Why Skylights Leak and How to Fix Them

A leaking skylight is more than an annoyance; it can damage ceilings, walls, insulation, and even structural framing. In Florida's high-rainfall environment, a small leak can quickly become a significant problem. Understanding why skylights leak helps you identify issues early and take appropriate action. This guide covers the common causes of skylight leaks and how to fix them for Lake County homeowners.

Is It Really a Leak?

Before assuming your skylight is leaking, understand that what looks like a leak isn't always water infiltration.

Condensation vs. Leaks

Many reported skylight leaks are actually condensation:

Signs of condensation:

• Water appears on the inside of the glass
• Dripping occurs without rain
• Problem is worse in early morning
• Occurs more during humid weather or winter months
• Fog or mist visible on glass interior

Signs of a true leak:

• Water appears during or after rain
• Water stains on ceiling or walls around skylight
• Dripping comes from edges or frame, not glass surface
• No correlation with indoor humidity levels
• Visible damage to surrounding materials

Why Condensation Happens

Skylights are vulnerable to condensation because:

• Glass is colder than surrounding surfaces
• Warm, humid indoor air contacts cold glass
• Moisture condenses on the coldest surface
• Florida's high humidity exacerbates the issue
• Poor ventilation allows humidity to build up

Solving Condensation Problems

If condensation is the issue:

• Improve ventilation: Run exhaust fans in bathrooms and kitchens
• Reduce indoor humidity: Use dehumidifiers if needed
• Upgrade glazing: Low-E glass stays warmer, reducing condensation
• Add ventilation: Vented skylights can exhaust humid air
• Check insulation: Poorly insulated shafts get cold

Common Causes of Skylight Leaks

True leaks typically stem from these sources.

Cause 1: Flashing Failure

Flashing is the most common source of skylight leaks. Flashing is the metal (usually aluminum or copper) that seals the junction between the skylight frame and the roof surface.

Why flashing fails:

• Age and weathering: UV exposure and thermal cycling degrade materials
• Improper installation: Incorrect overlaps or inadequate sealing
• Roofing work: Roof repairs or replacements that disturb flashing
• Storm damage: High winds can lift or shift flashing
• Corrosion: Metal deteriorates over time, especially in salt air
• Sealant failure: Caulk and sealant dry out and crack

Signs of flashing problems:

• Leaks appear around the edges of the skylight
• Water stains follow the frame perimeter
• Visible rust, gaps, or lifted sections on roof
• Leaks worsen during wind-driven rain

How to fix flashing leaks:

• Minor sealant issues: Apply roofing sealant to small gaps (temporary fix)
• Moderate damage: Repair or replace affected flashing sections
• Significant deterioration: Complete flashing replacement
• During reroofing: Always install new flashing with new roof

Professional repair is recommended for flashing work, as improper repairs often make problems worse.

Cause 2: Seal Deterioration

Seals between glass and frame, and around the frame perimeter, can fail over time.

Why seals fail:

• UV exposure: Florida's intense sun accelerates seal breakdown
• Thermal stress: Expansion and contraction cycles stress seals
• Age: All seals eventually reach end of life
• Poor quality: Cheap skylights use inferior sealants
• Chemical exposure: Cleaning products can damage seals

Signs of seal failure:

• Fog between double-pane glass (seal between panes failed)
• Leaks around frame edges
• Visible cracks or gaps in perimeter sealant
• Soft or crumbling seal material

How to fix seal problems:

• Perimeter seals: Remove old sealant, clean, apply new sealant
• Glass seals: Often requires glass or entire skylight replacement
• Frame-to-curb seals: Can be resealed by professional
• Severely failed seals: Skylight replacement may be most cost-effective

Cause 3: Improper Installation

Installation errors may not cause leaks immediately but often lead to problems over time.

Common installation errors:

• Incorrect flashing integration: Not properly overlapping with roofing
• Missing moisture barrier: No ice and water shield under flashing
• Inadequate slope: Water pools instead of draining
• Wrong curb height: Curb too low for roof pitch
• Missing or improper sealants: Gaps in the waterproofing
• Poor fastening: Movement from inadequate attachment

Signs of installation problems:

• Leaks that started soon after installation
• Water entry during normal rain (not just heavy storms)
• Visible gaps or misalignment
• Movement or rattling during wind

How to fix installation issues:

• Assessment: Professional evaluation of installation quality
• Selective repair: Fix specific deficiencies if limited
• Removal and reinstallation: For systemic problems
• Warranty claims: If installed recently, installer may be responsible

Cause 4: Roof Problems

Sometimes the leak isn't actually from the skylight itself.

