Renovation 4th Edition

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Renovation 4th Edition Page 22

by Michael Litchfield


  Passive ventilation: As air heats under

  rafters to block the rising air. slotted intake vents are, essentially, a

  the roof, it rises and exits through the ridge

  one-sided ridge vent. they require several courses of shingles to be

  vent, drawing cooler air up through soffit

  vents or vented drip-edges. Venting also

  removed, a 1-in. slot cut through the sheathing, and the intake vent to

  Soffit vent

  carries off excess moisture.

  be integrated into the shingle field so that it overlaps the course

  below and is overlapped by the course above.

  adding intake vents, however, may not be a viable solution if raf-

  ters are not deep enough to accommodate both insulation (R-30

  requires 8 in. of insulation) and 2 in. of clear space above the insula-

  tion to allow airflow. solid wood blocking between rafters also will

  stop airflow, creating hot spots of stagnant air between rafter bays. at

  some point, it may be more cost-effective to opt for an unvented

  roof—closing all vents to the exterior, insulating the underside of the

  roof, and turning the attic into conditioned space. doing so may

  increase the amount of living space you have, provided the attic is

  framed to support live loads and is accessible. unvented roofs and con-

  ditioned attics are discussed further in chapter 14 beginning on p. 398.

  mVR = minimum Venting Requirements

  Chapter 14 offers more information on ventilation. in brief, you need a

  minimum of 1 sq. ft. of ventilation per 300 sq. ft. of attic space. half

  the vent area will be intake vents, and half ridge or gable-end exit

  vents. for example, if attic floor space totals 2,500 sq. ft., total vent

  surfaces should be 2,500 ÷ 300, or 8.33 sq. ft. Ridge vents would

  therefore be half that, or 4.16 sq. ft. that area corresponds roughly to

  33 lin. ft. of ridge vents, based on net free vent area (nfVa) charts.

  Intake vents take many forms, including slotted

  vents that resemble half of a ridge vent. Intake

  vents are typically installed a few feet up from,

  and parallel to, the eaves.

  [PHOTO CREDIT: Mike Guertin]

  90

  Chapter 5

  Where complex roof framing or closed

  eaves rule out using ridge vents or slotted

  intake vents, eyebrow ventilators and

  rooftop turbines can help reduce heat in

  the attic.

  Have a boom truck deliver roofing

  supplies directly to the roof. Stack

  pattern, with no shingle cutouts to line up. When materials along the ridge so the rest

  installed, they look distantly like wood shakes.

  of the roof will be clear to work on.

  mateRiaLs: Rough numBeRs

  Shingle dimensions vary by maker. Three-tab

  shingles are typically 12 in. by 36 in. Laminated,

  architectural shingle dimensions are often metric,

  roughly 13 in. by 40 in. Most shingles are

  installed with a 5-in. exposure, although shingles

  with metric dimensions may specify a 55⁄8-in.

  P R O T I P

  exposure. Always follow the manufacturer’s expo-

  sure recommendations, no matter what type of

  When reroofing an old house,

  shingle it is.

  make sure rafters can support the

  calculating shingles needed. Begin by measur-

  weight of new shingles. some

  ing the roof accurately, making a sketch to scale

  thick “luxury shingles” weigh

  on graph paper as you go. Note valleys, ridges,

  480 lb. per square versus 250 lb.

  chimneys, skylights, plumbing vents, and other

  per square for 30-year architec-

  tural shingles or 200 lb. for stan-

  elements that require flashing, waterproof mem-

  dard three-tab singles.

  branes, or special attention. From that sketch, a

  building supplier can develop a final materials

  list for shingles, nails, underlayment, flashing,

  vents, and so on.

  Asphalt shingles come three to five bundles to

  the square (100 sq. ft.), depending on shingle

  dimensions. To calculate the number of squares

  Ridge vents allow hot air—and excess

  you’ll need to shingle the field, add up the square

  moisture—to exit the building. Here, a

  footage of roof surface and divide by 100. In

  perforated plastic ridge vent gets capped

  addition, you’ll need materials to reinforce shin-

  with shingles.

  gles along eaves and rake edges—either by

  installing a double layer of shingles along the

  roof perimeter or by applying a heavy starter strip

  before shingling.

  Roofs

  91

  If you’re installing laminated shingles, use

  nails per shingle, you’ll need about 31⁄3 coils

  three-tab shingles as an underlayer along the eaves (400 nails) to attach a square of shingles.

  and rakes. For this purpose, three-tab shingles

  Use corrosion-resistant roofing nails at least

  are far cheaper than laminated shingles and will

  11⁄4 in. long for new roofs; use 11⁄2-in. nails if

  lie flatter. If you’re installing woven valleys, you’ll you’re roofing over a previous layer. Ideally, nails

  interweave roughly one bundle of shingles per

  should sink three-quarters into sheathing or stop

  16 lin. ft. of valley. Finally, add two extra bundles

  just short of penetrating all the way through for

  1

  for waste, ridge and hip caps, and future repairs.

