How much does a modified bitumen roof cost?
Ashburn, VA

How much does a modified bitumen roof cost?

Ashburn, VA

How much does a modified bitumen roof cost?

$4.00 – $7.50cost per square foot installed
$4,900 – $14,600average total cost to replace

Get free estimates for your project or view our cost guide below:

$4.00 – $7.50 cost per square foot installed

$4,900 – $14,600 average total cost to replace


Get free estimates for your project or view our cost guide below:
Jennifer Carlson
Written by
Jennifer Carlson
Edited by
Kristen Cramer
Fact-checked by
Tom Grupa

Modified bitumen roof cost

A modified bitumen roof costs $4,900 to $14,600 on average. Modified bitumen roofing prices are $4.00 to $7.50 per square foot, depending on the roof size, shape, pitch, and whether the job includes repairs or old roof removal. Modified bitumen is best for low-slope or flat roofs.

Modified bitumen roof cost
Roof size (square feet) Total replacement cost
1,000 $4,100 – $6,600
1,200 $4,950 – $7,900
1,500 $5,900 – $9,800
1,700 $7,000 – $11,100
2,000 $8,300 – $12,700
2,500 $10,400 – $15,900
3,000 $12,500 – $19,100
3,500 $14,500 – $21,800

Average cost to install a modified bitumen roof

The following table shows the average cost to install a modified bitumen roof.

Average modified bitumen roof cost
Average modified bitumen roof cost
Average cost to install a modified bitumen roof
National Average Cost $9,750
Minimum Cost $3,100
Maximum Cost $22,700
Average Range $4,900 to $14,600

*Cost data is based on an average roof size of 1,200 to 2,400 square feet.

The average cost to install a flat roof is $3 to $11 per square foot. Flat roofs may be modified bitumen, metal, or an engineered rubber membrane known as ethylene propylene diene monomer (EPDM).

Modified bitumen roofing cost per square foot

Modified bitumen roofing costs $4.00 to $7.50 per square foot installed, depending on roof pitch, old roof removal, material quality, location, and installation complexity.

Modified bitumen roofing cost per square foot
Factor Cost per square foot
Old roof removal $1.00 – $1.30
Materials and supplies $0.70 – $2.20
Installation labor $2.30 – $4.00
Total cost $4.00 – $7.50

Find top-rated flat roof installers in your city.

The following factors affect the cost of a modified bitumen roof:

  • Labor costs $2.30 to $4.00 per square foot, depending on the install method. Modified bitumen roofs can be applied by hot-mop, self-adhesive backing, or a torch-down application.

  • LayersTorch down roofing costs $1.10 to $5.50 per square foot for materials, depending on whether its a 2 or 3-layer roofing system.

  • Roof size, slope, and pitch – Modified bitumen is only recommended for flat and low-pitch roofs. Large roofs and roofs higher than 15 feet from the ground may cost more.

  • Complexity – Two or more story homes cost more than single-story houses. Vents, skylights, chimneys, and complex roof shapes increase the final price.

  • Old roof removal & disposal – Removing an old roof costs $1.00 to $1.30 per square foot, or $1,000 to $3,500 total.

  • Roof repair costs $200 to $500 to patch minor leaks and cracks.

  • Installing a roof vent costs $200 to $700 on average.

  • Permits for roof replacement cost $150 to $500 on average.

  • Drains – Simple drain repairs or additions cost $40 to $300, while rerouting and installing new systems costs $600 to $1,000. Most flat roofs have an existing drainage system in place.

  • Underlayment – Adding extra insulation costs $100 to $600 on average.

  • Sealing or coating a roof costs $500 to $2,000 and offers added protection, waterproofing, and fire resistance.

  • Overlaying – Some contractors add an extra layer of roofing material instead of removing the old roof. However, overlaying a roof may cause further problems and void the warranty if the roof has more than two layers.

Torch-down modified bitumen roofing installation
Torch-down modified bitumen roofing installation

Modified bitumen roofing prices

Modified bitumen prices per roll

Modified bitumen costs $150 to $560 per roll, depending on the brand, supplier, polymer, color, and texture. Each roll covers approximately 100 square feet.

Types of modified bitumen roofs by polymer

Modified bitumen sheets come in two polymer types. Both types cost the same but are ideal for different climates:

  • APP Polymer: Atactic polypropylene (APP) uses plastic to reinforce asphalt and can be applied with heat or self-adhesive backing. APP resists UV rays and water well and is suitable for sunny, humid climates.

  • SBS Polymer: Styrene-butadiene-styrene (SBS) contains synthetic rubber and has a lower melting point—making it ideal for heat-welding—but can also be self-adhesive. SBS can withstand lower temperatures, making it better for cold climates.

Pros and cons of modified bitumen roofing

Modified bitumen is stronger, more flexible, and more UV-resistant than asphalt roofs. Heat-welding is often used to apply modified bitumen and can be dangerous, but many brands now make self-adhesive rolls.

Pros and cons of modified bitumen roofing
Pros Cons
  • Durable
  • Flexible
  • Affordable
  • Water-resistant
  • Long lifespan
  • Multiple ways to install
  • Only suitable for flat roofs
  • Torch-down method can be dangerous
  • Dark rolls absorb heat in summer
  • Vulnerable to standing water
  • Expensive if using 2 to 3 layers

  • Modified bitumen comes in several colors, which determines how much heat the roof absorbs or reflects.

  • Bitumen can withstand rain, wind, snow, and hail, though its seams may not handle standing water as well as other roof types.

What is modified bitumen roofing?

Modified bitumen is a flat, flexible asphalt material reinforced with polymerized plastic, fiberglass, or rubber. This material is designed for use on flat or low-slope roofs.

How long does a modified bitumen roof last?

Modified bitumen roofs last 10 to 20 years on average. Routine maintenance and quality installation may increase the roof's longevity.

Get free estimates from flat roofing companies near you.

Finding and hiring a roofing contractor

Before hiring a roofing contractor, be sure to:

  • Get three or more in-person estimates to compare. Beware of companies who recommend a full roof replacement when only repairs are needed.

  • Read their reviews on HomeGuide and Google.

  • Look for companies with:

    • A state contractor license

    • National Roofing Contractors Association (NRCA) certification

    • Roof Coatings Manufacturers Association (RCMA) membership

  • Select a certified, insured, bonded company with five or more years’ experience.

  • Be careful with extremely low or high price quotes.

  • Verify that the roofing contractor has experience with your roof type.

  • Ask for a clear written estimate and warranty before work begins.

  • Avoid large upfront payments. Instead, negotiate a payment schedule and save receipts.

Questions to ask

  • Are you licensed, insured, and bonded?

  • How long have you been repairing roofs?

  • Are you part of professional roofing organizations like the NRCA?

  • Can you provide references from past work?

  • Can you provide a detailed quote?

  • Does your quote include waste disposal or taxes?

  • How long will the project take?

  • What brand do you typically use? Are you a certified applicator of that product?

  • Which sealant or coating do you recommend for my roof type, if any?

  • What will you do in the event of unexpected bad weather?

  • How will you access my roof? What safety precautions will you take?

  • What additional fees may be required?

  • Will you obtain any necessary permits?

  • Do you offer financing?

  • What does your warranty include?