Quick cost benchmarks

• Residential flat roof replacement cost per square foot $3 to $11 installed
• Commercial flat roof replacement cost per square foot $4 to $11 installed
• Full tear-off with insulation often $9 to $15 per square foot depending on the material and access
• Typical totals by size
  • 800 sq ft $2,400 to $8,800
  • 1,500 sq ft $4,500 to $16,500
  • 3,000 sq ft $9,000 to $33,000
  • 10,000 sq ft commercial $50,000 to $120,000 plus logistics

These bands match what most roof estimating apps and flat roof price calculators show. Your number moves with tear-off layers, insulation thickness, penetrations, drains, and site access.

Calculator inputs and outputs

Inputs you select

• Roof size in square feet
• Roofing material EPDM, TPO, PVC, Modified Bitumen, BUR, GRP, Spray Foam, low-slope Metal
• Tear-off layers 0 to 2+
• Insulation thickness in inches optional tapered
• Penetrations and curbs pipes, vents, skylights, HVAC
• Edge metal linear footage
• Drains and scuppers count
• Stories and access level ladder, lift, crane
• Region or ZIP labor market and permit rules
• Complexity simple, medium, complex
• Warranty tier material only or NDL-style system

Outputs you get

• Low, mid, high estimate
• Line-item table with unit rates
• Notes for bidders spec and scope checklist
• Downloadable PDF of your roof estimate online

Pricing formula with unit rates

Total =
(Area × Base Material Rate)

• (Area × Tear-off Rate × Layers)
• (Area × Polyiso Rate per inch × Inches)
• Tapered Insulation Adder
• Penetrations × Unit Rate
• Curbs or Skylights × Unit Rate
• Edge Metal (lf × Unit Rate)
• Drains or Scuppers × Unit Rate
• Access Multiplier
• Region Multiplier
• Crane or Hoist Allowance
• Permits and Disposal
• Contingency 5 to 10 percent

Starter unit rates

• Tear-off $1.00 to $2.25 per sq ft per layer
• Polyiso insulation $0.45 to $0.85 per sq ft per inch
• Tapered insulation adder $1.25 to $2.75 per sq ft average coverage
• Penetrations $65 to $180 each
• Skylight or large curb $350 to $950 each
• Edge metal $6 to $16 per linear ft
• Drains or scuppers $90 to $450 each
• Crane or hoist $700 to $3,500 per day
• Permits $150 to $900 residential, higher for commercial
• Access multiplier 1.00 to 1.20
• Region multiplier 0.90 to 1.30

Use any roofing measurement app to confirm area and edge footage. The best roof measuring app for you is the one that captures clean polygons and exports CSV or PDF, which makes the roof cost calculator results easier to share.

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Cost per square foot by flat roof material

Flat roof material	Installed price per sq ft	Typical service life	Notes
Built-Up Roofing BUR	$3.50 to $7.50	20 to 30 yrs	Layered redundancy, good on busy roofs
Modified Bitumen	$4.00 to $7.50	10 to 20 yrs	Cold-friendly, phased work friendly
EPDM Rubber	$4.00 to $10.00	15 to 25 yrs	Large sheets, budget friendly
TPO	$4.00 to $10.00	10 to 25 yrs	White, reflective, common on commercial buildings
PVC	$5.00 to $12.00	20 to 30 yrs	Handles grease and chemicals
GRP Fiberglass	$3.50 to $7.50	25 to 50 yrs	Rigid surface, smaller roofs
Spray Polyurethane Foam	$3.50 to $7.00	40 to 50 yrs	Seamless, adds R-value
Low-slope Metal	$5.00 to $16.00	30 to 80 yrs	Long life, higher upfront
Concrete overlay	$4.00 to $15.00	50 to 60 yrs	Heavy duty assemblies
Coating restoration	$2.00 to $6.00	10 to 20 yrs	For dry, sound roofs only

Search terms you might use while comparing options flat roof prices per square foot, flat roofing cost per square foot, cost of a flat roof per square foot, commercial flat roof replacement cost per square foot.

The cost drivers that move your number

Tear-off and disposal

$1.00 to $2.25 per sq ft per layer. Gravel or ballast adds time and weight for dumpsters.

Insulation and taper

Polyiso at $0.45 to $0.85 per inch per sq ft. Tapered at $1.25 to $2.75 per sq ft in the sloped areas. Code R-values push thickness. Taper fixes ponding.

