DTU 40 Series (France)

In France, the DTU (documents techniques unifiés, unified technical documents) are the reference rules of the art for building work. They are drawn up under the Commission Générale de Normalisation du Bâtiment/DTU, with the Centre Scientifique et Technique du Bâtiment (CSTB) providing its secretariat. Since 1990 they have been progressively brought into the official French standards system, and most are now published as French standards with the prefix NF DTU.

The DTU 40 series covers pitched roof coverings (couvertures).

Parts of a DTU

A DTU normally consists of:

• a CCT (cahier des clauses techniques) – technical clauses for choosing and installing materials
• a CCS (cahier des clauses spéciales) – special clauses that define the limits of each trade's work and its obligations to other trades
• sometimes calculation rules

These documents apply contractually: they bind the parties when a contract refers to them, which most building contracts in France do. Insurers and courts also refer to them when judging whether work follows accepted practice.

Documents in the 40 series

Examples include:

• DTU 40.11 – natural slate roofing
• DTU 40.13 – fibre-cement slate roofing
• DTU 40.21 – clay tiles with locking or sliding relief profiles
• DTU 40.23 – flat clay tiles
• DTU 40.24 – concrete tiles
• DTU 40.35 – ribbed sheets made from coated steel
• DTU 40.36 – aluminium sheets, pre-painted or not
• DTU 40.41 – zinc sheet and long-strip roofing
• DTU 40.44 – stainless steel sheet and long-strip roofing
• DTU 40.5 – rainwater drainage works

Other numbers in the series cover further tile types and roof coverings.

How they are used

DTUs set minimum pitches according to climatic zone, site exposure and rafter length, along with laps, fixing methods, underlay, ventilation and flashing details. As a result, the same tile can require different minimum pitches in different parts of France.

Products and methods outside the DTUs are usually covered by a CSTB Avis Technique or Document Technique d'Application, which serve as evaluated alternatives.

Access

DTUs are sold rather than distributed free, which has been criticized as a barrier for individuals and small firms. In 2017 France's Conseil d'État held that NF standards cannot be made mandatory by regulation if they cannot be consulted free of charge.