Book Read Free

Renovation 4th Edition

Page 98

by Michael Litchfield


  trap it. Thus, instead of covering basement walls

  with polyethylene vapor barriers to stop mois-

  ture, the wiser course is to choose semiperme-

  able materials such as expanded polystyrene

  (EPS) panels, which allow any moisture that gets

  into the wall to dry to the inside rather than

  becoming trapped.

  Building on that insight, one “cure” for base-

  ment dampness due to condensation (flowing

  water is another issue altogether) is keeping the

  warm air in living spaces from coming in direct

  contact with masonry masses by insulating base-

  ment floors and walls. Andy Engel, a former

  editor of Fine Homebuilding magazine, put this

  theory to the test in his own basement. For the

  full account, see “The Stay-Dry, No-Mold

  Finished Basement” ( Fine Homebuilding issue

  #169), from which this section has been adapted.

  1. Assuming that concrete floors and walls are

  in good condition and that there is no standing

  water or running water present, attend to sources

  of exterior water before remodeling a basement.

  If the basement floor is not level or in good con-

  dition, you can place new concrete over it, after

  first scarifying it and removing loose material.

  Do not install a plastic vapor barrier between the

  new and old concrete.

  2. To install a floor, first lay down 1-in.-thick

  EPS panels directly to the concrete floor, fitting

  them as tightly as possible and then taping them

  to keep panels from riding up over each other.

  EPS’s compressive strength is sufficient that you

  can just cover it with a 1⁄2-in. plywood floor—

  there’s no need for sleepers. Apply a low-expand-

  ing foam around the perimeter of the EPS, and

  carefully tape every panel seam using Tyvek tape

  or a similar product. Use 21⁄2-in. concrete screws

  to screw the plywood through the EPS to the

  concrete; you’ll need to predrill screw holes first

  Because EPS allows a slight amount of moisture to migrate yet is impervious to moisture damage,

  and countersink the screw heads.

  EPS panels are an excellent choice for insulating basement walls. But panel seams must be carefully

  3.

  taped to isolate basement walls from conditioned living spaces.

  On walls, use 2-in. expanded polystyrene

  panels. First, apply an expanding-foam sealant

  to the walls, then friction-fit the panels in place.

  Energy Conservation and Air Quality

  417

  As with floor panels, tape joints carefully with

  SpRAyInG polyuRETHAnE

  Tyvek tape and go around the perimeter of each

  FoAM oVER An EXISTInG RooF

  wall with low-expanding foam to fill any gaps.

  This last example is more a case history of why

  With concrete floors and walls thus sealed, you

  two building professionals chose a spray-foam

  can construct 2x4 wood walls with no concerns

  roof than a how-to of its installation. As suggested

  about wood rot or mold because the concrete has on p. 410, the chemistry of polyurethane spray

  been completely isolated. Placed tight to the EPS, foam is so complex that the best technical advice

  the stud wall will keep the panels from migrating; I can give is to choose your insulation contractor

  local codes may also require that you mechani-

  carefully.

  cally attach the EPS to foundation walls as well.

  Green reasons for choosing a spray-foam

  4. Finally, cover the stud walls with 1⁄2-in.

  roof. Like many mid-century homes, the 1957

  paperless drywall. Because EPS is flammable,

  Eichler-designed house had clean lines, lots of

  the drywall is a fire-retardant code requirement

  glass, roof sheathing that doubled as a finished

  as well as an aesthetic consideration. By the way, ceiling, and a flat roof with so little insulation that

  if space is tight in the basement, furring strips or

  its inhabitants broiled in the summer and burned

  15⁄8-in.-wide metal studs are another option,

  through money during the heating season.

  though furring strips are likely to telegraph irreg-

  When the old tar-and-gravel roof began leak-

  ularities in foundation walls. The greater thick-

  ing, the homeowners—a green builder and a

  ness of 2x4 framing also allows you to run pipes

  landscape architect—started researching replace-

  and electrical wires in it.

  ment roofs that would be energy-conserving, leak

  proof, cost-competitive, and reasonably green.

  Ultimately, they chose a closed-cell, sprayed poly-

  urethane foam (SPF) retrofit because:

  1. Insulating inside was out. The exposed

  underside of the 2x6 tongue-and-groove roof

  deck was classic. Besides, the ceilings were just a

  shade above 8 ft. and the couple didn’t want to

  zzzzzz Cold-Climate Basement Insulation

  lose 4 in. to 6 in. of headroom to insulation.

  Use spray foam to seal rim joist,

  mudsill edges.

  2. Closed-cell SPF, with an R-value of 6.5 per

  Fill joist bays with EPS pieces.

  in., was the perfect antidote to the old roof’s dis-

  mal energy profile. The old roof assembly, with

  two layers of 1⁄2-in. fiberboard, achieved (maybe)

  Notch and seal rigid

  EPS foam panels around joists.

  R-3 or R-4. Four inches of SPF would bring it up

  to at least R-26; 6 in. would bring it to R-39.

