Building components · Roof Carcass & Edges
Eaves
Explains the eaves as the point where several unrelated requirements converge on one edge.
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 eaves is
The eaves is the bottom edge of a roof slope. It is where the roof structure bears on the wall, where water leaves the covering, where a gutter is commonly hung, and where a ventilated roof draws air in.
It matters disproportionately because those requirements are unrelated to each other and all have to be satisfied in the same few hundred millimetres — along with insulation continuity between roof and wall.
Boundaries
How it differs from nearby elements
The distinctions that keep this entry from being a restatement of its neighbours.
- It is not a fascia. The fascia is one component at the eaves; the eaves is the edge condition as a whole.
- It is not a verge. A verge is the edge at a gable, running up the slope; the eaves runs horizontally at the bottom.
- It is not a gutter. The gutter collects what leaves the eaves.
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.
- eave
- roof eaves
- roof foot
Dependencies
What it depends on
What has to be right elsewhere for this element to do its job.
- How the roof and wall insulation meet, since the eaves is a classic position for a gap between them.
- Whether the roof depends on ventilation entering here, and whether that path is open.
- How far the roof oversails, which affects how much weather reaches the wall below.
- How water is delivered from the covering into the gutter, and what happens when the gutter is full.
Considerations
Topics that genuinely apply here
Subjects worth discussing about this element. These are discussion topics, never measured values, ratings or performance claims.
Insulation continuity between roof and wall is hard to achieve at the eaves because the space narrows exactly where both layers need to meet.
Where a roof relies on ventilation, blocking the eaves path with insulation is a well-known way of creating condensation in the roof space.
The depth of the overhang affects how much rain reaches the wall beneath, which has consequences for the wall rather than the roof.
Gutters, fascias and the eaves generally are among the most frequently maintained parts of a building and among the least accessible.
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.
Junctions
Interfaces this element takes part in
Junctions where the condition between this element and another governs how the construction behaves. These name the junction and the subjects it raises; they are not details, arrangements or approved ways of building.
Eaves to Gutter Discharge
Where water leaving the roof covering has to land in the gutter rather than behind or beyond it.
Raises: Moisture · Drainage · Weathering · Buildability
Wall Head to Roof Insulation Continuity
Where the wall insulation and the roof insulation must meet at the eaves, in a space that narrows exactly where they need to join.
Raises: Thermal continuity · Moisture · Air leakage · Buildability
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.
- Pitched Roof
Related elements
Neighbouring components
Typed relationships to other elements. There is deliberately no generic “related” category: an edge that cannot be classified does not exist.
Clarifications
Commonly misunderstood
- That insulating up to the eaves as fully as possible is best. Where ventilation enters there, filling the gap causes problems.
- That the eaves is a finishing detail. It resolves structure, thermal continuity, ventilation and drainage at once.
Conversations
Questions for qualified professionals
Questions worth asking someone with the project in front of them. This page cannot answer them.
- How do the roof and wall insulation layers meet at the eaves?
- Does this roof rely on ventilation at the eaves, and is that path clear?
- How is water delivered into the gutter, and what happens if the gutter overflows?
- How is the eaves accessed for maintenance?
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 overhang dimension, ventilation area, insulation arrangement or gutter provision is stated here.
- Eaves design resolves structural, thermal and ventilation requirements together and is a design matter.
Roof Carcass & Edges
The battens, boards and edge elements that finish a roof structure and prepare it to receive a covering.
Browse all roof carcass & edges entries →