9 Easy DIY Steps To Fix Your Leaky Skylight On Your Commercial Roof

Commercial Skylights, just like residential skylights, are great for letting in natural light and fresh air into your building.  And they’re also prone to leaks, which can cause damage to your roofing material and interior walls. If you have a leaky skylight on your commercial roofing system, you’ll have to treat it a bit differently than you would a residential roofing skylight.  Continue reading we’re going to show you how to fix that leak in 9 easy D.I.Y steps to fix that leaky skylight on your commercial roof. 

The Commercial Roofing Skylight Basics.

You might not realize it at first because 1. it hardly rains in Los Angeles, CA and 2. the water looks so small. It’s easy to miss when it actually is raining outside, but when it’s sunny out, the sun shines through the skylight and makes the water visible.  In order to fix the leaky skylight on your commercial roof, we first need to know what is causing the leak in the first place. 

But before we get into that, you should know the basic anatomy of a skylight. Here they are:

There are 3 parts to a skylight:

  • Curb section – this is normally a wooden frame that is approximately 6 inches in height and placed over the opening of a roof.
  • Lens [Polycarbonate] section – this is placed on top of the curb and held in place with a metal frame and gasket.
  • Metal or plastic flashing – this gets wrapped around the curb so the roofing material can be secured to it to form a watertight seal.

Leaky Skylight

Capped Vs Capless Domed Commercial Skylights.

Industrial Skylights per regulation must be capped. With that being the case your industrial roof should be capped. If you find that you’re skylight is capless, then you might want to get the skylight replaced. Not only because capless is not up to code, but because fixing a leaky capless skylight will only be a temporary fix. 

Commercial Roofing Capless Skylight

commercial roofing capped skylight

Fixing The Skylight Leak.

Leaks can be complicated and hard to find. Sometimes it’s best to call a commercial roofer to take a look and find the leak. But the most common reasons are the age of the polycarbonate lens itself and the flashing.  

If you do notice a gap or a hole that is causing a leaky skylight here’s what you have to do.

Safety First.

Finally, getting on a roof is not as safe as it might seem. Falls are dangerous, and even a fall from 6 feet has the potential to kill. Humans are just not built to take impacts well, resulting in a lot of damage and usually death. There are several news reports every year of people (even firefighters) falling through skylights to serious injury or death. Even being near your skylight is dangerous without safety equipment and training. Skylights afford a false sense of security because you feel like the skylight will support you. In most cases, they will not.


Step 1. Clean The Leaky Skylight.

Using a wet rag clean off the skylight frame all around the skylight lens. This will help the seal stick and prevent any more leaks after you apply the seal. Which we will get to.

Step 2. Mask Tape All Around the Skylight.

After the skylight is cleaned off and because you want to do a clean job when you seal the leaky skylight. Apply masking tape all around the skylight. 

Step 3. Apply A Silicone Sealant.

Apply one coat of Silicone Seal liberally covering the glass and frame. Silicone sealants appear to work the best.  Apply the silicone liberally all around the skylight.

Step 4.  Embed Polyester Fleece into the Silicone Seal.

Embed Polyester Fleece into the Silicone Seal making sure to cover the metal and glass equally. The fleece is going to reinforce the sealant to help prevent leaks from the skylight. 

Step 5. Add A Second Layer Of Silicone Sealant On Top Of The Fleece.

Add a second coat of Sealant over the Polyester fleece. Make sure that no fleece material is visible.

Step 6. Remove The Masking Tape.

Remove the masking tape from around the skylight that you applied in step 2.

Step 7. Check Your Work 24 Hours Later. Apply 3rd Coat of Silicone Sealant if necessary. 

After 24 hours make sure to go back on top of the commercial roof and check your work. Look for a smooth transition between the skylight glass and the metal frame, and make sure the sealant is completely dry. If necessary for stubborn leaks or you still see a gap, you may need to apply a 3rd coat of the silicone sealant.

Step 8. Caulk Any Gaps In The Flashing.

If you find any gaps in the flashing area of the skylight. You’ll need commercial-grade caulking to caulk the gaps in the flashing area. The caulking brand that we use here at central roofing is Sikaflex caulking.


It’s important to note that if the lens is compromised then you’re only choice for a commercial roofing skylight would be to replace it. However, if it isn’t then the above easy steps should work to seal that leaky skylight. 

But if getting on your commercial roof sounds a bit sketchy or makes you feel uneasy, don’t risk your life and your belongings just to save a few dollars. It might seem like the easier and cheaper option, but your DIY “ skylight repair” usually doesn’t fix the issue, and makes it more difficult and more costly for professional commercial roofing companies to repair it properly. But if the roof is in good condition, it’s a minor leak, you take all the safety precautions then a skylight repair can be done easily yourself. 

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