Shingling around a skylight takes more than trimming shingles to fit. The water-shedding system depends on the skylight’s design, the roof’s slope, compatible flashing, and correctly layered roofing materials. A mistake at the corners or uphill edge can send water beneath the shingles and into the roof deck. This guide explains how to plan the work, install shingles and flashing in the right sequence, and recognize when a professional roofer is the safer choice.
How Skylight Flashing Works
Shingles shed most rainwater, but the roof opening around a skylight needs extra protection. Flashing directs water around the frame and back onto the roof surface. It works with the shingles and underlayment as a layered drainage system; it is not simply a strip of metal intended to seal every gap.
Many skylights use a manufacturer-specific flashing kit. A typical kit may include a lower apron or sill flashing, side pieces, and a head flashing at the uphill side. Some systems use separate step flashing along the sides; others use formed components that interlock with each shingle course. The exact arrangement depends on the model and roof covering.
The skylight installation instructions take priority over generic methods. Flashing pieces, overlap distances, fastener locations, and acceptable roof pitches can differ. A kit for one model may not fit another, even if the skylights appear similar.
Identify the Skylight and Check the Roof
Before removing shingles, identify whether the skylight is deck-mounted or curb-mounted. A deck-mounted unit attaches directly to the roof deck. A curb-mounted unit sits on a raised frame, or curb, built around the opening. These designs use different flashing arrangements, so the wrong kit or installation method can lead to leaks.
Look for a model number or label on the frame, then find the manufacturer’s installation guide and matching flashing kit. Confirm that the kit is approved for the specific skylight, roof material, and roof slope. If the model cannot be identified, contact the manufacturer or a roofing professional rather than improvising with unrelated flashing parts.
Inspect the surrounding roof for soft or rotted decking, damaged rafters, loose shingles, and signs of long-term water entry. New shingles will not fix a damaged roof deck. If deterioration extends beyond the immediate opening, the affected materials should be assessed and repaired before the skylight is reflashed.
Tools, Materials, and Safety
Materials commonly include matching shingles, the correct skylight flashing kit, compatible roofing underlayment, and manufacturer-approved fasteners. A roofing knife, tape measure, chalk line, flat bar, hammer, and suitable hand tools may be needed. The installation guide should specify which parts are supplied and which additional materials are required.
Roof work presents a serious fall hazard. Use appropriate fall protection, a secured ladder, and footwear designed for the conditions. Avoid working on wet, icy, windy, or excessively hot roofing. A roof that is steep, high, fragile, or difficult to access may require a trained roofing crew with proper safety equipment.
Do not rely on tar, caulk, or roofing cement as a substitute for correctly installed flashing. Sealants may be specified for particular details, but they can deteriorate and should not be used to compensate for missing, incorrectly overlapped, or incompatible flashing components.
Prepare the Roof Around the Skylight
If the work involves replacing shingles around an existing skylight, carefully remove enough roofing to expose the flashing and its overlaps. Work from the area above and beside the unit as required by the flashing design; a proper repair often requires lifting or removing more than the visibly damaged shingles. Avoid puncturing the underlayment or damaging the skylight frame.
For a new installation, the roof opening and skylight must already be framed and installed according to the skylight manufacturer’s instructions. Check that the unit is square, properly fastened, and installed at an approved slope. Structural framing and roof-opening work can affect the building’s integrity, so it should not be treated as ordinary shingle trimming.
Remove debris and inspect the exposed roof deck. Replace compromised sheathing before installing new roofing. Apply the specified underlayment around the opening and integrate it with the roof’s existing water-resistive layer. Underlayment placement and laps vary by product and local requirements; the goal is to direct water outward and downhill, not behind the flashing.
Install Flashing and Shingles in the Correct Sequence
The sequence is critical because each uphill layer should drain over the layer below it. A common arrangement uses lower flashing at the downslope edge, side flashing integrated with successive shingle courses, and upper flashing that directs water around the top of the skylight. However, some manufacturer kits use different shapes or sequencing. Follow the kit diagram rather than assuming all skylights are assembled the same way.
Start With the Lower Edge
Install the sill or apron flashing at the bottom of the skylight as directed. Its purpose is to carry water from the lower frame onto the shingles below. Position it squarely and use only the fastener locations and types specified by the manufacturer. Unapproved fasteners can create leaks or interfere with interlocking parts.
Place the lower shingles in their prescribed relationship to the apron. The shingles should lie flat and shed water away from the opening. Do not cut them so tightly that they buckle against the frame, and do not cover drainage channels or features intended to remain exposed.
