How thick should a stone foundation be for a building without a footing?

For a stone foundation built without a separate footing, the wall needs to be wide enough at the base to spread the load over the soil, and old New England fieldstone walls were often laid roughly 16 to 24 inches thick, sometimes wider at the bottom than the top. The exact thickness depends on the height of the wall, the load above it, and your soil, so a real number should come from an engineer or your local building code. [verify]

That is the short version. Here is the plain one.

A footing is the flat, wide base poured under a foundation wall, spreading the weight of the house over more dirt so the wall does not sink or tip. Old stone foundations often skipped the poured footing. Builders made the bottom of the wall wider, or set the first course of big flat stones right on firm ground, so the stone wall itself did the spreading.

With no footing, the wall is the structure. It has to be thick enough to stand on its own and carry the house. Go too thin and it can lean, bow, or shift over the years.

What decides the right thickness:

• How tall the wall is. A taller wall fights more soil pressure, so it needs more width.
• What it carries. A small shed is not a two-story house.
• Your soil. In New Hampshire that bottom layer is often disturbed backfill, the looser fill put back when the house was built. It drains slowly and holds water, which adds pressure against the wall.
• Frost. NH frost heave pushes ground up and in every winter, and a thin or shifted stone wall feels it first.

Because all four change house to house, no contractor can give you one universal inch count online. The real number belongs to an engineer or your local code official. [verify]

What we actually see on old stone walls here

A lot of New England homes sit on stone or fieldstone foundations with no real footing, and they have stood for a hundred years or more. The wall starts to fail when water gets behind it and the soil pressure wins. You see bowing, leaning, a stone working loose, or a gap opening at the floor wall joint.

When that happens, you usually do not need to tear the wall out and pour a new one. We fix what is there. We do repair, not new builds, so if you are planning brand new construction you want a builder for that part.

For a leaning or bowing stone wall we look at carbon-fiber straps, a power brace, or an auxiliary (sister) wall built against the inside to take the load off the old stone. Carbon-fiber wall stabilization runs $850 each. A power brace runs $1,300 per brace. An auxiliary wall runs about $1,350 per linear foot. If the wall is settling because the ground under it gave way, helical or push piers can stabilize and sometimes lift it back, and helical piers run $2,700 per pier for the first three, then $2,200 per pier after that. If sagging beams or posts above are part of the story, floor support and lally columns run $1,300 to $2,500.

A full foundation-wall rebuild or replacement is a bigger job. We price that after we see it. There is no online number for it, so be careful of anyone who throws one at you sight unseen.

Read more on our structural and foundation repair page, and on helical piers and supplemental support if you want the detail.

Water is usually the real enemy

Most failing stone foundations are not failing because the stone got weak. They fail because water keeps loading the soil against them. A stone wall is also rarely watertight, so a wet basement and a moving wall often show up together.

If your stone basement is also damp, the durable fix is interior drainage, not digging the outside out. We have seen exterior excavation fixes fail in about two to three years in our own work. Our Forever Dry System puts a full-perimeter interior drain, a sump pump, a 12-mil wall vapor barrier, and a dehumidifier to work, and it is 100% guaranteed to be dry for life! Basement waterproofing runs $3,000 to $30,000. If it is a dirt or fieldstone crawl space, that is crawlspace encapsulation instead.

You do not need every one of these. Many stone walls just need water managed and one stabilization step, and we will tell you when you do not need the big job.

Every repair is backed by the 603 guarantee. Carbon-fiber and helical work carry a 25-year warranty. Floor support carries 10 years.

Get a real number for your wall

The only way to know how thick or how sound your stone foundation really is, is to have someone look at it. We give a free inspection and a free estimate, and you get your quote within 24 hours.

Call us at 603-610-1770 or book your free inspection. We serve New Hampshire, Maine, and Massachusetts, and we are trusted by 5,000+ homeowners in New England with a 4.9 Google rating.

Related questions

Can you repair a stone foundation, or does it have to be replaced? Most of the time we repair it. Carbon-fiber straps, a power brace, an auxiliary wall, or piers can stabilize a leaning or settling stone wall without tearing it out. A full rebuild is a bigger job we price after we see it.

Why is my old stone basement always wet? Stone walls are rarely watertight, and the disturbed backfill soil around your foundation drains slowly and holds water. Interior drainage with a sump and vapor barrier keeps it dry. See basement waterproofing.

Do I need a footing under an old stone foundation? Old stone foundations often have no poured footing and have stood for a century. If yours is sound, you usually leave it be. If it is moving, you stabilize the wall rather than try to add a footing underneath.

Does frost really move a stone foundation? Yes. NH frost heave pushes ground up and inward each winter, and a thin or already-shifted stone wall feels it first. Managing the water around the wall reduces the pressure.