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Renovation 4th Edition

Page 58

by Michael Litchfield


  assembly of 1⁄4-in. steel

  joist ends will hang from the 2x12s

  plate. Those posts will

  bolted to both sides of the I-beam.

  transfer loads down to the

  Peeking up from under the I-beam is

  perimeter foundation.

  cribbing on which the shoring sole

  plate rests.

  One end almost in place. Raising a beam of this length

  and weight should be attempted only by professionals

  with specialized equipment. A W12x26 I-beam weighs

  26 lb./ft., so its total weight is 572 lb. As the worker at

  right raises the end of the I-beam, his partner, on the

  other side of the shoring, uses a ratcheted come-along

  to pull the beam end toward the opening in the wall.

  Foundations and Concrete

  245

  than enough room for jacks and posts, so place

  Replacing a Shal ow

  jacking posts as close as possible to the perma-

  nent post’s location. Raise the girder approxi-

  Foundation

  mately 1⁄8 in. higher than its final position to

  If you decide to replace a shallow foundation,

  facilitate insertion of the new posts.

  begin by checking local building codes for foun-

  dation specs appropriate for your area. Before

  steel Beams

  beginning foundation work, be sure to review

  this chapter’s earlier sections on shoring and

  If there’s limited headroom or clearance under

  jacking. Then survey the underside of the house

  the house, steel beams provide more strength per and the area around the foundation for pipes,

  equivalent depth than wood beams. If you’re

  ducts, and other potential obstructions. If you

  going to use steel beams, hire an engineer to size

  can reposition jacks or move shoring slightly to

  them and a specialist to install them: Steel

  avoid crushing or disconnecting drains, water

  I-beams are expensive and heavy, and they can be pipes, and the like, do so.

  problematic to attach to wood framing, without

  Remember, jacking timbers and shoring are

  special equipment to drill holes, spot-weld con-

  temporary supports. Complete the job and lower

  nectors, and so on. For commonly available sizes the house onto foundation elements as soon as

  and some sense of the weights involved, see

  possible. Work within your means, skills, and

  “Steel I-Beams” on p. 65.

  schedule: If you can’t afford a house mover to

  raise the house and replace the whole founda-

  tion, have him do it one wall at a time.

  replaCing mudsills

  Mudsills are almost always replaced when foun-

  dations are. With the framing exposed, it’s easy to

  zzzzzz girder (Beam) supports

  install new pressure-treated or redwood mudsills

  that resist rot and insects. At the same time,

  replace rotted or insect-infested pony-wall studs.

  (If just a few studs are rotted, cut away the rot

  and nail a pressure-treated sister stud to each. If

  Often

  Plywood gusset

  the bottom 1 in. to 2 in. of many studs has rotted,

  toe-nailed

  (on both sides)

  you might also install a thicker mudsill to make

  to post

  up for the amount you cut off stud bottoms.) If

  the siding is in good shape, remove just enough

  to expose the mudsills and rotten studs; the sid-

  BUILT-UP BEAM

  SAWN TIMBER BEAMS

  ing holds the pony-wall studs in place and keeps

  them from “chattering” while you cut them.

  You’ll also need to punch through the siding to

  install temporary needle beams, discussed earlier

  in this chapter.

  Once you’ve jacked up and shored the house

  framing, lay out the height of the new sill by

  snapping chalklines across the pony-wall studs.

  Lally column

  Use a laser level to indicate where the chalk

  Metal

  cap

  marks should go or, if the old foundation is level,

  post cap

  Lally column

  measure up from it. Although the line should be

  (metal)

  as level as possible, small variations will be

  accommodated when the concrete is poured up

  to the bottom of the mudsill.

  LVL BEAM

  PSL BEAM

  With the siding removed, use a square to

  (engineered lumber)

  (engineered lumber)

  extend the cutoff marks across the face of the

  studs; a square cut optimizes load bearing from

  When it’s necessary to construct a girder from several pieces of lumber,

  the stud onto the mudsill. Use a reciprocating

  support each girder joint by placing a post or column beneath it.

  saw to make the cuts. If the first stud chatters as

  Many building codes also require metal connectors or plywood gussets

  you attempt to cut through it, tack furring strips

  at such joints to join posts to beams.

  to all the studs, just above the cut-line to bolster

  successive studs. Then remove the old mudsill

  246 Chapter 10

  and rotted stud sections. Chances are the old

  mudsill will not be bolted to the foundation.

  leveling a House

  The replacement sill should be foundation-

  grade heart redwood, pressure-treated Douglas

  in theory, you can level a house using individual hydraulic jacks. and if the house

  fir, or yellow pine to resist insects and moisture.

