Why water leaks in
though the tile looks fine

The client looks at the tile, but the water comes from elsewhere. After years on roofs, we know where to look first.

Joins at chimneys and walls

The spot where the roof meets a chimney or a wall is the most vulnerable. If the sealing there fails, water gets in, however good the tile.

The valleys, again

Valleys collect water from two slopes. A badly made or clogged valley is a classic source of leaks, hard to suspect from the ground.

Water doesn't come in where it rains, but where the smallest crack is.

The membrane and condensation

Sometimes the "leak" is actually condensation, from a missing anti-condensation membrane or poor ventilation. The right diagnosis saves us from repairing where there's no need.