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.
Renovation 4th Edition Page 58