Renovation 4th Edition

by Michael Litchfield

  roofing to replace faulty flashing, reroofing may

  remove it, you could breathe it or smell asphalt-

  be the most cost-effective cure.

  shingle residue for years.

  Other than that, stripping is mostly grunt

  rafters and sheathing are undersize. If rafters work. Most strippers use a specially designed

  are too skimpy, the roof will sag, especially along

  tear-off shovel, starting at the top and working

  the ridge. If the sheathing is too thin, the roof

  down, scooping shingles as they go. Tear-off

  will sag between rafters and look wavy. The rem-

  shovel blades have a serrated edge that slides

  edy may be stripping the roof and nailing 1⁄2-in.

  under nail heads and a fulcrum underneath that

  plywood over old sheathing or bolstering under-

  pops nails up. Be sure to tear off all old building

  size rafters with new lumber, but let a seasoned

  paper (felt or rosin paper), too.

  professional make the call.

  shingles are prematurely worn, curling, or

  sheathing

  missing. If a roof is relatively new and these

  Once you’ve stripped off roofing, survey the

  symptoms are widespread, suspect product

  sheathing for damage and protruding nails. As

  defects, inadequate ventilation, faulty installa-

  you pound down nails, be sure to place your feet

  tion, or a combination of those factors. A layer of directly over rafters. Probe suspect sheathing and

  new shingles won’t lie flat over curling ones. So if

  A stripping shovel is a flat-nose

  replace any that’s soft. Cut bad sections back to

  shingles are curling—even if there is only a single

  shovel whose blade is serrated to peel

  the nearest rafter centers. For this, wear safety

  layer of roofing—tear them off.

  off shingles and grab nail shanks. The

  glasses and use a circular saw with a carbide-

  fulcrum on the back increases

  adjacent roof sections must be replaced. This tipped, nail-cutting blade because the blade will leverage as you pry up old nails is a judgment call. When a house has additions

  hit a lot of nails. Replacement pieces of sheathing and roofing.

  that were roofed at different times, they probably should be the same thickness as the original.

  will need reroofing at different times. Likewise,

  If the old roof was wood-shingled, it probably

  south-facing roof sections age 20% to 30% faster

  had skip-sheathing, which consists of 1x4s

  than north-facing ones. If you see signs of leaks,

  spaced 5 in. on center. Skip-sheathing allows air

  strip the whole roof, install flashing, and reroof.

  to circulate under wood shingles. If the boards

  are in good shape, you can nail on new wood

  stRipping an oLd Roof

  shingles after stripping old ones. But many con-

  P R O T I P

  Stripping a roof is one of the nastiest, dirtiest,

  tractors prefer to sheath over the 1x4s with 1⁄2-in.

  most dangerous jobs in renovation. If you can

  exterior-grade plywood (for rafters spaced 16 in.

  one of the hazards of strip-

  afford it, hire an insured contractor for this. Most on center) or 5⁄8-in. plywood (for rafters 24 in. on

  ping a roof is its mind-numbing

  roofing contractors know of tear-off crews that

  center). This stiffens the roof and makes it safer

  tedium. Besides staying alert,

  will obtain permits, rip off the old roof, and cart

  to work on, but plywood virtually eliminates air-

  earlier-mentioned safety consid-

  away the debris, or you might want to subcon-

  flow under shingles. Consequently, some builders

  erations apply here as well: scaf-

  tract the job through a roofer. Professional strip-

  install a synthetic mesh, Cedar Breather®, over

  folding with a safety rail, proper

  ping takes at most a couple of days. It’s money

  plywood to increase circulation, before nailing

  footwear, and another person

  well spent.

  on wood shingles.

  within earshot. if the roof is

  steep, wear a body harness

  If you must strip the roof yourself, remove all

  Run plywood lengths perpendicular to rafters,

  secured over the ridgeline.

  roof gutters and then minimize the mess by buy-

  centering plywood edges over rafter centers. Nail

  ing a heavy 6-mil plastic tarp to catch shingles

  every 6 in. with 8d galvanized nails. Between raf-

  and old roofing nails. So you won’t be picking

  ters, use H-clips to support panel joints and cre-

  shingle shards and nails from the lawn for years

  ate 1⁄16-in. expansion gaps. Sweep the roof well,

  to come, lay tarps from the house to the

  and hammer down nail pop-ups.

  Dumpster as well. To protect plants around the

  house, place sawhorses or 2x4 frames over them

  and cover with cloth drop cloths. Caution: Don’t

  cover plants with plastic or they’ll bake. Finally,

  lean plywood in front of windows so falling

  objects don’t break them. When the job is done,

  rent a magnetic roller (also called a magnetic nail

  Roofs

  81

  undeRLayment

  Once limited to building paper, underlayment

  now includes self-adhering rubberized sheets

  that replace metal flashing in some cases.

  Weather-resistant underlayment. Traditionally,

  underlayment has been 36-in.-wide, 15-lb. or

  30-lb. felt paper used as a weather-resistant layer.

