Vent Flashing and Chimney Repair in San Jose

Why are penetrations the most common leak point?

A penetration breaks the roof surface, and the flashing around it must join two different materials. Each joint is a place where the water can get behind the covering if it is not lapped correctly.

The flashing must run up under the covering above the penetration and over the covering below it. A flashing lapped the other way round lets water run down behind the metal and into the framing.

The pipe itself moves a little with the heat and the cold, and the boot must accommodate that movement. A boot that is rigid and tight to the pipe splits at the first movement, and the split then lets water run down the pipe.

How is a chimney flashed correctly?

A chimney is flashed with a step flashing along each side where the covering meets the masonry, and with a counterflashing set into the mortar joint above. The two must lap correctly, so water runs over the joint from the chimney to the covering.

The counterflashing is set into a cut in the mortar, and the joint is pointed so no gap remains. Where the mortar has cracked, the joint is repointed before the flashing is fixed.

The step flashing is laid piece by piece with each lap over the one below. The covering is then lapped over each step, so the chimney's water runs down the slope and not into the joint.

Why does the water appear far from the pipe?

Water runs along the pipe and the framing before it drops, so the stain can be a long way from the entry point. The attic trace follows the wet wood back to the penetration.

A pipe that leaks at its collar runs water down its length, and the water then travels along a rafter to the ceiling. The stain may show in a room that seems far from the pipe, and the owner who looks only at the stain will search in the wrong place.

The technician reads the attic from the stain back to the pipe, using the wet framing as the guide. The entry point is found and recorded before any repair begins.

What should a foothill owner check each season?

A foothill owner checks each penetration from the ground and from the attic, looking for rust on collars, split boots and cracked mortar at the chimney. A check each autumn catches the faults before the long storms.

From the ground, the rust on a vent collar and the lift on a chimney flashing are visible with binoculars or a camera. From the attic, the stain on the boards around a pipe is the sign of a leak that has already begun.

The owner keeps the photographs from each season in the file, so the change is seen and the repair is planned before the next storm.

The owner is also asked to note any new stain after each long storm, with its position relative to the nearest pipe or chimney. A short note of that kind is the quickest way to start a trace, and it saves a technician a search across the whole roof.

What does a split pipe boot look like on the roof?

A split boot shows a crack along its length or at the base of its neck, and the rubber often feels hard or brittle. A boot that has perished in the sun lets water run down the pipe at the first long rain.

The boot is usually black rubber with a metal flange at its base. When it splits, the crack often starts at the neck where the pipe passes through, and the water runs down the pipe into the framing. The technician looks at the neck of each boot from the ground or the ladder.

A boot is replaced rather than patched. A patch on rubber rarely holds in the sun, and the new boot is sized to the pipe and lapped under the covering above.

Why are the mortar and the flashing checked together?

The mortar holds the counterflashing and the flashing holds the water off the mortar. A failure in one puts the other at risk, so both are checked on each visit to a chimney.

A cracked joint lets water reach the back of the counterflashing, and the metal then fails from behind. A lifted flashing lets water run down the masonry and into the joint. The technician repoints the joint and re-sets the flashing in the same visit.

The masonry above the roof line is checked for cracks, and any spalling is noted in the record. A chimney that needs more than a repoint is referred on, and the owner is told plainly.