Why mortar ridges crack, and what replaces them
Mortar bedding cracks because the roof moves and the mortar cannot. Timber swells and shrinks with heat and damp, the tiles shift a little with it, and rigid mortar splits along the joint. Water gets into the crack, frost widens it, and the bedding lets go in pieces.
How often should ridge tiles be repointed?
Mortar bedding usually needs looking at between ten and fifteen years after it goes on. Some lasts longer than that. Exposed roofs, roofs on a hill and roofs near the coast go sooner.
Repointing is not a permanent fix. New mortar goes back onto a roof that still moves, so it cracks again on the same cycle.
Vision Roofing Services fits dry ridge systems. Each tile is fixed mechanically. There is no mortar to crack, so there is nothing to repoint.
What a dry ridge system does instead
A batten is fixed along the apex of the roof on brackets. It runs the full length of the ridge.
A breathable roll goes over each side of the ridge and seals against the top course of tiles. Air can pass out of the loft through it. Rain cannot get in.
Each ridge tile is then screwed down through a clamp into the batten. Nothing relies on mortar sticking to a tile.
The same tiles can often go back on. A sound clay or concrete ridge tile is lifted, cleaned and refitted.
How to tell your ridge mortar is going
Look along the ridge line from the ground with binoculars, or at a photograph taken on a phone at full zoom.
Hairline cracks running along the joint are the first sign. Lumps of grey mortar in the gutter or on the path after a windy night are the second.
A ridge tile sitting proud of the line, or rocking when the wind blows, has already let go.
From inside the loft on a bright day, daylight along the top of the roof means the bedding has gone.
The verge goes the same way
Mortar at the gable edge fails for the same reason as mortar at the ridge. It is rigid, and the roof is not.
Ridge and verge are usually done together, because the access is up once and the mortar on both is the same age.
Common questions
- How long do ridge tiles last?
- The tiles usually outlive the mortar under them by decades. A clay or concrete ridge tile can last as long as the roof covering, often forty years or more. It is the bedding that fails, not the tile, and a sound tile can be lifted and refitted on a dry system.
- How long should ridge tile mortar last?
- Ten to fifteen years is the usual working life. Sand and cement on a roof that moves is on borrowed time from the day it sets. Exposure, the mix that was used and how well the roof was pointed all change it.
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