  It keeps sheathing dry until shingles are installed,

  P R O T I P

  serves as a backup layer when water gets under

  shingles or flashing, and prolongs shingle life by

  some Wsu membranes may

  separating sheathing and shingles. (Without

  be degraded by petroleum-based

  underlayment, shingle asphalt can leech into wood

  roofing cements. if you need to

  caulk near Wsu, urethane caulks

  sheathing, or resins in sheathing can degrade the

  are probably the best choice, but

  shingle.) Heavy-duty, 30-lb. felt paper is often

  check product specs to be sure.

  specified in high-wear, high-water areas such as

  eaves and valleys. A standard roll of 3-ft.-wide,

  A hammer tacker allows you to staple building paper

  15-lb. felt paper covers roughly 400 sq. ft.; the

  quickly so the paper won’t slide down the roof as you roll

  it out. Later, secure the paper with tabbed roofing nails.

  same-size roll of 3-ft.-wide, 30-lb. paper covers

  only 200 sq. ft. because it’s roughly twice as thick.

  Because unreinforced lighter grades of build-

  covered by shingles, the better. Building paper

  ing paper (15 lb.) tear easily and wrinkle when

  was never intended to be an exterior membrane.

  wet, some types are now reinforced with fiber-

  When installing building paper on a sloped

  glass. Moreover, all asphalt-impregnated building roof, have a helper and work from the bottom up.

  papers dry out and become less water-resistant
r />   As you roll the paper out, it will tend to slide

  when exposed to sunlight, so the sooner they’re

  down the roof, so be sure to unroll it straight

  across the roof. The first course of paper should

  overlap a metal drip-edge nailed along the eaves.

  Align the paper’s lower edge to the lower metal

  edge and unroll the paper, stapling as you go.

  Staples are only temporary fasteners to keep the

  paper from bunching or sliding. Paper should be

  zzzzzz eaves, Rake, and underlayment details

  nailed down with tabbed roofing nails (also

  Rake drip-edge

  called Simplex® nails) shown on p. 70. Along roof

  over underlayment

  Roof sheathing

  edges and where the ends of the building paper

  Felt-paper

  overlap, space nails every 6 in.; don’t nail within

  underlayment

  1 in. of the edge. In the field, place nails in a zig-

  6-in. end lap

  zag pattern, spacing them 12 in. to 15 in. apart.

  For steep-slope roofs (4-in-12 or steeper),

  overlap horizontal courses of building paper 2 in.

  Overlap ends of seams (end laps) at least 6 in. To

  prevent water backup on low-slope roofs (less than

  4-in-12), building codes often specify two plies of

  36-in.-wide underlayment, with horizontal seams

  overlapped at least 19 in. and (vertical) end seams

  overlapped 12 in. Check your local code to be

  sure, for it may also specify self-sticking water-

  proof shingle underlayment along the eaves.

  If you’re installing wood shakes or slate, use

  2-in.

  shake liner, 18-in.-wide rolls of 30-lb. building

  overlap

  paper alternated between roofing courses.

  Stagger nails

  every 12 in.

  Waterproof shingle underlayment (Wsu).

  WSU is a heavy peel-and-stick bituminous mem-

  Eaves drip-edge

  brane that protects areas most likely to leak

  because of concentrated water flows in valleys,

  Nail drip-edges

  ice dams at eaves, or high winds at eaves and rake

  every 12 in.

  Nail underlayment

  edges. Many building codes also specify WSU in

  every 6 in. around edges.

  lieu of building paper where asphalt shingles are

  82

  Chapter 5

  Temporarily staple one side of the WSU to the sheathing, fold it in half lengthwise, and peel off the release sheet for that half. Roll out the untacked half, smoothing it from the valley outward. Pull the stapled half free and repeat.

  installed on low-slope roofs. In addition to being

  self-adhering, WSU also self-seals around nails,

  galvanic acTion

  making it a truly waterproof membrane.

  WSU comes in 9-in. to 36-in. widths. Brand

  A number of metals, if paired, will corrode one

  names include CertainTeed Winterguard™, W.R.

  another in a process called galvanic action. To be

  Grace Ice & Water Shield®, and GAF Weather

  safe, use nails or clips that are the same metal

  Watch®.

  as the flashing you install. Because water is an

  It’s vastly easier to install WSU along valleys

  electrolyte, any moisture present will increase

  than it is to use roll roofing or aluminum flash-

  corrosion. The following metals make up a group

  ing. And with WSU, there’s no need to trowel on

  known as the electrolytic sequence.

  wide swaths of roofing cement between 30-lb.

  building-paper layers to protect eaves from ice

  1. ALuMInuM

  6. TIn

  dams. Snap a chalkline to position the WSU.

  2. ZInc

  7. LeAd

  Then unroll and cut the membrane to length,

  align it to the chalkline, peel off its release-sheet

  3. STeeL

  8. cOpper

  backing, and press the material down. Most man-

  4. IrOn

  9. STAInLeSS STeeL

  ufacturers recommend rolling it once it’s down to

  5. nIckeL

  make sure it’s well adhered.

