How much does it cost to repair a flat roof?
Get free estimates from roofers near you
Flat Roof Repair Cost Guide
Updated: August 17, 2022
Flat roofs are commonly found on both commercial buildings and contemporary-style homes. Because there is little-to-no pitch or slope on a flat roof, they tend to develop issues relatively quickly, requiring repairs every few years. The most common issue with a flat roof is leaking, which may require a patch to correct the issue. But flat roofs can develop other issues, including alligatoring, blistering, bubbling, and sagging, with repair costs and methods varying accordingly.
The national average cost for professional flat roof repairs is between $300 and $1,250 for a 1,500 sq.ft. flat roof, with most homeowners paying $750 for flat roof leak repair. The low cost for this project is $50 for fixing a couple of cracked shingles. This project’s high price is $4,000 to repair serious hail damage to a flat roof, such as patching holes and filling cracks.
Average Cost to Repair a Flat Roof
|Flat Roof Repair Cost
|National average cost
Flat Roof Repair Cost per Square Foot
Roof repair specialists and companies usually decide how much to charge for their services based on the problem and the amount of repair work required. They take many factors into account, and they do not typically charge per square foot. However, the size of the damaged area can be an important factor. Expect to pay from $3 to $15 per square foot for professional flat roof repair. The table below shows the average repair costs for various roof sizes because some flat roofs over porches and garages are relatively small, while others cover the entire home.
|Average Repair Costs
|$150 - $750
|$300 - $1,500
|$450 - $2,250
|$600 - $3,000
|$1,500 - $7,500
|$3,000 - $15,000
|$4,500 - $22,500
|$6,000 - $30,000
Cost to Repair a Flat Roof by Type of Material
Flat roofs can be made from many materials, and some are more expensive and time-consuming to work with, leading to higher repair costs. You may need to pay more for your flat roof repairs if your roof is made from flat concrete rather than fiberglass. The table below shows a range of common roof materials and the average flat roof repair price per square foot for each.
|Average Repair Cost per Sq.Ft.
|$3 - $6
|$3 - $6
|$3 - $7
|$3 - $7
|$4 - $8
|$4 - $8
|$4 - $10
|$5 - $10
|$5 - $15
The cost to repair a flat roof made of GRP ranges from $3 to $6 per square foot. GRP is one of the cheapest flat roof materials. The acronym stands for glass-reinforced plastic. This material is flexible and easy to install but prone to weather damage. It can crack and split and may need patching. It also needs regular resealing.
Fiberglass Flat Roof Repair
Professional repairs for a fiberglass roof cost between $3 and $6 per square foot. Fiberglass is one of the most affordable materials for a flat roof, and they are made with plastic strands woven together into a strong mat, covered with special protective coatings. While fiberglass roofs withstand general weather conditions and wear and tear, they tend to crack, break, and dent easily. They are also very susceptible to water damage.
Modified Bitumen Flat Roof Repair
Repairing a flat roof made of modified bitumen averages $3 to $7 per square foot. Modified bitumen is a popular, affordable material for flat roofs, well-known for its versatility and resistance to extreme temperatures and UV rays. However, modified bitumen roofs are at risk of damage due to debris and impacts from hail and falling tree branches. Pooling of water on a modified bitumen roof can also make it wear down quickly.
Built-Up Roof (BUR) Repair
Fixing a built-up roof or built-up tar roof ranges from $3 to $7 per square foot. Built-up roofs are similar to modified bitumen roofs and have the same pros and cons. They are affordable, versatile, and easy to install, but they can be prone to impact, storm, and water damage if water pools on top for too long.
Repairing a single-ply membrane flat roof costs $4 to $8 per square foot. Single-ply membranes are popular and usually made of plastic or rubber materials, like TPO. They last long and resist water, but the membrane is prone to holes, splitting, and blistering.
Polyurethane flat roof repairs cost $4 to $8 per square foot. Polyurethane, or SPF, is a foamy material that offers a strong waterproof membrane. The downside to this material is that holes and bubbling may occur, so the roof may need to be patched or resurfaced regularly to keep it in good condition.
Concrete Flat Roof Repair
Expect to pay between $4 and $10 per square foot for concrete roof repair. Concrete is one of the strongest materials used for a flat roof, being completely water and weather-resistant. However, cracks and fissures may appear in a concrete roof over time and need to be filled in to prevent water from penetrating or ice freezing inside the gaps. It can cost a lot to repair flat concrete roofs if old and crumbling sections of concrete need to be dug out before new concrete can be poured.
