Building components · Service Zones & Penetrations
Service Chase
Explains the chase as material taken out of an element's own thickness, distinct from a void built into an assembly to hold services.
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 chase is
A chase is a groove taken out of a wall so that a pipe or a cable sits within the wall's thickness rather than on its face. It may be formed as the wall is built or cut into it afterwards, and it is closed by making good over the service so that the finished surface reads as flat.
What makes it worth naming is that a chase is subtractive. A void is space designed into an assembly; a chase is material removed from an element that was built solid, so the element is thinner wherever the chase runs, and the decision to take that material out is a decision about the element rather than about the finish.
Boundaries
How it differs from nearby elements
The distinctions that keep this entry from being a restatement of its neighbours.
- It is not a service void system. That system reserves a zone in front of or within an assembly so services never enter the element itself; a chase removes material from an element that had no such zone, which is why the two are alternatives rather than versions of one idea.
- It is not a wall cavity. The cavity is a designed separation between two leaves and is meant to stay clear; a chase is a groove within one leaf and is meant to be occupied by the service and then made good.
- It is not a builders work opening. An opening passes through the element so a service can cross it; a chase runs along the element and stays inside it, and a chase that reaches the far face has stopped being 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.
- chase
- wall chase
- conduit chase
Dependencies
What it depends on
What has to be right elsewhere for this element to do its job.
- What the wall is and what it does, since removing material from a loadbearing, separating or fire-resisting element is a different proposition from grooving a lining.
- Whether the chase was formed as the wall was built or cut later, which governs both how clean the recess is and what the cutting did to the wall around it.
- How deep it goes and in which direction it runs, because those are the terms in which the element's designer answers whether it can be chased at all.
- How it is made good afterwards, since the covering has to return the surface and, where the wall performs a separating function, the element's continuity as well.
Considerations
Topics that genuinely apply here
Subjects worth discussing about this element. These are discussion topics, never measured values, ratings or performance claims.
A chase in a loadbearing wall removes part of the section carrying load, which is why whether a chase can be cut is a question for the element's designer rather than for the installer holding the tool.
A chase cut into a separating wall reduces its mass locally, and chases cut back to back in the two faces of one wall reduce it in the same place twice.
Where the wall is relied on by the building's fire strategy, a chase interrupts it, and what is required to restore it is determined by qualified designers and by local requirements.
Chases are commonly cut after the wall exists and before the finish is applied, which is the moment in a programme when nobody is looking at the wall's original design.
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.
Clarifications
Commonly misunderstood
- That chasing is finishing work. Cutting into a wall is a change to the element, and in a loadbearing or separating wall it is a design question before it is a trade operation.
- That making good restores the wall. A filled chase returns the surface; whether it returns the element's structural, acoustic or fire behaviour is a separate matter and a separate provision.
Conversations
Questions for qualified professionals
Questions worth asking someone with the project in front of them. This page cannot answer them.
- What does this wall do structurally, and has the effect of chasing it been considered by whoever is responsible for that?
- Is the wall part of the building's separating or fire strategy, and what does chasing it require?
- Was the chase formed as the wall was built or cut afterwards, and what was cut through in the process?
- How is the chase made good, and does that provision restore anything beyond the visible surface?
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
- This entry describes a position. It states no chase depth, width, direction, permitted extent, fire rating or period.
- Whether a wall can be chased, and how, depends on what that wall does and is a matter for qualified professionals; verify against local requirements.
Service Zones & Penetrations
The voids, shafts, chases and openings left in the fabric so services can pass through it and be reached again afterwards.
Browse all service zones & penetrations entries →