Extending Footings in Boston with Foundation Underpinning
Older homes and additions sometimes rest on footings that were never sized for the load above them. Boston Concrete extends those footings deeper or wider in a controlled sequence of numbered bays, keeping the building supported throughout the work. Each project is engineered, and your free assessment includes a written timeline.
Why Underpinning Solves Footing Issues That Repair Cannot
A cracked foundation wall can often be fixed by reinforcing the wall itself. But when the root cause is a footing that is too shallow, too narrow, or sitting on poor bearing soil, wall repair alone will not stop the movement. The footing must be extended or rebuilt to carry the load properly.
Underpinning also enables basement deepening, where lowering the floor below the existing footing requires the footing to be extended downward first. And when an addition loads an existing footing beyond its original design capacity, underpinning brings that footing to the new engineered depth or width.
The method is always the same: the existing footing is supported in numbered bays while a deeper or wider section is poured beneath or beside it. Load transfers cleanly, and the building never sits on unsupported soil. This integrates with our foundation installation work and pairs with basement renovation projects. When cracking is confined to the wall above the footing, crack injection may be the answer instead.
Recent work
The underpinning sequence
Step-by-Step: How Foundation Underpinning Gets Done
Structural engineer designs the sequence
The engineer specifies footing depth, width, materials, and the exact order of bay excavation and pouring so the building remains supported at every stage of the work.
Excavate the first bay only
Following the engineered sequence, the first bay is dug out to the new footing depth. Adjacent bays remain untouched so the building's weight stays on supported soil.
Form, reinforce, and pour the new footing
The deeper or wider footing section is formed, rebar is placed, and concrete is poured. The new footing is pinned to the existing footing above with the engineered connection detail.
Cure and move to the next bay
Once the concrete has cured to full strength, the next bay in the sequence is excavated and poured. This cycle repeats until the entire footing has been extended to the new depth or width.
Why bays matter
The Bay Sequence Is What Makes Safe Underpinning Possible
Underpinning the entire footing at once would collapse the building. Bays solve this by keeping most of the footing bearing load while only a small section is excavated and poured. The engineered sequence ensures the building is always supported on solid ground.
Skipping ahead, excavating two adjacent bays simultaneously, or pouring without proper curing time risks settlement during the work. We follow the sequence exactly as engineered, and we apply foundation waterproofing to newly exposed walls before backfill to prevent water intrusion. The written estimate includes the full bay schedule so you can plan around the work timeline.
Bay sequence, basement deepening, additions and when underpinning is the right tool.
If settlement keeps happening after repair attempts, if the cracking is at the footing rather than just in the wall, if the soil bearing capacity has changed, or if you are adding load or lowering the basement floor. The assessment will tell us which is right.
Yes. The bay sequence means only a small section of footing is unsupported at any time, and the rest is bearing the load. Most homeowners stay in their homes through underpinning; we let you know if your situation is the exception.
Yes, that is one of the main uses. Lowering a basement floor below the existing footing requires the footing to be extended downward in bays; once underpinned, the floor can be excavated to the new depth and a new slab poured.
Only when the new load on the existing footing exceeds what the footing was sized for. The structural engineer for the addition determines that; we underpin the existing footing to the engineered detail when required.
Several weeks for a typical residential underpinning, because each bay has to be excavated, formed, poured and cured before the next bay starts. The full schedule is in the written quote so you can plan around it.
Homeowner reviews
What Boston Homeowners Say About Their Underpinning Projects
We added a second storey and the engineer said underpin. Boston Concrete did the sequence by the book, addition went on top, no settlement since. Done right.
T. J.
Boston
★★★★★
Settlement that two other contractors had tried to fix as wall cracks was actually a footing problem. Underpinning solved it. Cracks haven't moved since.
N. K.
Cambridge
★★★★★
Basement deepening project, underpinning first, then the new lower slab. Headroom we wanted, structure stronger than before. Worth every cent.
U. O.
Brookline
★★★★★
Engineered, sequenced, communicated every step. Lived in the house through the whole project, never felt unsafe. Underpinning is a craft and these guys know it.
G. H.
Quincy
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Practical reading on planning, finishes and caring for concrete in Boston.
Describe what is happening with the foundation, whether it is settlement, an addition, or basement deepening, and we will assess it free and provide a written quote with the full bay schedule.