Homeowners spend between $5 and $10 per square foot on EPDM flat roof repairs. EPDM stands for ethylene propylene diene terpolymer. This strong and tough material is secured with screws and fasteners. It stands up well to sun and water but may shrink, leading to surface tears and cracks that need patching and treatment with adhesive.
Flat Metal Roof Repair
Metal roof repairs average $5 to $15 per square foot. Various materials are used in metal flat roofs, including aluminum and steel, and metal roofs are known for their strength and solidity, lasting decades with minimal maintenance. However, changing temperatures can cause the fasteners and parts of a metal roof to expand and contract, potentially leading to pieces falling out of place or suffering damage that requires repairs.
Flat Roof Repair Prices by Type of Repair
Many different issues may arise with a flat roof, and the costs of flat roof repair are highly dependent on the problem and repair required. Some repair jobs are quick and simple, requiring minimal work, while others are more extensive and difficult, tending to cost more. The table below shows flat roof repairs and average costs for each, based on a flat roof of 1,500 sq.ft. Some of the price ranges are relatively wide because the price varies based on your roofing materials and the level of repair work.
|Type of Repair
|Average Repair Costs
|$50 - $100
|$75 - $500
|$150 - $400
|$200 - $750
|$250 - $1,000
|$300 - $1,750
Flat Roof Shingle Repair
Flat roof shingle repair averages $50 to $100 for each shingle. However, repairmen usually offer discounts if you need multiple shingles repaired, so you do not need to pay the same price for every shingle. The total cost of your repair depends on the number of damaged shingles and level of repair work. Most flat roofs do not have shingles because shingles are usually only installed when a slope is present. However, there are cases where certain areas of a flat roof can have shingled sections. Shingles may get cracked, split, or broken and could need to be treated with adhesive or patching materials to repair them.
Flat Roof Drain Repair
Flat roof drain repair costs between $75 and $500. The drain is an important part of the overall flat roof design, helping drain water away and preventing it from pooling on the roof and damaging the roof materials. Unfortunately, drains can clog, so they may need to be cleaned out. They may also become damaged and cracked in storms or extreme temperatures, so they might need patching or parts replaced.
Flat Roof Drip Edge Repair
Repairing flat roof drip edges ranges from $150 to $400. Drip edges are L-shaped metal pieces positioned at the edge of the roof. They can also be known as drip edge flashing and are used to divert water off the roof, away from any fascias, preventing it from pooling under the roofing materials. Metal drip edges are strong, but they become dented or damaged in storms or because of falling debris. So, they may occasionally require patching or cleaning.
Flat Roof Flashing Repair
Repairing flat roof flashing costs $200 to $750. Flashing is a thin metal material used to seal the edges of the roof and prevent water damage. It is usually made from steel, copper, or aluminum and resists water and weather. However, it naturally wears down over time or may become damaged due to impacts in storms.
Flat Roof Seam Repair
Expect to pay from $250 to $1,000 for professional seam repair on a flat roof. The seams of the flat roof can be its weakest point. This is where different sheets of material meet or roof parts connect. It is common for water to penetrate these areas more easily than other parts of the roof, potentially causing leaks and other damage. Seams may need to be treated with adhesive or sealing materials to repair them.
Flat Roof Membrane Repair
Professional repairs for flat roof membranes average $300 to $1,750. The membrane of a flat roof is the material that keeps water out, and this can include rubber, modified bitumen, and similar materials. Membrane punctures are one of the most common flat roof issues. Cement is spread around the damaged area to seal it, and new roofing materials are placed over the top to fix a punctured membrane. Membranes also suffer from cracks and blistering and may need patching or resurfacing.
Cost to Fix a Flat Roof by Type of Problem
Many different problems affect flat roofs, and most are caused by weather and temperatures. Others can be caused by accidents, impacts, or general wear and tear. The repair method depends on the problem. Fixing a leak is very different from dealing with a sagging roof, and the costs vary accordingly. The table below shows common flat roof issues and average repair costs for each, based on a 1,500 sq.ft. flat roof. Some of these ranges are wide because costs vary based on the roofing materials.
|Type of Problem
|Average Repair Costs (Labor Included)
|$75 - $500
|$150 - $300
|$150 - $300
|$150 - $1,250
|$150 - $1,500
|$250 - $1,000
|$350 - $1,000
|$350 - $1,250
|$400 - $1,300
|$750 - $2,500
|$750 - $4,000
If you have water pooling or ponding on your roof, expect to pay between $75 and $500 to fix it, depending on the problem. This is when small water puddles or pools form on your roof. It usually occurs when water does not drain properly. This may happen because the drain is clogged or broken, so you might need to have the drain repaired by patching holes or cracks or cleaning it, or you might need to replace drain parts. Water pooling in other areas could signify bigger issues, like sagging, which leads to even higher costs.
