How Much Does It Cost to Replace a Flat Roof?

torch-down modified bitumen installation on flat roof

Before homeowners replace their flat roof, they should be informed about the costs of different materials. Discover the most common flat roof systems and how they compare in installation procedures, price, aesthetics, benefits, and more.

Flat Roof Material Cost Breakdown

It’s difficult to provide an accurate estimate for the cost of flat roofs as each home and evaluation is different. But, flat roof replacements don’t vary as much as shingle replacements. And due to flat roofs being easier to install than conventionally pitched roofs, their replacements are typically cheaper than other common materials.

Average Price for 1,500 sq. ft. Flat Roof
Material Cost Per Square Foot Cost Per Average Full Replacement
Built-up Roofs $2.50 - $5 $5,000
Sprayed Polyurethane Foam $1.50 - $6 $5,625
Modified Bitumen $3 - $6 $6,750
Standing Seam Metal $5 - $10 $11,250
Rubber Roofs $10 - $20 $15,000

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Built-Up Roofs (BUR)

Built-up roofs, also known as tar and gravel roofs, are the cheapest replacement option.

Built-up roofs provide excellent waterproof and UV protection. They’re also highly resistant to fire and generally do not require a lot of maintenance or upkeep.

However, built-up roofs are heavy and can strain the home’s structural support. If you’re seriously considering a built-up roof, you’ll need a contractor to evaluate the overall structure of the home, including the roof, before proceeding with the installation.

Built-up roofs require a specific set of expertise to install, and the process takes longer than other materials. They cost $2.50 - $5 per square foot, and prices for new built-up roofs are about $5,000.


Sprayed Polyurethane Foam Roofs

Another flat roofing option involves spraying polyurethane foam directly over the existing roof system. This eliminates the need to remove the old roofing material. Once the first layer of foam dries, it is treated with a protective coat for added longevity.

Sprayed polyurethane foam is flexible, lightweight, and an excellent insulator, and it can last for many years without complications.

SPF roofs are relatively cheap per square foot, costing about $1.50 - $6. On average, a full replacement costs about $5,625

Modified Bitumen Roofs

roofer on modified bitumen flat roof

Modified bitumen is typically composed of asphalt or other rubber modifiers and solvents.

Homeowners can install some modified bitumen systems, as these systems are self-adhering, peel-and-stick systems. However, we recommend hiring a professional to ensure your flat roof replacement is installed correctly.

Modified bitumen systems installed with the torch-down method are extremely dangerous for a homeowner to perform himself, so hire a professional contractor to get it done safely and accurately.

Modified bitumen costs about $3 - $6 per square foot, with the average full replacement costing about $6,750.

Standing Seam Metal Roof

Standing seam metal roofs are a popular option for flat roof replacements due to the variability of materials and colors, their durability, and weight. Commonly made from interlocking panels of iron, steel, aluminum, or copper, standing seam metal can last for generations.

Standing seam metal costs between $5 - $10 per square foot, depending on your desired metal, and a full replacement usually runs about $11,250.

Rubber Roofs

Rubber may be the most expensive option, but it’s also the most durable material available and is highly preferred by contractors.

Rubber roofs, when installed properly, are highly resistant to tears, scuffs, and punctures. If the roof does develop a leak, it’s very easy to patch.

Rubber roofs cost about $10 - $20 per square foot, with a full replacement costing about $15,000.


Avoid DIY flat roof replacements.

hire a roofing contractor for roof replacements

Homeowners should not replace flat roofs by themselves. Installing tar and gravel roofs or torch-down modified bitumen roofs without the help of a professional contractor can lead to disaster. Homeowners who attempt these installations alone risk severe bodily harm and/or the possibility of burning down their homes.

Research the different materials available for your flat roof replacement and gather different estimates from several contractors. Hometown Roofing Contractors helps customers find qualified flat roofing contractors. Customers can research companies, request quotes, and see what other people have to say about their services.

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