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Modesto home addition pricing per square foot

Home Addition cost per square foot in Modesto, California in 2026.

Low

$45,000

Average

$85,000

High

$140,000

Modesto crews quote about $150 – $450 per square foot.

Multiply local unit rates by your real measurements.

What drives home addition prices in Modesto

Local labor, permitting and climate move Modesto prices away from the national average.

Labor market

Modesto labor rates sit close to the national average.

Permits

City permits apply to structural, roofing and fence work.

Climate

Valley heat drives cooling loads in summer.

Modesto unit pricing by material

Garage conversion$80 – $200
Sunroom$100 – $250
Bump-out$150 – $350
Single-room addition$150 – $400
Second story$200 – $500
In-law suite / ADU$180 – $450

Ways to lower your Modesto price

  • Build up or bump out rather than adding a new foundation footprint.
  • Keep plumbing on the existing wet wall — moving water and waste lines is the costliest change.
  • Convert existing space (garage, attic, basement) at half the per-square-foot cost.
  • Keep the roofline simple; complex tie-ins add framing labor and leak risk.
  • Lock the design before demolition — change orders during construction carry the biggest premiums.

Modesto questions

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