We start by distributing jacks around the perimeter of the
house at intervals determined by the size of the structure.
There are no real rules of thumb; you just have to properly
estimate the weight of the building and place jacks
accordingly. Obviously, a two-story structure will have jacks
at tighter intervals than a single story. The corners usually
hold themselves up pretty well, providing the framing is sound;
most of the weight is in the middle of the building.
We usually place jacks alongside existing piers, if there
are any, since these are already supporting the structure and
provide a place for shims and blocking as the house goes
As we distribute jacks, we scope out the areas where
we’ll have to excavate. Since the jacks must bear
directly underneath the sills, we usually have to do a fair
amount of digging to accommodate both the jacks and the
cribbing they rest on.
We take care not to position jacks or cribbing over any
septic lines, gas pipes, water supplies, and so forth. When
we’re working on an unoccupied house, it’s an easy
matter to disconnect the plumbing and electrical before the job
starts. If the house is occupied, we provide temporary wiring
and plumbing to ensure uninterrupted service to the home while
we work. We’ve learned by experience to watch out for
live electrical wires lying in the dirt.
While setting out the jacks, we also look for rotted sills
and joists — places where we’ll have to scab on new
framing or install "needle beams" (Figure 2).
2. After decades of settling into the
ground, this house (top) is showing serious
moisture damage. New floor joists (middle) provide
a sound structure for jacking. The framing nailed
to the wall helps to pick up individual studs and
the corner post. Note the new elevation of the
porch rail relative to the concrete porch (bottom)
as the house comes up.
Needle beams are temporary wood beams set in from the edge
of the house underneath and perpendicular to the joists. The
needle beams stay in place for the duration of the job and are
used for jacking until the house is high enough so that the
sills can be replaced.