CostGuideHQ

Floor Joist Repair Cost: $1,000–$20,000 (Average $6,000) in 2026

Author: CostGuideHQ Editorial·✓ Fact-checked·Updated July 2026·6 min read·4 sources·US national averages, USD
Quick answerQuick answer: Floor joist repair costs $1,000 to $20,000 nationally, averaging about $6,000 (HomeAdvisor). Sistering runs $100 to $300 per joist, while full replacement costs $1,000 to $2,000 per joist. Damage extent, joist count, and the underlying cause, whether foundation, water, or termite damage, drive the final bill.
  • A typical floor joist repair project costs $1,000 to $20,000, averaging about $6,000 nationally (HomeAdvisor).
  • Sistering, bolting a new joist alongside the damaged one, costs $100 to $300 per joist, far less than a full replacement at $1,000 to $2,000 per joist (HomeAdvisor).
  • Per square foot, joist repair runs $10 to $67 depending on damage severity and accessibility (HomeAdvisor).
  • The underlying cause matters: foundation repair runs $1,800 to $6,500 (up to $20,000 in severe cases), water damage repair $2,000 to $6,000, and termite removal $250 to $2,000 (Bob Vila).

How much does floor joist repair cost?

National average
$6,000
total project
Typical range
$1,000–$20,000
Most projects
High end
$20,000+
Premium / complex
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Cost by material / type

TypeLowHigh
sistering (reinforce existing joist)$100$300
full joist replacement$1,000$2,000
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Rough estimate only — get local quotes for exact pricing.

What affects the cost?

  • Repair method — sistering (bolting a new joist alongside the damaged one) costs $100 to $300 per joist, far less than a full replacement at $1,000 to $2,000 per joist (HomeAdvisor)
  • Extent of damage and number of joists affected, which is why per-joist repair or replacement runs $500 to $2,000 depending on severity (Fixr), and per-square-foot pricing spans $10 to $67 (HomeAdvisor)
  • Labor rates — contractors charge $65 to $100 per hour (HomeAdvisor) or $25 to $100 per hour, sometimes $15 to $50 per square foot, elsewhere (Bob Vila, Fixr)
  • Underlying cause driving the sag — foundation settling ($1,800-$6,500, up to $20,000 in severe cases), water damage ($2,000-$6,000), or termite damage ($250-$2,000 for removal alone) all add cost on top of the joist work itself (Bob Vila)
  • Building permits and structural assessment — permits run $50 to $2,000 (Bob Vila) and a structural engineer inspection costs $343 to $724 (Bob Vila)
  • Related flooring work bundled into the job — subfloor repair adds $2 to $10 per square foot or $500 to $700 per room, and subfloor replacement runs $1,800 to $3,000 per room (HomeAdvisor)
  • Accessibility and local labor rates, plus permit/inspection requirements, which This Old House notes vary the total by affected area size and extent of structural work

Why does floor joist repair cost so much?

Because “floor joist repair” covers everything from bolting a reinforcing board next to one joist to rebuilding an entire room’s structure. HomeAdvisor puts the national average at $6,000, with a normal range of $4,000 to $12,000 — minor fixes can run as low as $1,000, while full-room replacement climbs to $20,000. The repair method drives most of that spread: sistering, where a new joist is fastened alongside the damaged one instead of removing it, costs $100 to $300 per joist, while full replacement runs $1,000 to $2,000 per joist (HomeAdvisor). Per square foot, expect $10 to $67, depending on how much damage there is and how easy the joists are to reach. Fixr and This Old House both put the outer bound of a professional job at $20,000, which lines up with HomeAdvisor’s ceiling for larger jobs.

What affects the cost?

