Soldier pile & lagging · Cantilever wall · Slope where there's room
Shoring an infill basement with the neighbor four feet away
A builder is putting up a four-storey building with a full basement on a double-width lot. On one side, a c. 1900 brick building stands four feet past the lot line. The front comes close to the sidewalk. The other side and the rear are open. The cheapest support of excavation is the wall you don't build, so the first question is which sides actually need one.
Illustrative example — composite site, not a completed ESC project.
- New building
- Four storeys over a full basement
- Lot
- 60 ft × 100 ft
- Cut
- About 11 ft below grade
- Tight side
- Brick neighbor 4 ft past the lot line
- Open sides
- An 18.5 ft side yard and a 30 ft rear yard
- Ground
- Fill over glacial till; water below the cut (typical; confirm by borings)
The situation
The basement takes the cut to about eleven feet. Laid back at one and a half to one, an eleven-foot cut needs about sixteen and a half feet of ground behind the basement wall, plus a couple of feet to work in at the bottom.
On the left, a c. 1900 three-storey brick building on shallow footings stands four feet past the line, and the new basement wall runs a foot and a half inside it. There is no room to slope that side, and nothing may go under the neighbor's lot without their written consent.
The front wall sits ten feet behind the sidewalk, which is not enough to lay the cut back without undermining the walk. The right side keeps an eighteen-and-a-half-foot side yard for a driveway, and the rear yard is thirty feet deep.
What drives the design
Room to slope
Every side gets the same test: is there about one and a half times the cut depth, plus working room, between the basement wall and anything that must not move? Where there is, that side is laid back and needs no wall.
The neighbor's footing
A shallow masonry footing four feet past the line puts its load right against the top of the cut. The wall on that side is designed for that load, and its piles are drilled, not driven.
Nothing under the neighbor's lot
Without a written agreement, no tieback may cross the line. At eleven feet, a drilled soldier pile wall can stand as a cantilever instead.
The sidewalk
The front of the cut is ten feet from the public walk. A wall there keeps the walk, and whatever runs under it, where it is.
Cantilever soldier pile and lagging on the neighbor's side and along the front; slope the side yard and the rear.
- HP12 soldier piles about seven feet apart in 24-inch drilled holes, toed about thirteen feet below subgrade in the till. Drilled, not driven, beside the masonry.
- Three-inch hardwood lagging placed in lifts as the excavator comes down, packed tight behind and left in place.
- Piles set just inside the lot line; nothing crosses it.
- Where a wall meets a slope, it runs on until the slope no longer reaches the line, so the corners don't ravel.
- Slopes on the right side and at the rear, at the angle the engineer of record and the competent person set for the soil actually found.
Illustrative example — composite site, not a completed ESC project.
- Note 1: Neighbor's masonry wall on a shallow footing, 4 ft past the lot line
- Note 2: HP12 soldier pile about 7 ft on center, in a 24 in drilled hole
- Note 3: 3 in hardwood lagging, placed in lifts as the excavator digs
- Note 4: Toe about 13 ft below subgrade in the till: a cantilever, no tiebacks
- Note 5: The neighbor's footing load bearing on the retained ground (1:1 line, for illustration)
Illustrative example — composite site, not a completed ESC project.
- Lot line
- Neighboring building
- New building footprint
- Soldier pile & lagging (piles drilled, not driven)
- Cut laid back — no support
- Gap that decides the design (measured on the drawing)
- Synthetic lot for illustration: 60 × 100 ft, with the new building against the left side.
- Wall along the left side and the front: about 63 LF and 59 LF, the ends tapering where they meet the slopes.
- Dashed lines are the tops of the laid-back cuts: an 11 ft cut at 1.5 to 1 needs about 18.5 ft with working room, which the right side yard just provides.
- Piles drilled, not driven, set just inside the lot line. Nothing under the neighbor's lot.
The order of work
- 01Week 0. Walk the lot with the foundation plan and mark which lengths get a wall and which are sloped.
- 02Days 1–5. Drill rig in from the street; drill and set the piles along the left side and the front.
- 03Weeks 2–3. Lag in lifts behind the excavator, with readings on the neighbor's wall at each lift.
- 04Then. The wall stays in place and the builder's foundation goes in against it.
Who carries what
ESC
the earth-support subcontractor
- Soldier piles, drilled and set
- Timber lagging as the excavator digs
- Wall runs extended where they meet the slopes
- Drill spoils to the builder's stockpile
General contractor
or the builder
- Foundation, waterproofing and backfill
- Dewatering, if water turns up
- Sidewalk and street permits
- Survey, layout and utility locates
Excavator
often the GC's own crew
- Bulk excavation in lifts, to the wall's sequence
- The laid-back slopes on the right side and rear
- Spoils off site
Engineer of record
designs and signs
- Wall design for the neighbor's load
- Slope angles for the soil found
- Movement limits for the neighbor
Others
- Neighbor: access for a condition survey
- Surveyor: monitoring points
- City: street occupancy for the rig
Budget range
Budget range · budget, not a quote
$104,000–$172,000
Computed from ESC’s published unit prices, book rev 1 issued September 14, 2026 and valid through December 13, 2026: the low quantities at the book’s low rates to the high quantities at its high rates, rounded out to the nearest $1,000. It is a budget for this composite site, not a quote for yours.
The basis, line by line
Drill rig to site and back, one visit
$23,750–49,250
1 LS × $23,750–49,250
One continuous visit for the pile drilling.
Book row MOB-DRILL-LOCAL
Cantilever soldier pile & lagging, per SF of exposed face
$80,625–122,500
1,250–1,400 SF × $64.50–87.50 per SF
Left side about 63 LF and front about 59 LF at up to 11 ft, with tapering ends where they meet the slopes: about 1,250 SF if the ground allows steeper slopes, 1,400 SF at 1.5 to 1.
Book row SOE-FACE-SPL †
Budget figure. Depends strongly on ground and configuration; confirm with a firm quote.
Not in this range
- Excavation, the laid-back slopes and spoils (excavator)
- Dewatering, if water turns up above subgrade (builder)
- Wall design (engineer of record, or the design-build option if the contract delegates it)
- Condition survey of the neighbor and monitoring (surveyor), unless added
- Sidewalk and street occupancy permits (builder)
Where a real job lands
The slope angle the ground allows sets the length of the tapering ends; the wall on the neighbor's side is needed either way.
Low end: open site, repetitive work, good ground, larger quantities. High end: tight access, obstructions, variable ground, small quantities. Book rates carry prevailing wage.
Every rate in the published bookWhat we’d need to firm it up
- Foundation plan with the basement wall's distance to each lot line
- Borings, or confirmation there are none
- Basement slab and footing levels, and existing grades
- The neighbor's footing depth, if a test pit is allowed
- Target excavation start
More on the techniques
Send us the address and drawings
We'll send back how we'd approach yours: the support we'd use, the order of work, and a budget range from our published prices. We work for builders, GCs and developers.
Or email plans to bids@earthsupportcorp.com