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Our Amazing Guide on how to seal a skylight leak

Date: June 14, 2022

Skylights are natural solutions to interior lighting and even ventilation. They are like windows on a roof, and they are designed to withstand everything the roof goes through, including adverse weather conditions. Have you ever wondered how How to seal a skylight leak?

There are some situations that may, however, make them susceptible to leakages. When this happens, the skylights have to be fixed to avoid damage to your house's interior.

Types of Skylights

There are generally two types of skylights based on their function. To know where and how to repair them, it is good to understand how they work.

Most skylights are custom-made for roofs with asphalt shingles, but extra flashing is used when installing them on tile or metal roofs.

  • Vented skylights

Skylights that can open offer many advantages such as lighting and ventilation. A homeowner with an open skylight has a privacy advantage since the skylights can be opened instead of windows.

They also offer moisture control in areas that tend to build up condensation, such as kitchens and bathrooms.

Operable skylights function as windows more than skylights and are often found in attics on the slope of the roof. They are hinged and are manually opened by hand like you would a window.

  • Fixed skylights

Fixed skylights don't open up and mostly offer the function of light control. They are installed on high ceilings, and therefore fixing them may require extra equipment.

They last longer for about 8-15 years, and leaks commonly occur at the skylight edges if the pane is in good condition.

The build of skylights

Skylights are like windows on a roof, but they have flashing to prevent leakages, and modern ones have channels that carry away condensation. If a skylight is faulty, there is a good chance the leak is coming from two places:

  • The flashing
  • The panes 

Leaks are easy to occur in fixed skylights over time compared to vented skylights. This is because any faults in vented skylights don't go unnoticed, and they can be fixed earlier.

Fixed skylights are also commonly installed in out-of-reach areas and are prone to damage at the flashing between the roof and the panes. When the seal between the flashing and the roof wears off, a leak may occur.

Some reasons for Leaking Skylights and how to seal a skylight leak

If your skylight is leaking, there is a high chance it may not be closing fully for a vented skylight and worn-out seals for fixed skylights.

Below are some common reasons your skylight might be leaking:

  • A faulty skylight

If the skylight opens, check the rubber gasket around the frame for signs of deterioration or mold. That would indicate the skylight isn't sealing all the way, and moisture is dripping between the window casing and the frame.

This can be fixed by replacing the gasket. The skylight may also be obstructed by small pieces of debris, and the leak may be stopped if they are removed. A cracked piece of the skylight may have moisture around it, which you can discover during an inspection.

It is feasible to remove the damaged component and repair it, but in most cases, you will need to replace the skylight.

  • Faulty roof flashing

If there are leaks after moisture and any skylight defects are ruled out, there is a high chance it is either seeping under the flashing, which may be faulty.

 A roof leak from the upper parts of the roof slope is easier to fix since the source is known. If it, however, comes from lower sections of the roof, it may be harder to find the origin since water travels along the roof deck.

Leaks due to faulty or damaged roof flashing can be discovered through the physical condition of the flashing. Curled or broken flashing allows water to pass through.

Roof cement can be used to fill in the gap if the leak comes from a hole in the roof. It can be easily DIY-fixed, or you can instead call a professional roofing firm.

If the skylight continues to leak despite the repair of any holes around the seal, the issue may lie elsewhere. This calls for professional aid since some common roof leaks can pass as skylight leaks, therefore, making it harder to diagnose and repair.

  • Condensation

Look for signs of moisture on the glass while you're inspecting the skylight. It may pass as a leak, especially if it collects at certain points. It forms due to the difference in temperature and humidity between either side of the skylight.

Condensation is best treated by allowing fresh air to circulate in the house. If the skylight is fixed, you can use a fan, and if it is a vented one, you can simply open it.

You should also check for and remove any debris covering the skylight's weep holes, which are tiny holes that allow water condensation to drain.

How to fix a leaking skylight

A gable roof edge with a blue sky background

Most leaking skylights can be easily fixed through a few steps. The first line of action is dependent on the type of skylight you have, but the course of action is to determine the source of the leak.

To pinpoint the source of the leak:

Vented skylights are designed to open, and there could be a few reasons why there is a leak. They have a longer checklist compared to fixed skylights.

1. Check that the vented skylight is completely shut. There could be a leak during a downpour since the skylight isn't shut completely.

2. Check for debris around the hinges and edges of vented skylights. The watertight seal around the skylight won't fully function if there is debris like leaves and twigs that leave an opening.

3. Check the condition of the rubber gasket around the frame. A damaged seal allows water to pass through and moisture to drip between the frame and the casing.

4. Check for any cracks on the skylight pane. Cracks, no matter how small, may contribute to moisture formation and leaking.

5. Check the condition of the flashing around the skylight.

6. Check that the weep holes of the skylight are free from debris and anything that may be blocking them.

Common fixes for skylight leaks

The roof and its parts are designed to protect the house interior against damage by the elements. This includes leaks as water damages not only the property but also the roof itself.

Skylight leaks should therefore be worked on as soon as possible. Some of the common fixes include:

  1. Sealing any leaking parts

Sealants are used on both skylights and windows to keep water out. As with any other item, these need to be replaced over time as the most prevalent problem with skylights is deterioration.

