By QED Consulting Engineers — structural & civil engineers, Notting Hill, Melbourne
Knocking down part of a building — a rear section before an extension, an old lean-to, or internal structure to reconfigure a home — sounds simpler than a full demolition. But partial demolition that affects the structural soundness of what remains generally needs a building permit and an engineer, because the tricky part isn't what comes down. It's keeping what stays up.
Here's what's involved.
Does partial demolition need a permit?
Generally, yes — where it affects the building's structure. Some minor demolition can be exempt, but once the work touches load-bearing elements or could affect the structural soundness of the remaining building, a building permit is typically required.
The distinction matters: removing a non-structural garden wall is very different from removing part of a house that other parts rely on. Confirm your situation with your building surveyor before you start.
Why the "remaining structure" is the real issue
In any demolition, loads travel through the building along a load path down to the ground. When you remove part of a structure, you can interrupt that path — leaving other elements carrying loads they were never meant to, or unsupported entirely.
An engineer's job in partial demolition is to work out:
- What the removed section was carrying, and where that load now needs to go
- How the remaining structure behaves once part of it is gone
- What temporary support (propping) is needed during the work to keep everything stable
- What permanent structure is needed to replace lost support
Get this wrong and the consequences range from cracking to collapse. It's the opposite of intuitive — the danger is in the part you're keeping, not the part you're removing.
Temporary support during the work
A recurring theme: while a section is being removed, the structure around it often needs temporary propping so nothing moves before the permanent support is in place. The engineer specifies this, and the builder executes it. Skipping or improvising it is where partial demolitions go wrong.
Common partial demolition scenarios
- Before an extension — removing a rear wall or section to connect the new structure
- Removing an old addition — a lean-to, sunroom or previous poor-quality work
- Opening up internally — which shades into load-bearing wall removal
- Reconfiguring a commercial space — removing internal structure in a fit-out
Each needs the same core assessment: what was the removed part doing, and how is that handled.
Where the engineer fits
The structural engineer assesses the structure, designs the temporary and permanent support, and provides documentation for the permit. The builder or demolisher carries out the work to that design. Our residential structural engineering and commercial engineering teams handle partial demolition assessments across Melbourne.
One more consideration: where demolition is close to an adjoining property, protection works obligations and a dilapidation record may also apply — worth checking early.
Planning to remove part of a building?
Talk to a Melbourne structural engineer before anything comes down.
Frequently asked questions
Do I need a permit for partial demolition?
Generally yes, where it affects the building's structural soundness. Minor non-structural demolition can be exempt. Confirm with your building surveyor.
Does partial demolition need a structural engineer?
Usually — the engineer works out how the remaining structure behaves once part is removed, and designs the temporary and permanent support.
What's the main risk in partial demolition?
The remaining structure. Removing part of a building can leave other elements carrying loads they weren't designed for, so the load path has to be re-established safely.
What is temporary propping?
Temporary support that holds the structure stable while a section is removed and before permanent support is in place. The engineer specifies it; the builder installs it.
