Who this guide is for
- Owners adding sockets, switches or pipework to a solid-walled room
- Anyone planning first fix in a building with masonry internal walls
- People whose electrician has asked where the runs are allowed to go
- Readers deciding between burying a service and routing it elsewhere
- Anyone preparing a record of buried services for a property
Subtractive, not additive
A chase is a groove taken out of a wall so that a pipe or 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 the finished surface reads as flat.
The decision to take that material out is a decision about the element rather than about the finish. A chase in a loadbearing wall removes part of the section carrying load, which is why whether one can be cut is a question for the element's designer rather than for the installer holding the tool.
The first question is what the wall is doing
Removing material from a loadbearing, separating or fire-resisting element is a different proposition from grooving a lining. In a non-loadbearing masonry partition the wall is still holding itself up, so the same logic applies with less weight behind it.
Cutting into an existing internal masonry wall can also reveal a wall that is in fact carrying load. Establishing which applies before any work starts is the sequence that protects everything downstream.
Depth, direction and how close two chases come
How deep a chase goes and in which direction it runs are the terms in which an element's designer answers whether it can be chased at all. Two chases cut back to back in the opposite faces of one wall reduce the same place twice, which is a distinct condition from two chases spread along a run.
In a separating wall, a chase also reduces the wall's mass locally, and back-to-back accessories can matter more to the outcome than the wall itself. None of this is visible once the finish is on.
Timing: a narrow window shared by everybody
Chases are cut after the wall is up and before the finish goes on. That is a narrow window shared by everybody who needs something buried, and it is the moment in a programme when nobody is looking at the wall's original design.
Where the wall is built from solid gypsum units, the window closes earlier still: service routes have to be agreed before the wall goes up, because there is no cavity to fall back on and openings are set out rather than cut afterwards.
Making good returns a surface, not an element
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, determined by qualified designers where the wall is relied on for any of them.
The finish is also part of the wall rather than a layer over it. Bonded plaster or board on adhesive follows the background, so a chase made good carelessly shows through decoration later, and a movement joint plastered straight across has stopped being a movement joint.
The run that never needed to be buried
Every service that can be kept out of the masonry is a chase not cut. The coordination question is which runs genuinely have to be buried and which can be taken through a ceiling, floor or riser zone instead, and it is resolved before the wall is finished because afterwards the answer is a wall being cut.
Where a service might reasonably need replacing within the life of the building, whether it belongs in the masonry at all is worth raising while the route is still on paper.
The record nobody else will make
The positions of chases and of anything built into the wall are invisible once the finish is on, and unlike a framed partition there is no cavity anyone can look into later. A record made between the wall going up and the finish going on is the only record there will be.
Chasing coordination checklist
- 1Establish what this wall is doing before anything is cut into it
- 2For an existing wall, confirm whether it is carrying load
- 3Ask where chases may be cut, in what direction, and where they may not
- 4List every service proposed for burial in the wall
- 5Ask which of those could be routed through a ceiling, floor or riser instead
- 6Check whether any two chases fall back to back in opposite faces
- 7Confirm whether the wall has any fire or acoustic duty attached to it
- 8Ask who determines what is required where such a wall is interrupted
- 9Agree when chasing happens relative to the finish
- 10Confirm how each chase is made good and by whom
- 11Photograph the wall with chases open and services in place
- 12Record chase positions before the finish goes on
- 13Place that record where the building owner will find it
Common mistakes to avoid
- Treating chasing as finishing work rather than a change to the element
- Equating a chase with a cable run in a framed cavity
- Cutting chases back to back in the two faces of one wall
- Assuming making good restores what the wall was relied on to do
- Leaving service routes undecided until a solid wall is already built
- Burying a service that will predictably need replacing within the building's life
- Finishing over a movement joint and expecting it to keep working
When to involve a professional
- Whether a wall can be chased, and how, depends on what that wall does and is a matter for qualified professionals
- Where a wall is relied on by the building's fire strategy, what is required to restore it at an interruption is a regulated determination
- Cutting into an existing internal masonry wall may affect an element holding itself up, and may reveal one carrying load
- Acoustic behaviour belongs to the complete assembly with its junctions and penetrations, and belongs with a qualified acoustic professional
- How the positions of buried services will be recorded for the owner is worth agreeing before work starts
Frequently asked questions
Questions readers ask about this topic
Why is chasing a masonry wall different from wiring a stud wall?
A cable in a framed cavity occupies space that was already designed into the wall. A chase removes material from an element that was built solid, so the wall is thinner where the chase runs and the reduction is permanent.
Who decides where a chase may go?
The designer of the element, because depth, direction and position are the terms in which that question is answered. It is not a decision for whoever arrives with the conduit, and in a loadbearing wall it is a design question before it is a trade operation.
Does making good put the wall back?
It returns the surface. Whether it returns the wall's structural, acoustic or fire behaviour is a separate matter needing a separate provision, and where the wall is relied on for any of those the answer is determined by qualified designers.
Can I chase a solid gypsum block partition?
Chasing a solid partition has limits set by the block maker and the design team, and the absence of a cavity means service routes have to be agreed before the wall is built rather than resolved afterwards. The maker's guidance on chasing is the starting point.
How do later occupants find out what is buried?
Only from a record made between the wall going up and the finish going on. There is no cavity to look into, so a photograph of the open chases with services in place is the only practical map anyone will ever have of that wall.
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