Roof-related causes:

• Damaged shingles around skylight: Provide water entry point
• Clogged valleys: Water backs up near skylight
• Failed roofing adjacent to skylight: Water travels to skylight location
• Debris accumulation: Traps moisture against skylight
• Poor drainage: Roof design directs water toward skylight

How to identify roof problems:

• Leak occurs even when rain isn't hitting skylight directly
• Damage visible on roofing near (but not at) skylight
• Gutters above skylight are clogged or damaged
• Water stains extend beyond immediate skylight area

How to fix roof-related leaks:

• Shingle repair: Replace damaged shingles
• Valley maintenance: Clear debris, repair flashing
• Gutter cleaning: Ensure proper drainage
• Debris removal: Keep roof clear around skylight

Cause 5: Structural Movement

Building movement can stress skylights and cause leaks.

Why movement causes leaks:

• Foundation settling: Shifts entire structure
• Framing movement: Rafters and trusses flex
• Thermal expansion: Different materials expand at different rates
• Storm stress: High winds flex roof structures

Signs of movement-related problems:

• Cracks in ceiling around skylight
• Skylight appears tilted or shifted
• Gaps that open and close seasonally
• Leaks that vary with temperature changes

How to address movement:

• Assessment: Determine cause of movement
• Structural repair: Address foundation or framing issues
• Flexible sealing: Use sealants that accommodate movement
• Reinstallation: May need to remove and properly resecure skylight

Cause 6: Age and Material Degradation

All skylights eventually reach end of life.

What degrades over time:

• Seals: Harden, crack, and fail
• Gaskets: Dry out and shrink
• Flashing: Corrodes and becomes brittle
• Acrylic glazing: Yellows, becomes brittle, can crack
• Frame materials: Metal corrodes, vinyl becomes brittle

Lifespan expectations:

• Budget skylights: 10-15 years
• Quality skylights: 15-25 years
• Premium skylights: 25-40 years
• In Florida's climate: Expect toward lower end of ranges

When age is the issue:

• Multiple leak locations
• Visible deterioration throughout
• Repair costs approach replacement cost
• Previous repairs haven't lasted

In these cases, replacement is typically more cost-effective than continued repairs.

Florida-Specific Leak Causes

Our climate creates unique challenges.

Hurricane and Storm Damage

Tropical systems stress skylights severely:

• Wind-driven rain: Water forced under flashing
• Debris impact: Cracks glass or damages frames
• Extreme pressure changes: Can break seals
• Prolonged exposure: Hours of heavy rain finds any weakness

Post-storm inspection:

• Check for visible damage
• Look for new water stains inside
• Inspect flashing for lifting or gaps
• Document any damage for insurance

UV Degradation

Florida's intense sun accelerates aging:

• Seals and gaskets deteriorate faster
• Acrylic glazing becomes brittle
• Colored materials fade and degrade
• Sealants break down more quickly

Heavy Rainfall

Florida's 50-60 inches of annual rain tests every installation:

• Minor flashing gaps become leaks
• Marginal slopes flood instead of draining
• Debris accumulation causes water backup
• Any weakness is eventually exploited

Diagnosing Your Skylight Leak

Proper diagnosis leads to effective repair.

Visual Inspection Checklist

From inside:

• Check for water stains on ceiling and walls
• Look for peeling paint or bubbling
• Note where water appears during rain
• Check for mold or mildew
• Examine the light shaft for stains or damage

From outside (with safe access):

• Inspect flashing condition
• Look for gaps or lifted sections
• Check roofing condition around skylight
• Clear any debris from area
• Note any rust, corrosion, or visible damage

Water Testing

For leaks that only appear in heavy rain:

1. Have someone inside watching
2. Use garden hose to wet specific areas
3. Start at bottom of skylight
4. Work up systematically
5. Note which area triggers the leak

This helps identify the specific leak location.