  has only one or two low spots, you may succeed. However, the framing of a house

  It should be end-nailed upward into the solid

  will usually have sagged and settled, increasing the likelihood that jacking one area

  remnants of each stud, using two 16d galvanized

  will raise an adjacent area too much. Heavily loaded points in multistory houses may

  common nails. Use a pneumatic nailer to nail up

  resist being raised at all, and when they finally do move, it’s often sudden, loud,

  the new mudsill; it does the job quickly. However,

  and frightening.

  predrill anchor bolt holes into the new mudsills

  before nailing them to stud ends. Anchor bolts

  leveling a house is far more likely to succeed if done by a house mover with a

  will secure house framing to the foundation after

  unified hydraulic jacking system, in which jacks are interconnected, via hoses, to a

  you pour it.

  central console that monitors the load on each jack. instead of 12 workers trying to

  turn 12 jacks at exactly the same time, a single operator at the console can ensure

  removing old Foundations

  that the jacks rise at the same—or variable—rates to the desired height.

  the desired height is determined beforehand by the foundation contractor, house

  To tear out an old foundation, you’ve got several

  options. All require safety glasses, hearing protec-

  mover, structural engineer, and—on occasion—the architect. most often, the house

  tion, heavy gloves, a mask, patience, and a strong

  mover works from a master reference point outside, against which house corners are

  back. Before a
cquiring heavy and expensive

  read to determine whether they need raising or lowering. (For example, corner 1

  equipment, try to break out a section of the old

  might be listed as +3⁄4 in., corner 3 as –1⁄2 in., and so on.) once the corners are lev-

  foundation using a 9-lb. sledgehammer and a

  eled, the framing in the middle of the house is fine-tuned.

  6-ft. pointed steel bar. Old concrete without rebar

  even when professionals level a structure, there’s invariably damage to the finish

  is often cracked and soft. Once you’ve removed a

  surfaces inside, such as cracked plaster or popped drywall seams, door latches that

  small section, the rest may come out easily.

  no longer meet strike plates, trim that’s askew, and windows and doors that bind as

  If the concrete is too thick and hard, rent a

  they’re opened and closed. Consider all this before you jack. raising only the most

  towable air compressor and jackhammer. A 90-lb.

  out-of-level areas may be more cost-effective than leveling floors perfectly.

  jackhammer will break almost anything, but it’s a

  moreover, gently sloping floors may add character to an older house.

  beast to maneuver; a 60-lb. hammer is light

  enough to lift onto a foundation wall and almost

  always strong enough to break a wall apart. A

  60-lb. electric jackhammer is less powerful than a

  compressor-driven one, but it may have enough

  muscle to get the job done.

  Or you can rent a gas-powered saw with a

  10-in. concrete-cutting blade that cuts 4 in. to

  5 in. deep, letting you cut the concrete into

  This old mudsill rotted out because the foundation was

  Once the needle beams are in place to pick up the loads

  A 60-lb. jackhammer is powerful

  too close to the ground. After using a laser level to

  that were previously carried by the pony wall, you can cut

  enough to bust concrete yet light

  transfer the height of the new foundation, this builder

  the pony-wall studs and remove the sill.

  enough to lift onto the foundation.

  snapped a chalkline across the pony-wall studs to indicate

  Jackhammering is bone-rattling

  the height of the new sill.

  work, so have workers take turns at it.

  Foundations and Concrete

  247

  manageable chunks. A third option is roto-

  ConCrete FormWork

  hammering a line of 5⁄8-in. holes across the foun-

  Correctly positioning 11⁄2-in.-thick formboards

  dation and then splitting along that line with a

  can be tricky, and there are myriad ways to do so.

  large mason’s chisel and a hand sledge.

  Here’s a relatively foolproof method in which you

  Should you encounter rebar, you’ll either need erect the inner (house side) form walls first, by

  an acetylene torch to cut through it or a metal

  nailing them to 2x4 form-hangers nailed to joists.

  abrasive wheel in a circular saw or grinder. Rebar This method also enables easy access for tying

  cutting is monstrously hard work.

  rebar, reattaching sills, and the like.

  inner form walls. If floor joists run perpendicu-

  lar to the foundation wall, start by nailing 2x4

  form-hangers into the joists at both ends of the

  foundation wall section being replaced. The 2x4s

  should extend down into the foundation trench,

  Blocking

  zzzzzz Concrete Forms for a shallow Foundation

  Joist

  stopping 1 in. to 2 in. above the tops of footing

  Rim joist

  forms, if any. Position each 2x4 so its edge is

  exactly 91⁄2 in. from the outside face of the foun-

  Top plate

  dation (8-in.-thick concrete plus 11⁄2-in.-thick

  of pony wall

  formboard). Nail the bottom formboard to the

  2x4s, then add 2x4 form-hangers between the

  first two. Spacing 2x4 form-hangers every 32 in.,

  Plumbed

  use two 16d nails to nail them to each joist. Then

  2x4 form-hangers

  stack additional formboards atop the first until

  the top board is slightly above the bottom of the

  mudsill. As shown in “Concrete Forms for a

  Sheathing

  Shallow Foundation” at left, run diagonal 2x4

  11/2-in.-thick

  braces from joists to the 2x4 form-hangers to

  2x4 brace

  spacer

  stiffen the inner form wall, thereby keeping it

  plumb and in place (see also the photos on the

  3-in. clearance for

  Brace

  facing page).

