Rainwater drainage in new buildings in Portugal

Independent site: we are not a public authority, and this is not legal or tax advice.

A building must drain rainwater quickly and completely from every part of the property, with rainwater pipes kept separate from sewage pipes (Regulamento Geral das Edificações Urbanas, art. 91.º).

Ask for a free check

Law

Regulamento Geral das Edificações Urbanas (RGEU, Decreto-Lei n.º 38382/51)

Article

91.º

Rule

Rainwater that falls anywhere on the property must drain away quickly and completely

Pipes

Rainwater downpipes must be independent of the pipes for sewage and used water

Yards and open space

A waterproof strip at least 1 metre wide must run along the building to protect the walls from damp, sloped so water drains quickly to a trapped drain (art. 76.º)

Where it applies

Inside urban perimeters and the protection zones of towns; elsewhere only where the council has extended it (art. 1.º)

Official text

pgdlisboa.pt/leis/lei_mostra_articulado.php?nid=1217&tabe...

Sources

pgdlisboa.pt/leis/lei_mostra_articulado.php?nid=1217&tabe...
pgdlisboa.pt/leis/lei_mostra_articulado.php?nid=1217&tabe...
pgdlisboa.pt/leis/lei_mostra_articulado.php?nid=1217&tabe...
pgdlisboa.pt/leis/lei_mostra_articulado.php?nid=4024&tabe...

Checked

2026-11-05