DOES FLEX SEAL WORK ON GUTTER SEAMS?

A MY GUTTER DOCTOR PRODUCT REVIEW

If you’ve had cable tv throughout the years than you have likely seen commercials or infomercials for Flex Seal products. Remember the commercial where they sealed a boat using the spray on sealant? Yup, that’s flex seal. According to their commercials you can seal just about anything using their spray on liquid rubber sealant coating, including gutter seams. But, does flex seal really work on gutter seams? Let’s ask My Gutter Doctor.

spraying flex seal on gutter

WHY DO GUTTER SEAMS NEED TO BE SEALED?

Anywhere two sections of gutter come together to form a corner the seam needs to be sealed using a water proof sealant. This prevents the water from being able to leak through any cracks. In addition to gutter corners, end caps and downspout outlets also require to be sealed to avoid leaks.

gutter slope issues cause water to collect in gutter corner

Clear Sealant Was Used To Seal This Gutter Seam

Over the years we have seen many different variations of sealants and/or adhesives used to seal gutter seams. Everything from clear silicone, caulk, roof tar, duct tape, or even spray on rubber sealants such as Flex Seal. Some of these types of sealants can last a long time and some of them do not work very well at all.

DOES FLEX SEAL WORK ON GUTTER SEAMS?

Unfortunately, Flex Seal does not work properly to seal gutter corners or leaks. Even by following the multi step application process properly, the seals are eventually going to fail. Sooner rather than later in most cases. Below are the main reasons we would never ever suggest Flex Seal for sealing gutter seams.

MULTI STEP APPLICATION PROCESS

Flex Seal’s directions for sealing gutters is to clean and dry the surface before applying the first coat. Allow 48 hours to dry before applying the next coat. Then repeat and keep applying coats until the leaking stops. However, if it rains in between applications, the moisture will likely ruin everything. In addition, most homeowners aren’t able to schedule 2-4 different times to drag the ladder out to complete the repair, so they often don’t apply adequate coats.

spraying flex seal into gutter

DOES NOT HOLD A SEAL

Gutter companies do not use or suggest Flex Seal because it is not an effective product for gutter seams. Since most gutter companies offer warranties on their repairs, they depend on products that will stand the test of time. For example, we offer a 3 year warranty on gutter seals that guarantees the gutters will not leak for 3 years. If we were to start using Flex Seal, we would have to change our warranty from 3 year to 3 days. Otherwise we would be getting a lot of service calls to re-seal miters we already sealed.

COMPROMISES THE GUTTER SURFACE BY LEAVING RESIDUES AND ADHESIVES

Arguably the #1 problem with putting Flex Seal on gutter corners is that it leaves residue behind in the gutters. No matter what method you use to clean the inner gutter surface, Flex Seal is not coming out of there.

flex seal residue in gutter

In order for gutter sealants to work properly they need to be able bond to the surfaces. For this to work properly the surfaces need to be 100% clean. During a typical gutter corner re-seal service the existing caulk is able to be scraped clean of the seam before the new sealant is applied. However, once someone sprays Flex Seal into the gutter, the gutter is permanently coated with rubber. Therefore, flex seal ruins the chance of being able to salvage and re-use the miter.

We get a lot of calls to seal gutter corner leaks. Sometimes the customers let us know beforehand that they tried to fix the leaks themselves. Right away we immediately cringe, because Flex Seal comes to mind. But thankfully that also lets us know right away that the miter will likely need to be replaced.

flex seal stains on outside of the gutter

LEADS TO REPLACEMENT

As previously mentioned Flex Seal leaves behind gunk that is not removable from the gutter surfaces. Therefore once gutter corners that have been sealed with flex seal start to leak, they will likely need to be replaced to seal properly again.

The above photo shows a miter that was sealed using a faulty sealant. The discoloration is not able to be cleaned from the outer surface, therefore replacement is the only way for this to come clean. Also since the inside of the gutter is likely a mess, a new sealant will have a low chance of success.

F.A.Q.S

I’VE NOTICED OTHER ARTICLES THAT SUGGESTED FLEX SEAL FOR GUTTERS. WHY WOULD OTHER COMPANIES SAY THAT FLEX SEAL WORKS FOR SEALING GUTTER SEAMS?

The reason is quite simple. Money. We took a look at several articles online that suggested Flex Seal and discovered they all had one common interest. They all sell Flex Seal products, or offer their products through Affiliate Links. Therefore articles that suggest these products are either paid advertisements, or they are geared towards boosting sales of the product because they sell it.

IS FLEX SEAL SUGGESTED BY PROFESSIONAL GUTTER COMPANIES?

Gutter companies do not use or suggest this type of product because of it’s ineffectiveness, and also because it leaves residue that does not remove.

DOES FLEX SEAL WORK ON GUTTER LEAKS?

If applied properly (to dry surfaces) Flex Seal can work temporarily at best at stopping gutter leaks. If applied to wet surfaces the seal has no chance of working properly.

HOW LONG DOES FLEX SEAL LAST IN GUTTERS?

Depending on how many coats were applied, and if they were allowed to dry and cure properly between each application, will determine the amount of time the seals last. If not applied properly it could leak as soon as the next big rain. And with multiple layers applied properly the seal could last 6 months to a year.

IS FLEX SEAL A PERMANENT FIX FOR GUTTER SEALS?

For gutter corner seams, Flex Seal is not a permanent fix. We would only recommend using it in emergency situations, but with the expectancy of replacing the miter later down the road.

WHAT GUTTER SEALANTS DOES MY GUTTER DOCTOR USE AND SUGGEST?

We use brands of sealants that are specifically designed for sealing gutters and seams. Such as Geocel 2320, Geocel 2300, Quad by OSI, and GS121 by OSI.

Proper Gutter Sealant Is Used To Seal A Gutter End Cap

CONCLUSION:

If you are attempting to fix a gutter corner leak on your home and considering Flex Seal, STOP!!! Flex seal is not recommended for gutter seams because it:

DOES NOT SEAL PROPERLY/LEAKS
COMPROMISES THE SURFACES BY LEAVING ADHESIVES
LEADS TO REPLACEMENT

If a company is advertising that they recommend Flex Seal for gutter seams, then that company probably sells Flex Seal and are therefore trying to boost their sales. Otherwise they are likely participating in Affiliate Sales which is where they get a percentage of the sale if you purchase by using the link on their website. In our opinion, anybody else that honestly recommends Flex Seal for gutter seams doesn’t have any real experience with gutters.

Although we do not recommend flex seal for gutter seams, that doesn’t necessarily mean that all of their products are not good. We are sure there are situations that Flex Seal does work for, such as flat tire or a plumbing issue. Or maybe even sealing a boat like in the commercial. Nonetheless we’ll give the benefit of the doubt for the other products since we have not tried them.

Lastly we just wanted to point out that we are not offering any type of Affiliate Links and there are no paid advertisements on our website. That is because My Gutter Doctor is here to give you honest advice on gutter systems and gutter repairs.

For more honest advice about the gutter system you should Ask My Gutter Doctor!