Whether you are a homeowner or commercial real estate owner, when it comes to replacing your flat roof, you most likely want cost-effective solutions. It can be difficult to know which solution, however, is best for your property without understanding what factors into replacement costs. Understanding the financial implications includes knowing the details that affect cost and what your material options are. Let’s dig into what goes into a flat roof replacement cost breakdown, so you can make an informed decision about replacing your flat roof.

Major Cost Factors of Flat Roof Replacement

So, how much is it to replace a flat roof? The answer can vary depending on several major factors, including size of your roof, materials used, extent of the damage to your existing roof, and your location. Overall, as of 2024, flat roof replacement cost per square foot can possibly range between $4 to $30, with an average between about $6-$9 per square foot. Digging into the variables that affect this average cost is important in calculating your flat roof replacement cost breakdown.

Roof Size and Complexity

It stands to reason that the bigger your roof the more expensive it will be to replace. The square footage of your roof times the square footage cost will give you an idea of how size calculates into replacement costs.   The complexity of your roof factors in as well. Not all roofs are built the same and it may appear that flat roofs are just that–flat, but this is far from the truth. There are architectural variables on all roofs, including chimneys, skylights, multiple levels, varying slopes, irregular shapes, vents, or other features. The complexity of these features can add additional labor costs and may also require experts on certain features to do some of the work to ensure the integrity of your roofing system. This will invariably add to your replacement costs.

Roofing Materials

Your flat roof cost will also depend on the quality of your roofing materials and what type of flat roofing system you decide to use. This may be the largest and more variable expense in a flat roof replacement. The quality, durability, and the complexity of installing the roofing system will factor into your total flat roof replacement cost.   On the low end of the roofing material spectrum is fiberglass while metal is on the high end. Metal roofing can cost up to five times more per square foot to install than fiberglass, yet its longevity is more than double that of fiberglass, increasing its cost savings over time. There are also plenty of material options that fill in the mid-range of the flat roof replacement cost spectrum.  Polyurethane, single-ply membrane, and modified bitumen roofing all fall in this mid-range, costing about the same to install and at a slightly higher cost than fiberglass. Built-up tar roofing is slightly higher than these three lower, mid-range systems due to its intensive labor costs while EPDM (rubber roofing) or TPO roofing is in the higher mid-range, costing below metal but above the other flat roofing materials.

Existing Roof

The condition of your existing roof plays into the flat roof replacement cost breakdown because it has to be removed before a new roof can be installed. The larger the roof and the more complicated the removal the more it will cost. Labor is usually charged by the hour, so the longer something takes to do the more it will cost. This includes the removal of your existing roof along with its clean-up and disposal.   The cost to replace a flat roof also depends on the condition of your existing roof. For example, if the roof slab needs to be replaced along with your flat roof membrane then your flat roof replacement cost bottom line will increase.

Geographic Location

Where your property is located also factors into a flat roof cost. For example, flat roof replacement in Minnetonka, Minnesota might be more than in Santa Fe, New Mexico. But since your building is located in Minnetonka and you are most likely not moving it, you will pay the cost for a Minnetonka flat roof replacement. Pricing fluctuates according to local market conditions and climate, which can impact the cost of materials and labor. Roof replacements generally cost more in areas that experience extreme weather or severe storms. For example, Minnetonka experiences extreme weather temperatures, severe thunderstorms with high winds, and large snow events. All of which require more durable roofing materials, better insulation, and stronger construction techniques. This adds up to higher overall costs. Local labor rates, permit requirements, material availability, and shipping costs all factor into the overall flat roof replacement cost breakdown too. Researching local costs and requirements is important to figure into your budget.

Other Potential Factors in the Cost to Install a Flat Roof

There are other factors that can increase your flat roof replacement costs. These factors include your choice of roofing insulation and underlayment, roof accessibility, drainage systems, and warranty costs.

Roofing Insulation and Underlayment

Roofing insulation does not only differ by the type of materials used but also the roofing construction techniques used. Both can affect your flat roof replacement cost bottom line.

How Insulation Is Added

Insulation is a part of your roof construction and can be added in several different ways, including:

• Cold roof: Insulation is added below the roof deck and inside the joists and rafters, leaving space above for ventilation.
• Warm roof: Insulation is added on top of the roof deck to maintain a constant temperature on and below the deck.
• Inverted roof: A waterproof layer is added for protection with insulation added above it.
• Hybrid roof: A combination of cold and warm roofing techniques that adds insulation both above and below the roof deck.
• Curved roof: An arched surface is added to the roof to facilitate drainage and requires extra insulation.
• Tapered roof: To facilitate water drainage and to guard against pooling, a slight slope on the roofing surface is achieved by varying the thickness of the insulation
• Green roof: Much as the name suggests, vegetation is planted on the roof’s surface to support drainage. A waterproofing layer and insulation is needed with a green roof even though the vegetation acts as an extra layer of insulation as well.

