Spanish Minimum Roof Pitch (CTE DB-HS1): By Material

The requirement

Roof pitch — pendiente, in the CTE — is how steep a roof plane is. Lay a material flatter than it can handle and rain works its way back under the laps instead of running off. Spain’s national building code, the Código Técnico de la Edificación (CTE), fixes this material by material in Documento Básico HS, Sección HS1 “Protección frente a la humedad”, §2.4.3.1, Tabla 2.10.

Unlike a single national minimum, DB-HS1 gives a different pendiente for every roofing material and profile — because a deep tile profile sheds water differently to a flat sheet:

These are percentage slopes, not degree angles. DB-HS1 states every figure as a pendiente — rise divided by run, expressed as a percentage — so a “32%” tile minimum is not the same shape of number as the degree figures you might be used to from another country’s code. Convert before you compare.

The table’s scope is limited. Tabla 2.10’s figures apply to a roof plane (faldón) under 6.5 m, at normal exposure, and assuming the site’s climate zone is unfavourable — the conservative case. Go past any of those conditions — a longer roof plane, a sheltered or highly exposed site, a milder climate zone — and DB-HS1 hands the minimum off to a UNE product standard instead: UNE 127100 for concrete tile, UNE 136020 for ceramic tile. So the Tabla 2.10 percentage above is a starting figure for the conservative case, not an automatic answer for every roof plane.

Flat roofs are a separate table

DB-HS1 covers flat roofs (cubiertas planas) in a different table, Tabla 2.9, right next to Tabla 2.10 — and it gives ranges, not single minima. Most protection types — gravel, self-protected membrane, fixed or floating paving — sit at 1–5%. A green roof (ajardinada, with a soil layer) runs 1–15%. This page focuses on pitched roofing; if you’re detailing a flat roof, work from Tabla 2.9’s ranges, not the pitched-roof table above.

Worked example

You’ve framed a roof plane. The rafter climbs 1 m over a 4 m run. What’s the pendiente, and is it steep enough?

1. Get the rise and the run. Rise is how far the roof climbs — 1 m. Run is how far it travels flat to get there — 4 m.
2. Turn it into a percentage. Divide rise by run and multiply by 100: 1 ÷ 4 × 100 = 25%. (The roof-pitch calculator does this bit for you, and can also convert it to degrees if that’s what you’re used to.)
3. Check it against your material’s minimum. Laying zinc, minimum 10%? At 25% you’re well clear. Laying teja plana con encaje, minimum 50%? At 25% that same roof is a long way under — too flat for that tile, even though it was fine for the zinc sheet.

Related

• Spanish Building Regulations hub — how the one national CTE and its Documentos Básicos work.
• NCC minimum roof pitch (Australia) — a code that fixes pitch in degrees rather than percentage slope, for comparison.

Sources

• CTE Documento Básico HS, Sección HS1 “Protección frente a la humedad”, §2.4.3.1, Tabla 2.10 (pitched-roof minima by material) and Tabla 2.9 (flat-roof ranges) — edition of 14 June 2022, Ministerio de Vivienda y Agenda Urbana. Read it at codigotecnico.org.
• UNE 127100 (concrete roof tile) and UNE 136020 (ceramic roof tile) — the standards DB-HS1 defers to outside Tabla 2.10’s scope (roof plane over 6.5 m, or outside the assumed exposure/climate case). Paid AENOR standards, not reproduced here.

Read this first. These figures are from the current DB-HS1 articulado. Always confirm the current edition at codigotecnico.org before you build to it, and check whether your roof plane, exposure and climate zone actually fall inside Tabla 2.10’s stated scope before using its percentage directly.