A plain tile is a flat, rectangular roof tile without side interlocks. Because there is no interlock, the tile has to get its weathertightness from overlap rather than from a locking profile — which is why plain tiling looks and behaves rather like slating.
Plain tiles are classically made of fired clay, but they are also produced in concrete, fibre cement, timber and plastics such as composite or hard rubber. The bevertail tile — the familiar tile with a rounded bottom edge — is essentially a variety of plain tile.
Double-lap coverage
Where an ordinary interlocking or pantile roof gets by with a single layer, plain tiles are normally laid double lap: each tile overlaps not only the course directly below it but also part of the course below that. At every point of the roof plane there are then at least two tile thicknesses, and the vertical joint between two tiles is always covered by the tile above.
That makes the covering secure but also heavy: a plain tile roof contains far more tiles per square metre than a roof of large interlocking tiles. When replacing an interlocking roof with plain tiles the roof structure must always be recalculated — the extra dead load is not a detail.
Roof pitch
The flat, uninterlocked form places demands on the pitch:
- From roughly 35 degrees plain tiling can in principle be used without extra measures.
- Between roughly 30 and 35 degrees an underlay is needed, because wind-driven rain and snow will otherwise get in at the joints.
- Below 30 degrees plain tiles are not advised; the lap is then insufficient to hold back ponding water.
Always follow the manufacturer’s fixing instructions: minimum pitch, gauge and lap differ per model.
Use on walls
Plain tiles are also hung vertically as wall cladding, for example on a gable or a dormer cheek. On a wall the “pitch” is 90 degrees, so shedding water is no problem there; the batten structure does have to stay ventilated and the tiles must be mechanically fixed.
Practical points
- Fixing. Being light and flat, the tile is vulnerable to wind uplift. At verges, eaves, ridges and on tall buildings the tiles must be secured with clips, hooks or nails.
- Bond. Tiles are laid in broken bond so that the joints do not line up.
- Battens. Battens at the correct gauge are essential; that gauge follows from the tile’s cover length, not the other way round.
- Maintenance. Broken tiles can be replaced individually — one of the big advantages over a fully bonded covering.
Related terms
- Roof tiles
- Bevertail tile
- Interlocking tile
- Roof slate
- Slate roof
- Roof pitch
- Batten / counter batten
- Roof boarding
Want to know more about building terms? Take a look at our knowledge base on fredsdiyplans.com.