Problems With Flat Roofs (Residential Edition)

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Flat roofs are not a buy and forget product. Flat roofs require yearly attention and monitoring of any potential problems. The first priority for the homeowner is to establish a relationship with a roofing company you trust because you need to schedule frequent inspections throughout the year and especially after every heavy storm or hail storms. We'll cover the following problems with flat roofs: Standing Water, Biological Growth, Accumulated Debris, Weight Capacity, Vulnerability to Wind Gusts, Blistering, Alligatoring, and Shrinkage.

Please use the comment section below to contribute or ask questions.

Homeowners pay for a flat roof with the expectation it will last at least 15 years. Unfortunately, most flat roofs only last around 10 years. Today, we'll cover the problems you will run into with your flat roof and how to deal with these problems.

There are a variety of roof technologies, but they all fall into one of two categories:

  1. Water shedding
  2. Water proofing

Flat roofs require a roofing company that will water proof your flat roof. The company you hire must be obsessed with water proofing details and you must quiz them on water proofing before they earn your business of installing your new flat roof. I've met many expert roofers that have been in the business so long they have gotten complacent and overlook specific details when installing pipe jacks or skylights. These are perforations to the roof that will be the main source of leaks, if not done correctly.


Standing Water:

This is a huge problem, even though it sounds completely normal. Standing water weights 62.4 pounds per cubic foot and puts incredible pressure and load on your flat roof. Mold and fungus will grow quickly. The water will attract animals, insects, and rodents; all of which will directly contribute to the deterioration of the roof. With enough water and not enough support, your roof is sure to collapse as we demonstrate later in the article. It's evident the water ponding is a big issue to the roof, but it also causes problems to the foundation of your structure. The water isn't draining properly and not being guided to the optimum location away from your home.

Standing Water Weights 62.4 pounds per cubic foot

Ponding is a sign of a larger issue at hand, which is lack of optimal water shedding away from the structure of the house. Invest in the repair along with downspouts guiding the water to the sidewalk.

89% of roof leaks occur around the pipe boot vents. The only way to guarantee the roof doesn't leak around these areas is to use a weldable, one-piece design flat roof pipe boot by Bullet Products called the Bullet Boot TPO ($25.93 each).

Biological Growth From Standing Water:

Plant life will thrive with standing water. Soon enough, a tree could dig its roots into the roof. Flat roofs need to have a slight slope to guide the water away to the downspouts. Try to control the direction of the water flow as much as possible. This should be planned before the roofing company begins the installation. Planning is attributed with 90% of the success of your flat roof project.

Problem with Flat Roofs - Biological Growth from Standing Water

There is a roof system called a green roof where they intentionally grow vegetation on top of the flat roof, but that isn't covered today in this article. Just for fun, we included an image of a house in Norway where is it common to grow trees on top of their pitched roofs. Go Norway, you can have that trend! I hope it doesn't get popular in our neighborhoods.

In Norway, it's normal to grow trees on roofs.

Accumulated Debris:

Neighborhoods with mature trees will make things difficult for your flat roof. The trees will have an over abundant supply of debris falling onto your flat roof. To minimize this problem, keep all trees trimmed so the branches don't get within 10 feet of your home. The flat roofs allow branches, leaves, and other debris to accumulate on your flat roof and blocks the drainage system. In addition, a large pile of leaves traps moisture. In the winter, the leaves go through a cycle of freeze/thaw, then refreeze throughout the winter season. Meanwhile, your flat roof is aging and having a reduction in shelf life.

Problem with Flat Roofs - Accumulation of Debris

Weight Capacity of Your Roof Sub-Structure:

Building Code prohibits more than two layers on your property's roof. Most commercial roofing contractors don't have the integrity to stand behind this standards. There are many roofing contractors that refuse to properly advise the commercial property owner to remove the existing layers (when the existing roof has 2 or more layers) before beginning the roof project.

The integrity of each element of a building is critical to its stability. However, no component carries more potential for property damage or personal injury than the roof. A poorly performing foundation or failing exterior cladding can be inconvenient, unsightly, and expensive to fix. An overworked roof collapsing can ruin your financial health and long-lasting consequences.

There are telling signs of stress you should not ignore. Becoming familiar with the signs can prevent serious damage. The telltale signs that point to problems with the roof’s materials, design, functionality, or all three are usually only visible on the roof itself. Most people don't have roof inspections every year or after every storm; so, to them, it's a surprise but it doesn't have to be one. Property owners can help protect themselves from costly repairs and legal liability by becoming familiar with these signs and calling on forensic engineering, a trusted and knowledgeable roofing company.

Problems with Flat Roofs - Weight Capacity Failure

There are many negative consequences from roof collapses or any kind of structural failure, it is imperative to design houses and buildings using the latest industry standards. Those standards are the International Building Code (IBC), with strict interpretation to loads and material strength provided by the American Society of Civil Engineers (ASCE) Standard 7 – Minimum Design Loads for Buildings and Other Structures.

Problems with Flat Roofs - Weight Capacity Failure (2nd Example)

These standards detail how roofs should be installed and the details to sustain two different types of loads.

  1. Dead Load -It includes the weight expected to live on the roof.: for example HVAC equipment etc...
  2. Live Load - These vary in duration and could be seasonal. Examples of live load is foot traffic and weather related loads.

Vulnerability to Wind Gusts:

Flat roofs are many sheets of material combined to form one waterproofing membrane, a little wind damage can turn into serious wind damage with just a few gusts of wind. The whole roof can peal off and require immediate need for replacement.

