Spanish Wet-Room Waterproofing: What CTE DB-HS1 Doesn't Cover

The requirement

Here’s the honest answer: CTE DB-HS1 sets no shower or wet-room membrane requirement. Unlike Approved Document C in the UK or TGD C in Ireland, DB-HS1 is freely published and genuinely official — but its scope, like theirs, is the building envelope, not internal wet-room tanking.

Documento Básico HS1, “Protección frente a la humedad” (protection against damp), part of the CTE’s Salubridad (HS) basic-document set, deals with damp coming from the ground (through floors and foundations), from façades (driving rain, wall construction), and from roofs. A direct read of DB-HS1 confirms it does not itemise shower recess, bath surround or wet-room floor waterproofing detail — there’s no membrane-extent table or wall-height figure for a bathroom anywhere in it.

So if you’ve been told “the CTE says” a shower wall or wet-room floor needs waterproofing to a given extent, that instruction isn’t coming from DB-HS1. Spain, like the UK, Ireland and France, leaves internal wet-room waterproofing detail to a different body of standards.

Where the actual numbers live

Spanish wet-room waterproofing in practice runs through UNE norms — the Spanish national standards published by UNE (Asociación Española de Normalización), several of which mirror or align with European (EN) standards. The most relevant is UNE-EN 14891, “Liquid applied water impermeable products for use beneath ceramic tiling bonded with adhesives” — the harmonised European product standard that liquid waterproofing membranes used under tile are tested and classified against. Manufacturer products are typically certified to UNE-EN 14891 and carry a European Technical Assessment (ETA) or equivalent product approval setting out exactly how, and to what extent, that specific membrane system is installed.

UNE-EN 14891 is a paid standard, distributed through UNE (or CEN, for the underlying EN text) — this page names it and explains its role, but doesn’t reproduce its classification or test-method detail. The figures that actually matter for a given job — membrane thickness, coverage rate, cure time, upstand height — live in the individual product’s ETA or technical data sheet, which is manufacturer-specific and freely available from the manufacturer, not the standard itself.

What this means on site

With DB-HS1 silent on the detail, the compliance route runs through the product and its certification:

1. Choose a membrane system certified to UNE-EN 14891 (or a locally recognised equivalent) — check the product’s ETA or Declaration of Performance rather than assuming any liquid membrane qualifies.
2. Follow that product’s technical data sheet and ETA exactly — coats, coverage rate, cure time, reinforcing mesh at joints, upstand height at drains and junctions. That documentation is the actual specification you build to, since DB-HS1 doesn’t provide one.
3. Check for regional or municipal add-ons. Some autonomous communities layer their own technical guidance or habitability-decree requirements on top of the CTE — the same pattern as room height and floor area (see the sibling ceiling-height page below) — so confirm whether your region adds anything to the national position.
4. Keep the paperwork — the product’s ETA/Declaration of Performance and evidence of correct installation — as your compliance record, since there’s no DB-HS1 clause number to cite.

Related

• Part of the Spanish Building Regulations hub — one national code, with the DBs that set the rules.
• Building the room around it? See Does Spain have a national minimum room height? — another case where the CTE stays silent and a different instrument fills the gap.

Sources

• CTE Documento Básico HS1, “Protección frente a la humedad” (consolidated text, Real Decreto 450/2022) — confirmed by direct read to cover ground, façade and roof moisture only, with no shower or wet-room waterproofing clause. Freely published. Read it at codigotecnico.org.
• UNE-EN 14891, “Liquid applied water impermeable products for use beneath ceramic tiling bonded with adhesives” — the harmonised European/Spanish product standard wet-room membranes are certified against. Paid, published by UNE/CEN; not reproduced here. See une.org.

Read this first. DB-HS1 is freely published and official, but its scope is the building envelope, not internal wet-room detail — always check the specific membrane product’s ETA or Declaration of Performance, and confirm whether your autonomous community layers any additional requirement on top of the national CTE, before you rely on any waterproofing detail. (Verified against DB-HS1 as at 2026-07-31.)