  Spray foam was also particularly well suited to

  this roof because it had parapets, which defined

  2-in. rigid foam

  the edges of foam. (Exterior spray foam only

  works on flat or low-pitch roofs; for pitches

  Paperless drywall

  greater than 4-in.-12, rigid-foam panels are the

  Construction adhesive

  over-roof-deck choice.)

  3. A spray-foam roof could be applied directly

  to the old roofing once it was prepped and

  cleaned up a bit. (See the photos on the facing

  Wood furring strips

  page.) Not stripping the old roof and sending the

  or flat-framed 2x4 wall

  debris to the landfill was also a big green plus.

  Pressure-treated

  Besides, spraying-over would save the labor costs

  sole plate

  of stripping the old roof.

  Cementitious board

  12 in.

  4. Four inches of closed-cell polyurethane is a

  class II water retarder, a semi-impermeable

  membrane that makes leaks all but impossible.

  As the foam expands and adheres aggressively, it

  would seal the many pipes and conduits running

  across the roof of a house with no cavity under

  the sheathing in which to hide pipes.

  418 Chapter 14

  The flat roof of this 1957 Eichler-designed house was a good candidate for a polyurethane spray-foam roof.

  5. Compared with the obvious alternatives, an

  SPF roof was actually less expensive than install-

  ing and then insulating either a new torch-down

  roof or a PVC membrane. And that d
idn’t even

  include the cost of stripping the old roof. There

  were energy-efficiency rebates available for

  installing an SPF roof, but the couple was so

  busy that, as the gent put it, “We couldn’t afford

  the time to save money.”

  6. So was this spray polyurethane foam a green

  choice? Yes and no, but mostly yes. Since the

  A good deal of prep work must precede the foam spraying.

  early days of sprayed foam insulation (the earliest Here, electrical conduits running above the roof had to

  foams were urea-formaldehyde based), the insu-

  be raised so they would be accessible after 4 in. of foam

  was added.

  lation industry has cleaned up its act a lot.

  Although the two chemical components of SPF

  Polyurethane foam can be sprayed

  are largely petroleum based, once the polyure-

  right over old roofing—a big selling

  thane mixture foams and cures, it is chemically

  point—but the old roof must be clean

  inert and doesn’t offgas. (Manufacturing PVC, in

  and well attached. Here, a worker

  installs tabbed roofing nails every

  comparison, involves some particularly toxic

  2 ft. to 3 ft. to secure the old roofing.

  chemicals.) Not sending old roofing to the dump

  is a plus, as is the excellent R-value of the

  material. (Sometimes it takes oil to save oil.)

  An SPF roof can also be quite durable when the

  polyurethane is sprayed with a special acrylic top

  coating that protects the foam against UV degra-

  dation. Lastly, the foam’s light color will reflect

  Spray foam adheres aggressively, so it’s important to mask

  sunlight so, all in all, it should be a relatively

  everything you don’t want foamed. Here, polyurethane

  cool roof.

  foam is being applied to the chimney. In the background,

  is the masked-off parapet.

  Polyurethane foam expands to seal everything sticking

  out of the roof. Once sealed with a special acrylic topcoat,

  the polyurethane foam will be protected from UV

  degradation. Once cured, the closed-cell foam is also

  strong enough to walk on.

  Energy Conservation and Air Quality

  419

  15 Finish Surfaces

  People have used plaster in buildings

  since prehistoric times. Archaeologists have

  unearthed plaster walls and floors dating to

  6000 b.c. in Mesopotamia. And the hieroglyphics

  of early Egypt were painted on plaster walls. In

  North America, plaster had been the preferred

  wall and ceiling surface until after World War II,

  when gypsum drywall entered the building boom.

  Although drywall represents a historic shift in

  building technology, the shift was more one of

  evolution than revolution because drywall’s core

  material is gypsum rock—the same material used

  since ancient times to make plaster.

  Readers interested in installing drywall should

  get a copy of Myron Ferguson’s Drywall (The

  Taunton Press, 2012), far and away the best book

  (and video) on the subject.

  Drywal

  Sometimes called Sheetrock® after a popular

  brand, drywall consists of 4-ft.-wide panels that

  are screwed or nailed to ceiling joists and wall

  studs. Sandwiched between layers of paper, dry-

  wall’s gypsum core is almost as hard and durable

  as plaster, though it requires much less skill to

  install. Appropriately, the term “drywall” distin-

  guishes these panels from plaster, which is applied

  wet and may take weeks to dry thoroughly.

  Panel joints are concealed with tape and usu-

  ally three coats of joint compound that render

  room surfaces smooth. Each panel’s two long

  front edges are slightly beveled, providing a

  depression to be filled by joint tape and com-

  pound. Each layer of joint compound should be

  allowed to dry thoroughly before sanding smooth

  and applying the next coat.

  Sturdy scaffolding keeps you safe and allows you to focus on the task at hand. This lightweight

  setup can be rolled easily from room to room.

