Why do mechanical systems cost so much?

Plumbing, HVAC, and electrical together routinely hit 20% of a home's direct cost. Plumbing alone is typically 8–12 fixtures at $700–$1,200 each plus rough-in. HVAC is usually priced per square foot of conditioned area.

What's not in these percentages?

Land, well and septic, long utility runs from the street, impact fees beyond normal permits, and custom structural steel. These are real project costs but outside the 'construction cost per square foot' frame.

How accurate is a percentage-based breakdown?

Good for understanding where money goes, poor for writing checks. Two homes at the same square footage can have radically different division splits. An itemized estimate from your plans is the only reliable budget.

New Home Construction Cost Breakdown (2026)

When you build a new home, roughly 15% of the budget goes into the foundation, 20% into rough structure, and a third or more into finishes — but the exact split depends heavily on your choices. Here's how a typical 2,400 sq ft standard-finish home in the Southeast breaks down, and what shifts each number.

Typical budget breakdown

Based on a ~2,400 sq ft new residential build at standard finish in the Southeast (2026 pricing). Percentages are of direct construction cost, excluding contingency, markup, and tax:

Prep & preliminaries (permits, plans, insurance, management): ~6–9%
Excavation & foundation: ~8–12%
Rough structure (framing, trusses, sheathing): ~13–18%
Roofing & exterior enclosure (roof, windows, siding, doors): ~10–15%
Mechanical systems (plumbing, HVAC, electrical): ~18–24%
Interior finishes (drywall, cabinets, counters, flooring, paint, trim): ~22–30%
Specialties (appliances, fixtures, closets): ~3–6%
Site work & landscaping: ~3–6%

The biggest swing categories

Not all categories move equally with finish level:

Interior finishes — the widest range; a builder-grade vs. high-end finish here can be a $50,000+ swing
Mechanical systems — relatively fixed per SF; plumbing fixture count and HVAC scope drive variation
Foundation — changes with foundation type (slab/crawl/basement) and site conditions, not finish level
Rough structure — scales with square footage and roof complexity more than finish level

What gets added on top

After direct construction cost, a real budget adds:

Contingency: ~5–10% of direct cost (unknown site conditions, minor scope creep)
Builder markup / overhead & profit: ~10–20% (if using a GC)
Sales tax on materials: ~6–9% (varies by state)
Together these add roughly 20–35% to the direct construction total

From percentages to real line items

Knowing the percentages is useful, but a budget you can build from needs the line items behind them — framing lumber quantity, window count, plumbing fixture schedule, tile area — each priced to your region and derived from your plans.

Upload your plans to Build 360 and get the full breakdown, automatically — every cost code, material and labor, Low/Expected/High band, and a schedule.

New Home Construction Cost Breakdown: Where the Money Goes