French Wet-Room Waterproofing: NF DTU 52.2 and the SPEC System

The requirement

In France, NF DTU 52.2 is the rule book for wet-room tiling. It rates each room by how wet it gets. The wettest rooms, like shower and bath zones, need a membrane under the tile. That system is SPEC, set out in CSTB’s CPT n° 3714. Both are paid standards.

France does this its own way. Australia’s NCC prints its rule in a public code clause. France does not. The rule sits in a DTU instead. DTU is short for Document Technique Unifié. That is a trade standard you must buy, not free public guidance.

Like BS 5385-1 in the UK, they are paid copyright works. The same goes for DIN 18534 in Germany. This page names the French texts and tells you what they do. It does not copy the class tables or the membrane specs.

Where the actual numbers live

Which room falls in which class? That list sits in NF DTU 52.2 itself. So does the point where a SPEC membrane stops being a choice and becomes a must. The membrane detail then sits in CPT 3714. Neither text is free to reprint. Need the class table for a job? That is an AFNOR or CSTB purchase. This page cannot stand in for it.

There is free help too. The Programme RAGE scheme puts out a guide on wet-room sealing. ADEME and AQC run it. The guide gives hands-on site tips. It does not copy the paid DTU text. It will not replace the DTU either. But it is handy reading for a chippy on site.

What this means on site

The binding detail sits in a paid standard. So here is the play:

1. Buy the current texts. Get NF DTU 52.2 and CPT 3714 from AFNOR or CSTB. Do it before you price or detail wet-room tiling. It matters most at the wet end of the scale. Shower and bath zones will likely need a SPEC membrane.
2. Read the free RAGE guide too. It is built for this exact gap. The law is silent and the detail is paid. The guide fills the space between them.
3. Follow the membrane maker’s SPEC instructions to the letter. That means application, primer, upstands and drain details. CSTB’s Avis Techniques, its product approvals, cover named SPEC products. That level of detail is what governs the install.
4. Keep the paperwork. Note the DTU and CPT texts you worked to. Keep the product’s Avis Technique or data sheet. Keep proof of a correct install. That is your record of compliance.

Related

• Part of the French building-codes hub. It shows how the décence rules, access exemptions and the NF DTU standards fit together.
• Building the room around it? See France’s minimum ceiling height: the 2.20 m décence rule. That rule’s real number also lives outside a permit clause.

Sources

• NF DTU 52.2, “Mise en œuvre des revêtements de sol et murs par collage” — the standard governing wet-room tiling and its wet-severity classification. Paid, published by AFNOR; not reproduced here. See afnor.org and boutique.afnor.org.
• CSTB Cahier des Prescriptions Techniques (CPT) n° 3714 — the SPEC (Système de Protection à l’Eau sous Carrelage) waterproofing-membrane system referenced by NF DTU 52.2 for the wettest classifications. Paid, published by CSTB. See cstb.fr.
• Programme RAGE, “Étanchéité des pièces humides” — a free, practical guide from ADEME/AQC aimed at wet-room waterproofing on site. See programmerage.fr.

Read this first. NF DTU 52.2 and CPT 3714 are both paid, copyrighted AFNOR/CSTB publications — always confirm the current edition directly with AFNOR or CSTB, or via a current CSTB Avis Technique for the specific product you’re using, before you rely on any classification or membrane detail. (Verified as at 2026-07-31.)