Caulking and sealing are simple fixes that can be done by the homeowner, and they can be done quickly. If the leak is around the skylight lens, use silicone caulking to seal it and if it is at the flashing, use roofing cement to fix it.

It is important to have weather seals installed on your roof because they create an additional watertight barrier. For the most part, this is a simple remedy that can be completed within five minutes.

  • Reinstalling the Flashing

Flashing is leakproof when installed correctly and is included in high-quality skylights. Invest in good skylights to avoid having to pay for the damages later.

When installing the flashing, it shouldn't be nailed onto the roof in the sensitive parts to leaks. Removing the shingles and flashing is typically the best option if nails, decayed or rusted flashing, or gaps in the step flashing are found along with the skylight frame.

You should hire a professional to fix the skylight, and as much as it may cost you extra money, it is worth having the best skylights and the professional to do the installation.

  • Use the right materials.

A roofer can fabricate their own flashing from aluminum at a cheaper cost than buying a kit inclusive of the right flashing. When this happens, the homeowner is most likely to experience leaks.

The roofer uses caulk at the corners to keep water out because cheap metal cannot be soldered or welded. Caulking dries and shrinks over the course of five to ten years, which is more expensive in the long run.

It may take a long time before you notice a leak since water penetrates surfaces like ceilings slowly before there is visible damage.

  • Check the Insulation

Warm air from within the home will freely flow upward if there is insufficient or no insulation leading to a difference in humidity between the home interior and exterior.

Condensation can form if it comes into contact with the glass, causing leakages when it collects in one area.

  • Reseal the Flashing

If the flashing is the source of the leak, the next step is to use a caulk gun and the appropriate sealant to go up on the roof. You should use a sealant designed for roof flashing to get the best results.

If there are visible signs that the old caulk has begun deteriorating, use a putty knife to remove any loose debris, and then apply a fresh coat of sealant to the recently exposed area.

For shingle roofs, peeling back the shingles is necessary to evaluate the flashing where it meets the roof. When installing a skylight, make sure the sealant is applied extensively to the margins of the flashing, particularly around the skylight's head.

  • Replace the Skylight Itself

When the glass of a skylight is cracked, it needs to be replaced. Cracked skylights are easy to get worse in an area that experience hailstorms. Minor cracks may be worsened by future damages, and it is better to replace the skylight than to seal the cracks.

The consequences of faulty skylights

A house with a faulty skylight is at risk of damage. If you do not pay attention to leaking skylights:

  • Damage to furniture

Your furniture and house items will get damaged when they come into contact with water. Any cushions and cloth will develop stains and a musky smell.

These conditions also favor the breeding and infestation of pests, some of which may cause allergies.

  • Leaks in the ceiling

Water dripping through a skylight may pool on the roof interior. This creates watermarks on the ceiling that appear as circular patches, and they may make the ceiling sag.

Leaking ceilings damage the house interior, and they can lead to damaged electronics as well. Water that pools in the ceiling can also cause the paint to chip off.

  • Chipped paint

Water running along the wall not only creates stain marks along the wall but also causes the paint to peel due to different temperature gradients.

If water seeps into the wall, it may also weaken the adhesion between the paint and the wall. Paint will therefore peel in patches creating an uneven and exposed surface to mildew growth.

  • Mold growth

Mold and mildew do well in constantly damp conditions. They may grow on the walls, baseboards, and even furniture.

These organisms also invite pests and other organisms into the house, which further damage the house.

  • Rot development

Wood develops rot in constantly damp conditions. When leakages occur, water that pools on wooden floors ad structures get absorbed by the wood.

This weakens the structural integrity of your house as the wood will no longer be able to hold its intended weight. Wooden floorboards also tend to deform, causing creaking and noisy footsteps when walking on.

Frequently asked questions

What are some signs of a Failing Skylight?

Regular maintenance on your skylight ensures you avoid small problems that may further develop and cause leaks. There are some early signs you need to look for on your skylight that later damages the skylight.

  1. Stains on your skylight

If the lower part of your skylight has stains running from the top, the leak may originate from the upper part. You may fix these leaks simply by removing and reapplying the old caulk.

Stains also tell you that it is time to do regular maintenance. They may also indicate a build-up of debris around the skylight.

  • Damaged flashing

 If your flashing is damaged, be it rusted or dented, it is time to get your skylight fixed. Damaged flashing allows more water into the roof than cracks or wasted sealing.

You should also make sure that there is a watertight connection between the flashing and the roof.

How much does it cost to Repair Skylight?

Vented skylights that are damaged may have to be replaced, especially if they are automated. A faulty mechanism for opening them may put your house at risk even if the skylight is in good condition.

A manual skylight opened by hand costs about $300-$600.

An automated vented skylight that is remote-controlled costs about $600-$100 and an extra $200 or $300 to have a rain sensor installed.

How to seal a skylight that is leaking
About Mikku & Sons
Our roofing company was founded in 2001 by Michael Riutta, who is still part of the ownership and management team. Between Michael, his two sons and co-owners, Devin and Joshua, and our crew members, we have many years of experience to handle any type of roof repair or roof installation solutions you may need.
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