What is an eaves drip gap?
An eaves drip gap is the narrow space between two buildings that stand just clear of one another, into which rainwater from the roofs drips and is carried away. You find them mainly in historic town centres, between deep-plan houses built alongside each other over centuries. In Dutch the space is called an ozendrop, in German-speaking regions a Traufgasse or Ehgraben. The name refers to the eaves: the lowest roof edge from which water drips where there is no gutter.
What it did
- Carried water away. The bottom of the gap was usually paved to a slight fall, often with cobbles or slabs, so that roof water could run out to the street or the watercourse.
- Slowed fire spread. Between timber and later masonry houses, the open strip acted as a fire gap. Many medieval town ordinances required a clear strip between houses for exactly that reason.
- Gave access. A wider gap served as a rear entrance or narrow alley, sometimes wide enough for a cart, sometimes barely a hand’s width.
- Ventilated. The strip allowed air movement along the flank walls and gave chimney sweeps access.
Many of these gaps were closed over time with boarding or masonry, because they collected rubbish, vermin and intruders — or simply because the adjoining building was extended.
What it means in practice
- Maintenance is difficult. A closed or very narrow gap cannot be inspected. Blockage by leaves and rubble leads to water rising into the flank walls — a common but hard-to-trace source of damp in old buildings.
- Ownership is often unclear. The strip lies on or along the boundary and may be jointly owned. Covering, closing or building over it needs the neighbour’s agreement; check the registered boundary and the title deeds first.
- Water rights. Boundary law generally prevents you from discharging roof water onto a neighbour’s land. Anyone closing such a gap must still carry the roof water away over their own property.
- On a listed building the gap is often part of the historic fabric and cannot simply be altered.
Related terms
- Boundary line
- Easement
- Encroachment
- Rainwater drainage
- Gutter
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