Flat Roof Replacement Cost Calculator

In recent years flat roofs have grown in popularity because of their distinctly modern look, as well as ease of installation and repair. When it comes to cost, a flat roof is cheaper than the majority of sloped roof materials, with the exception of composite shingles.

On average, the price to install or replace a flat roof is $5-10 per square foot. A 1,600 sq.ft. flat roof costs $8,000 - 16,000. This includes tear off, insulation and the new roofing membrane. Final prices depend on the quality of the material, roof size and complexity, your contractor and location.

Estimate installation prices for the following flat roof materials: 1. Single Ply Membranes (TPO, PVC, EPDM Rubber); 2. Modified Bitumen; 3. Rolled Roofing.

Roof Size:	x ft.
Curbs (Skylights / Chimneys / Hatches)	#
Parapets length:	ln. ft.
Insulation:	1/2" Fiberboard 1" ISO Board (6-R) 2" PolyISO (12-R) 3" PolyISO (18-R) 3.3" PolyISO (20-R)
Roof Pitch:	Flat (0) 1/12 (4.5 degrees) 2/12 (9.5 degrees) 3/12 (14 degrees)
Old Roof Removal:	YES - 1 layer YES - 2 layers NO
Job Complexity:	Simple Medium difficulty Difficult
Roofing material:	EPDM (Black Rubber) PVC Roof 50-mil TPO Roof 45-mil Tar & Gravel/BUR Rolled Roofing GAF Liberty / Flintlastic
Region (US Only):	National Average New England Mid Atlantic South Atlantic East South Central West South Central East North Central West North Central Mountain Pacific
Low End $0 Mid Range $0 High End $0 See Costs in Your Area! Start Here - Enter Your Zip Code

This tool estimates the total installation cost for new or retrofit projects, completed by a professional contractor. The quote includes:

- All materials
- Labor
- Tear-off roof cost
- Dump fees
- Building permits
- Profit & overhead

You will see three price estimates - LOW-END, MID-RANGE and HIGH-END. These are based on National Average roof costs.

How to use roof calculator

1) Measure your house/building from corner to corner.

If there are overhangs, be sure to include these into the Dimensions field. 12" overhang over 100 foot eave span adds 100 sq. ft. to the total roof area, which can cost as much as $1,000 or more.

2) Enter the exact number of large penetrations / curbs (hatches, skylights and/or chimneys).

Penetrations require special flashing work and will add significant cost for each unit. If you do not include them, you will see a huge discrepancy between this estimate and one from a contractor, because he WILL include these.

3) Enter the length of parapet walls (and metal cap).

The parapets can add significant roof surface and extra work, so do not discount them. Your roofer WILL charge you for these.

4-6) Select Insulation Thickness, Roof Pitch, Tear-off Layers.

7) Select Job Complexity.

This can be vague, but if you have multiple penetrations, curbs, roof-to-wall flashing, difficult drainage, choose the Medium or even Complex setting. Also, be aware of ease of access to the roof. If your contractor needs to hire police detail, or if your roof is 7 stories off the ground, the cost WILL go up.

8) Select the material you want.

You can get a price for the chosen material, and then re-calculate again for a different one, to compare. EPDM roofing is the most popular choice, because its the budget-friendly option. TPO is the second most frequently installed option on residential properties.

9) Select your region in the US.

Prices may differ as much as 30% depending on where you live.

What is the best material for a flat roof?

Most existing commercial and residential flat roofs are covered with an EPDM Rubber membrane, or Rolled / Built Up / Tar systems.

Rubber roofing is the cheapest membrane roof. The cost for the membrane alone starts at $1.5 per square foot. This is why EPDM continues to be the most popular cover for a flat roof among businesses and homeowners. Moreover, ease of installation further contributes to such a large volume of installs. If you are looking to do a quick re-roof before selling your home, or replacing a roof on a rental property, EPDM rubber is a good material to consider.

PRO TIP: If your current roof is EPDM rubber, consider repairing it - either yourself or by hiring a contractor specializing in flat roofs.

Most rubber roofs can be fixed for a fraction of new replacement cost, and service life can be extended by 3-7 years!

TPO:In the last decade, TPO roofing has started to gain major recognition. This single ply membrane offers good value. It provides better quality and durability than rubber, but cheaper pricing than a premium material, such as PVC. You can expect to pay around $1.79 - $2.25 per square foot of TPO material, when you include all required accessories. Many higher-end residential new construction projects or re-roofs now specify a TPO membrane.




PVC: In my experience, IB PVC is the most reliable thermoplastic material. I've been installing it for over 12 years, and while I have tried a number of other products, I still always go back to IB. While it is more expensive, about $1.90 per square foot, you get superior durability, longevity and leak-free performance, compared to all other materials.

Experienced roofers, builders and architects know that PVC roofing is top of the line. It is therefore often used in luxury residential and commercial building projects. If you are planning to stay in your home for at least another 5 years, and don't want to deal with roof leaks and repairs, PVC is the best option.

Here is an example of a PVC roof installation on a residential home:

Does roofing brand matter?

In your online research, you may notice that there are many different companies selling flat roof membrane products. It can be confusing to figure out which one you should get. This is particularly true when it comes to selecting a TPO roofing product. Because its so popular, there are many small - time manufacturers that produce TPO, and sell it at discounted rates. However, their quality and longevity is often questionable.

