Skylight Installation in Mill Valley, CA

What Skylight Installation Involves on a Hillside Roof

Skylight installation cuts an opening through the roof deck, frames a curb to building code, and sets a fixed or vented unit with new flashing so daylight comes in and water stays out. On Mill Valley hillsides, it starts with a roof inspection.

We read the pitch, the sheathing under the shingle, and the direction the framing runs. A steep gable over a living room allows options a low-slope mansard or gambrel never will.

The Parts Doing the Real Work

• Step flashing is woven into every course of shingle along the uphill side of the curb, which is where leaks usually begin.
• Counter-flashing caps the top edge and stops water wicking back under the metal.
• A self-adhered ice-and-water shield wraps the curb and runs up beneath the shingle field.
• Synthetic underlayment replaces old tar paper and roofing felt across the surrounding square.
• Sealant and roof cement close the corners, but they only back up the metal. They are never the primary waterproofing.
• Insulation and a vapor barrier sit below the shaft so the opening never becomes a cold spot that collects moisture.

How We Install One, Start to Finish

Our rule is simple. The roof has to be watertight before the unit goes in, not after.

1. Roof estimate and layout — we measure from the attic, check rafter spacing, and confirm the opening clears every truss, joist, and the ridge beam.
2. Interior protection — drop cloths go down and we mark the paint line so patch work matches when we leave.
3. Tear-off and framing — a pry bar and roofing shovel strip shingle, felt, and old underlayment, then we frame the curb to the right angle.
4. Flashing detail — ice-and-water shield first, then step flashing, apron flashing at the low edge, and counter-flashing at the high edge, all ring-shank nailed and hand-sealed.
5. Tie-in — the field course goes back in staggered courses with the starter course locked into the existing pattern.
6. Finish and cleanup — insulation, drywall patch, and debris to the dumpster.

One unit runs one to three days. A ladder handles single-story work; a steep rooftop gets a scaffold and a safety harness, and the nail gun runs off an air compressor so no fastener is overdriven.

What's Included in a Standard Installation

• Removal of the existing asphalt shingle, felt, and underlayment around the opening — no recover or overlay sitting on a failing substrate.
• A framed curb sized to the unit and pitched so the glass sheds water toward the eave.
• A full flashing kit: step flashing, apron flashing, counter-flashing, and boot flashing near a pipe boot or vent boot.
• Self-adhered ice-and-water shield and synthetic underlayment across the surrounding roofing square.
• Interior shaft work — insulation, vapor barrier, drywall patch, and a check of the attic fan and soffit vent.
• Final roof inspection, photos of the detail, and every bit of debris hauled off site.

How a New Unit Ties Into the Rest of the Roofing System

A skylight is only as good as the assembly around it. Water that gets past the curb will find the ridge vent, the valley, or the chimney flashing next, so we treat the whole area as one job.

• Drip edge along the eave and rake keeps water off the fascia and stops it curling back under the starter course.
• Ridge cap and ridge vent sit at the top of the slope, so the opening stays far enough down to leave ventilation alone.
• Overhang, canopy, and awning areas below the roof shed water too, and a new downspout should not dump straight onto them.
• Hip and verge lines change how step flashing gets set, so pitch and geometry get measured before anything is ordered.
• Parapet walls and coping on a flat section need a different termination, and the scupper has to stay clear so ponding water drains.
• Purlin, batten, and counterbatten runs decide where the opening can sit and how the curb is supported.
• Plywood and OSB sheathing take fasteners differently, and a soft roof deck may need decking repairs first or the unit settles out of square.
• Deck screws hold the curb framing, ring-shank nails lock the shingles, and caulk, adhesive, and mastic close the small gaps.
• Snow guards and anchor points matter on steep pitches. An anchor in the wrong place becomes next year's leak.

Weatherproofing is a system. Waterproofing the curb is one piece of it, not the whole story.

Warning Signs You Need Replacement, Not Another Patch

What We See on Mill Valley Rooftops

• Ceiling staining or a slow drip that only appears when fog hangs heavy and moisture seeps into the frame.
• Cracked or fogged glass, which means the seal failed and the unit is no longer insulating.
• Granule loss, curling shingle, or end-of-life wear in the asphalt around the curb.
• Rot or decay in the sheathing below the curb — usually a soft spot you can feel from the attic.
• Staining along the valley or chimney flashing nearby, a sign of a systemic leak running longer than you think.
• A sag in the roofline above the opening, or daylight visible around the frame.
• Paint peeling or stucco spalling on the soffit and fascia below.
• An ice dam at the eave after a cold snap pushing meltwater under the drip edge. Uncommon here, but not impossible.