Penetrations and curbs

Pipes and stacks at $65 to $180 each. Skylights and HVAC curbs at $350 to $950 each. Walk pads by service paths help the new roof last.

Edge, drains, parapets

Edge metal at $6 to $16 per lf. Drains and scuppers at $90 to $450 each. Parapet cap and flashing can be an allowance.

Access, height, logistics

Access multiplier 1.00 to 1.20. Crane or hoist often needed above two stories. Busy sites may need traffic control.

Region and permits

Region multiplier 0.90 to 1.30. Permits and inspections vary by city and by type of project.

Labor share

Labor is often 55 to 65 percent of the total on standard scopes. Complex detailing and high roofs push it higher.

Worked examples with transparent math

A 600 sq ft residential garage, Modified Bitumen

• Base rate 600 × $5.50 = $3,300
• Tear-off 1 layer 600 × $1.50 = $900
• Insulation 2 inches 600 × 2 × $0.70 = $840
• Edge metal 80 lf × $9 = $720
• 2 penetrations × $110 = $220
• Permits and disposal $350
• Access and region multipliers 1.00
• Contingency 7 percent $461

Estimate $6,791

A 1,500 sq ft residential warm roof, TPO with taper at drains

• Base rate 1,500 × $6.25 = $9,375
• Tear-off 1 layer 1,500 × $1.60 = $2,400
• Insulation 3 inches 1,500 × 3 × $0.70 = $3,150
• Tapered adder (60 percent field) 900 × $1.80 = $1,620
• Edge metal 160 lf × $10 = $1,600
• 4 penetrations × $120 = $480
• 2 drains × $300 = $600
• Permits and disposal $600
• Access 1.00, region 1.00
• Contingency 7 percent $1,391

Estimate $21,216

A 10,000 sq ft commercial roof, white TPO, two-layer tear-off, crane

• Base rate 10,000 × $6.50 = $65,000
• Tear-off 2 layers 10,000 × 2 × $1.80 = $36,000
• Insulation 3 inches 10,000 × 3 × $0.70 = $21,000
• Tapered adder 10,000 × $1.80 = $18,000
• Penetrations 45 × $125 = $5,625
• Curbs 8 × $650 = $5,200
• Edge metal 500 lf × $12 = $6,000
• Drains 6 × $300 = $1,800
• Subtotal $158,625
• Access 1.10, region 1.05 subtotal × 1.155 = $183,722
• Crane two days $5,000
• Permits and disposal $4,500
• Contingency 7 percent $13,525

Estimate $206,747

These examples mirror what a flat roof estimator or roof estimating app would produce when fed the same inputs.

Regional adjusters and seasonality

• Labor and permits vary by metro. Use a region factor from 0.90 to 1.30.
• Peak season late spring through summer often carries a premium.
• Mild-climate winter work can save money if the forecast cooperates.
• Remote sites can add travel and lodging to the final bill.

If you want an instant roof quote that reflects your ZIP, add the region field in the calculator and re-run the numbers.

Repair, restore, or replace

Use this simple decision path before you price a full replacement.

Coatings cost less when the roof is dry and tight. Wet or loose systems need tear-off.

Warranty options and lifecycle math

• Manufacturer warranty basic material coverage or upgraded system coverage.
• Contractor workmanship covers installation errors for a set term.
• Lifecycle costs price the system, factor in energy savings from white membranes and added R-value, then plan a renewal coating at year 10 to 15 if the spec allows it.

Bid-ready scope checklist

• Dimensions per roof section with a sketch or export from your roofing measurement app
• Layer count and whether ballast or gravel is present
• Penetration and curb schedule
• Edge linear footage, drains, scuppers
• Target roofing material and warranty tier
• Required R-value or inches of polyiso
• Tapered plan and slope to drains
• Walkway pads where techs service equipment
• Ask for unit prices on change items penetrations, edge, drains, crane days, deck repairs

This makes comparing an online roofing quote to in-person bids far less messy.

Common mistakes that inflate cost

• Ignoring taper where ponding exists
• Missing edge metal footage on takeoffs
• Under-counting penetrations and curbs
• Not planning hoisting on multi-story sites
• Leaving permits, disposal, and a 5 to 10 percent contingency out of the budget

FAQS About Flat Roof Replacement Cost Calculator