How long does a foundation last

A poured concrete foundation lasts 80 to 100 years or more. A concrete block foundation lasts 80 to 100. A stone foundation on an old house can be two hundred years old and sound.

Foundations essentially do not wear out. What fails is everything that manages water around them, and that is what the numbers below are really about.

What lasts how long

The two short rows are the ones that matter. A sump pump lasts seven to ten years and a footing drain thirty to fifty, and both are protecting something that lasts a century.

What actually ends a foundation

Water, in five forms: poor grading, failed gutters, a broken footing drain, a leaking pipe, and a high water table nobody planned for.

Soil movement. Expansive clay swelling and shrinking seasonally, frost heave in the north, and consolidation of poorly compacted fill under a newer house.

Tree roots, drawing moisture out of clay soil on one side of a house in summer, which is a genuine and under-appreciated cause of differential settlement.

Poor original construction. Footings too shallow, no reinforcement, fill that was never compacted. Nothing degrades; it was inadequate from the start and it shows up in year fifteen.

Adjacent work. A neighbour's excavation, a new driveway raising the grade, a pool dug close to the house.

Note what is absent: age. A hundred-year-old stone foundation in a house with good drainage frequently outperforms a thirty-year-old poured wall in a house where the downspouts discharge at the wall.

The maintenance that actually extends it

In order of value per dollar:

1. Downspouts discharging six to ten feet from the house. Ten dollars each. Nothing else comes close.
2. Gutters that work, cleaned twice a year.
3. Grade falling six inches over the first ten feet, checked every few years because soil settles.
4. Six inches of foundation exposed above soil, so siding is not in ground contact.
5. Testing the sump pump quarterly and replacing the backup battery on schedule.
6. Watching the water bill for the leak that would otherwise wash out soil for months.
7. Watering the perimeter during drought in expansive clay regions, which sounds odd and is the standard local recommendation because it stops the soil shrinking away.
8. Sealing new cracks to keep water out of them.

That list costs under $200 a year and it is the difference between a foundation that lasts a century and one that needs $16,000 of piers in year forty.

Reading your own foundation

Once a year, walk the perimeter and the basement with a torch:

• New cracks, marked with a pencil and the date. A crack that has not moved through a wet and a dry season is one you can seal and forget.
• Horizontal cracks in a basement wall, which are the serious ones.
• Stepped cracks in block, following the mortar.
• Doors and windows that have started sticking.
• Floors that slope, felt with a marble or measured properly.
• The grade and the downspouts, every time.
• Efflorescence, the white deposit, which means water is moving through the wall.

Three of these in the same corner is a pattern worth an engineer's $700. One alone is usually nothing.

Frequently asked questions

Do all foundations crack?

Concrete shrinks as it cures, so nearly every poured foundation develops hairline vertical cracks in the first few years. That is normal. Width, direction and whether it is still moving are what distinguish normal from significant.

Does a foundation need to be replaced eventually?

Almost never. Foundations are repaired, underpinned or reinforced. Complete replacement happens with a whole-house lift and is extremely rare outside major renovation.

Is an old stone foundation a problem?

Not inherently. Many are two hundred years old and sound. They need repointing with lime mortar rather than modern cement, which is harder than the stone and causes damage, and they tolerate moisture in ways modern walls do not.

How do I know if movement is active?

Measure it. Mark each end of a crack with a pencil and the date, or fix a crack monitor for $15, and read it monthly for a year. Movement through a wet and a dry season is active; no movement is historic.

Does a house settle for a set period?

Most initial settlement happens in the first two to five years. Movement that starts in year twenty is not settling in; it is a change in conditions, usually water, and it is worth finding the cause.