Skylight Leaking: Causes, Fixes & When to Call a Pro
Skylight leaks typically occur due to failed caulking, damaged flashing, or cracks in the glass—all of which allow water to seep around the frame and into your home. Most DIY fixes involve re-caulking the perimeter or patching small cracks with silicone sealant, costing $15–$50 in materials. For structural damage or persistent leaks after resealing, professional roofers should inspect the flashing and underlying roof decking.
Step-by-Step Fix
- 1
Inspect the skylight inside and out
Enter your attic or upper floor during or after rain to pinpoint where water is entering—note wet stains, drips, or puddles around the skylight frame. Go outside (safely on a ladder or roof) and check the skylight's perimeter for visible cracks, missing caulk, loose flashing, or debris buildup around the frame. Compare both locations to confirm the leak point.
- 2
Clean the skylight frame and surrounding area
Remove leaves, dirt, and moss from the roof around the skylight using a soft brush or leaf blower. Wipe the interior and exterior frame edges with a dry cloth to remove dust and old caulk residue. Clear any standing water or debris in the gutter or valley near the skylight so water flows freely away.
- 3
Remove old caulk and prepare the surface
Use a caulk removal tool or putty knife to scrape away dried or cracked caulk around the skylight perimeter—work slowly to avoid gouging the frame. Sand the cleaned areas lightly with 120-grit sandpaper to roughen the surface for better adhesion. Wipe away dust with a damp cloth and let the area dry completely (at least 2 hours in dry weather).
- 4
Apply new silicone or polyurethane caulk
Load a tube of waterproof silicone or polyurethane caulk into a caulk gun and apply a continuous, even bead around the entire skylight frame—both where the frame meets the roof and where the glass meets the frame. Smooth the caulk with a wet finger or caulk tool to ensure it fills gaps and adheres fully. Allow the caulk to cure for 24 hours before exposing it to rain.
- 5
Inspect and reseal the flashing if needed
If caulking alone doesn't stop the leak, examine the metal flashing that sits beneath the skylight shingles—look for rust, gaps, or separation from the roof deck. Apply roofing cement or additional caulk under lifted edges of the flashing and press it firmly down. For severely corroded or buckled flashing, note it for professional replacement.
- 6
Test the repair and monitor for leaks
Run water gently over the skylight with a hose (from a safe distance) and check inside for drips—do not spray forcefully or aim directly at seams. Monitor the area during the next heavy rain and note whether water stops entering. If leaking persists after 48 hours of curing, contact a professional roofer to inspect the flashing and roof structure.
⚠️ Safety Notes
- Always use proper fall protection when working on a roof or ladder near a skylight; wear a safety harness and ensure someone is present on the ground.
- Do not use a pressure washer on the skylight or surrounding roof area, as high pressure can force water under flashing and damage the seal.
- Silicone caulk takes 24 hours to cure fully—do not expose it to water or heavy rain during this time, or the seal will fail.
When to Call a Pro
If the leak persists after re-caulking, the skylight glass is cracked, the flashing is rusted or severely bent, or water is pooling inside the wall cavity, contact a licensed roofer immediately—these signs indicate structural damage that requires professional flashing replacement or skylight reinstallation.
Frequently Asked Questions
- Why is my skylight leaking?
- Skylight leaks are most commonly caused by failed or missing caulk around the frame, damaged metal flashing underneath the shingles, or cracks in the glass itself. Over time, caulk shrinks and dries, and flashing can rust or separate from the roof, allowing water to seep in.
- Can I fix a leaking skylight myself?
- Yes, you can fix most leaks caused by failed caulk or flashing by re-caulking the perimeter and applying roofing cement—this costs $15–$50 and takes 1–3 hours. However, if the glass is cracked, the flashing is severely corroded, or the leak continues after resealing, hire a professional roofer.
- How much does it cost to repair a leaking skylight?
- DIY re-caulking costs $15–$50 in materials. Professional flashing repair or resealing runs $200–$500, and full skylight replacement costs $500–$2,000 depending on size and type.
- What type of caulk should I use on a skylight?
- Use 100-percent silicone or polyurethane caulk rated for outdoor and roofing use—avoid acrylic or latex caulk, which breaks down quickly in sunlight and moisture. Look for products labeled waterproof, UV-resistant, and suitable for metal and glass.
- How long does skylight caulk last?
- Quality silicone or polyurethane caulk typically lasts 5–10 years before it begins to shrink, crack, or peel. Check your skylight seal annually and re-caulk every 7–8 years or when you notice gaps or damage.
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