Altdeutsche Deckung

The Altdeutsche Deckung ("Old German covering", also Altdeutsche Schieferdeckung) is a traditional German method of slating in which slates of varying height and width are laid in courses that rise at an angle across the roof. It is the classic slate roof of the Rhineland and the German uplands, and German roofers call it the "queen of laying methods" (Königin der Deckarten) because it is difficult and demanding to execute.

How it works

• Shaped slates. Each slate is dressed to a set outline. The shape of the cut, the Hieb, comes in standard variants: normal, sharp (scharfer Hieb) and blunt (stumpfer Hieb).
• Rising courses. The courses (Gebinde) are not parallel to the eaves but climb diagonally across the roof. This rise (Gebindesteigung) lets water run off sideways along the lap. The steeper the roof, the smaller the rise needed.
• Graded sizes. Course heights reduce from the eaves to the ridge, with the largest slates at the eaves, where most water flows, and the smallest at the ridge. Depending on rafter length, the difference between the largest and smallest course is about 40-80 mm (1.6-3.1 in). Grading also makes the roof look taller.

Because slates can be sized and shaped to suit, the method adapts well to complex roofs with towers, dormers, valleys and curves.

Related methods

• Wilde Deckung ("wild covering") follows the same principles but uses undressed stones that the roofer shapes on site.
• A template variant uses the same slate geometry in uniform sizes, giving a flatter, more regular appearance.
• The French method (Französische Deckung) uses rhombic or hexagonal slates laid in courses parallel to the eaves.

Background

Slate roofing on the Rhine and Mosel goes back to the Romans, who laid slate in bonded patterns to fixed rules, and the craft reached a high point in the Middle Ages. Reference sources describe the Altdeutsche method, with irregular rhombic slates laid diagonally to the eaves, as the most common form in the Rhineland.

German slating compared

German slating uses roughly 250 slate formats, generally 4-6 mm (about 0.16-0.24 in) thick, about 5 mm (0.2 in) on average, and a wide range of laying methods. French practice concentrates on about 10-15 rectangular formats, 2.5-4 mm thick, while British slating uses only rectangular slates, often large. Slate roofers in Germany are trained at the federal training centre (BBZ) in Mayen.

Sources and gaps

Minimum pitches for the method under the ZVDH technical rules: published information is limited.