Roof flashing repair in Sunnyvale, CA

Flashing is the thin metal that seals the joints on a roof where water would otherwise get in: around chimneys, vents, walls, skylights, valleys and roof edges. Flashing repair means resealing, re-securing or replacing that metal. When a leak returns after the surface was patched, worn flashing is a prime suspect.

What roof flashing does

A roof sheds water by overlapping layers, like fish scales. Wherever the roof meets something else, or changes direction, those overlaps break. Flashing bridges the gap and sends the water back onto the roof surface and down toward the gutter.

Different joints use different flashing. These are the ones you will hear roofers mention.

Signs your flashing has failed

• Stains on the ceiling or wall next to a chimney, a wall that meets the roof, or a vent.
• Rust streaks, gaps or bent metal where the roof meets a chimney or wall.
• Cracked, shrunken or missing caulk and old roofing cement smeared along a joint.
• Water stains on an outside wall below the line where the roof meets it.
• Leaks mainly in wind-driven rain, when water is pushed sideways into joints.
• A leak that returns in the same area after the surface was patched.

Several of these look like a general roof leak, because the stain shows up inside the house either way. Our job is finding where the water actually enters, and flashing is one of the first places to look.

Why flashing fails

• Heat and cold. Metal and roofing expand and shrink every day, which slowly works joints loose and cracks sealant.
• Sun. Ultraviolet light dries out caulk and rubber boots. Sunnyvale's long dry, sunny months are hard on both.
• Rust and corrosion. Older steel flashing rusts through, and some mismatched metals corrode each other where they touch.
• Installation shortcuts. Pieces that don't overlap enough, exposed nails, or caulk used in place of metal fail early.
• Movement and impact. Settling, wind, falling branches and foot traffic bend or lift flashing.

Sealant is a maintenance material, not a replacement for metal. A repair that is only a bead of caulk usually has a short life.

How flashing is repaired

1. Inspect the whole joint, not only the spot that leaks. If one section failed, its neighbors are often close behind.
2. Remove loose material: old sealant, rusted metal and any roofing cement that is hiding the problem.
3. Check the wood underneath. If the deck or the framing is wet or soft, it needs to be dried or replaced first.
4. Reseal or replace. Sound flashing with small gaps can be resealed with a compatible sealant. Rusted, bent or missing flashing gets replaced with new metal that suits the roof.
5. Rebuild the layers. Shingles or tiles are lapped back over the new metal so water runs off the way it was designed to.
6. Seal exposed edges and fasteners, using sealant as the finishing touch and not as the main barrier.

Shingles can cause trouble here too. Look at shingles that have lifted around a vent when flashing looks fine but the leak persists.

Chimney flashing and chimney crickets

A chimney meets the roof on four sides, which makes it one of the toughest joints to keep watertight. The base flashing sits on the roof, step flashing runs up the sides, and counter-flashing is set into the masonry and laps over the top. Mortar that crumbles around the counter-flashing is a common cause of leaks here.

On the uphill side, water hits the back of the chimney and can pool or pile up debris. A chimney cricket, also called a saddle, is a small peaked structure built behind the chimney to split the water and send it around both sides. Building codes commonly call for one on wider chimneys, and we can tell you what applies to yours.

Installing a cricket means framing a small ridge, covering it with roofing and metal, and tying it into the existing flashing. It is often done together with chimney flashing repair, since the roof is already opened up.

Roof vent repair and pipe boots

Every plumbing vent, exhaust vent and attic vent is a hole in the roof with a seal around it. The usual failures are simple:

• The rubber collar on a pipe boot cracks or splits, and water runs down the pipe.
• A box vent loosens or its flange lifts, letting rain in at the corners.
• Exposed nails around a vent back out or rust.
• A vent cover is damaged by wind or a falling branch.

Replacing a cracked boot or a damaged vent cover is often a small, targeted repair, as long as the area around it is checked for hidden water damage.

Drip edge, fascia and soffit

Drip edge is the L-shaped metal strip along the roof edges. It guides water into the gutter and keeps it from creeping back under the roofing and onto the fascia. Where it is bent, rusted or missing, water runs behind the gutter and rots the wood.

Fascia is the board along the roof edge that the gutter attaches to, and the soffit is the underside of the overhang. Warning signs include peeling or bubbling paint, soft or dark wood, stains on the underside of the eaves, and sagging gutters. Repair usually means replacing the rotted sections, fixing or adding drip edge, and making sure soffit vents stay clear so the attic can breathe.

Fix the cause of the water first. New fascia boards on top of a leaking edge will rot the same way.

Flashing on tile, flat and shingle roofs

The principles are the same on every roof, but the work is not. On a tile roof, flashing often sits beneath the tiles, so tiles have to be lifted, set aside and put back, which is part of tile roofs where flashing sits under the tiles. On a flat roof, flashing runs up parapet walls and around edges, and the details are covered under parapet and wall flashing on a flat roof. On asphalt shingle roofs, the metal is woven between shingle rows, so replacing flashing usually means removing and re-laying shingles around it.

What affects the cost of flashing repair

This site doesn't quote prices. These are the factors that change the amount:

• Which flashing. A single vent boot is a different job from a full chimney.
• Roof material. Tile and slate-style roofs take more time because the roofing has to be lifted and replaced.
• Height and access. Steep roofs and tall chimneys need more safety equipment.
• Hidden damage. Rotted decking, framing or fascia adds repair work.
• Extras. A cricket, new drip edge or masonry repair around the chimney each adds to the scope.

What to ask any roofer

• Will the flashing be resealed or replaced, and why?
• What metal and sealant will be used?
• Will you check the wood underneath and the shingles or tiles around the joint?
• Can I see photos of the problem and the finished work?
• Does the repair come with a written workmanship warranty?

Questions about this repair