Each of these flat roof building techniques will have different materials and labor costs that will affect the overall cost of your roof replacement.

Insulation Materials

Roofing materials do not only include your flat roofing system, but also the materials used for your insulation and underlayment. Roof insulation is important to protect against heat loss and gain as well as condensation buildup that can cause mold growth, rotting, leaks, and dampness. The type of insulation you use can factor into your upfront installation costs, but it can also lower your overall energy costs and extend your roof’s lifespan. The trade-off, over time, for using high-quality insulation and underlayment can be well worth the investment.

Higher-quality products include:

1. Polyisocyanurate (PIR) insulation: Lightweight and stable product with a high R-value rating. It offers highly effective insulation in both warm and cold roofs.
2. Expanded polystyrene (EPS) insulation: Lightweight and durable product offering thermal insulation and comes in a variety of thicknesses. Only good for warm flat roofs.
3. Extruded polystyrene (XPS) insulation: Dense and rigid material with excellent thermal and compressive strength properties. Good for both warm and cold roofs.
4. Mineral wool/rock wool/stone wool insulation: A natural or recycled material offering good thermal and fire-resistant properties and versatile installation as it is available in batts, rolls, or boards. May, however, need an added protective layer for waterproofing purposes.
5. Spray foam insulation: A versatile and effective insulation option for flat roofs that is applied as a liquid and then expands to provide an airtight and seamless layer. Its airtight qualities offer both moisture and thermal protection. It can be used for both warm and cold roofs and is ideal for curved roofs.

Roof Accessibility

Not all roofs are easily accessible and safety is a high priority for roofers. If reaching your rooftop proves more difficult, special equipment may need to be used to ensure both access and safety, such as safety harnesses or scaffolding. The usage of extra equipment will increase the time and labor costs of your roof replacement.

Drainage Systems

Drainage systems also come with variables, but a flat roof cannot properly protect your property without one. Improper drainage can cause pooling, leakage, and even foundation problems. A bad drainage system can shorten your roof’s lifespan and possibly even your buildings. Not something you want when you are investing in a new roof. If a drainage system needs to be added, moved, or upgraded it will increase the cost of your roof replacement. This may also include the addition of a sealant to the top of your roof for added protection against the elements.

Warranty Costs

Adding an extended warranty to your new roof, for either or both the roofing materials and the construction will mean long-term protection of your investment. These extended warranties may buy peace of mind, but they will also increase your out of pocket expenses.

Professional or DIY Flat Roof Replacement?

Although a small flat roof repair can be a DIY project, especially if you are comfortable with do-it-yourself construction projects, a professional flat roof installation is more than highly recommended when it comes to roof replacement. It is essential to ensure the integrity of your property. Roof replacement is not a DIY project.

Professional roofers will:

• Inspect your roof before beginning any work and again after removing your old roof for decking or structural damage
• Prepare your roof and the surrounding property for the work to be done
• Deliver your roofing materials
• Remove and dispose of your existing roof and any debris
• Prepare your roof surface and install underneath roofing components and a drip edge
• Install new underlayment, your new roofing system, and a sealant

Reducing Flat Roof Replacement Costs

The integrity of your roof may be one of the most important features of your home or commercial property, yet one wants to overpay for a roof replacement. Here are a few tips to help reduce the costs of this important property project:

• Research roofing contractors in your area that specialize in flat roof installation and get a quote from at least three of them
• Look at your roof replacement as a long-term investment and choose quality roofing materials with high durability and longevity ratings.
• Schedule your roof replacement during a less busy time of year for contractors

Read More: 7 Way to Finance a New Roof

The Lifespan of Flat Roofing Systems

Flat roofs can last anywhere between 20 to 50 years, depending on the roofing materials used. The lifespan can be extended through the use of quality products and proper routine maintenance.   The higher upfront costs of a high-quality roof can be worth the expense as more often than not quality products last longer. Needing to repair or replace your roof less often can be more cost-effective over time.   Regular and routine maintenance, including annual inspections, can keep your roof functioning well into the future. Make sure to follow the manufacturer’s guidelines for cleaning and maintenance for the flat roofing system you are investing in.   A properly installed roof is also important. A roof that is not installed properly will not function as it is intended and can damage that integrity of your structure. To start the lifespan of your new flat roof off on the right foot, having it properly installed by a roof replacement company is a must.

Read More: How Long Does a Flat Roof Last? Lifespan, Factors, and Tips 

Hiring a Professional Roofer

When it comes to flat roof replacement, hiring the right professional roofing company can help control your flat roof replacement cost. By hiring a reputable and professional flat roofing service who understands the different flat roofing systems on the market and has years of experience installing flat roofs, you can cut down on the headaches that can be associated with roof replacements. Summit Construction specializes in high-end, quality construction with an extensive portfolio of exterior construction projects and knows the importance of proper flat roof installation. Book your appointment and discover how having a responsive and professional flat roofing contractor on your side can make your roof replacement have the quality you deserve at the cost you can afford.