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Building components · Terminations

Drip Edge

Explains a small geometric feature that prevents a specific and very common form of staining and saturation.

Form:Profile or trimRoles:Weather controlDrainageProtection

Educational reference entry. What this element has to do, and whether any particular arrangement of it is adequate, depends on the whole assembly, the loading, the exposure, local requirements, the manufacturer's instructions and qualified professional design.

Overview

What a drip is

Water running off a horizontal surface does not simply fall. It tends to cling to the underside and run back toward the building, wetting the wall beneath. A drip edge interrupts that: either the edge projects far enough that water falls clear, or a groove in the underside breaks the surface so the water cannot continue past it.

It appears wherever a horizontal surface projects — sills, copings, string courses, balcony edges, canopy edges — and its absence is one of the most reliably visible defects on a building facade.

Boundaries

How it differs from nearby elements

The distinctions that keep this entry from being a restatement of its neighbours.

  • It is not a flashing. A flashing covers a junction; a drip is a shape at an edge and has no junction to cover.
  • It is not a gutter. A gutter collects water; a drip simply makes it fall clear.
  • It is not decoration, although the projections that provide it are frequently read as architectural detail.

Terminology

Common names and aliases

These names describe the same element. The library keeps one entry per component so that a trade term or a regional name never becomes a second, thinner page.

  • drip
  • throating
  • drip groove
  • water check

Dependencies

What it depends on

What has to be right elsewhere for this element to do its job.

  • The projection or groove being continuous, since water finds any point where the interruption stops.
  • The groove being deep and sharp enough to break the water's path rather than merely marking the surface.
  • Being kept clear of paint build-up, mortar or dirt that can bridge the groove.
  • The edge being level or falling outward, since a back-fall delivers water inward regardless of the drip.

Considerations

Topics that genuinely apply here

Subjects worth discussing about this element. These are discussion topics, never measured values, ratings or performance claims.

Moisture

Water running back under a projecting element wets the wall directly beneath it, and repeated wetting of one band of wall is what produces the characteristic staining.

Durability

Persistent local saturation beneath a projecting element leads to frost damage and finish failure in that band rather than across the wall.

Buildability

A drip groove that is filled by later painting or rendering has been removed as effectively as if it was never formed.

Materials

Commonly formed from

Material families this element is commonly realised in. This states common practice only — it is not a statement that any of these materials suits this component in a particular building, which depends on the whole assembly and on qualified review.

Materials LibraryStone Copings and Cills →Stone units are commonly formed with a throated underside for exactly this purpose.Materials LibraryPrecast concrete panels →Precast sills, copings and bands are cast with a drip groove in the underside.Materials LibraryAluminium →Pressed metal edge trims form a drip at membrane and cladding terminations.Materials LibraryLead sheet →Dressed metal edges are formed to throw water clear at flashings and copings.Materials LibraryCement render →A bellcast or throated edge is formed in the render itself at the base of a rendered surface.

Assemblies

Building systems this element is met in

The role this component fills inside each assembly. A role describes what the element does there — it is not a statement that this component suits that system in any particular building.

Edge and terminationParapet System →Throws water clear of the parapet face at the coping edge.Edge and terminationWindow Opening Interface →Ensures water leaving the sill falls clear rather than tracking back to the wall.Edge and terminationDirect Render →The formed edge at the base of the render that stops water tracking behind it.Edge and terminationRainscreen Facade →Edge trims shed water clear at the base and at horizontal interruptions of the facade.Edge and terminationBracket Supported Balcony →Keeps water leaving the balcony edge from running back onto the facade beneath.

Where it is met

Application contexts

Building contexts where this element is commonly encountered. Association is not recommendation: appearing here does not mean the component suits every instance of that context, or any particular one.

  • Boundary Structure
  • Building Envelope
  • Facade
  • Flat Roof
  • Opening

Clarifications

Commonly misunderstood

  • That a projecting element sheds water automatically. Without a drip, water commonly runs back along its underside.
  • That staining below a sill or coping means the element is leaking. It frequently means water is tracking back under it instead of falling clear.

Conversations

Questions for qualified professionals

Questions worth asking someone with the project in front of them. This page cannot answer them.

  • Does this projecting element have a drip, and is it continuous?
  • Has the groove been bridged by paint, render or mortar?
  • Does the element fall outward, or is there any back-fall?
  • Is the staining beneath consistent with water tracking back rather than with a leak?

Go deeper

Related Build Design Hub guides

Planning guidance behind the decisions this element involves.

Preparation

Related planning checklists

Owner-side preparation before the conversation where this element comes up.

What this entry does not do

  • No projection, groove size or position is stated here.
  • Whether a particular edge requires a drip, and in what form, is a design matter.

Terminations & Weathering

The elements where a plane stops, turns up, sheds water or is deliberately interrupted — parapets, upstands, flashings, drips, weeps and movement joints.

Browse all terminations entries →