Make the lift-vs-retrofit foundation decision

What you're deciding

The foundation assessment from phase 1 gave you a recommendation. Now you decide. Three paths:

Option A — Retrofit in place

The existing foundation stays. The structural engineer designs reinforcement: new footings poured against existing, sister joists at the rim, retrofit anchor bolts, possibly new interior shear walls.

• Construction time: 4–8 weeks of foundation work, then normal addition framing.
• Cost adder: $25K–$75K vs. an addition on a sound foundation.
• Family impact: house is unlivable during foundation work; mostly livable during the rest if you're sheltering in place.
• Best for: sound poured-concrete foundations from ~1950 or later that need reinforcement but not replacement.

Option B — Lift and replace foundation

The house is jacked up 4–8 ft on cribbing, the existing foundation is demolished, a new foundation is poured, the house is dropped back.

• Construction time: 8–14 weeks of foundation/lift work, then normal addition framing.
• Cost adder: $80K–$150K vs. a sound-foundation addition.
• Family impact: house is unusable for the entire foundation phase.
• Best for: brick-and-mortar, rubble, or unreinforced concrete foundations; pre-1930 bungalows on poor soil.

Option C — Lift + new ground floor (or basement)

The house is lifted and a fully new ground floor is built underneath; the original house becomes the second floor; the addition becomes the third. End result is a three-story house with a brand-new ground floor.

• Construction time: 6–10 months total.
• Cost adder: $200K–$400K vs. a normal addition. Total project lands at $700K–$1M+.
• Family impact: out of the house for the duration. No question.
• Best for: owners who want to materially expand square footage, fix every system, and end up with a near-new house. Often makes more financial sense than tearing down and rebuilding.

How to choose

1. Foundation condition. If the engineer flagged the foundation as "compromised," Option A is off the table.
2. What the family wants. Option A finishes faster; Option B/C produce a fundamentally different house.
3. Budget. Option C nearly doubles the project budget but also nearly doubles the finished square footage.
4. What the lot can support. Some lots (slopes, environmental zones) make Option C impractical regardless of budget.

Document the decision

Write a one-page memo signed by you and the designer that states:

• The chosen path (A / B / C).
• The structural strategy (engineer's summary).
• The rough cost band with the path adder included.
• Move-out window expectation.
• Constraints driving the choice (foundation condition, budget cap, family timing).

This memo gets attached to the design contract and shapes every downstream document.