  • Repair method. Sistering costs $100 to $300 per joist versus $1,000 to $2,000 per joist for full replacement (HomeAdvisor).
  • Damage extent and joist count. More affected joists mean more labor and material, which is why per-square-foot pricing spans $10 to $67 and Fixr’s per-joist range runs $500 to $2,000 depending on severity.
  • Labor rates. Contractors charge $65 to $100 per hour (HomeAdvisor), or a broader $25 to $100 per hour, sometimes billed at $15 to $50 per square foot instead (Bob Vila, Fixr).
  • Accessibility. Joists reachable from a basement or crawl space are cheaper to fix than joists buried under finished flooring, since exposed joists don’t require tearing up the floor first.
  • Permits and inspection. Because joists are structural, permits run $50 to $2,000 and a structural engineer inspection costs $343 to $724 (Bob Vila).

What if the sagging floor has an underlying cause?

The joist repair itself is often the smaller bill. Bob Vila’s figures show foundation repair running $1,800 to $6,500, and up to $20,000 in severe cases, water damage repair costing $2,000 to $6,000, and termite removal running $250 to $2,000 before any joist work even starts. These are typically quoted as separate line items from the sistering or replacement labor, which is why a homeowner chasing a sagging floor back to its root cause can end up paying well past the $6,000 average for the joists alone. Related flooring work adds up too: subfloor repair costs $2 to $10 per square foot or $500 to $700 per room, and full subfloor replacement runs $1,800 to $3,000 per room (HomeAdvisor). Getting a structural engineer to diagnose the cause first, at $343 to $724, is often cheaper than guessing and paying twice (Bob Vila).

How can I lower the cost of floor joist repair?

  • Ask about sistering before replacement. If the joist isn’t too far gone, sistering at $100 to $300 per joist is a fraction of the $1,000 to $2,000 full-replacement cost (HomeAdvisor).
  • Fix it early. Catching a sagging floor before it spreads limits the job to fewer joists and avoids the $2,000 to $20,000 range that comes with larger sagging, uneven, or sunken floor repairs (Fixr).
  • Get a structural engineer’s opinion first. A $343 to $724 inspection can pinpoint whether you’re dealing with a $1,000 joist fix or a $6,500-plus foundation problem (Bob Vila). Steve Frederickson, registered professional engineer, at This Old House, says “if you build to code minimums, you most likely will have some kind of bounce” — a reminder that not every springy floor points to a costly structural problem.
  • Address the root cause, not just the symptom. Termite damage, water intrusion, or foundation settling will keep stressing new joists if left untreated, and those repairs run $250 to $6,500 depending on the cause (Bob Vila).
  • Get multiple quotes, especially for larger jobs, since labor rates alone range from $25 to $100 per hour across contractors (Bob Vila, Fixr).

Prices vary by region, accessibility, and what’s actually causing the sag, so treat the figures above as a planning budget. A structural engineer or licensed contractor should confirm the cause and scope before you commit to a repair method.

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Frequently asked questions

How much does it cost to repair a floor joist?
Most floor joist repair projects cost $1,000 to $20,000, averaging around $6,000 nationally (HomeAdvisor). The exact number depends heavily on how many joists are affected and whether the fix is sistering or full replacement.
What's the difference between sistering and replacing a joist?
Sistering bolts a new joist alongside the damaged one for reinforcement and costs $100 to $300 per joist. Full replacement removes and replaces the damaged joist entirely, running $1,000 to $2,000 per joist (HomeAdvisor).
How much does floor joist repair cost per square foot?
Expect $10 to $67 per square foot, with the wide spread reflecting how much damage there is and how accessible the joists are (HomeAdvisor).
Does the price include fixing what caused the sagging floor?
Usually not. Foundation repair runs $1,800 to $6,500 (up to $20,000 in severe cases), water damage repair $2,000 to $6,000, and termite removal $250 to $2,000, and these are typically priced as separate line items from the joist work itself (Bob Vila).
Do I need a permit to repair floor joists?
Often yes, since joists are structural. Bob Vila puts permit costs at $50 to $2,000, and a structural engineer inspection, sometimes required before work begins, runs $343 to $724.
Why do cost estimates for floor joist repair vary so much?
Sources define the job differently. HomeAdvisor's $4,000 to $12,000 typical range covers whole-project joist work, Bob Vila's $1,000 to $5,000 figure is one line item inside a broader sagging-floor repair, and Fixr's $2,000 to $20,000 range covers sagging, uneven, and sunken floors that need joist reinforcement. All the sources agree the low end starts around $1,000 and the high end can reach $20,000.
Will I need to replace my subfloor or flooring too?
Sometimes. Subfloor repair adds $2 to $10 per square foot or $500 to $700 per room, and full subfloor replacement runs $1,800 to $3,000 per room, on top of the joist repair itself (HomeAdvisor).
What labor rate should I expect from a contractor?
Most contractors charge $65 to $100 per hour (HomeAdvisor), though other sources cite a broader $25 to $100 per hour or a per-square-foot rate of $15 to $50 (Bob Vila, Fixr).

