Flat Roof Cost Calculator

Find out the average cost to tear off and replace flat roof for commercial and industrial property. Flat Roof Cost Calculator quickly estimates the total cost to install the following roofing materials.

  • Modified Bitumen (Torched Down 2-PLY)
  • EPDM (Black Rubber)
  • TPO Roof 45-mil
  • Tar & Gravel/BUR

Pricing is for new or retrofit flat roof projects and includes all materials, roof accessories and labor by a professional, licensed contractor.

The cost of replacing a flat roof typically ranges from $9 to $10 per square foot, but can increase to a range of $12 to $15 per square foot, depending on factors such as the roof’s dimensions and intricacy. This price includes expenses for removing the old roofing, installing insulation, and applying the new roofing membrane. The ultimate cost is influenced by material quality, roof size, job complexity and your geographic location.

Roof Size
x ft.
Curbs (Skylights / HVAC / Hatches)
Old Roof Removal
Job Complexity
Roofing Material
Low End
${{ lowEnd }}
Mid Range
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High End
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Over the past few years, flat roofs have gained increased favor due to their contemporary aesthetic, straightforward installation, and repair convenience. The typical expense for replacing a flat roof ranges from $5 to $10 per square foot. The installation of a basic 1,600 square foot flat roof comes to $8,000 to $16,000, contingent upon the material of your preference. 

How to Use the Flat Roof Calculator

1. Begin by measuring your property from one corner to the other. Enter those dimensions into the “Roof Size” fields

2. Enter the number of curbs, such as hatches, skylights, or HVACs. These features require specialized flashing work and will contribute to the overall cost for each unit. It’s crucial to include them in your calculations to obtain a more accurate estimate, as a professional contractor will certainly consider these features.

3. Select the desired insulation thickness.

4. Enter the number of tear-off layers.

5. Choose the level of job complexity. This might vary, but if your project involves multiple penetrations, curbs, roof-to-wall flashing, or challenging drainage, opt for the Medium or Difficult setting. Additionally, consider factors like the ease of roof access. If your contractor needs to hire police detail or if your roof is situated seven stories above the ground, expect an increase in costs.

6. Pick the roofing material you prefer. You can obtain a price estimate for your chosen material and then recalculate for a different one to make a comparison. Modified Bitumen or Torched Down 2-PLY roofing is a popular choice due to its cost-effectiveness, while TPO is the second most commonly used material for commercial flat roofs.

7. Indicate your geographical location. Prices can vary by as much as 30% if outside of the GTA location.

Understanding Your Price Estimate

You will receive three price estimates: LOW-END, MID-RANGE, and HIGH-END. These estimates are based on the average roofing costs and includes the following:

– All necessary materials
– Labor expenses
– Costs for tearing off the existing roof
– Disposal fees
– Building permits
– Profit and overhead charges


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