  ⁄2-in.- to 5⁄8-in.-thick sheathing. If the roof has an

  Shingle colors often vary from one production exposed roof overhang (you can see the under-

  lot to another. To avoid having a new roof with a

  side of the sheathing), use 3⁄4-in. nails (along the

  patched-together look, specify that all bundles

  overhang) for a new roof; 1-in. nails for roofovers.

  come from the same lot when you order. When

  When ordering, don’t forget tabbed roofing

  your order arrives, check the lot numbers on the

  nails for underlayment and metal-compatible

  bundles and open a few bundles from different

  nails for attaching flashing or valley clips.

  lots. If lot numbers don’t match and the color

  variation is noticeable, call the supplier. If the

  shingLe Layout

  color varies only slightly, you might mix lots

  We’ll assume that the roof has been stripped of

  every other shingle during installation. Finally,

  old shingles, that failed sheathing has been

  have shingles delivered directly to the roof. Many replaced, and that the roof is safe to walk on.

  suppliers will place bundles on the roof by means reconnoiter the roof. Use a tape measure to see

  of truck booms or conveyor belts.

  whether the roof is square, the ridge is parallel to

  roofing nail quantities vary according to

  eaves, the rake edges are parallel, and whether—

  method: hand nailing, power nailing, or some

  overall—the width of the roof requires shifting

  combination of the two. Typically, use four nails

  shingle courses left or right. To determine square,

&n
bsp; per shingle, or about 2 lb. of nails per square if

  measure diagonally from both ends of the ridge

  you’re hand nailing. However, high-wind areas

  down to the opposite eave corner; if the readings

  require six nails per shingle, or 3 lb. per square.

  are roughly equal, chances are the roof is square.

  Roofing nails come in 5-lb. and 50-lb. quantities.

  If the ridge is parallel to eaves within 1⁄2 in., run

  Boxes of pneumatic nails typically contain

  shingle courses right up to the ridge. But if ridge-

  120 nails per coil and 60 coils per box. At four

  to-eaves readings differ by 3⁄4 in. or more, you’ll

  shingling terms

  these definitions will help you make sense of roofing terms.

   course: a horizontal row of shingles.

  zzzzzz three-tab shingles

   Butt edge: the bottom edge of a shingle.

  Tab

  Offset

   exposure: typically, the bottom 5 in. of the shingle, left

  Self-seal strip

  exposed to weather. shingles with metric dimensions are usually

  exposed 55⁄8 in.

   cutouts: slots cut into the exposed part of a three-tab shingle

  to add visual interest and allow heat expansion.

   Offset: the distance that shingle slots or ends are staggered

  from course to course.

   Self-seal strip: the adhesive on the shingle face, which,

  when heated by the sun, fuses to shingles above and prevents uplift.

   Fastener line: on shingles with a 5-in. exposure, a line roughly

  Exposure

  55⁄8 in. up from the butt edge. nails along this line will be covered by

  the shingles above. (if shingles don’t have such lines marked, nail just

  below the self-seal strip.)

  Butt edge

  Cutouts

   control lines: Chalklines snapped onto underlayment to help

  align courses and cutout lines.

  Fastener line

  (not found on all shingles)

   underlayment: a water-resistant sheet material—usually

  building paper—that covers the roof sheathing.

  92

  Chapter 5

  need to compensate by adjusting shingle expo-

  sures as you approach the ridge.

  The last two measurements, for parallel rakes

  and roof width, are of most concern if you’re

  installing three-tab shingles. Because three-tab

  shingle patterns align vertically, avoid cutting

  shingle tabs less than 2 in. wide along either rake

  edge—tabs that short look terrible. It’s far better

  to shift the shingle layout (and thus the vertical

  control lines) slightly right or left so the shingle

  piece is larger. For additional strategies for

  installing three-tab shingles, see Mike Guertin’s

  fine book, Roofing with Asphalt Shingles (The

  Taunton Press, 2002).

  establishing control lines. After installing drip-

  edge along the eaves, many pros measure only

  once, to establish a horizontal control line paral-

  lel to the eaves, to which they nail the shingle

  starter course. After the starter course is down,

  they use only the exposure gauge of their pneu-

  matic nailer or shingle hatchet to position suc-

  cessive courses.

  After installing drip-edge along the eaves, double the first course of shingles or, as shown, install a

  starter strip. The lower edge of the starter strip overhangs the drip-edge by 1⁄

  To make sure courses stay evenly spaced and

  4 in. to 3⁄4 in.—or even

  1 in. if bowing eaves or rake boards require it.

  straight, however, snap horizontal chalklines at

  regular intervals onto the underlayment (build-

  ing paper). Snapping chalklines every second or

  third course won’t take much time and will

  ensure professional-looking results.