When to Call a Professional

Get expert help when:

• You can't safely access the roof
• The leak source isn't obvious
• Multiple attempts at repair haven't worked
• Damage is significant or widespread
• Structural issues are suspected
• Insurance claims may be involved

Repair Options by Problem Type

Different issues require different approaches.

DIY-Appropriate Repairs

Some minor repairs are suitable for handy homeowners:

Sealant touch-ups:

• Clean old sealant thoroughly
• Apply quality roofing sealant
• Works for minor gaps (temporary solution)
• Cost: $10-$30 in materials

Debris clearing:

• Remove leaves and debris from around skylight
• Clear any blocked drainage paths
• Cost: Free

Cleaning and maintenance:

• Clean frame and glass
• Lubricate operating mechanisms (vented skylights)
• Check weep holes for blockage
• Cost: Minimal

Professional Repairs

Most skylight leak repairs benefit from professional attention:

Flashing repair or replacement:

• Remove roofing around skylight
• Install new flashing properly integrated with roof
• Re-roof around skylight
• Cost: $400-$1,500 depending on extent

Seal replacement:

• Remove and clean all old sealant
• Apply appropriate new sealants
• May include reglazing if needed
• Cost: $200-$600

Curb and frame repair:

• Repair or replace damaged curb
• Ensure proper height and slope
• Integrate new flashing
• Cost: $500-$2,000

Complete skylight replacement:

• Remove old skylight entirely
• Repair any damaged decking or framing
• Install new skylight with proper flashing
• Cost: $1,500-$4,000+ depending on type and size

Prevention: Avoiding Future Leaks

Protect your skylight investment with proper maintenance.

Annual Inspection Routine

Every year, preferably in spring:

• From inside: Check for any staining, peeling, or moisture
• From outside: Inspect flashing, seals, and surrounding roofing
• After major storms: Do a quick check for damage
• Document condition: Photos help track changes over time

Maintenance Tasks

Regular upkeep extends skylight life:

• Clean glass: Improves light transmission and lets you see seal condition
• Clear debris: Keep leaves and twigs away from skylight
• Check seals: Look for cracks or gaps
• Lubricate mechanisms: Vented skylights need periodic lubrication
• Trim nearby trees: Reduce debris and prevent branch impact

When to Reroof

Coordinate skylight work with reroofing:

• Always replace flashing: New roof should include new skylight flashing
• Consider skylight age: Replace older skylights during reroofing
• Upgrade if needed: Opportunity to improve size, type, or location
• Fresh sealing: New roofing ensures complete resealing

Choosing Quality Products

For new installations or replacements:

• Reputable brands: VELUX, Sun-Tek, Fakro have good track records
• Proper sizing: Match to Florida's rainfall and wind requirements
• Quality glazing: Low-E, impact-rated where required
• Professional installation: Critical for long-term performance

When Replacement Makes More Sense Than Repair

Sometimes fixing isn't the right answer.

Consider Replacement When:

• Skylight is over 20 years old
• Multiple leaks or problem areas exist
• Repair costs exceed 50% of replacement cost
• Glazing is damaged, fogged, or yellowed
• Frame is corroded or warped
• You're reroofing anyway
• Previous repairs haven't held up
• Energy efficiency upgrades are desired

Benefits of Replacement

New skylights offer:

• Modern sealing technology
• Better energy efficiency
• Improved glazing options
• Fresh warranties
• Opportunity to change size or type
• Peace of mind

Working with Insurance

Storm damage may be covered by homeowner's insurance.

Documenting Storm Damage

• Photograph all visible damage
• Note date and nature of storm
• Don't make permanent repairs before adjuster visit
• Keep any debris from damaged skylight
• Get professional assessment of damage

Filing a Claim

• Report damage promptly
• Provide documentation
• Get contractor estimates
• Understand your deductible
• Consider whether claim is worthwhile for minor damage

Getting Expert Help

Skylight leaks benefit from professional diagnosis and repair.

At Pro Specialty Services, we diagnose and repair skylight leaks throughout Lake County. Our experience with Florida's challenging climate helps us identify problems accurately and fix them correctly the first time. Whether you need a simple seal repair or complete skylight replacement, we provide honest assessments and quality workmanship.

Don't let a leaking skylight damage your home. Contact us for an inspection and repair estimate. We'll help you determine whether repair or replacement is the right solution for your situation.