Residential Flat Roof Repair 101

flat roof repair

In this repair guide, we'll discuss...

Main Causes of Flat Roof Damage

Incorrect installation is one of the primary reasons residential flat roofs need repair. A poorly installed flat roof is susceptible to weathering and water damage, which can become an expensive fix if not repaired immediately.

Installed correctly, a flat roof can last 20 or more years before needing repairs or replacement, depending upon the type of roofing material. Rain, hail, strong winds, and UV rays can shorten a flat roof's lifespan, but you can combat the elements by following a consistent roof maintenance plan.

man applying residential flat roof

Residential Flat Roof Maintenance Tips

Maintenance is critical to the life of any roofing system, and inspecting your residential flat roof on a regular basis will preserve its integrity. Below are five common problems to watch out for in order to lengthen the life of your roof.

Ponding Water

When water is allowed to accumulate, it can severely deteriorate the state of your roof. Ponding water will increase exposure to UV rays, algae, and accelerated heat aging.


Blisters will look like raised sections on top of the surface and pose a significant threat. When liquid is trapped between sections of the membrane, the trapped liquid will expand, causing augments in your roof.


Cracking can be attributed to a number of factors. UV rays break down the membrane and can cause cracks, along with poor workmanship and excessive weight on the roofing system. While appearing minor, cracking can lead to serious problems and should be addressed as soon as possible.

Snow Build-up

Snow can’t slide off flat roofs, and excess snow can overload the weight limit and cause roof collapses. And if the snow does melt but doesn’t drain properly, you’ll have a ponding water problem. Hire a professional to remove snow from your flat roof if it exceeds a foot, as serious injuries occur every year due to inexperienced property owners.

Loose Fasteners

If fasteners become loose it can be disastrous for a flat roofing system. Loose fasteners no longer anchor the roof to the building, leaving your property more susceptible to wind damage and a potential tear-off. During the installation, the instructions should specify the type of fasteners that should be used on your roofing system. 

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Blister Repairs

Flat roofing leaks usually occur at low spots or where the felt has been damaged, and the leak is typically directly below the damaged area. Look for cracks in the membrane or a large blister. If there’s water pooled near the blister, mop it up and let the surface dry. Then, brush off any debris.

1) Cut open the blister

Use a sharp knife to cut the blister open along the middle. The cut should reach far enough down so that you can pull up the blistered layer, but not far enough to reach the intact roofing felt beneath it.

2) Remove the water under the blister

Lift the cut edges of the membrane. Then, press the edges in towards the center, squeezing out the remaining water between the roofing layers. If the membrane is fully saturated with water, you may need to use a propane torch with a flame-spreader to dry out the bottom layer. Next, slowly move the flame over the inside layers of the blister, carefully monitoring the material so it does not burn or bubble. 

Use extreme caution if you choose to handle a propane torch on your roof. Flames can cause severe damage to property if mishandled. Contact a professional if you're not comfortable using a propane torch.

repairing flat roof with propane torch

3) Reseal the membrane

Spread a thick coating of roof cement over the bottom edges of the felt you pulled up, and firmly press down to reseal the membrane.

4) Nail the membrane into place

Along each side of the cut, use as many 6D galvanized nails as necessary to hold the membrane in place. Then, spread roof cement over the entire blistered area, ensuring all nail heads are well covered.

LEARN MORE: A Comprehensive Guide to Residential Flat Roofs

Hole and Tear Repairs

Large or small tears and holes in a flat roof can be effectively repaired by the homeowner. With the proper tools and materials, you can fix the problem successfully. However, if there’s significant damage or excessive amounts of water present, we suggest contacting a qualified flat roofing contractor.

Fixing a small hole or tear

Sparingly apply an approved rubber roof lap sealant to the affected area. This will be a fast solution to the problem, but should not be used as a permanent repair.

Fixing a large hole or tear

Buy a self-adhesive flashing that will provide a minimum of 3 inches of coverage on either side of the hole/tear being repaired. Start by thoroughly clean the area of any debris and soak up any ponding water. Allow it to dry completely. Then, apply an EPDM primer with a scrubber pad, and when it's dry to the touch, firmly adhere the adhesive flashing, moving from the center outwards with a hard roller. Lap sealant can also be applied along the edges of the repair as extra protection.

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What’s the Cost of a Residential Flat Roof Repair?

The costs of repairing a flat roof will depend on your location, the type of repair, and which contractor you work with. 

Average Cost of Flat Roof Repairs
Repair Service Cost
Specific Leaks $200 - $600
Recovering with PVC Membrane $2.50 - $4.00 per square foot
Tear-off $4.00 - $9.00 per square foot
Cracks Throughout the Membrane $200 - $1,000

The best way to avoid major roof damage is to clean the roof of leaves, tree limbs, and standing water on a regular basis. It’s also important to have leaks repaired as soon as you notice them in order to avoid further damage.

While you may think that tackling a small repair yourself is a good way to save on repair costs, that’s not always the case. Most reputable roofing companies will offer you some type of workmanship warranty and/or leak-free guarantee on flat roofing repairs, so you can be sure the leak is fixed right and won’t “spring” again several weeks or months down the line.

When It's Time for Replacement

There are two situations that warrant an entire roof replacement...

1. It's reached the end of its life cycle

The life cycle of flat roofing materials varies from as little as five years for rolled asphalt, to 7 - 10 years for EPDM rubber, or as long as 30+ years for PVC.

2. It has incurred structural damage

If the original flat roof has not been installed properly, the result will be ongoing maintenance and problems requiring constant upkeep. If the insulation under the roof is wet, it cannot dry out, which will cause mold issues and structural damages. Constant moisture or improper drainage will lead to serious structural problems causing the need for a full replacement. 

Find a Residential Flat Roof Repair Specialist

Not all roofing contractors specialize in residential flat roof repairs, but Hometown works with some of the top flat roof repair specialists in the business. Hometown makes it easy for customers to compare roofing contractors. You’ll have access to a variety of options and receive free quotes for your project.