridge is not parallel to the

  P R O T I P

  eaves, there may be a discrepancy of s
everal inches

  Note the offset requirements in “Wood Shingle

  between measurements at one end of the roof and

  save exceptionally wide

  Basics” (p. 99), which are essential for a long-

  the other. If so, start adjusting exposures so that

  wood shingles to use along a val-

  lasting roof.

  the top course of shingles will be more or less

  ley, so you can nail as far as pos-

  Double the first courses of shingles along the

  sible from the center of a valley.

  parallel to the ridge. If there’s a discrepancy of

  eaves, extending them beyond the drip-edge by

  no matter how wide that shingle

  2 in., for example, you should reduce exposures

  1 in. Double shingles along rakes, overhanging

  is, use only two nails to secure it.

  on the narrow end of the roof by 1⁄4 in. per course.

  rake trim by 1 in. In addition, install metal drip-

  if you think a shingle may split,

  edge along eaves and rakes. When nailing the

  open valleys. Refer to previous sections in this

  flex it gently to be sure it’s

  bottom course of doubled shingles along the

  chapter on underlayment and valley flashing

  sound.

  eaves, nail them about 1 in. up from the butt

  before you start. For most wood-shingle roofs, an

  edges; if possible, sink the nails into the edge of

  open valley is the way to go. The exposed metal

  the fascia board. Those two nails will be covered

  flashing clears water effectively and it’s not likely

  by the top course of doubled shingles. Nail that

  to clog with debris. In addition, shingles running

  course with two nails placed 11⁄2 in. above the

  alongside an open valley require less fitting and

  exposure line.

  cutting than those in closed valleys.

  You can shingle out from a valley or into a val-

  ley from roof planes on either side. In either case,

  start by snapping parallel chalklines along both

  sides of the metal valley flashing; each line should

  be at least 3 in. from the center fold of the flash-

  ing. As each course approaches the valley, don’t

  100 Chapter 5

  nail the last four or five shingles immediately;

  shingLe RepaiRs

  just arrange them so that wide shingles end in

  To remove wood shingles, use scrap blocks to ele-

  the valley. Where shingles cross a chalkline, use a vate the butt ends of the course above. Work the

  utility knife to notch the shingle at those points.

  blade of a chisel into the butt end of the defective

  Keep nails as far as possible from the valley

  shingle, and with twists of your wrist, split the

  center: 5 in. away is minimum. A bead of ure-

  shingle into slivers. Before fitting in a new shin-

  thane caulk under the leading shingles should

  gle, remove the nails that held the old one. Slide

  keep the edges from lifting.

  a hacksaw blade or, better, a shingle ripper (also

  closed valleys. Run shingles into the valley until known as a slate hook) up under the course

  they meet oncoming shingles from the other side. above and cut through the nail shanks as far

  At that juncture, rough-cut each shingle about 1⁄4 in. down as possible. If you use a hacksaw blade,

  proud to establish the correct angle. Then use a

  wear a heavy glove to protect your hand.

  block plane to back-bevel the leading edge. By

  Wood shingles should have a 1⁄4-in. gap on

  cutting and planing, you create a compound

  both sides, so size the replacement shingle 1⁄2 in.

  angle so that the shingles fit tightly; this can be

  narrower than the width of the opening. Tap in

  done only on the roof, shingle by shingle—a slow the replacement with a wood block. If the

  job. For best weathering, alternate miters right

  replacement shingle won’t slide in all the way,

  and left from course to course. Build up several

  pull it out and whittle down its tapered end,

  courses in the valley, and shingle out to the rest

  using a utility knife. It’s best to have nail heads

  of the field.

  covered by the course above, but if that’s not pos-

  ridge treatments. Be sure to read the com-

  sible, place a dab of urethane caulk beneath each

  ments on venting a ridge on pp. 90–91. In brief,

  nail head before hammering it down. Use two 4d

  cut back sheathing at least 1 in. on either side of

  galvanized shingle nails per shingle, each set in

  3

  the ridge board. Then run underlayment and

  ⁄4 in. from the edge.

  shingles to the edge of the sheathing before nail-

  ing a ridge vent over the opening.

