Introduction

Skylight callbacks eat margin. The leak shows up after a wind-driven rain or thaw, you go back for free, and it happens again. This guide shows you how to stop the cycle: diagnose the real source, choose the right retrofit path, reflash correctly, and prevent ice-dam or condensation “faux leaks.” We’ll also cover how to scope and present the work so clients understand what’s included and what isn’t.

Table of Contents

• Key Takeaways
• Diagnose Before You Touch the Roof
• Choose the Right Retrofit Path
• Step-By-Step: Reflash a Curb-Mounted Skylight
• Low-Slope and Metal Roof Considerations
• Prevent Ice-Dam Repeats and Condensation Faux Leaks
• Price, Paperwork, and Client Communication
• Frequently Asked Questions
• Conclusion

Key Takeaways

• Most skylight leaks trace back to flashing and curb height, not the glass. Manufacturers commonly call for a minimum 4 inch curb above the finished roof, and more in snow zones.
• Deck-mounted units typically need a roof slope of at least 3:12; below that, use curb-mounted details with pan flashing.
• A proper retrofit uses ice-and-water shield wrapped up the curb (about 6 inches) and tied at least 12–18 inches onto the field.
• Crickets behind skylights wider than roughly 24–30 inches reduce ponding and wind-driven backflow.
• Clear scope notes, photos, and e-signatures reduce disputes and speed approvals; many contractors find this can shave days off decision time.

Diagnose Before You Touch the Roof

The Problem

Many contractors swap a skylight or reseal trim only to find the leak returns. The real cause is often hidden: low curbs, missing underlayment upturns, poor side-step flashing, or condensation from a leaky shaft.

The Solution

Run a disciplined diagnosis before proposing work.

What to Check

• Interior first:
  • Stains or tracks along the drywall shaft indicate condensation or air leaks.
  • Rust on the frame suggests long-term moisture, not a single event.
• Attic/ceiling cavity:
  • Wet insulation around the shaft points to air leakage and vapor issues.
  • Look for daylight at the curb-to-drywall transition—common air leak path.
• Roof exterior:
  • Curb height: manufacturers commonly recommend at least 4 inches above finished roof; in snow regions, 8 inches or more is typical practice.
  • Roof slope: deck-mounted units are generally suited for slopes 3:12 and steeper.
  • Underlayment: verify ice-and-water membrane band around the curb and upturns of about 6 inches.
  • Flashing set: intact sill pan, step flashing up sides, and head flashing/counterflashing with proper overlaps (about 4 inches minimum laps is a common benchmark).

Water Test (Controlled)

• Start low at the sill for 10–15 minutes.
• Move up the sides, then the head flashing last.
• Keep someone inside to spot the first appearance—where water shows first often tells you the failed plane.

Real-World Example

A 3:12 asphalt roof with a 2 inch curb was leaking at the head after wind-driven rain. No ice-and-water upturns, no head cricket. Raising the curb to 6 inches, adding a head cricket, wrapping ice-and-water 6 inches up the curb and 18 inches onto the field, and redoing the step flashing eliminated callbacks through two winters.

Choose the Right Retrofit Path

The Problem

You can reflash, replace the unit, raise the curb, or do all three. Picking wrong leads to cost overruns or a repeat leak.

The Solution

Match the path to slope, curb height, unit condition, and roofing type.

Real-World Example

On a 2:12 modified-bitumen roof, a deck-mount skylight kept leaking at the head. Converting to a curb-mount with a welded pan, 8 inch curb height, and a tapered cricket removed ponding and solved the leak.

Step-By-Step: Reflash a Curb-Mounted Skylight

The Problem

Partial patching and silicone beads don’t address missing underlayment upturns, poor pan flashings, or bad laps.

The Solution

Complete, layered flashing tied into the roof system.

Materials and Setup

• Ice-and-water membrane
• Step flashing (common 5x7 inch pieces for shingles)
• Sill pan and head flashing (fabricated or kit)
• Counterflashing (integral with skylight curb cap or separate metal)
• Shingles to patch back, nails, sealant as manufacturer-approved

Steps (Asphalt Shingle Roof)

1. Strip back shingles 18–24 inches around the curb; remove old flashings.
2. Repair deck if needed; ensure clean, dry surface.
3. Underlayment:
   • Run ice-and-water across the sill, extending 12–18 inches onto the field and up the curb about 6 inches.
   • Wrap sides similarly; maintain about 4 inch overlaps between sheets.
   • At the head, install a full-width band 12–18 inches onto the field and up the curb 6 inches.
4. Sill Pan:
   • Install metal sill pan with end dams. Overlap onto the shingles below by about 4 inches.
5. Step Flashing (Sides):
   • Interleave each shingle course with step flashing. Each piece laps the one below by about 2 inches, with 4 inches minimum cover on the shingle field.
6. Head Flashing and Cricket:
   • Fabricate/install a head flashing that extends at least 8–10 inches upslope.
   • Add a cricket where unit width is roughly 24–30 inches or greater to split flow.
7. Counterflashing:
   • Use manufacturer’s curb cap or separate counterflashing that sheds over the step/head flashings.
8. Re-shingle and Seal:
   • Nail per shingle manufacturer; keep fasteners high in flashing zones.
   • Use manufacturer-approved sealant sparingly at cut edges—don’t rely on caulk for waterproofing.
9. Water Test and Photo Document:
   • Hose test head last; confirm dry interior. Photograph layers for your file and client.

