How Roof Flashing Fails Around Walls, Vents, and Skylights

What Roof Flashing Does

Flashing is shaped and installed to redirect water away from joints and openings. It may be made from metal, membrane, or system-specific materials.

Common flashing locations include:

• Roof-to-wall intersections
• Chimneys
• Skylights
• Plumbing vents
• Exhaust vents
• Valleys
• Dormers
• Parapet walls
• Equipment curbs
• Roof edges
• Changes in roof slope

The flashing must overlap and integrate with surrounding roofing in the correct order. Water should move over each layer, not behind it.

Step Flashing and Wall Flashing

Where a sloped roof meets a vertical wall, individual pieces of step flashing may be woven with shingles. Counterflashing or wall cladding then protects the upper edge.

Failures occur when:

• Pieces are missing or too small
• Flashing is surface-caulked rather than properly integrated
• Siding is installed too close to the roof
• Fasteners are placed in exposed water paths
• Counterflashing separates
• Wall repairs disturb the sequence
• Debris traps moisture against the transition

A long bead of sealant along the wall is not a substitute for correctly layered flashing.

Vent and Pipe Flashing

Plumbing vents and other round penetrations often use a boot or flashing assembly. Florida heat can dry rubber components, while ultraviolet exposure and thermal movement cause cracking.

Watch for:

• Split or brittle rubber
• Gaps around the pipe
• Rusted metal bases
• Exposed or backed-out fasteners
• Sealant pulling away
• Improper overlap with shingles or tile

A small opening around a vent can admit water repeatedly and remain difficult to see from the ground.

Skylight Flashing

Water around a skylight does not automatically mean the skylight unit itself failed. The source may be:

• Step or head flashing
• Deteriorated sealants
• Cracked components
• Condensation
• Debris above the unit
• Water entering farther upslope
• Improper original installation

Adding sealant around the visible frame may temporarily change the symptom while leaving the actual defect untouched. A lasting repair begins with identifying the path.

Chimney Flashing

Chimneys require several flashing details, including step flashing, counterflashing, apron flashing, and sometimes a cricket or diverter on the upslope side.

Problems may develop from:

• Corrosion
• Mortar deterioration
• Counterflashing pulling out of masonry
• Missing cricket drainage
• Patch layers hiding older defects
• Movement between the chimney and roof

Because chimneys interrupt a large area of runoff, even a small opening can receive significant water.

Valley Flashing and Drainage

Valleys collect water from two roof slopes. Some systems use exposed metal, while others use membrane and overlapping roof materials.

Debris, cut edges, fastener placement, corrosion, underlayment damage, and poor installation can create leaks. Valley repairs must preserve the drainage channel rather than narrowing it with patch material.

Why Florida Weather Ages Flashing

Flashing and surrounding materials expand and contract at different rates. Heat, ultraviolet exposure, salt air, wind, and heavy rain stress joints year-round.

Sealant may shrink. Fasteners may loosen. Coatings may deteriorate. Dissimilar metals may react. Roof work by solar, HVAC, satellite, or remodeling contractors can disturb flashing that performed correctly before the project.

Signs of Flashing Problems

• Stains near exterior walls or chimneys
• Moisture around skylights
• Rust streaks
• Loose or bent metal
• Cracked sealant
• Debris collecting at transitions
• Repeated leaks after surface patching
• Water entering only during wind-driven rain

Do not rely on the interior stain location alone. Water may travel before it appears.

What a Proper Flashing Repair Requires

The repair should:

• Expose enough surrounding material to identify the defect
• Remove failed or incompatible patch materials
• Replace damaged flashing with compatible components
• Restore correct overlaps and drainage
• Repair underlayment or deck when needed
• Reinstall roofing without damaging adjacent materials
• Follow manufacturer and system requirements

A repair should correct the assembly, not simply cover the visible opening.

Crowther Roofing Inspects the Transitions

Crowther Roofing’s RoofCheck™ includes flashing, roof-to-wall details, penetrations, valleys, edges, drainage, and previous repairs. The roofing division operates throughout Florida under license CCC039822.

Give the Small Details Proper Attention

Flashing occupies a small percentage of the roof area and causes a large percentage of leak investigations. When stains appear near a wall, vent, skylight, chimney, or valley, schedule a complete diagnosis before adding another layer of caulk.