Foundation FAQs: Your Top 12 Questions, Answered

Foundation problems feel urgent, and most of the advice online comes from companies selling the repair. Below I am sharing straight answers to the questions you are most likely to ask, in the order you are likely to ask them.

1. How can you tell if foundation problems are serious?

   Look at the pattern, not one crack. Your foundation problem is more serious when cracks are horizontal, stair-stepped, wider at one end or still growing, and when doors stick, floors slope or a wall bows. Mark any crack with the date and measure it. If you see several of these signs together, call a structural engineer.

2. When should I worry about a crack in my foundation?

   Worry when a crack is wider than about 1/4 inch, offset so one side sticks out, horizontal, or growing over time. A thin vertical crack that stays the same is usually concrete shrinkage. Our foundation cracks guide shows you how to read each type.

3. How big is too big for a foundation crack?

   There is no single limit, but about 1/4 inch is a useful warning line. NAHB treats masonry cracks over 1/4 inch as items for repair, and the concrete industry guide CIP 7 says a typical builder warranty covers poured wall cracks over 1/8 inch. Direction and growth matter too, so a thin horizontal crack can matter more than a wider vertical one.

4. Can a cracked foundation be repaired?

   Yes. Most cracked foundations can be repaired. Crack injection seals a stable crack, straps or anchors brace a bowing wall, and piers support a sinking footing. The right repair depends on what moved and why, and our guide to foundation repair methods compares each one.

5. How much does foundation repair normally cost?

   This Old House puts foundation repair at about $5,179 on average, with most homeowners paying between $2,224 and $8,134. Crack filling costs $250 to $800, piers cost $1,000 to $3,000 each, and lifting a whole house costs $20,000 or more. The method decides the price, so get quotes on the same scope.

6. Is foundation repair worth the cost?

   Usually, when the damage is structural. Movement left alone can damage walls, floors, doors and plumbing, and it can make your house harder to sell or finance. Confirm the cause first, because some cracks need only monitoring or a drainage fix.

7. Will house insurance pay for foundation repair?

   Usually not. Most US property policies exclude earth movement, and standard policies also exclude settling and the cracks it causes. A covered sudden event, such as a burst pipe, may be different. Read your policy and ask your insurer before you start repairs.

8. Do you need a structural engineer for foundation repair?

   You should use one for structural work, such as a bowing wall, a sinking footing or a large pier job. An engineer gives you an independent diagnosis and a written scope that contractors can price. Our foundation inspection guide explains who to hire and when.

9. How much does it cost for a structural engineer to inspect a foundation?

   This Old House puts a structural engineer's foundation inspection at about $600 on average, with a typical range of $300 to $1,000. Engineers charge about $100 to $500 per hour, and most visits take one to two hours. Complex jobs and detailed reports cost more.

10. Is it worth encapsulating a crawl space?

    It is worth it when your crawl space stays above about 60% humidity in humid weather, or your joists read above 20% moisture. It is not worth it if the space is already dry or if standing water has not been fixed first. Encapsulation costs about $5,500 on average, and many crawl spaces need less.

11. Is waterproofing a basement worth it?

    It is worth it when water enters regularly or when you plan to finish the space. Fix your gutters, downspouts and grading first, because those cheaper fixes often solve the problem. Basement waterproofing averages about $5,000, with most jobs between $3,000 and $10,000.

12. How serious is mold in a crawl space?

    It is a warning sign that needs fixing, but it is rarely an emergency. Mold shows that moisture stays high, and the same moisture can rot your wood framing over time. Stop the water first. The EPA says you can usually clean an area under about 10 square feet yourself, while larger areas need a professional.

These answers are general information and don't replace an on-site inspection. Sources are listed in the guide for each topic, and you can browse all our independent foundation and moisture guides from the homepage.