Time and Outcome

Many contractors schedule about 4–6 labor hours for a two-person crew on a straightforward reflash; complex tie-ins or rot repairs add time. It’s common for thorough reflashing to cut repeat call risk dramatically compared to patching.

Low-Slope and Metal Roof Considerations

The Problem

Details that work on a 6:12 asphalt roof fail on 2:12 mod-bit or standing-seam metal if you copy-paste methods.

The Solution

Adapt to roof system and slope.

Low-Slope (Typically Less Than 3:12)

• Prefer curb-mounted skylights with welded/soldered pan flashings tied into the membrane.
• Extend membrane up the curb about 6 inches; terminate with a metal counterflashing.
• Crickets are advisable behind wider units to prevent ponding and backflow.

Metal Roofs

• Use factory-compatible curbs with closure strips and butyl sealants.
• Maintain panel-specific details so the system can expand/contract without stressing the curb.
• Head flashing should bridge ribs; consider a small cricket to shed water sideways.

Real-World Example

A standing-seam roof leaked at the skylight sides due to missing closures. Adding high-temp butyl closures under the pan legs and a formed head flashing that cleared the ribs stopped wind-driven ingress.

Prevent Ice-Dam Repeats and Condensation Faux Leaks

The Problem

Clients swear it “only leaks after snow” or “only when it’s cold.” That often points to ice dams or interior moisture condensing.

The Solution

Address building science, not just metal.

Ice Dams

• In general, an ice barrier membrane should extend from the eave up the roof to at least 24 inches inside the warm wall line; around skylights, wrap the curb and tie into this field membrane.
• Add a head cricket to reduce drift buildup.
• Where appropriate, consider heat cable as a last-resort helper, but fix insulation and air sealing first.

Condensation

• Air seal the shaft-to-drywall and curb transitions (foam/caulk as appropriate).
• Insulate the shaft to the same R-value as surrounding roof/attic.
• Ensure the bath/kitchen exhausts aren’t dumping into the attic near the skylight.

Example

A “leak” only during cold snaps turned out to be condensation wetting the shaft. Sealing the shaft joints and adding insulation around the chase stopped drips with no exterior work required.

Price, Paperwork, and Client Communication

The Problem

Skylight jobs can balloon: rot at the curb, hidden low-slope conditions, or clients expecting a new unit when you priced a reflash.

The Solution

Write a clear, photo-backed scope with options and assumptions.

Scope Anchors You Can Reuse

• Inclusions: remove and replace shingles within about 18–24 inches; install new sill, step, and head flashings; wrap ice-and-water up the curb roughly 6 inches; water test.
• Exclusions/Assumptions: no structural changes; skylight unit reuse as-is unless noted; curb height increase only if selected; decking/rot repair billed if discovered.
• Options: curb raise to about 6–8 inches; head cricket; skylight replacement (match size/model where available).
• Warranty: workmanship on flashing for a defined period; manufacturer warranties per product.

Faster Admin, Less Back-and-Forth

• Capture site details with voice and photos before you climb down. With Donizo, contractors commonly record the on-roof narrative and images, then generate a clean, branded proposal the same day using voice-to-proposal. Clients can e-sign, and you can convert accepted proposals to invoices in one click—cutting office time and reducing re-typing errors.

Example

On a two-option skylight job (reflash vs. reflash + curb raise), a clear photo-backed proposal with e-sign got approval overnight. Many contractors find this kind of workflow saves 2–3 hours of admin and trims days off the yes/no limbo.

Frequently Asked Questions

When Should I Replace the Skylight Instead of Just Reflashing?

If the frame is warped, the glazing seals are fogged or cracked, or the unit is out of warranty and brittle, replace it. Reflashing won’t cure a glazing or frame leak, and you don’t want responsibility for an aging unit that fails later.

Do I Really Need to Raise a Low Curb?

If the curb is less than about 4 inches above the finished roof, especially in heavy rain or snow exposure, raising it reduces splash-back and drift buildup. Many manufacturers and roofers treat 6–8 inches as a practical target in snow regions.

When Is a Cricket Required?

Use a cricket behind skylights roughly 24–30 inches wide or more, or where uphill flow concentrates. It splits water around the unit and reduces ponding and wind-driven backflow at the head.

Can I Reuse Existing Step Flashing?

It’s rarely worth it. Reusing old, bent, or nail-punctured pieces invites leaks. Fresh, correctly lapped step flashing interleaved with each shingle course is standard practice.

How Do I Run a Reliable Water Test?

Start low and slow. Wet the sill for 10–15 minutes, then move to the sides, then the head last. Keep someone inside to watch the first drip. If it only leaks under high flow at the head, suspect missing head flashing, no cricket, or low curb.

Conclusion

Skylight leaks are usually about layers and heights, not tubes of caulk. Diagnose first, pick the right path for the roof system and slope, then install a complete flashing assembly tied into underlayment with proper laps and curb heights. Document your layers with photos and set clear expectations in the scope. If you want to speed the paperwork, capture notes by voice on-site and turn them into an e-signable proposal with Donizo. Once the client signs, convert it to an invoice in one click and get back on the roof.