Building components · Drainage Elements
Gutter
Explains the gutter as a collection channel with a defined capacity, and what happens when it is exceeded.
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 gutter is
A gutter runs along the low edge of a roof and collects the water that leaves the covering. It carries that water along its length to an outlet, where it enters a downpipe.
It has a finite capacity determined by its size, its fall and how far water has to travel to reach an outlet. Exceeding that capacity does not produce a gradual reduction in performance: the gutter overflows, and the water lands on whatever is beneath.
Boundaries
How it differs from nearby elements
The distinctions that keep this entry from being a restatement of its neighbours.
- It is not a downpipe. The gutter collects horizontally; the downpipe carries vertically.
- It is not a valley. A valley is a roof geometry where two slopes meet; a gutter is a channel that collects.
- It is not a fascia, although the gutter is commonly fixed to one.
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.
- gutters
- eaves gutter
- rainwater gutter
- guttering
Dependencies
What it depends on
What has to be right elsewhere for this element to do its job.
- The roof area draining into it, which is what determines the flow it has to carry.
- Its fall toward the outlet and the distance water has to travel.
- Being clear, since the capacity of a blocked gutter is whatever the blockage leaves.
- Its supports, because a gutter full of water and debris is far heavier than an empty one.
Considerations
Topics that genuinely apply here
Subjects worth discussing about this element. These are discussion topics, never measured values, ratings or performance claims.
An overflowing gutter delivers concentrated water to the wall and ground beneath, and persistent overflow is a common cause of damp at the top of a wall.
Gutters need clearing, and whether they can be safely reached determines whether that happens.
Standing water and debris in a gutter shorten its life and that of what it is fixed to.
Long runs expand and contract, and joints have to accommodate that without leaking.
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.
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
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.
- Site Drainage
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 a gutter overflowing in heavy rain is normal. It indicates the capacity, the fall or the clearance is inadequate for the flow.
- That gutter size is a matter of appearance. It follows from the roof area draining into it and the outlet arrangement.
Conversations
Questions for qualified professionals
Questions worth asking someone with the project in front of them. This page cannot answer them.
- What roof area drains into this gutter, and what capacity does it have?
- How far does water travel to reach an outlet, and what fall is provided?
- How is the gutter accessed for clearing?
- Do the supports account for the weight of a full gutter?
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 size, fall, capacity, outlet spacing or rainfall figure is stated here.
- Rainwater drainage design is a calculation based on roof area and rainfall intensity, and is professional work.
Drainage & Rainwater Elements
The gutters, outlets, downpipes, channels, chambers and traps that collect water, carry it and let it be inspected.
Browse all drainage elements entries →