Underpinning · Tight side yards · Hand work
Digging out a triple-decker basement with three- and five-foot side yards
A developer is turning the basement of a c. 1905 triple-decker into living space. That means taking the floor down about two and a half feet, which puts new bearing well below the old fieldstone footings — and below the footings of the houses next door, six and nine feet away.
Illustrative example — composite site, not a completed ESC project.
- Building
- c. 1905 wood-frame triple-decker, three storeys over a basement
- Lot
- 32 ft × 90 ft
- Side yards
- 3 ft on one side, 5 ft on the other
- Neighbors
- Similar houses, 6 ft and 9 ft from our walls
- Foundation
- Fieldstone walls, footings about 1.5 ft below the floor
- Ground
- Glacial till with sand seams (typical; confirm by test pit)
- Goal
- Basement floor down about 2.5 ft
The situation
The house is a detached three-family from around 1905, with fieldstone foundation walls and a basement a little under seven feet high. It stands three feet off one side line and five feet off the other, with houses much like it beyond.
Taking the floor down about two and a half feet for living space puts the new bearing roughly three and a half feet below the old footings. The neighbors' footings are probably no deeper than ours were, so on the tight side the ground under their footing sits close to the ground each pit opens.
The side yards are too narrow for any machine. Everything is dug by hand from inside the basement and carried out through the bulkhead.
What drives the design
The neighbor on the tight side
Six feet away, the next house's footing sits close to the zone a pit this deep can loosen. Short bays, quick pours and readings on that wall keep its foundation still.
A wood frame on a stone wall
Fieldstone foundations can shed stones when the ground beside them is removed. Each pit is shored, and the stone above it is checked and grouted where it is loose, before the next pass.
No room for a machine
Three to five feet between the house and the line rules out a rig, an excavator or a conveyor down the side. Hand work from inside sets the crew size and the pace.
The whole perimeter, in order
Lowering the full basement means underpinning every wall. The sequence runs around the house so that no wall loses support over more than one bay at a time.
Hand-dug pit-and-pour underpinning around the full perimeter, in three passes, with the tight side watched from the first pit.
- Four-foot bays under the stone footing, taken about three and a half feet down to new bearing in the till.
- Three passes around the house, one bay in three per pass, so each wall always stands on at least two-thirds of its length.
- Each bay dug, shored, cast in concrete and dry-packed tight to the stone before the next bay in its pass opens.
- Loose stone over an open bay grouted before the pour, so nothing drops into the pit.
- Survey points on the tight-side neighbor's wall, read before each pour.
Illustrative example — composite site, not a completed ESC project.
- Note 1: Fieldstone side wall carrying the wood frame above
- Note 2: Underpinning: concrete cast in a four-foot bay, about 3.5 ft below the old footing
- Note 3: Dry-pack rammed tight to the underside of the stone
- Note 4: New floor about 2.5 ft down, on the new slab and stone
- Note 5: The neighbor's footing, 6 ft away
- Note 6: The neighbor's footing load spreading down (1:1 line, for illustration)
Illustrative example — composite site, not a completed ESC project.
- Ground not yet dug
- Open bay, shored
- Cast, with the dry-pack joint (gold) under the old footing
- Numbers under the bays give each bay’s pass.
Illustrative example — composite site, not a completed ESC project.
- Lot line
- Neighboring building
- Building worked on
- Yard or open ground
- Underpinning in sequenced bays
- Gap that decides the design (measured on the drawing)
- Synthetic lot for illustration: 32 × 90 ft, a detached house with side yards of 3 and 5 ft.
- Underpinning around the whole perimeter: about 140 LF, or roughly 35 bays of 4 ft.
- On the 3 ft side the neighbor's wall is 6 ft from ours: survey points on it before the first pit.
- All by hand from inside the basement; spoils out through the bulkhead.
The order of work
- 01Day 0. A test pit at each side wall: footing depth and width, what the stone sits on, and any water.
- 02Week 1. Condition surveys of both neighbors, and survey points on the tight side.
- 03Weeks 1–7. Three passes around the perimeter; each bay dug, shored, cast and dry-packed before the next in its pass.
- 04Then. Level bearing all around the basement for the developer's slab.
Who carries what
ESC
the earth-support subcontractor
- Test pits at each side wall
- Underpinning bays: dig, shore, cast, dry-pack
- Readings on the tight-side neighbor during the pits
- Pit spoils out to the builder's container
General contractor
or the builder
- Container, hauling and site protection
- New slab, drainage and waterproofing
- New column footings inside the basement
- Neighbor access agreements
Excavator
often the GC's own crew
- The floor between the walls: hand work, or a compact machine lowered in through the bulkhead
Engineer of record
designs and signs
- Underpinning details and bay sequence
- New floor and bearing levels
- Checks on the stone walls above the new concrete
Others
- Surveyor: condition surveys and survey points
- Neighbors: access for the surveys
- City: building permit
Budget range
Budget range · budget, not a quote
$120,000–$320,000
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 $5,000. It is a budget for this composite site, not a quote for yours.
The basis, line by line
Underpinning bays around the perimeter
$124,250–316,050
35–49 CY × $3,550–6,450 per CY
35 bays (about 140 LF at 4 ft) at 1.0 to 1.4 CY each; the width of the stone footing decides which.
Book row UP-PIT-POUR †
Budget figure. Depends strongly on ground and configuration; confirm with a firm quote.
Not in this range
- Digging the floor between the walls, spoils and hauling (builder)
- New slab, drainage, waterproofing and column footings (builder)
- Underpinning design and bay sequence (engineer of record)
- Condition surveys and readings (surveyor), unless added
- Repointing or grouting the stone walls above the new concrete (mason), unless added
Where a real job lands
No rig on this one: the book's per-yard rate already covers the hand digging, pit shoring and dry-pack. Footing width and the true number of bays decide where in the range a real job lands.
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
- Structural drawings: the new floor level and the underpinning details
- A test pit on each side wall: footing depth, width and what it sits on
- The neighbors' foundation depths, if anyone knows them
- Bulkhead or window access for spoils and a concrete line
- Target start, and when the slab follows
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