  420

  Drywall Types, Uses, and Specifications

  drywall type

  maximum

  available

  and thickness (in.)

  common uses

  framing spacing

  lengths (ft.)

  regular

  

  1⁄4

  Renovation, covering damaged

  16 in. o.c., as double layer

  8, 10

  surfaces; curved surfaces

  over framing, single layer over

  existing plaster, etc.

  

  3⁄8

  Renovation, mostly on walls

  16 in. o.c.

  8, 10, 12

  

  1⁄2

  Most popular thickness,

  16 in. o.c.

  8, 9, 10, 12, 14, 16

  walls and ceilings

  

  5⁄8

  Ceilings, walls needing rigidity

  24 in. o.c. on walls, 16 in. on ceiling

  8, 9, 10, 12, 14

  moisture-resistant (mr)

  

  1⁄2

  High-humidity areas such as

  16 in. o.c.

  8, 10, 12 (other sizes

  bathrooms, kitchens

  special order)

  

  5⁄8

  Bathroom ceilings

  24 in. o.c. on walls, 16 in. on ceiling

  8, 10, 12 (other sizes

  special order)

  paperless

  

  1⁄2

  Walls in mold-prone areas such as

  16 in. o.c.

  8, 9, 10, 12, 16

  basements, bathrooms, laundries

  

  5⁄8

  Ceilings in mold-prone rooms

  24 in. o.c. on walls, 16 in. on ceiling

  8, 10, 12, 14, 16

  usg sheetrock ultralight

  

  1⁄2 non-fire rated

  Hang on walls and ceilings: reduced-

  24 in. o.c.

  8, 10, 12, 14, 16

  weight panels won’t sag

  

  5⁄8 non-fire rated

  Ceiling applications with wet ceiling

  24 in. o.c.

  8, 10, 12, 14, 16

  textures, heavy insulation, high

  humidity

  

  5⁄8 fire rated

  Same uses as type X; check local codes

  24 in. o.c.

  8, 10, 12, 14, 16

  before ordering

  fire-resistent (type x)

  

  5⁄8

  Satisfies 1-hour fire rating

  24 in. o.c.

  8, 10, 12

  fire-resistent (type c)

  

  1⁄2

  Satisfies 1-hour fire rating

  24 in. o.c.

  8, 10, 12

  

  5⁄8

  Exceeds ASTM standards, OK in

  24 in. o.c.

  8, 10, 12

  multifamily housing units

  Always check local codes for acceptable type, thicknesses, and framing spacing.

  Finish Surfaces

  421

  DRyWAll TypES

&n
bsp; to attach it. However, neither thickness is sturdy

  enough to attach directly to studs in a single layer.

  Drywall’s paper facing and core material can be

  Two layers of 1⁄4-in. drywall are routinely bent

  manufactured for special purposes to make it

  to cover curving walls, arches, and the like.

  more flexible, moisture-resistant, fire-resistant,

  Attach the second layer with construction adhe-

  sound isolating, scuff-resistant, and so on.

  sive and screws. If the curved area has a short

  Paperless drywall is also available for use in inte-

  radius (3 ft. to 5 ft.), wet the drywall first (dis-

  rior rooms where mold could be a problem

  cussed in detail later in this chapter). There’s also

  because of high humidity.

  a 1⁄4-in. flexible drywall with heavier paper facings

  Several factors will determine the size and

  designed for curved surfaces, but this usually

  type of drywall you choose:

  needs to be special-ordered.

   Where it will be used. Local building codes

  Moisture-resistant drywall (MR board) is also

  may require moisture-resistant (MR) drywall in

  called greenboard, after the color of its facing.

  high-humidity rooms or fire-resistant (type X or

  Its moisture-resistant core and waxed, water-

  type C) panels elsewhere to retard fires.

  repelling face are designed to resist moisture in

   Distances it must span. Because gypsum is

  bathrooms, behind kitchen sinks, and in laundry

  relatively brittle, the drywall must be thick

  rooms. In general, it is a good base for paint, plas-

  enough to span the distance between ceiling

  tic, or ceramic tiles affixed with adhesives and

  joists without sagging and between wall studs

  for installation behind fiberglass tub surrounds.

  without bowing (see “Drywall Types, Uses, and

  Although MR board can cover most bathroom

  Specifications” on p. 421).

  walls, it should not be used above tubs or in

  shower stalls. In particular, it’s not recommended

   Skill and strength of installers. The longer

  as a substrate for tile in those areas because sus-

  the sheets, the heavier and more unwieldy they

  tained wetting and occasional bumps will cause

  are to lug and lift, especially a concern if you’re

  the drywall to deteriorate, resulting in loose tiles,

  working alone or if ceilings are high. Fortunately, mold, and water migration to the framing

  USG Sheetrock UltraLight Panels will lighten the behind. As a substrate for tile around tubs and

  load somewhat, as they weigh one-third less than showers, cementitious backer board is far more

 

‹ Prev