Skylight Leak Repair and Reflash

Purpose

Most reported skylight leaks are not the skylight. They are the flashing kit, the head detail, or condensation the occupant has reasonably called a leak. This procedure guarantees those three are separated before anything is quoted, and that when a reflash is the answer the curb height and the flashing sequence are both checked against the unit manufacturer's instructions rather than against what was there before.

Selling a unit that did not need replacing is the most expensive wrong answer in this group, because the customer pays for glass, the stain comes back the next cold morning, and the shop now has to explain both.

Scope

Covers diagnosis and reflashing of deck-mounted and curb-mounted unit skylights in steep-slope asphalt shingle roofs, residential and small commercial: separating condensation from water entry, curb height, and flashing kit sequence.

Does not cover replacing the glazing unit or servicing an operator, blind or rain sensor, which belong to the skylight manufacturer's service channel. Does not cover framing a new opening or extending a curb, which is carpentry this SOP triggers but does not perform. Course lifting and hand sealing belong to the shingle repair and blend-in standard; whole-slope water testing belongs to leak diagnosis by water testing.

Roles and responsibilities

Three sources, and they do not look the same

Condensation forms on the coldest surface in the room, which in winter is the glass and the metal frame. It runs down the sash, collects at the bottom rail, and shows up at the interior trim as clear water with no staining above it. It tracks temperature, not rainfall. Many units drain that water through weep channels at the bottom of the sash, so blocked weeps produce interior water on a dry day and are a cleaning job, not a roofing one.

Water entry through the flashing kit stains the shaft above the sash, not just at it, and follows rain. The kit is three parts installed in a fixed order: an apron or sill at the down-slope end lying over the shingles below, soakers or step pieces up both sides one per course, and a head flashing at the up-slope end tucked under the courses above. This is the same two-layer logic the chimney flashing SOP owns, and it fails the same way, by someone sealing across the head instead of lapping under it.

Curb height is what the third source usually comes down to. The manufacturer's instructions state a minimum height from the finished roof surface to the top of the curb, commonly 4 in, and the code defers unit skylight installation to those instructions. A layover reroof, an added ice barrier or a thicker shingle consumes that height without anyone measuring it, and a curb that is short cannot be reflashed to a detail that works no matter how good the metal is.

Procedure

1. Set access and fall protection, and treat the skylight as a hole. Access runs under the ladder setup standard and the fall protection setup SOP. Nobody steps, kneels or leans on a skylight, in place or removed. Acceptance: anchorage set, everyone connected, and a plan for how the opening will be covered if the unit comes out. Wrong looks like a tech using the curb as a foothold. Stop rule: no work starts until the opening protection is on the roof rather than in the truck. Hazard: a skylight is a hole under 29 CFR 1926.501(b)(4), and any cover used has to meet 1926.502(i) - capable of supporting at least twice the expected load, secured against displacement, and marked.

2. Separate condensation from water entry before quoting anything. Ask when the water shows and go look inside. Acceptance: a recorded answer to whether the water tracks rain or cold, plus a note on whether the shaft above the sash is stained or only the sash itself is wet, plus a weep-channel check. Wrong looks like a reflash quoted from a photo of a wet sill. Stop rule: cold-weather water with a dry shaft is condensation until proven otherwise, and the visit turns to weeps, shaft insulation and interior humidity rather than to the roof. Hazard, commercial: reflashing a condensation complaint means the shop has been paid for work the customer will correctly say did not fix anything.

3. Attribute the entry, then decide unit or flashing. Where the evidence points to real entry, run the isolation sequence in the leak diagnosis by water testing SOP with an observer inside, and inspect the glazing unit for a fogged pane, a crazed dome, or a torn perimeter gasket. Acceptance: a named entry point - head, sill, one side, or the glazing itself - with an observer's clock time. Wrong looks like a whole slope hosed at once. Stop rule: entry at the glazing unit itself, or an insulated pane that has fogged, stops the roofing scope and goes to the skylight manufacturer's service channel with the model and date code off the unit label. Hazard: a cracked pane is a laceration route and pieces fall inward, so the room below is cleared and the shaft is covered before anything is touched.

4. Protect the interior, then open the field. Cover the shaft or the room below, then lift the courses above the head and along both sides per the shingle repair and blend-in standard and remove the old kit whole. Acceptance: interior covered, old apron, soakers and head flashing out and counted, courses below the sill undisturbed. Wrong looks like fasteners, granules and old sealant landing in a bedroom through an open shaft. Stop rule: cracked mat takes the stop rule in that SOP, and any opening left for more than a moment gets its cover back on. Hazard: debris falls straight through a skylight opening onto whoever is under it, so nobody is in the room below while the kit is off.