Types, Materials, and What Drives Cost

Cost depends on the unit, the roof pitch, and how much surrounding roofing comes apart. A fixed skylight costs least because there is nothing to open or seal twice.

• Fixed skylights bring in light with no moving parts, which suits a hallway or stairwell.
• Vented skylights open for airflow and pull heat out of an upstairs room.
• Solar-powered blinds run off the unit's own panel, so nobody fishes wire through a finished ceiling.
• Sun tunnels move daylight into a windowless hall through a tube instead of a full opening.
• VELUX and Solatube are the two brands we install most, and both publish flashing kits matched to roof type.
• Tile, clay tile, and concrete tile roofs need a curb detail nothing like asphalt shingle, and slate or wood shake — cedar shake especially — cracks when it is handled carelessly.
• Three-tab shingle, architectural shingle, and metal panel each take a different counter-flashing profile.
• Standing-seam panel and corrugated panel need a pan-and-boot detail, since you cannot weave flashing into a metal rib.

On flat sections we work in membrane systems — TPO, EPDM, and PVC membrane — plus built-up roof and modified bitumen where tar, asphalt, and bitumen are already part of the assembly. Older flat roofs sometimes need a torch-applied cap or a reflective coating first.

Fog, Winter Rain, and Your Roofline

Coastal fog hangs here until mid-morning, and atmospheric rivers drop a season of rain in a few days. Both punish a skylight that was flashed poorly.

Fog drives moisture into every gap in the sealant. Rain finds the low side of the curb first. Between the fog coming off Mount Tamalpais and the tree cover near Muir Woods National Monument, some rooftops here see very little direct sun.

That is why the ice-and-water shield runs up past the curb on the uphill side, and why we keep the gutter and downspout clear. A clogged gutter backs water up under the eave and behind the fascia, which looks exactly like a skylight leak and usually is not.

Mild temperatures mean low snowfall risk, so steam ice and true ice dam removal rarely come up in conversation. The real threats are year-round moisture and winter wind. If hail damage or a fallen limb opens something up, we start with a roof repair scope before anyone talks roof replacement.

Permits, Insurance Claims, and Energy Efficiency

Skylight installation is a permitted alteration in most Marin County jurisdictions, and inspection covers the framing, the flashing, and curb height above the finished surface. Skipping the permit causes trouble at resale.

If a storm tore a unit loose or drove water into the decking, homeowner insurance often covers it. We photograph the failure, note the storm date, and hand you a line-item estimate for your adjuster. When the scope comes up short, we help build a supplemental claim and can walk through a proof of loss form and any claim deadline.

A sealed double-pane unit with proper insulation is the simplest energy efficiency upgrade on this list. Solar-powered blinds and coated glass cut heat gain in a west-facing room. Green roofing and cool coatings suit flat sections but change how the curb gets detailed, so plan them together.

• Clear the gutter and downspout before the first big storm, and check the sealant line around the curb every fall.
• Roofing technology has improved the hardware — self-adhered membranes and better flashing kits buy years of service.
• Sustainability in roofing usually means choosing a long-lived assembly you will not tear off in ten years.

Questions Homeowners Ask Us

How long does skylight installation take?

Skylight installation usually takes one to three days for a single unit. A second unit, tile matching, or rot in the sheathing can push it to four.

Will a new skylight leak?

A correctly flashed skylight should not leak. Failures come from bad sealant, missing counter-flashing, or a curb framed too low. The metal work matters more than the unit.

Does a skylight hurt energy efficiency?

A modern double-pane unit with a sound seal and an insulated shaft has little effect on energy use. Old single-pane units lose heat fast and are worth replacing.

Can you install a sun tunnel instead?

Sun tunnels cost less and use far less roof space when you need light, not a view. They run on a tube and a small dome, so the opening is much smaller.

Do you repair existing skylights?

Yes. We service and reseal existing units, replace failed flashing, and refit glass when the frame is still sound. Sometimes a repair is the right call and we say so.

Are you a licensed roofing company?

We are licensed & insured. If you are hunting for roofers near you who will put the flashing detail in writing, ask any roofing contractor that question before you hire.

What Neighbors Tell Us

Most of our calls come from referrals across Alto, Cascade, Homestead Valley, Muir Beach, and Strawberry. We can often mend a small failure, restore a curb detail, or renovate an aging shaft without replacing the whole unit.