Roof Tiles, Ridge Capping And The Leaks They Cause

A tiled roof leaks in a small number of predictable places, and a cracked tile in the middle of a field is rarely one of them.

Water gets in at the joins: the ridge, the hips, the valleys, the flashings around a penetration, and the abutment against a wall. Those are the places where something other than tile is doing the work.

The ridge and hip capping

The capping is bedded and pointed in mortar, and mortar has a service life.

It cracks, it loses its bond, sections lift, and water runs under the capping and into the roof space. This is the single most common source of leaks on tiled roofs over about twenty years old, and from the ground it looks fine.

Repointing with a flexible pointing compound rather than straight mortar is the current method, because the roof moves and rigid mortar does not. A full rebed, where the capping is lifted and re-bedded, is the larger job and it is what an old roof usually needs rather than another layer of pointing over failed mortar.

Valleys

The valley is the metal gutter where two roof planes meet, and it carries more water than anything else on the roof.

It fails three ways. It rusts through, which is a matter of age and of what was originally installed. It silts up with leaves and debris, which dams the water and pushes it sideways under the tiles. Or the tiles alongside it were cut too tight or too wide, so the water runs where it was not meant to.

Clearing the valleys is routine maintenance and it is the one thing most often not done, which is the same oversight as the gutters in [gutter guard, roof safety and working at height](/blog/gutter-guard-roof-safety-and-working-at-height).

Flashings and penetrations

Everything that comes through a roof is a potential leak: a vent, a flue, an aerial mount, an air conditioning penetration, a solar bracket, a skylight.

Each one depends on a flashing, and a flashing depends on being properly dressed to the tile profile and sealed tight against the penetration itself. Sealant alone is a repair with a short life, and a flashing that was never dressed correctly will leak as soon as the sealant goes.

The ones we see most are air conditioning penetrations and aerial mounts, because both were often installed by somebody whose trade was not roofing. It is the same pattern as [TV antennas and reception in apartment buildings](/blog/tv-antennas-and-reception-in-apartment-buildings) and [installing a split system in a strata building](/blog/installing-a-split-system-in-a-strata-building), where the penetration is incidental to the main work and gets treated that way.

Skylights have their own version of this, with condensation adding to the picture, covered in [skylights, roof windows and condensation](/blog/skylights-roof-windows-and-condensation).

Abutments against a wall

An abutment, where a lower roof runs into a wall, needs a flashing stepped into the brickwork or properly tucked and sealed under a render stop.

This is where an addition most often leaks, because the new roof was built against an existing wall and the flashing was done last and done quickly.

Why the stain is never under the hole

Water entering at a ridge runs down the underside of the tile batten, along a rafter, across the ceiling framing and appears wherever it finds a join in the plaster.

Which can be metres away and on the other side of a room. Chasing the stain is how a roof gets repaired three times without the leak stopping. The entry point is found by looking at the roof in the places water actually gets in, and by getting into the roof space in the rain or after it.

That diagnostic problem is the same one in [roof and gutter leaks that are not plumbing](/blog/roof-and-gutter-leaks-that-are-not-plumbing), which is where most of these calls start.

The maintenance that prevents it

Clear the valleys and gutters at least annually, and more often under trees.

Look at the ridge pointing every few years, from the roof rather than the ground.

Check every penetration after any trade has been on the roof, because a flashing lifted to run a cable does not put itself back.

Replace broken tiles promptly, not because they are the main leak path but because a broken tile lets debris and water into places that then fail.

Do it with proper access, because a roof is the most common place a maintenance job becomes an injury, and the access requirements are part of the job rather than an extra.

Repairs and the trades around them get scoped as one piece of work, so the roofing, the ceiling repair inside and the painting that follows are sequenced by one team rather than booked separately after each one finishes.

Our maintenance work. Talk to us about a property.