Roof Debris Removal
Debris removal from a flat roof costs between $150 and $300. Since these roofs are flat, there is more risk of dirt and debris piling up on top of them, rather than rolling down and falling off the sides like on a sloped roof. Therefore, it is important to have debris removed from your flat roof, for aesthetic and protective reasons, because too much dirt and debris could lead to the roofing materials wearing down more quickly.
Flat Roof Snow Removal
Snow removal for a flat roof averages $150 to $300. Snow can pose a big threat to flat roofs. As it builds up slowly over time, there is no slope to help it fall off the roof. As the weight builds up, pressure on the roof rises, and the roof may begin to sag. There is also a risk of ice dams, leaks, and other snow-related damages, so it is vital to clear snow pile-ups from any flat roof.
Repair a Hole in a Flat Roof
Fixing a hole in a flat roof costs from $150 to $1,250, depending on the hole size and the work required to repair it. Holes in a flat roof may appear from weathering or impacts from heavy items like branches during storms. People walking on the roof can also cause holes. Small holes can be patched or filled in quickly, but larger holes require extra work and materials, leading to higher repair prices.
Flat Roof Crack Repair
Fixing a crack in the roof ranges from $150 to $1,500, depending on the crack size and materials used. Cracks can occur in many roofing materials, including concrete and fiberglass, and if left alone, they can become bigger, wider, and more likely to lead to leaks and extra damage. This is why it is important to fill cracks quickly, and you pay less for small crack repairs than for long and deep crack repairs. Flat roof specialists can usually fill in cracks or patch over them.
Expect to pay between $250 and $1,000 for blistering repair. This is also called bubbling. It is when little pockets of air or moisture become trapped between the layers of membrane on the roof, causing little bubbles or blister-like lumps to appear in the membrane. If left alone too long or exposed to heat, these blisters eventually expand and burst, exposing the more fragile parts of the roof below and resulting in cracks and tears on the membrane. They need to be resealed or covered with a fresh membrane material.
Repairing alligatoring on a flat roof costs between $350 to $1,000. Alligatoring is when the roofing material ages and starts to crack and crease over time, taking on the appearance of alligator skin. This can be unpleasant aesthetically and risky for safety reasons because roof materials that show alligatoring signs are more likely to rip, tear, and leak. The solution is usually to patch the area with a new piece of membrane or material, but sometimes, you can cover the affected area with a sealant.
Repairing flat roof shrinkage costs between $350 to $1,250. Flat roof shrinkage is common in flat roofs made from rubber materials like EPDM and modified bitumen. It occurs when the roofing materials shrink, causing fasteners and flashing to loosen and the material tears. Torn sections must be patched and adhered, and loose fasteners or flashing pieces need refitting.
Flat Roof Leak Repair
The average cost to repair a leaking flat roof is between $400 and $1,300. Leaks are usually the biggest cause for concern for homeowners with flat roofs because water entering the home can do substantial damage and needs to be dealt with quickly. Leaks may be caused by issues with the seams, rips, or tears in the membrane or holes and cracks in the roof material. To fix them, flat roof repair specialists usually need to patch or seal the affected area.
A sagging flat roof costs between $750 and $2,500 to repair. Sagging is a worrying sign in a roof because it shows that the actual framework or structure of the roof is under threat. This may happen for various reasons, such as water damage to the deck or buildups of ice and snow putting too much weight on the roof. If only small sections are affected, they may be repaired with simple reinforcement, but if large parts of the roof are affected, repair costs can be very high because new structural beams will be needed.
Repairing hail damage to a flat roof averages $750 to $4,000. Hail damage is a concern for flat roof owners because hail can damage the membrane and other parts of a flat roof, potentially leading to dents, rips, holes, tears, and leaks. Depending on the size and depth, these damages can be patched or filled. Huge roof sections might need to be replaced in the worst cases.