As a rule of thumb, its best to get your roof from a reputable manufacturer that has been making these membranes for decades. These are GAF, Duro-Last, Versico, IB, Sika Sarnafil, etc. While you will pay a bit of a premium for the "brand", you will have the peace of mind of owning a high quality roof.

You should also ask your roofing contractor which material he would recommend. A seasoned roofer will have installed various single ply membranes from different brands, and will know which one has had the least problems. His advice is important, because you need to get a roof that performs well in your particular geographic location.

Membranes from different brands have different chemical formulations, and some do better in certain climates than others. For example, some TPO roofs don't last long when exposed to extreme heat for a long time, such as in Texas or Arizona. You roofer will know which product can protect your home from local weather conditions.

This is another reason why you want to hire someone who has worked with flat roofs for at least a decade. A newbie roofer may have good technical skills, but he will not have enough experience to recommend the best roofing material.

Tear off considerations

When replacing a flat or low slope roof, building code in most states limits you to no more than two layers of material. For example, if you have EPDM rubber now, you may put on a new PVC or TPO membrane.

On the other hand, if you have Modified Bitumen (Mod. Bit.) or gravel and tar, with rubber on top, you need to remove the rubber roof. Removing EPDM or another single ply membrane is simple and relatively inexpensive. To tear off one layer of membrane costs $0.45 per square foot, and two layers costs $0.60 per square foot. Thus, tearing off 1,600 of single ply roofing will cost you $720 - 960, depending on the number of layers being taken down.

However, if you need to tear-off Tar + Gravel of multi-layer rolled roofing, the cost will go up significantly. One layer tear off runs about $1.5 per square foot, where as two layers costs $2 per square foot. You will pay $2,400 - 3,200 to remove an old tar roof from your house. Its so expensive because rolled roofing is very heavy, many dumpsters need to be ordered, and it can only be removed using special equipment.

Our roof estimator takes tear off costs into consideration when calculating your price quote. Make sure you select an appropriate number of tear-off layers to get an accurate quote.

Installation advice

Compared to standard asphalt shingles, most contractors charge 20-35% more to install a flat or low slope roof. Out of the total installation cost on a new flat roof, around 70% will be the cost of labor!

The cost of installation starts at $5 - 5.5 per square foot, but can go up to as much as $7-9 per square foot, depending on roof size and complexity. Installing a roof on a two or more storie home will cost at least 30% more than a single storie house. Moreover, curbs, corners and penetrations, such as chimneys, vents and skylights will all increase the total cost, because they need to be flashed in order to be watertight. This adds more hours of labor, and drives up the final price.

Overall, labor costs are higher because flat roofing is a specialized field that requires expert knowledge, tools, and a particular set of skills. This means that a regular contractor, who shingles roofs, will NOT be able to properly install a single ply membrane or any other flat roofing material.

Many people try to save money on installation and believe promises of general contractors who are willing to charge less, just to get your business. Chances are your new roof will leak shortly after they are done. Sometimes it takes as little as 1-2 heavy rain storms for the damage to show.

In fact, most flat roofs leak due to faulty installation. Even the best, most expensive membranes will fail, if a contractor does not know what he is doing.

Also, keep in mind that once your roof leaks, you will need to spend a lot of money on repairs. Depending on the material, patching up a leaking membrane can cost an average of $350-600. If there are many leaks and damaged insulation, the cost of repair can be well over $1,000. Because the cost of repairing a flat roof is so high, its really not worth it to try to save a few hundred bucks and hire an unqualified installer.

We strongly recommend working only with licensed pros who specialize in the field of flat roofing, and have references of recently completed jobs.

Where should a flat roof be installed?

In addition to serving as a beautiful and durable cover for the house, a flat roof has a number of other useful applications. Many homeowners prefer to install it over a porch, a house addition or a garage. One of the biggest architectural trends is to have a house with a sloped roof and build a modern looking addition with a flat roof. Moreover, a flat roof membrane can even be used to build a deck!

If you are building a brand new home or an addition, remember that your flat roof will not actually be flat. For the best water drainage, it should have a slope of at least 1/8 inch per foot. The minimal slope allowance for flat roofs, according to most building codes is 1/4 inch per foot.

Because a flat roof tends to collect water and sheds it much slower than a pitched roof, it may not be an ideal option if you live in an area that gets a lot of heavy rains and snow storms. EPDM rubber roofs are particularly notorious for developing leaks as a result of ponding water.

Flat roofs last the longest in a mild, dry climate that does not have severe temperature fluctuations. Still states in the northern parts of US do have their fair share of houses with flat roofs, and its perfectly fine to install a flat roof in a state like Massachusetts or Vermont. You just have to be ready for more frequent maintenance checks and potential repairs.

Did you know? a flat roof with proper insulation will be 30-40% more energy efficient than asphalt shingles, which are used on the majority of sloped roofs. This can save you hundreds of dollars in heating and cooling costs. For maximum savings, you need to make sure that you are installing rigid foam insulation (Poly Iso) with a proper R-value.

Additional Resources

Here are related guides about different types of flat and low-slope roofs, and how much they cost.

2018 Flat Roof Guide

EPDM Rubber Roofing

PVC Roofing Cost Calculator

TPO Membrane and Installation Prices

Repair and Replacement Options for Flat Roofs