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Flat Roof Replacement – Cost and Options

Calculating flat roof replacement cost is not straightforward due to the large number of flat roof materials and construction options. However, fear not in this RenoCompare cost guide we will give you flat roof replacement costs per square foot for each type of flat roof available. We will also advise you on when to consider replacing your flat roof and when to consider a flat roof inspection from the professionals.

Average Flat Roof Replacement Cost

The average cost to replace your flat roof ranges from about $4.35 to $11.75 per square foot. The wide price range reflects significant cost differences in your flat roof replacement options.

Flat roof replacement will set you back $8,700 to more than $23,000 on an average home and garage with a 2,000 square foot roof.

These costs include removing the old roof, prepping the roof for the new material and installing it. They do not include repairing damage.

When to Replace your Flat Roof

There’s a good case to be made for proactive flat roof replacement. When a flat roof fails, water damage to the interior of a home can occur quickly and extensively – and expensively!

When is it time to replace your flat roof?

Signs of roof degradation include leaks, visible wear or fraying of materials, seams or layers separating and cracks in the material.

If the flat roof hasn’t had major repair issues, replacing it when it reaches 85-90 percent of its maximum life expectancy might save the high cost of water damage from sudden failure.

Here are six common flat roof options with expected longevity.

  • Modified bitumen: 12-18 years
  • Built-up roof (BUR): 10-30 years based on quality of installation and number of roof layers
  • EPDM: 15-25 years
  • TPO: 18-30 years
  • PVC: 20-33 years
  • Spray-on roofing: 18-22 years, and it can be recoated twice without roof removal

For more detailed information on these options visit our flat roof materials page.

Flat roofing material warranties range from 15 to 35 years. Most are pro-rated, and beyond 10 years, failure can almost always be blamed on poor installation or maintenance rather than material defects. In short, few flat roofs last as long as their warranty.

Unsure? Have your Roof Inspected

If you’re buying a property with a flat roof, or a roof you installed is 15+ years old, hiring a roofing inspector to evaluate its condition is money well spent. Average flat roof inspection cost is $190 with a low of about $75 and a high of $300+ for large homes and/or complex roof systems.

An independent home inspector rather than a roofer is your best source for an unbiased view. The inspector should not make any recommendations of a roofing contractor unless you ask for one. Simply make sure the inspector you hire has a wealth of experience evaluating flat roofs of the type you have.

Flat Roof Replacement Options

Here are your choices along with flat roof replacement cost per square foot for each. There is more information on these roof types in our Flat Roof Overview Guide.

Modified Bitumen – It’s called mod bit for short and built with layers of polymer-modified bitumen typically bonded with heat. A cap layer of rolled asphalt roofing with UV-reflective granules completes installation.

Modified bitumen replacement cost is $4.35 to $7.25 per square foot.

Built-Up Roof (BUR) – A built-up roof features alternating layers of fiberglass ply mats with a coating of asphalt or other bonding material. The layers are covered with stone or gravel that protect the layers from sun damage.

BUR roof replacement price is $6 to $8.50 per square foot.

EPDM: Ethylene propylene diene monomer rubber (EPDM) is a seamless single-membrane roof glued to a rigid substrate.

EPDM roof replacement costs $5 to $8.25 per square foot.

TPO: Thermoplastic polyolefin is a polymerized single-membrane roof. The material can be seamed, so installation is less of a challenge.

TPO roof cost is $6.25 to $9.50 per square foot.

PVC: Polyvinyl chloride is a tough single-layer roof that handles foot traffic better than other single-membrane options. It also has seams.

PVC flat roof replacement cost is $8.35 to $11.25 per square foot.

Silicone spray roofing: 20 years, and can be recoated twice without roof removal.

Flat roof replacement cost per square foot is $8.85 to $11.75 for spray-on roofing.

This summary table shows types with flat roof replacement cost and longevity.

Roof Type
Replacement Cost Per Square Foot
Longevity
Modified Bitumen $4.35 – $7.25 12-18 years
Built-up Roof $6.00 – $8.50 10-30 years
EPDM $5.00 – $8.25 15-25 years
TOP $6.25 – $9.50 18-30 years
PVC $8.35 – $11.25 20-33 years
Spray Silicone $8.85 – $11.75 18-22 years

Choosing the Right Roof Replacement Option

If you’re replacing a flat roof and want to try something new, a contractor can tell you which options will work on your roof with the least amount of modifications to its structure. That aside, here are popular flat roof replacement options.

Upgraded mod bit: Homeowners that have had success with a modified bitumen roof but want the next roof to last longer often choose a built-up roof with at least three combination layers of material and asphalt.

Moving to single membrane roofing: If you don’t like the smell and mess of a modified bitumen or built-up roof, or are concerned about its weight, one of the single-layer flat roof options is a popular choice.

Making use of the roof: If your roof serves as a balcony for relaxing or entertaining a few people at a time, then a PVC roof is the ultimate choice. It wears well and doesn’t scratch or gouge easily. Spray-on silicone roofing is another good option.

The greatest factor in getting the best wear from a roof is proper installation. Hallmarks include installation per manufacturer guidelines, no low spots where water can pond and a top layer or coating of sun protection suitable to the material used.