Work Up the Sides With Each Shingle Course
Continue upward along both sides, installing flashing and shingles in the order shown in the instructions. Where a kit calls for step flashing, each piece is typically integrated with a shingle course so that the next uphill layer covers the appropriate part of the piece. The exact overlap and fastening pattern are product-specific.
Keep the side details even and the shingles aligned with the surrounding roof. Cut shingles cleanly around the skylight without damaging the flashing or leaving a gap large enough to expose the roof deck. Follow any required clearance around the frame, and keep water channels open. Do not drive nails through areas the instructions identify as no-nail zones.
Finish the Uphill Edge
Install the head flashing at the top of the skylight using the prescribed overlap with the side components and underlayment. Upper shingles or other specified roofing pieces should shed water over the head flashing, not behind it. The top edge is especially important because runoff from the roof above concentrates there.
Where the skylight manufacturer specifies a diverter, cricket, or saddle, install it as directed. Such features can help route water and debris around the uphill side, particularly where roof geometry or a large skylight concentrates runoff. Do not add or omit components based solely on appearance; confirm the requirement for the unit and site.
Common Mistakes That Cause Skylight Leaks
- Using the wrong flashing kit: A kit designed for another skylight, roof covering, or slope may not fit or drain correctly.
- Reversing overlaps: Water can travel beneath flashing if uphill components do not lap over downhill components as specified.
- Fastening in the wrong places: Extra nails, misplaced screws, or fasteners through drainage areas can create leak paths.
- Relying on sealant: Caulk or roof cement cannot make an incorrectly layered system dependable.
- Cutting shingles too close or too far away: Tight cuts can buckle; excessive gaps can expose vulnerable materials.
- Covering drainage channels: Debris and water may become trapped if designed openings are blocked.
- Ignoring the roof slope: A flashing kit may not be approved for the actual pitch.
- Leaving damaged decking in place: Flashing cannot correct rot or structural deterioration beneath it.
Check the Finished Work
Before calling the job complete, compare the installation with the manufacturer’s diagrams. Check that the flashing pieces are seated, shingles lie flat, overlaps run in the correct direction, and no required channel or opening is covered. Confirm that fasteners are installed only where permitted and that the surrounding roof has not been left with exposed nails or damaged shingles.
Inspect the ceiling and the area around the skylight after rainfall, but do not assume a dry interior immediately proves the work is sound. Water can travel along framing or underlayment before appearing indoors. A professional roofer can review details that are difficult to verify from the ground, particularly on steep or complex roofs.
Never test a skylight by directing a high-pressure hose at the flashing. If a controlled water test is appropriate, it should be conducted carefully and in stages by someone who understands how water moves through the assembly. High-pressure spray can force water beneath roofing that would normally shed rainfall.
When to Hire a Roofing Professional
Professional installation is a prudent choice when the roof is steep or high, the skylight model is unknown, the flashing kit is unavailable, or the roof deck shows damage. It is also appropriate when the repair involves structural framing, a complex roof intersection, persistent leaks, or a roof covering that is difficult to handle without specialized tools.
Local building codes, permit requirements, and manufacturer warranties may affect the work. Requirements vary by location and project. Before starting, check with the local building department and review the skylight and roofing product documentation. For a major roof replacement, a qualified roofer can coordinate the skylight, flashing, underlayment, and shingle installation as one drainage system.
Frequently Asked Questions
Can shingles be installed over skylight flashing?
Some shingles must overlap or integrate with parts of a flashing system, while other flashing surfaces are intended to remain exposed. The correct treatment depends on the kit design. Follow the specific instructions; covering an exposed apron or blocking a drainage channel can impair water flow.
Is roofing cement enough to stop a skylight leak?
No. Roofing cement may be permitted for a limited detail, but it is not a replacement for correctly installed flashing and shingles. A leak may require removal of roofing to find and repair the failed overlap, damaged component, or underlying deck.
Can a skylight be reflashed without replacing the shingles?
Sometimes, but access to the flashing and its required overlaps may necessitate removing nearby shingles. The feasibility depends on the skylight design, condition of the roofing, and installation method. A roofer can determine whether a localized repair is reliable or whether broader replacement is needed.
Key Takeaway
Successful shingling around a skylight depends on using the correct compatible flashing kit and maintaining the intended drainage sequence from the top of the roof to the bottom. Follow the manufacturer’s instructions, preserve water channels, and treat damaged decking or unsafe roof conditions as reasons to pause and seek professional help.