• Phazes Roofing

Common issues for a leaky skylight

Some of the most nefarious leaks start at subpar installation points. One common subpar installation are skylight units. While most Skylights are famous for, or maybe should be infamous for being a primary sources of a roof leak.

Over time seals and flashing can deteriorate, providing an opportunity for water to penetrate your roof. Modern skylights are less prone to leaks than older versions, but even the best skylight can leak if it isn't installed with care and serviced properly. Skylights often leak because their flashing is damaged, corroded, or improperly installed. Often, those "leaks" are the result of other less obvious problems. One example, water could get through the roofing up-slope of a skylight and then leak out around the skylight's framing.

The first step in any skylight repair is to identify the source of the leak with a thorough inspection. You’ll want to make sure the leak is not just excessive condensation that has moved along the underside of the glass and dripped down the side of the interior. This occurs more often in very cold climates, in single-glazed skylights, and in damp locations like bathrooms, kitchens, and greenhouses.

If your skylight opens, check that it is fully closed, and that weather seals are in good condition. In addition, think about whether the leak occurs only in winter, in fall, or when there is snow or ice on the roof. If so, then look behind the skylight for leaves, ice, snow or other debris that might be blocking the downhill flow of water and causing it to back up under the roof shingles.

There are several possibilities as to why your skylight is leaking. The leak might not be a leak at all, but the result of condensation forming on the inside of the glass during cold weather. It could also be caused by an unrelated roof leak above the skylight that is finding its way out through the ceiling opening around the skylight.

If the leak appears to be coming from the skylight itself, start by cleaning around the skylight to remove any leaves or debris. Next, examine the exterior of the skylight and flashing carefully for any gaps or flashing that may have been improperly installed.

If you still can’t find the source of the leak, use a garden hose to try and reproduce the leak and narrow it down. Is the water coming from the lens, the frame, or the flashing around the skylight?

Depending on the location of the leak, you may need to:

  • Use roofing cement (can or tube) to seal any gaps or holes in the flashing. Apply 100% silicone caulking (tube) to seal leaks around the skylight lens.

  • Replace or repair the metal flashing around the frame of the skylight.

  • Try making the easier repairs with roofing cement or silicone caulking first before tackling more difficult fixes, like replacing the flashing.

You’ll also want to look carefully at your roofing, paying particular attention to vent flashing or other roof penetrations. A leak in these locations can travel quite a distance before finding its way to an indoor opening at the skylight. For roof and skylight inspections, hire a contractor skilled in roofing repairs.

Leaks at the insulated-glass frame may have permitted water to enter the window structure, forcing apart and damaging the seal of the insulated glass itself. If it’s determined that the insulating glass unit of the skylight has failed, you may be able to re-seal the unit against further water leakage. However, only a replacement of the skylight will remove the condensation and opaque skylight glass of a failed window unit.

If the skylight leak is at the roof flashing, it may be possible to make temporary repairs using roof flashing cement around the perimeter of the unit. However, proper repairs will require removing shingles near the skylight, installing appropriate flashing, and reinstalling new shingles in the area. Most skylights have integral flashing or a special flashing kit that is specifically designed for the skylight and roofing material.

Skylight Repair Tips:

  • Apply 100% silicone caulking (tube) to seal leaks around the skylight lens.

  • If your skylight is still leaking, replace/repair the metal flashing around the frame of the skylight.

  • Use roofing cement (can or tube) to seal any gaps or holes in the flashing.

Check out our videos for some of the work we have done and see what's the source of your leaky gutters!

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