  If you’re installing three-tab shingles, it’s also

  wise to snap a pair of parallel, vertical control

  lines 6 in. apart to line up the slots of alternating

  shingle courses, as shown in “Laying Out Three-

  Tab Shingles” on p. 95. With a 6-in. offset, the

  slots of every other course line up, creating a

  strong visual pattern. If slots don’t align, the

  installation will look sloppy. Laminated shingles

  have no slots to align, so you won’t need vertical

  control lines.

  instaLLing shingLes

  After attaching drip-edge to the eaves and rolling

  out underlayment over the drip-edge, install the

  starter course along the eaves. You’ll cover the

  starter course with the first course of shingles.

  Instead of doubling shingles along the roof rakes,

  Running starter courses along the rakes isn’t

  install a starter strip. It’s stiff enough to resist wind

  imperative, but it’s smart because starters stiffen

  uplift. And, seen from below, it presents a much

  P R O T I P

  cleaner, straighter line than individual shingles.

  the overhanging shingle edges and create a clean-

  er sightline from below.

  many roofers prefer hand nail-

  The starter course. First, determine how much

  ing the first half-dozen shingle

  the starter course will overhang the drip-edge:

  courses rather than pneumatic

  1⁄

  nailing. that’s because the hose

  4 in. to 3⁄4 in. overhang is typical, but some roof-

  ers allow as much as 1 in. if eave or rake boards

  of a pneumatic nailer makes foot-

  are bowed.

  ing more treacherous along the

  eaves, where there’s little time to

  Along the eave, extend your tape measure past

  catch yourself before rolling over

  the drip-edge the amount of the overhang. If that

  the edge.

  overhang is 1 in., make crayon marks on the

  underlayment at 7 in. and at 12 in. Do this at

  Roofs

  93

  both ends of the roof, and snap chalklines

  unbroken line. Still, trimming three-tab shingles

  P R O T I P

  through both sets of marks. The 7-in. line indi-

  is cheaper, so here’s a quick look at that method.

  cates the top of the starter course; the 12-in. line

  Traditionally, the starter course was just a full

  score shingles on the back-

  indicates the top of the first course of shingles.

  shingle turned upside down so its tabs faced up,

  side, using a utility knife. if you

  Starter courses can be three-tab shingles with

  but that placed the shingle’s self-seal strip too

  try to cut through the granules

  the bottom 5 in. cut off or a starter strip that

  high to do much good. It’s far better to measure

  on the front, the blade will go

  awry and soon dull. When you

  comes on rolls in various widths. Starter strips

  down 7 in. from the top of the shingle, trim off

  score along a straightedge and

  have the advantage of stiffening shingles above

  the bottom 5 in., and snap off the shingle tabs.

  snap along the cut, you’ll get a

  and, viewed from below, providing a cl
ean,

  Align the top edge of the starter shingles to

  straight, clean edge.

  the 7-in. control line and nail them down, four

  nails per shingle. If you’re installing a starter

  strip, align its top edge to the 7-in. control line.

  Next, install starter courses over rake drip-edges,

  using the same overhang you used for eaves.

  Rake starter strips overlap eave starter courses

  using pneumatic nailers

  when they meet at lower corners. Along both ends

  of the roof, measure up from the 12-in. control

  Because pneumatic nailers can easily blow nails through shingles, some codes spec-

  line and snap horizontal chalklines for the shin-

  ify hand nailing. and it’s safer to hand-nail the first five or six courses along the eaves,

  gle courses to come. As noted earlier, a horizontal

  where stepping on a pneumatic hose could roll you right off the roof. Wear safety glasses

  chalkline every two or three shingle courses is

  when using nailers.

  plenty. Once that’s done, you’re ready to install

  those concerns aside, pneumatic nailers are great tools if used correctly. here’s how:

  the first course of shingles.

   don’t bounce-fire a nailer until you’re skilled with it. (to bounce-fire, you hold

  One final note: Building-paper underlayment

  the trigger down and press the nailer’s nose to the roof to fire the nail.) shingles must

  tears pretty easily if it gets too much traffic, so

  be nailed within a small zone—below the sealer strip but above the cutouts, if any—

  only roll out one strip of building paper at a

  and it’s hard to hit that zone if the nailer is bouncing around. instead, position the

  time. Install shingle courses until you are close

  nailer nose where you want it, then pull the trigger.

  to the upper edge of the felt paper, then roll out

   trigger-fire the first nail of every shingle. do this to keep shingles from slipping,

  the next strip so that its lower edge overlaps the

  even if you’re skilled with pneumatic nailers. once the first nail is in, you can bounce-

  one below.

  fire the remaining ones.

  shingling the field. Install the first course of

   hold the nailer perpendicular to the roof so nails go in straight, and keep an eye

  shingles over the starter course. If you’re right-

  on nail depth as the day wears on. nail heads should be flush to the shingle; if they’re

  handed, start at the left side of the roof and work

  underdriven or overdriven, adjust the nailer pressure.

 

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