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Rubble, fieldstone & early block
Stone Foundation Repair in Schenectady, NY
A fieldstone cellar doesn't leak the way a poured wall leaks. There's no single crack to find and seal — the whole wall weeps through joints where the lime mortar has washed out over a century. That changes the repair completely, and most of what's marketed as basement waterproofing doesn't apply.
(518) 617-4320If your house predates 1940, this is probably the page you want.
Why stone walls behave differently
A poured concrete wall is a monolithic slab with defined weaknesses: it cracks, and you seal the crack. A rubble foundation is several hundred individual stones held in position by mortar, resting on soil or on a rough stone footing. Water doesn't need a defect to get through it. Every mortar joint is a potential path, and after a hundred and thirty New York winters a good number of them are open.
Three practical consequences follow, and they govern everything on this page:
- Injection doesn't work. Crack injection assumes a solid wall with a discrete crack. Resin pumped into a rubble wall migrates into voids and behind stones and accomplishes very little.
- Sealing the inside face is counterproductive. A rubble wall carries moisture through its full thickness. Trap it behind an impermeable coating and it moves to the next available exit, usually taking mortar with it as it goes.
- The wall is load-bearing in a way that punishes carelessness. Nothing is bonded. Excavating hard against the base, or raking joints too deep too fast, can pull stones out of the bottom course. Sequence and restraint matter more than equipment.
Repointing, done properly
Repointing is the core repair on these walls. Failed mortar is raked out to sound material, the joint is cleaned and dampened, and fresh mortar is packed in and tooled. Done well it lasts decades. Done badly it accelerates the wall's decay, which is why the material choice below is not a technicality.
- Assessment. Which joints are actually failing, how deep the loss goes, and whether any stones have shifted. On a full cellar this takes an hour with a light and a probe.
- Raking out. Loose and eroded mortar is removed to roughly two to two and a half times the joint width. Hand tools around anything fragile.
- Cleaning. Dust and debris blown or brushed out. Mortar won't bond to a dirty joint.
- Packing. Fresh mortar worked in tightly in layers rather than one deep pass, so it cures properly and doesn't slump.
- Tooling and curing. Finished to match the original profile, then kept damp for several days. Rushing the cure is the most common way a repoint fails early.
Not sure whether your joints need repointing or your wall needs drainage? Usually it's both, and the order matters. Call (518) 617-4320.
The mortar question — and it matters
This is the single most consequential decision in the job, and it's where inexperienced contractors do real damage to old houses.
The principle: mortar must be softer than the stone it joins. Mortar is the sacrificial element in a masonry wall — it's meant to take up movement and to erode over decades so the stone doesn't.
Nineteenth-century walls were laid in soft, permeable lime mortar. Repoint one in hard modern Portland cement and you invert the relationship: the joints become stronger and less permeable than the stone. Moisture that used to pass through the mortar is redirected into the stone itself, where in a freeze-thaw climate like ours it spalls the faces. The wall then fails at the stone rather than the joint, which is both worse and effectively irreversible.
On pre-1900 rubble the correct answer is usually a lime-based or lime-rich mortar matched to the original. It's more expensive, it cures more slowly, and it's the difference between a repair and slow damage. Ask any contractor bidding your stone cellar what mix they intend to use. If the answer is a bag of standard mortar mix and no further thought, keep looking — and that question alone will tell you more about who you're dealing with than any brochure.
Drainage does the heavy lifting
Repointing restores the wall. It does not stop water arriving at it. On a rubble foundation with groundwater against the outside, fresh mortar in the joints is a delaying action unless the water is dealt with too.
In practice the durable combination is: get surface water away from the wall outside (gutters, downspouts, grade), intercept groundwater at the footing with an interior perimeter drain, and repoint the wall while the floor is open and access is good. Doing those as one job rather than three visits saves real money.
Where the lot allows it, exterior excavation is the most complete answer, because it lets the wall be repointed from outside, sealed, and backfilled against a new footing drain. On the tighter lots common in the Stockade and Central Park it's frequently impossible, which is why interior drainage is the workhorse here.
What not to do to an old stone wall
- Don't sandblast it. It destroys the stone faces and any historic surface. Low-pressure water and hand tools.
- Don't parge over failing mortar. A cement coat over open joints hides the problem while it continues underneath, and it comes off in sheets a few winters later.
- Don't spray foam directly onto the interior face. Common advice, poor idea on rubble: it traps moisture in the wall and hides deterioration from view.
- Don't excavate the full length hard against the base in one go. Rubble walls rely on lateral support. Work in sections.
- Don't let anyone tell you it needs replacing before a second opinion. Full rebuild is occasionally right and frequently oversold. It's a five-figure recommendation; treat it like one.
If your house is in a historic district
The Stockade is a locally designated historic district and listed on the National Register, and the GE Realty Plot is National Register listed as well. Exterior work visible from the street — excavation, grading changes, anything touching visible masonry — can trigger local review. Interior work generally doesn't. Check with the City before committing to an exterior scope, because approval timelines can affect scheduling, and a contractor who has never heard of the Historic District Commission is a contractor who hasn't worked much in this city.
What it costs
Depends on joint condition, access, and mortar spec.
Isolated failed areas rather than a whole wall.
Four walls of a typical city lot, lime-based mortar.
Protective and cosmetic. Not a waterproofing layer.
Above poured-wall rates for the reasons on the cost page.
Where stone has been lost or a section has failed.
Most Schenectady stone jobs are a combination: drainage plus partial repointing, landing somewhere between $6,000 and $15,000. See the full cost page for how that compares with everything else.
Stone foundation questions
Can a stone foundation ever be genuinely dry?
The floor can be dry, reliably. The wall will always carry some moisture — that's how the assembly works, and a wall that carries a little moisture and dries out is behaving correctly. The achievable goal is a dry floor, humidity in a sensible range, and mortar that isn't washing away. Anyone promising a rubble wall dry to the touch year-round is describing an exterior excavation, a full seal, and a considerably larger invoice.
There's sand on the floor along the wall. What is that?
Almost certainly your mortar. Lime mortar erodes to sand as water moves through it, and a steady accumulation along the base of a wall means active joint loss. It's the clearest early signal that a wall needs repointing, and worth acting on before joints open enough for stones to shift.
Should I insulate a stone basement?
Carefully, if at all. Insulating the interior face of a rubble wall makes it colder and wetter within the assembly, and impermeable insulation traps moisture where you can't see it. If the space is being heated, a ventilated approach or exterior insulation is far safer. This is a genuine building-science question for old masonry and worth getting specific advice on rather than following general remodeling guidance.
Is a bulge in a stone wall as serious as in a block wall?
Take it at least as seriously. Rubble walls fail by stones displacing rather than by a wall cracking, and once movement starts there's no reinforcement to arrest it. Measure it with a string line, and if there's a measurable bulge or any stone sitting proud of its neighbors, get it looked at now. More on structural movement.
Do you work on houses in the Stockade?
Yes, and they need contractors who understand that the wall is older than the concept of a footing drain. Access is the recurring constraint — narrow lots, no machine access, and review requirements on visible exterior work — which means interior solutions carry more of the load there than they would in Niskayuna or Rotterdam.