What are some ways to fix a sinking foundation of an old house?

A sinking foundation on an old house gets fixed by carrying the weight back down to solid ground and locking the structure in place. The common repairs are helical or push piers driven below the soft soil ($2,700 per pier for the first three, then 2, 200perpierafterthat), newlallycolumnsandfloorsupportundersaggingbeams(1,300 to 2, 500), sillandbeamreplacementwherethewoodhasrotted(7,000 to $40,000), and an auxiliary (sister) wall when a foundation wall is bowing (about $1,350 per linear foot). The right one depends on what is actually moving, and that is why we look first.

Why an old foundation sinks

In an older New England house the dirt around the foundation is disturbed backfill. That is the loose soil that got put back after the house went in. It drains slowly and holds water. Over decades it settles, and the footing settles with it. Add NH frost heave pushing on the walls every winter and you get cracks, sticking doors, and floors that pitch toward one corner.

Sometimes it is not the footing at all. A rotted sill or a tired carrying beam will let the middle of the house drop while the foundation stays put. We figure out which one you have before anyone quotes a fix.

The repairs, and when each one fits

Piers carry the weight to solid ground. When the footing has settled into soft soil, helical or push piers go in below that soft layer and transfer the load to firm soil or bedrock. We can often lift the structure back toward level as we go. We self-perform this work in-house, and the piers carry a 25-year engineered warranty. Helical pier work runs $2,700 per pier for the first three, then $2,200 per pier after that.

Lally columns and floor support catch a sagging middle. If your beam is bowing or a post has rusted out in the basement, new steel posts and proper footings stop the floor above from dropping further. Floor support runs $1,300 to $2,500 and carries a 10-year warranty.

Sill and beam replacement fixes rotted wood. Old houses sit on a wood sill on top of the foundation. Years of moisture rot it, and the framing loses its seat. We jack, replace the bad wood, and set it back down. That work runs $7,000 to $40,000.

An auxiliary wall straightens a bowing foundation. When a wall is pushing in from frost and soil pressure but the footing is sound, we build a sister wall against it to take the load. That runs about $1,350 per linear foot, with a 25-year warranty.

For lighter wall movement you may not need a wall at all. Carbon-fiber straps (850each, 25 − yearwarranty)orapowerbrace(1,300 per brace) can hold a wall that is bowing but not failing. If your only issue is a hairline crack letting water in, that is crack injection ($1,000 to $3,000). You do not need piers for a crack. We will tell you that on the inspection.

A note on the bigger jobs. A full foundation-wall rebuild, steel I-beams, or wall anchors are real fixes, but we price those after we see it. There is no way to quote a wall rebuild from a phone call. And if you are thinking about a brand-new foundation under a new addition, that is new construction. We do repair, not new builds.

What drives the cost

How far the house has settled, how deep the soft soil runs before piers hit something solid, how many piers or posts the engineering calls for, and how much rotted wood comes out with the sill. A single sagging beam is a different day than a whole side of the house on piers. Every job starts with a free inspection and a free estimate, and we get you the quote within 24 hours. If the number is big, financing runs through Hearth, subject to approval, and we make nothing on it.

You can read more on our structural and foundation repair work, the helical piers page, sill replacement, and supplemental support. What we promise on every one is on the 603 guarantee.

For how foundation settlement and structural movement get classified, the DOE Building America program (basc.pnnl.gov) covers foundation building science, and the Insurance Information Institute (iii.org) explains what a standard homeowners policy does and does not cover for earth movement [verify].

Got a floor that pitches or a wall that is leaning? Call us at 603-610-1770 or book your free inspection and we will tell you what is actually moving and what it takes to stop it.

Related questions

Can a sinking foundation be lifted back to level? Often, yes. With helical or push piers we can lift the structure as we drive them, though how far depends on the soil and the framing. We will give you a realistic target on the inspection, not a promise we cannot keep.

How do I know if it is the foundation or just a rotted sill? Sticking doors and a sloping floor can come from either one. A dropped middle with the foundation still plumb usually points to a sill or carrying beam. We check both before we quote.

Is a foundation crack a structural problem? Not always. A hairline crack that only leaks water is crack injection work ($1,000 to $3,000). A wall that is bowing inward is structural and needs straps, a brace, or an auxiliary wall. The inspection sorts which one you have.

Do you replace whole foundation walls? Yes, we do that work, but we price it after we see it. A wall rebuild depends too much on what we find behind it to quote sight unseen.