  WSU is more easily installed with two people,

  When you pair up materials, the metal with

  but if you’re working alone, fold the WSU in half

  the lower number will corrode faster. If you must

  lengthwise, and temporarily staple one edge of

  pair two different metals, you can retard galvan-

  the membrane to a chalked guideline. Peel off the

  ic action by insulating between the metals with

  release-sheet backing from the unstapled half of

  a layer of 30-lb. building paper.

  the WSU, and flop the adhesive side of the mem-

  brane over onto the sheathing. Finally, yank the

  stapled edge free, peel off the backing from the

  second half, and stick it to the sheathing.

  Because WSU is self-adhering, you needn’t nail it;

  you need to use staples only to keep the sheet

  from sliding around before sticking it down.

  Roofs

  83

  When installing flashing, use the fewest nails

  Roof Flashing

  possible and avoid nailing in the center of a flash-

  Because underlayment directs water away from

  ing channel, where water runs. If possible, posi-

  sheathing, it’s technically flashing, too. More

  tion nails so the heads will be covered by roofing.

  often, however, roof flashing refers to sheet metal Where you must leave nail heads exposed—for

  that protects building seams or edges from water example, when installing skylight flashing or wall

  penetration or diverts water around pipes, chim-

  cap flashing—put urethane caulk under the nail

  neys, dormers, and other penetrations. Metal

  heads before driving them down or use gasketed

  flashing is widely used because it’s durable and

  roofing nails.

  relatively easy to cut and shape. Always replace

  old flashing when installing a new roof.

  dRip-edge fLashing

  Drip-edge diverts water away from roof edges so

  mateRiaLs

  it won’t be drawn by capillary action back up

  Various sheet materials are suitable for flashing.

  under shingles or sheathing. Drip-edge also cov-

  Unformed, they come in sheets 10 ft. long or in

  ers and protects sheathing edges from gutter

  rolls of varying lengths, widths, and gauges.

  splashback and ice dams along the eaves and

  Copper is the longest lasting and most expensive. gives rake edges a clean, finished look. The

  Lead is the most malleable but also the most vul-

  crimped edge of drip-edge flashing also resists

  nerable to tears and punctures. Galvanized steel

  bending and supports overhanging shingles.

  ranks second in longevity, but it’s so rigid that

  Drip-edge is sold in varying widths and comes

  you should buy it preshaped or rent a metal-

  in an L shape or a lopsided T shape. Install drip-

  bending brake to use on site.

  edge along the eaves first, nailing it directly to

  Lightweight aluminum is commonly shaped

  sheathing, using 4d big-head roofing nails. Space

  on sit
e, and it’s a good compromise of cost and

  nails every 18 in. or so. Underlayment along the

  durability. There’s also painted steel flashing, in

  eaves will overlap the top of the drip-edge. Along

  case you don’t like the glare of bare metal.

  the rake edges of a roof, install underlayment

  zzzzzz Lower Roof Corners

  Rake drip-edge

  Felt-paper

  underlayment

  Eaves drip-edge

  Flange slides into

  rake drip-edge.

  Drip-edge flashing allows water to drip free from roof edges. Here, copper drip-

  edge is being retrofitted under an existing roof before being fastened with 3d

  copper flashing nails. An uninstalled piece is shown lying atop the shingles.

  Rake drip-edge folds to

  cover eaves drip-edge.

  Underlayment runs over the eaves drip-edge, and rake drip-edge

  runs over the underlayment. Thus, at lower corners the rake drip-

  edge will overlay the eaves drip-edge.

  84

  Chapter 5

  zzzzzz an open Valley

  36-in.-wide felt paper

  Open valleys are well suited to

  or peel-and-stick WSU

  thicker roofing materials, such as

  membrane

  laminated asphalt shingles, wood

  24-in.-wide standing-seam

  shingles, and shakes. Because

  valley flashing

  roofing cement may not be

  compatible with peel-and-stick

  Shingle points snipped

  WSU, use urethane caulk under

  at 45° angle

  shingle edges. The crimp in the

  valley flashing prevents cross-

  No nails within

  6 in. of valley center

  val ey runoff from running under

  shingles.

  Urethane caulk

  under shingle edges

  Clips allow

  expansion/

  contraction.

  Hemmed edge

  to stop water

  1-in. crimp

  Minimum 6 in. clear, unnailed

  metal on both sides of seam

  DETAIL

  before applying drip-edge. In corners, where rake variations, such as the closed-cut valley as shown

  edges meet eaves, run the rake drip-edge over the in “Closed Valleys” on p. 86.

  eaves drip-edge. Slitting the vertical leg of the

  Prepare valleys by sweeping away debris, ham-

  rake drip-edge makes it easier for you to bend it

  mering all sheathing nails flush, and then lining

  over the leg of the eaves drip-edge.

  the valley with underlayment. Traditionally, this

  In general, drip-edge flashing 6 in. wide or