Flat Roof Calculator estimates the cost of replacing your flat roof with a new single ply or built-up roof. Prices can be estimated for both residential and commercial flat & low slope projects.
Calculate costs for following flat roofing materials: EPDM (rubber) roof, TPO & PVC white single ply roofs in 50-mil, 60-mil and 80-mil thickness, as well as built-up roofs such as Tar & Grave & Rolled Bitumen.
Typical cost for a new flat roof is $4.95 to $8.60 per square foot for EPDM rubber and $5.95 to $9.10 per square foot for TPO single ply roof, without insulation upgrades.
Estimate Flat Roofing Cost in OHTo get accurate pricing, simply enter your roof dimensions, pitch, new insulation thickness, any curbs or protrusion flashing (skylights, hatches, roof-top AC curbs, drains, etc), optional tear-off (removing old roofing material), and parapet walls.
Top Flat Roof Materials
In the past 10-15 years, low-slope and flat roofing market has largely moved away from open-flame (torch-down) built up roofs, such as Hot Tar & Gravel, Bitumen, etc., to energy efficient single ply membrane roofs. Single ply materials are dominated by TPO, EPDM and PVC materials.
PVC and TPO are heat welded products, while EPDM rubber is glued material.
In most cases, EPDM roof is black, and not energy efficient. Therefore, most new flat roof materials are white TPO and PVC installs.
Average Cost To Replace Flat Roof
All single ply flat roofing materials are priced based on membrane and insulation thickness.
Most common membrane thicknesses are 50-mil, 60-mil and 80-mil. Thicker is more expensive, as it will usually last longer, and offer longer warranties.
Cost of TPO Roof
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TPO is the most popular single-ply flat roofing membrane material, due to lower cost, and heat-welded seams.
Basic 50-mil TPO will cost about $5-6 per square foot without any upgrades or extra work, such as tear off, curb flashings, or extra insulation.
60-mil will cost $5.65 to $6.55 per square foot. Most expensive will be the 80-mil product, coming in at $7.65-$8.70 per square foot.
Most common thickness of a TPO membrane roof is 60-mil, due to reasonable cost, and 20-year warranty period.
TPO roofing ins the most widely installed single ply material in the US, as of 2023. Most TPO roof installations are on commercial & industrial buildings, which have large surface area, and where cost per square foot is critical.
However, this does not make a TPO roof inferior. The heat-welded seams provide great leak-resistance, and options for potential repairs (if needed).
Keep in mind though – there is no “uniformity” among TPO products from different manufacturers. Even products from the same manufacturer may not be compatible, if there is more than 3-5 years difference in production date, as TPO formulations often change (mostly to reduce costs).
Cost of PVC Roof
PVC roofing is a more “aged” option, compared to TPO, and will usually cost 10-25% more, due to “higher quality”, longer successful track record, and optional chemical resistance.
PVC roofing offers time tested (many roofs over 40 years old, are still in service) proven technology that helps protect millions of large and small building around the world.
50-mil PVC roofing will cost about $5.95 to $6.90 per sq. ft.
60-mil PVC roofing will cost about $6.75 to $7.70 per sq. ft.
80-mil PVC roofing will cost about $8.15 to $9.20 per sq. ft.
The most common thickness of a PVC membrane roof is 60-mil, due to reasonable cost, and 20-year warranty period.
PVC materials are generally “cross-compatible”. This means that if you have a leak (puncture or leaking seam/flashing), you can simply clean the surface and weld in a new patch, using material from almost any manufacturer. In most cases, repairs can be performed regardless of roof age.
Cost of EPDM Rubber Roof
An EPDM roof, is an old and proven single ply material, which offers competitive cost, and ease of installation, and does not need any heat-welding equipment.
However, lack of heat-welded seams, make it not the best material for a situation where you have ponding (standing) water on the roof.
60-mil EPDM roofing will cost about $5.15 to $6.70 per sq. ft.
80-mil EPDM roofing will cost about $6.85 to $7.80 per sq. ft.
Most common thickness of EPDM rubber is 60-mil, due to lower cost.
All EPDM rubber roof products are cross-compatible, and the most critical part in both installation and repair applications, is using good EPDM Primer
or glue.
Since all seams and flashing on an EPDM roof are glued, SEAM primer is the “weakest” link in the long term performance of a rubber roof. The best primers are older “high VOC” products.
However, many states in the US made it forbidden for sale, and now a new “safer LOW VOC” primers must be used. However, Low VOC primers tend to not perform as well as older products.
Therefore, our recommendation is to use a PVC or TPO roof instead.
How To Use Flat Roof Replacement Cost Calculator
Using our Flat Roof Cost Calculator is straight forward, and most common options are pre-selected.
Step 1) Enter your roof size (length & width). If your roof is NOT of square/rectangular shape, you can calculate total square feet on a paper, and enter simplified sizes.
For example: If you have an “L” shaped roof, with one section being 20×50 and another section 20×20, you will have 1400 total sq. ft. You can enter this size as 14×100 or 20×70 or 40×35, etc. Any of these combinations will yield the same result.
Step 2) Select desired roofing material. Since EPDM rubber is the most “CALCULATED” type of flat roof (43% out of 270,000+ estimates), we positioned it as #1. Keep in mind though – in terms of TOTAL sq. ft. installed in US, 60-mil TPO is the most used product.
Step 3) Select your roof slope / pitch. This setting will slightly affect your results, as higher slope mean larger roof.
Since this is a flat roof calculator, we provide options from Zero (completely flat) up to slope of 3. Above 3 pitch, it’s not a “flat” or “low slope” roof anymore, and a membrane material should not be used. Roof shingles or a metal roof is ideal for steeper roofs above 3 pitch.
If you need a steep(er) slope roof, use our Steep Roof Calculator to estimate costs.
Step 4) Select your desired insulation Type & Thickness. While thickness of 1″ and higher are listed as “PolyISO”, in reality EPS and Styrofoam insulation costs are very similar, and can be interchanged in a flat roof application. However EPS and Styrofoam would require some sort of separation layer, which would increase cost. Thus, the ideal insulation type is PolyISO.
Step 5) Select your desired Tear-off (roof removal) option. While most states and jurisdictions in US & Canada allow up-to 2 layers of roofing material, it is always recommended to remove old roofing, and repair any wood / substrate damages, before installing a new roof, and potentially trapping moisture. This is especially critical for a flat roof, which is very prone to leaks.
Step 6) Enter total number of box penetration flashings, such as Curbs (for a roof-top Central AC), roof hatch / skylight or chimney.
Step 7) Optional settings: Click “Show More Options” to reveal additional inputs such as Roof Drains, Pipe Flashings and Parapet Walls.
Step 8) Click the “Calculate” button and get 3 instant price quotes – Low End, Medium Range and High End pricing.