  A Medley of Roofing Types

  The ridge vent can be finished in one of

  Although this section covers modest repairs a

  two ways:

  novice can make, most of the roofs discussed

   Shingle caps. Use a pneumatic nailer to

  here should be installed by a specialist. You’ll

  attach preassembled shingle caps over the

  also find suggestions for determining the quality

  vent. Because the mesh underlayment and the

  of an installation as well as a few tips.

  ridge vent are compressible, they would move

  if you tried to hand-nail them. Shoot 2-in. to

  fLat Roofs

  21⁄2-in. galvanized shingle nails through the

  shingle caps; nails should penetrate the roof

  Actually, no roof should be completely flat, or it

  sheathing at least 1⁄2 in.

  won’t shed water. But “flat roof” is a convenient

  

  term for a class of multimembrane systems. At

  Ridge boards. These butt to each other;

  one time, built-up roofs (BURs) once represented

  for a weathertight fit, they should be mitered.

  half of all flat roof coverings. BURs consisted

  To establish the miter angle, lap two pieces of

  of alternative layers of heavy building paper and

  scrap at the peak and, using an adjustable

  hot tar. Today, modified bitumin (MB) is king,

  bevel, transfer this angle to your tablesaw.

  with cap membranes torched on to fuse them to

  Test-cut several pieces of scrap until the fit is

  fiberglass-reinforced interplies or base coats.

  tight, then rip down the ridge boards on the

  MB systems are durable and adhere well to dis-

  tablesaw. Because ridge boards should be as

  similar materials and difficult joints, but an

  long as possible, get help nailing them down. If

  inexpert torch user can damage the membranes

  it takes several boards to achieve the length of

  and set a house on fire. For that reason, future

  the ridge, bevel end joints 60° and caulk each

  roofs are likely to employ hot-air welding, cold-

  with urethane caulk. Using 8d galvanized ring-

  press adhesives, and roll membranes with self-

  shank roofing nails, nail the ridge boards to

  sticking edges.

  the rafters, using two nails per rafter. Then go

  back a
nd draw the beveled joint together by

  causes of flat-roof failure. Whatever the

  nailing it with 6d galvanized box nails spaced

  materials, flat roofs are vulnerable because water

  every 12 in. As you work, push down on the

  pools on them, people walk on them, and the

  ridge boards to force them together. To avoid

  sun degrades them unless they’re properly

  splitting boards, predrill them or use a

  maintained. Here are the primary causes of

  pneumatic nailer to shoot nails through the

  membrane damage:

  roofing layers into the rafters.

  Roofs

  101

  LAyING A FLAT ROOF

  Once the granular membrane is down, its overlapping

  edges are often lifted and torched again to ensure sound

  adhesion and a waterproof seam.

  The intersection of flat and sloping

  roof sections is worth extra attention.

  Run MB membranes at least 10 in.

  In the final phase of a modified bitumen roof, an installer

  Roofers refer to the molten material being forced out by

  (vertical height) up the sloping

  torch-welds a granular surface membrane to an interply

  the pressure of the trowel as wet seams—the mark of a

  section. Then overlap those mem-

  sheet or directly to a base sheet. The granular surface

  successful installation.

  branes with the underlayment

  is somewhat more expensive at installation, but it is

  materials and the composition

  cost-effective in the long run because it doesn’t need

  roofing material so water can run

  periodic recoating.

  down unimpeded.

   Water trapped between layers because

   Trowel on a 1⁄4-in.-thick layer of an

  the roofing was installed too soon after rain or

  elastomeric mastic, such as Henry 208 Wet

  when the deck was moist with dew. Trapped

  Patch®, carefully working it into both sides of

  water expands, resulting in a blister in the

  the split. Extend the mastic at least 2 in.

  membrane. In time, the blister is likely to split.

  beyond the split in all directions.

   Inadequate flashing around pipes,

   Cut a piece of “yellow jacket” (yellow

  skylights, and adjoining walls.

  fiberglass roofer’s webbing) slightly longer

  

  than the split and press it into the mastic; this

  Drying out and cracking from UV rays—

  reinforces the patch.

  usually after the reflective gravel covering has

  been disturbed.

 

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