Average Cost to Repair a Flat Roof by Method
A range of different methods may be used to repair your roof, depending on the issue. When holes and cracks appear, patching and resealing may be necessary. Resurfacing might be required for situations involving alligatoring and blistering. Costs vary, depending on the method, and the table below shows common repair methods and average prices for each, based on a standard 1,500 sq.ft. flat roof. Price ranges are wide because of the different materials and the level of work required. For example, patching a small hole in a GRP roof is much cheaper than patching a deep crack in a metal roof.
|$150 - $1,500
|$250 - $1,500
|$400 - $1,250
The average cost for patching a flat roof is between $150 and $1,500. The reason for this wide range is that small holes and cracks in inexpensive materials cost far less than bigger holes or cracks in more expensive flat roof materials. Patching is one of the most common forms of roof repair and is used to deal with issues like small cracks and holes in the roof. It can be a cheap and simple method to cover up small damages and prevent them from getting worse.
Professional flat roof resurfacing or refurbishment ranges from $250 to $1,500. The range is relatively wide due to the materials and level of work because some roofs only need minor resurfacing but others need more extensive work. Usually, resurfacing is the go-to repair method when roofs are old and suffering from issues like blistering and alligatoring. Resurfacing helps cover damaged areas with fresh materials, giving new life to older roofs.
Expect to pay between $400 and $1,250 for resealing a flat roof. Resealing, also known as recoating, can be an important process if the existing seals are damaged or worn. Sealing is vital to prevent water from penetrating the roofing materials and getting down to the deck or into the home or building. It is recommended to reseal your roof every 2 to 4 years, and you especially need frequent resealing if you live in an area with heavy rain and snow.
Labor Cost to Repair a Flat Roof
Contact professional roofing companies or experienced roofing contractors for roofing repairs. They have the experience and know-how to repair damage to your flat roof, with hourly rates ranging from $50 to $150 per hour. Some professionals may have call-out fees of $50 to $100, which may be waived if you hire them to carry out the necessary repairs. Some also charge extra if you live in an isolated area that requires a lot of travel to get to. A professional repairman always inspects the roof before beginning repairs to assess the damage, and they should conduct checks after the repairs to ensure the roof has been correctly fixed. These checks are usually included with the standard labor costs. You may have to pay $100 to $175 if the inspection is not included in the repair cost.
Emergency Flat Roof Repair Cost
If you suddenly spot your roof sagging or have water coming down into the home through a hole or crack in the roof, it is vital to get emergency roof repairs as soon as possible. Many roofing companies charge extra for emergency same-day service or urgent repairs on holidays and weekends. Expect to pay between $100 and $200 more than usual for this repair. Some companies have minimal emergency charges of around $150 to $200. It is best to get emergency roof repair if you feel your roof is in danger of collapsing, your family’s safety is at risk, or the roof has a bad leak that could damage the home.
A good way to reduce the need for roof repairs and reduce the risk of having issues with your flat roof is to look after it correctly and carry out routine checks and maintenance tasks. Call in a professional roofing company once a year to carry out simple checks and inspections, at a rate of around $100 to $175. Or, you can inspect the roof yourself.
When inspecting the roof, look closely at key areas like the membranes, drain, drip edge, and flashing. Try to spot any cracks, holes, alligatoring, bubbling, blistering, or other signs of damage that might get worse later. Call professionals to have these issues repaired as soon as possible. The earlier you identify issues, the simpler the repairs will be.
It is especially important to check a flat roof after a storm or a snowfall. Storms can blow debris and branches onto the roof, which could cause damage. Snowfall may accumulate on the roof, so it might need to be removed if it does not melt or drain away quickly. Also, inspect the drain and check that water is flowing down, rather than pooling around the top.
Another tip for flat roof maintenance is to ensure the surrounding trees are regularly trimmed, removing any overhanging branches. Otherwise, those branches could fall onto the roof during a storm or strong winds, leading to impact damage like cracks and holes.
Cost to Replace a Flat Roof vs Repair
Flat roofs are not known to have very long lifespans. On average, many flat roofs last around 10 to 15 years, although some newer materials last considerably longer. If your roof is approaching 10 years and needs repairs, you may find that it is more cost-effective in the long term to replace the roof rather than to repair and then replace it within a few years.
If the roof needs extensive repairs or has damage to several areas, replacement may be your better option. The cost of flat roof replacement is around $7,000 to $12,000 on average, based on a standard 1,500 sq.ft. roof, and this includes the new roof and tearing off the old one. So, if your roof is under 10 years old and has only one or two issues, your best option is to repair the roof to extend its lifespan and get the most use out of it.
|$300 - $1,250
|$7,000 - $12,000
Enhancement and Improvement Costs
A gutter guard system costs between $1,200 and $2,000 to cover all your gutters. Installing a leaf guard over your gutters and a roof drainage system helps prevent issues like debris clogs and ponding.
