Tiled roof and roof covering — laying of tile and concrete roof tiles

Tile roofing is one of Denmark's oldest roof forms, and many bricklayers lay both tile and concrete roof tiles. A sloped tile roof works because each tile overlaps the next, so rain and meltwater is channelled outward and downward to the gutter. The tiles are hung and tied to horizontal battens, and below them an undertile protects against water and wind-driven rain that makes it through anyway. It is precision work: courses level and true, tight overlaps, and a ridge that holds.

Roof tiles are CE-marked building products. Clay roof tiles (fired clay) are declared according to DS/EN 1304, and concrete roof tiles according to DS/EN 490. The properties — dimensions, bearing capacity, frost resistance and water-tightness — are listed in the product's Declaration of Performance (DoP). Clay roof tiles come in many forms: pan tiles, interlocking tiles (with ridges that lock the tiles together), monk and nun tiles and beaver tiles. Concrete roof tiles are typically supplied as profiled or flat tiles.

A modern tile roof is a layered system where each layer has a task. The sequence from bottom to top is crucial for both tightness and for the structure to dry out:

• 01Rafter/roof structure — carries the roof and provides the slope.
• 02Under-roof — the secondary water barrier under the tiles; drains water and blown snow that escapes to the gutter.
• 03Battens/counter-batten — along the rafter above the underlay; creates a ventilated gap so moisture under the tiles can dry out.
• 04Batten strips — horizontal wooden strips across the rafters; the roof tiles are hung and tied to them.
• 05Roof tiles — the visible, water-repellent layer, laid in bond with staggered butt joints (same principle as in masonry).

Batten spacing (the distance between batten top edges) is not a fixed number. It is determined by the specific roof tile coverage length and permitted overlap and by the roof pitch: the flatter the roof, the greater the overlap (and thus the smaller the batten spacing), so the roof stays tight. The manufacturer states a minimum and maximum batten spacing for the tile. The battens are set so the number of courses fits the roof surface height — you want to avoid ending with half a course up at the ridge.

Each roof tile has a minimum roof pitch it can be laid at and still remain watertight. If the pitch falls below that, the requirement for the underlay increases. The type of underlay is therefore chosen according to roof pitch, tile type and how exposed to rain/wind the roof is. The minimum pitch and required underlay class are looked up with the manufacturer and in the underlay guidance — they are not fixed for all roofs.

• 01Fixed roof underlayment (boards/panels with slate/tiles on top) — for low slopes and exposed roofs; most robust.
• 02Suspended substructure — for steeper slopes where the requirement is more lenient.
• 03Diffusion-open versus airtight underlayment — selected based on the construction; a ventilated gap above the underlayment is required so moisture can dry out.