Sources

Figures synthesized and cross-checked across these sources (retrieved 2026-07-28):

  • HomeAdvisor — Average cost $6,000, normal range $4,000 to $12,000. Minor fixes as low as $1,000; full room replacement up to $20,000; entire level replacement up to $30,000. Per joist: $100 to $300 or more for sistering, $1,000 to $2,000 each for full replacement. Per square foot: $10 to $67. Labor $65 to $100 per hour. Subfloor repair $2 to $10 per square foot or $500 to $700 per room; subfloor replacement $1,800 to $3,000 per room.
  • Bob Vila — Sagging floor repair typically costs $300 to $6,500. Subfloor repair $300 to $2,500; floor joist repair $1,000 to $5,000; foundation repair $1,800 to $6,500 (up to $20,000 in severe cases); sill plate repair $95 to $100 per linear foot; band board/rim joist sistering $38 to $42 per foot; support column repair (steel jacks) $500 to $550 per jack; water damage repair $2,000 to $6,000; termite removal $250 to $2,000. Labor $25 to $100 per hour or $15 to $50 per square foot. Structural engineer inspection $343 to $724; building permits $50 to $2,000.
  • Fixr — Overall floor repair $500 to $3,000, national average $1,600. Sagging, uneven, and sunken floors needing joist reinforcement run $2,000 to $20,000. Floor joist repair or replacement costs $500 to $2,000 per joist. Floor leveling $1,200 to $20,000 per room. Labor $25 to $100 per hour or $15 to $50 per square foot, flat rate $100 to $250 for smaller jobs.
  • This Old House — Professional floor joist repairs typically range from $1,000 to $20,000, varying with affected area size, extent of structural work, local labor rates, and permit/inspection requirements. DIY sistering materials run $1 to $5 per linear foot for lumber, $3 to $14 per tube for construction adhesive, $3 to $6 per box of screws/nails, and $7 to $63 per sheet of plywood for subfloor reinforcement.

HomeAdvisor gives the cleanest whole-project figure: average $6,000, normal range $4,000-$12,000, with minor fixes as low as $1,000 and full-room replacement reaching $20,000 (entire-level replacement up to $30,000 in the most extreme case). Bob Vila frames 'floor joist repair' as one line item ($1,000-$5,000) inside a broader sagging-floor problem that overall runs $300-$6,500 — narrower because it includes minor subfloor-only fixes at the low end. Fixr's range for sagging/uneven/sunken floors needing joist reinforcement is $2,000-$20,000, and This Old House puts professional floor joist repairs at $1,000-$20,000. range_low_usd ($1,000) reflects the agreed low end across HomeAdvisor's minor-fix threshold, Bob Vila's floor-joist-repair line item, and This Old House's stated low end. range_high_usd ($20,000) reflects the ceiling shared by HomeAdvisor's full-room-replacement figure, Fixr's sagging-floor ceiling, and This Old House's range. national_average_usd ($6,000) is HomeAdvisor's stated average, which sits centrally in the synthesized range and near the midpoint of HomeAdvisor's own $4,000-$12,000 normal range. by_type is a per-joist figure (sistering vs. full replacement), sourced from HomeAdvisor's clean method-based split — Fixr's $500-$2,000 per-joist figure doesn't separate repair method, so it's cited in cost_factors rather than folded into by_type. Figures generally price the joist work itself; related causes (foundation, water, termite damage) and finish flooring/subfloor replacement are commonly separate line items.