Flat Roof Painting Repair
Painting a flat roof averages $500 to $1,500, and the price depends on your roof’s accessibility and paint. It is cheaper for painters to work on easily accessible roofs, and the job should be completed quickly if the roof is easy to climb on and off. Given that some flat roof materials are dull or not aesthetically appealing, some homeowners and building owners paint them to improve their appearance.
Insulate a Flat Roof
Insulating a flat roof averages $1,000 to $2,000. Installing insulation can be a good choice in areas with low temperatures, trapping more heat inside and reducing the building’s reliance on electricity or gas-powered heating systems. It reduces utility bills and improves building efficiency.
Waterproof a Flat Roof
This process should be done by a professional and costs $150 to $1,000, depending on the roof size. Flat roofs are water-resistant because of the materials used. However, you can add an extra layer of waterproof protection with a rubber coating, additional membranes, or roofing resin.
Ventilation and Drains
New roof ventilation costs between $300 and $700, while the average cost for a new drainage system ranges from $2,000 to $7,000. Vents promote airflow and prevent moisture buildup beneath the roof, while drains guide water from the roof. Both enhancements help the roof last longer.
Felting a flat roof costs $500 to $1,500. The price depends on factors like the number of felt layers and the roof size. Felting a roof adds insulation and protection and may extend your roof’s lifespan.
Additional Considerations and Costs
- DIY. It may be possible to carry out small flat roof repairs on your own, such as clearing out a clogged drain or patching a small hole or crack with simple patching kits or sealant tubes. However, if you have any doubts or are dealing with serious roof damage, it is best to contact professionals.
- Building code. Building codes vary from place to place and state to state. Some impose limits on the number of materials and membrane layers you have on a flat roof. Research the code rules in your area before having your roof resurfaced or replaced.
- Warranty. Flat roof installations often come with warranties, ranging from 10 to 30 years. Know which warranty you have, how long it lasts, and what it covers.
- License. Work with licensed professional roofers when repairing your roof because unlicensed workers could make mistakes and cause more harm. Always check the license of any professionals you hire.
- Insurance. It can be harder than normal to get insurance for flat roofs. Some insurance companies do not accept flat roofs, while others accept them but charge a higher-than-average rate. Research and compare your options to find the best insurance policy for your flat-roof home.
- Gutters. If your roof’s gutters also need maintenance or repair, you could negotiate a discount or deal with your flat roofing contractors by asking them to fix the gutters when working on the roof.
- Location. Flat roof repair costs can be influenced by the roof location. For example, flat garage roof repair costs may be lower than flat roof balcony repair if the garage is easy to access.
- Torch down. Torching down a roof costs between $4,500 and $9,000. Torch down roofing involves using a blowtorch to seal the layers of roofing materials.
- Tear off. Tearing off a flat roof costs between $1 to $3 per square foot, so a 1,500 sq.ft. roof costs $1,500 to $4,500. The price mostly depends on your roofing material and layers because roofs with multiple layers take more time to tear off. This process involves removing the existing roof and disposing of the old materials and membranes to prepare the space for a new roof.
- How much does it cost to fix a flat roof?
Repairs have a range of costs, depending on the issue. Most people pay $300 to $1,250 for repairs.
- Do all flat roofs leak?
A roof in good condition should not leak. Flat roofs have a shorter lifespan and are more likely to leak than other roofs, but this does not indicate a problem.
- When should you replace a flat roof?
If your roof has significant or widespread issues or if it is more than 10 years old, it may be time for a replacement. You may also want to replace the roof if it is damaged regularly and costs a lot in repair bills.
- How much does it cost to reseal a flat roof?
Resealing a roof averages $400 to $1,250, based on a 1,500 sq.ft. roof. The price depends on the roof size, sealant type, and roof condition.
- What is the average cost of re-roofing a flat roof?
The average cost of a new flat roof is around $7,000 to $12,000, with most people paying $8,250 for a 1,500 sq.ft. single-ply membrane roof.
- What causes a flat roof to leak?
Leaks in flat roofs usually occur because there are cracks or holes in the membranes. These holes appear due to impacts, debris, storm damage, and general wear and tear.
- Can you replace a flat roof yourself?
It is technically possible to replace a flat roof yourself, but this job is best handled by professionals.
- How do you extend the life of a flat roof?
The best way to extend your roof’s lifespan is to keep it in good condition, inspect it regularly, and fix problems quickly. You can also consider applying a Polyglass coating to protect it and ensure the drainage systems are properly maintained.