  concrete pump hose

  Anchor bolt

  If the joists run parallel to the foundation,

  first add blocking between the rim joist and the

  Termite

  Mudsill

  first joist back, across the top of the pony wall.

  shield

  Stake

  Nail the 2x4 form supports to the blocking, much

  as just described for perpendicular joists. Once

  11/2-in.

  form boards

  the inside forms are complete, you can cut, bend,

  Minimum 8 in.

  and assemble the rebar; attach the mudsill to the

  Rebar

  above grade

  pony-wall studs; and insert anchor bolts before

  building the outside form walls. Even if local

  building codes don’t require steel-reinforced

  Wedges

  positioning

  Form ties

  FounDaTion FaceS

  traditionally, the outside face of a foundation

  wall is flush to the edge of the house framing,

  allowing sheathing to overhang the foundation

  1 in. or so, covering the joint between foundation

  Perforated

  and framing. However, contractors who install a

  steel stake

  lot of stucco argue that a foundation face flush

  Dobie blocks keeping

  to the outer face of the sheathing better pro-

  rebar 3 in. above soil

  tects the sheathing edge and creates a stucco

  In this example, foundation walls are flush to the sheathing,

  edge that’s less bulky—that is, one that sticks

  and the trench walls serve as forms for the footings. Details

  out less beyond the foundation wall.

  will vary slightly, depending on the direction of joist (as

  described in the text) and on other framing particulars.

  248 Chapter 10

  foundations, adding steel is money well spent

  (see “Adding Steel” on pp. 250–251).

  outer form walls. If your foundation is shallow

  and the sides of the trenches are cleanly cut, you

  may not need formboards for footings. But if

  your footings will have formboards, install them

  before building the foundation’s outer form walls.

  If there are no footing formboards, drive 4-ft.-

  long perforated steel stakes into the footing area

  to secure the bottom formboards for the outer

  form walls. Plumb and space these stakes out

  11⁄2 in. from the outside face of the foundation to

  allow for the thickness of the formboards. Use

  two stakes per formboard to get started. Use 8d

  dupl
ex nails to attach formboards to the steel

  stakes. Install this first outer formboard a little

  higher than the inner formboard initially, then

  hammer the stakes down to achieve level. You

  may need several tries to drive stakes that are

  plumb and accurately positioned because the

  points of the stakes often are deflected by rocks.

  Use a magnetic level to plumb the stakes.

  Once the steel stakes are correctly positioned

  and the bottom formboards are nailed to them,

  add 2x4 form-hangers so you can hang additional

  formboards above. But first, nail spacers to the

  pony-wall studs to compensate for the thickness

  of the 11⁄2-in.-thick formboards. If the pony-wall

  studs are sheathed, nail 11⁄2-in.-thick spacer

  Use prelooped wire ties to splice lengths of rebar, overlapping rebar sections at

  boards to the studs so the back face of the form-

  least 12 in. Note the cleanly cut sides of this trench, which will serve as forms

  board lines up with the exterior sheathing. If the

  for the poured foundation footings. An electric demolition hammer with a

  studs aren’t presently sheathed, nail up 2-in.-

  shovel bit was used to cut this dense soil.

  thick spacers to accommodate the thickness of

  the formboards and the sheathing to come. If the

  outer face of the foundation wall aligns to the

  face of the sheathing, you can easily cover that

  often-troublesome joint with siding.

  As you install each formboard atop the pre-

  ceding one, set the form ties that tie together

  inner and outer formboards. Form ties are

  designed to space the formboards exactly the

  right distance apart; they are available in 6-in.,

  8-in., 10-in., and 12-in. lengths. Use wire to tie

  the form ties to each vertical rebar, typically

  spaced 32 in. on center. At the ends of each

  form tie, insert metal wedges into the slots to

  keep forms from spreading when filled with

  concrete. The top formboard should overlap

  the mudsill slightly.

  The outer formboards are braced by the

  plumbed 2x4 form-hangers, which are in turn

  supported by diagonal braces running down to

  perforated steel stakes or to 2x4 stakes driven

  To use this rebar cutter-bender,

  into the ground. Under the house, diagonal brac-

  you feed rebar parallel with the

  base arm for bending, as shown,

  es run from the inner form-hangers to the joists.

  Ready for concrete—the form walls are up and braced.

 

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