Flat Roof Problems - Vulnerable to Wind Damage

Below is an image of how wind affects the flat roof. As the wind passes through your home, it creates lifing forces that can peal away the flat roof membrane.

How Wind Damages Flat Roofs


Blistering, a type of flat roof surface defect, occurs when air (sometimes water) gets trapped between the cap membrane layer and the base layer. Blistering leads to guaranteed roof failure over time. The bubble like effect is worse in the day when the sun's heat causes it to enlarge. Please don't ignore any of these problems because the problem can skip the ability to be repaired to the worst case scenario which is the full replacement of your roof.

Problem with Flat Roofs - Blistering

Problem with Flat Roofs - Blistering (2nd Example)


Alligatoring is a type of blistering. It could be that alligatoring occurs in areas where the constant expansion and contraction of the membrane dries out the cap layer to this extreme. Alligatoring occurs after the initial blistering shown in the previous images.

Example of Problem with Flat Roofs - Alligatoring


Shrinkage is guaranteed to occur on flat roofs made from synthetic rubber membranes, such as EPDM. It causes seams to delaminate and separate which breaches the waterproofing and renders your roof useless.

Though EPDM is a popular choice in the construction of flat roofs due to its durability, all EPDM roofs will eventually experience shrinkage. Manufacturing or installation defects serve as the catalyst to the natural shrinkage expected from the this roof technology.

Example of Flat Roof Problem - Shrinkage


Have your flat roof inspected yearly. It's best to monitor and stay proactive on cracks or fissures on the flat roof membrane.

In particular, look for cracks around ridges. Imperfections appear on flat roofs over a period time due to water exposure and extreme weather. It's always better to be safe than sorry, so pay attention to detail. Hire a roofing contractor you trust to help you with honest inspections. Having a leaky flat roof can be prevented.

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I have black stains on my roof. How can I get rid of them? My neighbors have them, too; now that I think about it

Hi Aristi, thank you for your question. Use oxygen bleach to clean your roof and please read the article we wrote because it explain with great detail how to do it correctly. We even gave tips on ladder placement. Better yet, let us do it. Contact us for exact pricing. ( Our roof cleaning service starts at $200 and goes up from there. Thank you

It's my understanding buying a class 4 shingle will lower my insurance premium, but will it lower my coverage?

Hi Bailey, thank you for the excellent question! The safe answer is "please check your coverage detailed in your policy". For the more thorough and deeper way to answer your question, I asked many colleagues and only one had a unique answer. Robert from Oklahoma City said one of his clients that bought class 4 shingles did receive a lower premium, but he lost the hail coverage. I was shocked to learn about this real world example about how this specific insurance company handled this upgrade. It could strictly be a case of correlation and not causation, but it's still interesting. Thank you for taking the time to ask your question.

One of your employees left a postcard on my door and I figured you could answer my question - What questions should i ask roofing companies before i hire them?

Hi Chad! thank you for your question. Several very important questions you need answered before hiring a roofing company are: - what is the square footage of my roof? - what waste % are you calculating for the complexity of my roof? - what brand/type of shingles are you offering me? - how much are you paying for the shingles from your supplier? - show me your certificate of insurance - show me your certificate of worker's comp insurance - show me where you have added me as an additional insured on your insurance policy - do you have a 3 day cancellation fee? if so, waive it. - how much will deck repairs be per sheet of plywood when decking is exposed and visible? - show me the list of materials necessary to install to keep the asphalt shingle warranty valid - what are the additional steps you are taking to protect my home from debris and nails being left behind? - provide me a full list of materials that are being installed on my roof. - what is warranty for labor? for how long? This list of questions is a great place to start. Most roofing companies don't want you to ask them because they are underinsured, overcharge for materials, cut corners by reusing your old roof parts, etc... I hope this helps!

A company is telling me I can get my roof for free from the insurance and they would cover the deductible if I hire them. Is this true? (I'm in Texas)

Please don't do that. The insurance deductible is a contractual agreement you have with your insurance company. In Texas, Texas Law House Bill 2102: It is illegal for contractors or roofers to offer to waive a deductible or promise a rebate for all or part of a deductible. Under the new law effective September 1, 2019; violators could get up to a $2,000 fine and up to six months in jail. If a contractor offers to waive a deductible, report it to the Texas Attorney General’s Consumer Protection Hotline at 800-621-0508. Do not commit insurance fraud by accepting unethical and illegal practices. Thank you for your question

This article will certainly help me make an informed decision.

Hi KD, glad we could help. We'll have a new feature on the website where you'll be able to get a Date of Loss for your insurance roof claim. Coming soon, FREE!

How long should it take for a company to give an estimate?

Hi Holly, responsiveness is a great way of showing a customer we care. We can do an informal estimate within a few hours and a formal estimate within 24 hours.

The last roofer gave me a two line estimate so I asked for more information. Haven't heard anything yet.

Hi Melinda, a detailed estimates should have detailed line items of the type of products including brand, quantity, color (if possible), with price. If you would like contact us and we can help you with a detailed quote. Thank you.

Great information. What city are you referring when you give the $350 to $450 average?

Hi Sally8100, thank you for your comment. This article is referring to Texas and Oklahoma City.


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How will I know how many layers of flat roof my house has before I commit to re-doing the roof? I don't want the roofers to discover a second or third layer and then the job exceeds budget

Hi Kasey, thank you for your excellent question. Pay the roofing company to perform the test on a small area of your flat roof before you start the project. Have the contingency in place that the price paid for the test includes the repair in the event you don't proceed with your new flat roof.




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