Chimney guides

Chimney Flashing Under Terracotta Barrel Tile

This is the hardest chimney detail in California roofing and the one done badly most often, because the shortcut looks finished.

Barrel tiles lifted aside to expose the underlayment and new metal at a stucco chimney

Short answer

Flashing under terracotta barrel tile has to be done by lifting the tiles, stepping and counter-flashing the metal against the underlayment, and relaying the tiles. What happens instead is that tile gets bedded in mortar over the top of the joint. It sheds water for a year or two, then the mortar cracks — and because water is now getting in under the tile rather than over it, the damage stays hidden until it shows inside.

How the roof actually works

Tile is not the waterproof layer. The underlayment beneath it is. Tile is a rain screen that takes the weather and sheds the bulk of the water, and anything that gets past it is caught and drained by the membrane underneath.

That means chimney flashing has to be integrated with the underlayment, not with the tile. Metal laid on top of tile, or tile bedded in mortar against the chimney, puts the seal in the wrong plane entirely. Water gets under the tile — which it always does — and then runs along the underlayment to whatever the nearest penetration is.

What correct looks like

Tiles lifted. Step flashing or a pan flashing dressed onto the underlayment and up the chimney. Counter-flashing let into a reglet cut in the masonry or stucco and folded down over it. Then the tiles relaid, and the tiles closest to the chimney frequently cut to fit rather than forced.

Why mortar bedding is so common

It is much faster, it needs no metalwork skill, and when it is finished it looks solid and permanent. It also fails within a couple of seasons and hides where the water is going.

On a stucco chimney

Most California chimneys are stucco over masonry or over a framed chase, and that changes the counter-flashing detail.

The metal has to be let into a cut reglet and the stucco made good over it. Caulking metal to the face of stucco is not a detail — it is a delay. Hard California sun degrades surface sealant quickly, and when it goes the water goes behind the render, which is where hollow-sounding stucco comes from.

Tap the stucco while you are there

Hollow means the render has debonded and water has been behind it. On a chimney that usually points back at the flashing or the crown, and it is worth knowing before anyone re-renders.

Coordinating with a reroof

The best moment to do this is while the roof is open, and on a tile roof that moment may not come again for decades.

If roof work is planned, raise the chimney detail before the contract is signed and establish in writing who is responsible for it. Split responsibility is how it ends up done at speed by whoever gets there last. Barrel tile that is carefully lifted can nearly always go back; tile that has been walked on cannot, and matching old tile is genuinely difficult.

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Frequently asked questions

How do I know it is the flashing and not the crown?

Timing. Flashing leaks appear with wind-driven rain and often stop in ordinary showers. A cracked crown leaks whenever it rains. A hose test working upward in sections settles it.

Roofer or chimney company?

Either, provided they lift and relay the tile and cut a reglet. That is the question to ask rather than which trade they call themselves.

Can it be repaired without disturbing the tiles?

Not properly. A repair that avoids lifting tile is a sealant patch, and on a tile roof that is a short-lived one.