5. Measure the curb height against the manufacturer's minimum. Measure from the finished roof surface to the top of the curb at all four corners. Acceptance: four readings, all at or above the minimum the unit's instructions state, written down with the minimum they were compared to. Wrong looks like a new kit installed on a curb that is an inch short because the old kit was. Stop rule: any reading below the stated minimum stops the reflash - the curb gets extended by a carpenter to the required height plus a margin, and the customer decides before the crew comes back. Hazard: cutting or extending a curb over an open shaft puts tools and offcuts directly over the room below, so the opening is covered under the step 1 rule while carpentry happens.

6. Set the flashing kit in the sequence the instructions give, bottom to top. Apron first over the course below, then soakers up both sides one per course, then the head flashing under the courses above. Acceptance: one soaker per course on each side, every fastener covered by the piece or the course above it, head flashing tucked under with no sealant across its top edge, and the parts installed are the kit matched to this unit's model and this deck or curb mounting. Wrong looks like a generic flashing improvised out of coil stock. Stop rule: a missing kit part is not substituted; the job pauses for the correct part rather than being closed with cement. Hazard: metal edges and the corners of a bent head flashing are laceration points at head height when you are kneeling above them, so cut-resistant gloves stay on and offcuts get pouched rather than set on the slope.

7. Close the opening, reseal the field, and prove the head with a directed test. Remove interior covers, hand seal every shingle unsealed in step 4, tug-test the tabs, then run water on the head flashing only for at least 10 minutes with an observer inside. Acceptance: every cover accounted for and removed, tabs holding, and a dry shaft and sash after the full dwell. Wrong looks like a crew leaving on the strength of the flashing looking right. Stop rule: any water inside during the head test means the kit is opened again on this visit, not on the next one. Hazard: this step puts the assembly back in service, and the directed test is the only field evidence that the detail you disturbed sheds water, so the roof is not released until it runs; if the cement has not cured before rain, the band is covered under the emergency tarp SOP.

The record this produces

A skylight entry carrying: whether the water tracks rain or cold and whether the shaft above the sash was stained; the weep check result; the unit's model and date code off the label; the attributed entry point with the observer's clock time; the four curb readings and the manufacturer minimum they were compared against; the kit part number and mounting type; covers placed and removed; shingles lifted and hand-sealed; and the head-test dwell and result.

The estimator reads the curb readings, because a short curb will be short on every skylight on that roof, not just this one. The office reads the cold-weather line when the customer calls again in January. The next tech reads the model and date code instead of climbing up to get it.

Worked pass: 24 by 48 in deck-mounted unit, 6:12 slope, twelve-year-old skylight

Complaint is a stain on the shaft drywall about 8 in above the head of the skylight, appearing after heavy rain. Step 1: anchorage set, both techs connected, a marked cover staged for the opening. Step 2: the occupant confirms it follows rain, not cold, and the shaft is stained above the sash rather than the sash being wet, so this is entry.

Step 3: head zone tested for 10 minutes with an observer inside, water appears at minute 6 on the shaft above the head. Glazing is clear, not fogged, and the perimeter gasket is intact, so this is the kit. Step 4: room below cleared and covered, courses lifted, old apron, two soaker runs and head flashing out.

Step 5 fails. Curb height from the finished roof surface reads 3 in, 3 in, 3-1/8 in and 3 in at the four corners, against the 4 in minimum in this unit's instructions. The original curb was framed to that minimum, and a layover reroof plus a new ice barrier consumed the difference. The stop rule fires: the reflash stops with the opening covered and marked, the customer authorizes carpentry, and the curb is extended 2 in to a finished 5 in, which is 1 in above the stated minimum.

On the return, the field is a laminated shingle at 5-5/8 in exposure and the skylight runs 48 in along the slope, so 48 divided by 5.625 is 8.53 and each side takes nine soakers, eighteen in total. Step 6: apron, eighteen soakers, head flashing under the courses above, all parts from the kit matched to this model and to deck mounting, no sealant across the head. Step 7: sixteen shingles were unsealed across the head and both side runs, hand-sealed at four spots each, so sixty-four dabs, all sixteen tabs holding on the tug test. The head zone is run again for 10 minutes with the observer inside and the shaft stays dry.

The curb is the finding worth carrying. Nothing about the old kit looked obviously wrong from the roof, and a crew that reflashed without measuring would have delivered a correct-looking assembly on a curb an inch too low, then argued about it after the next storm.

References

• 29 CFR 1926.501(b)(4) for fall protection at holes and 1926.502(i) for the cover strength, securing and marking requirements that apply to a skylight opening
• 29 CFR 1926.501(b)(13) and 1926.502(d), the fall protection duty and arrest criteria governing roof access for this work
• The skylight manufacturer's installation instructions for the specific model, which set the minimum curb height, the flashing kit part numbers, and the mounting type; the IRC defers unit skylight installation to them
• See related: the leak diagnosis by water testing SOP, the chimney flashing and counterflashing repair SOP for the two-layer logic, and the shingle repair and blend-in standard