When a retaining wall needs an engineer
A low garden wall with nothing near it is one thing. A wall supporting a driveway, a building, a boundary or a significant change in level is another: if it moves or fails, the consequences are expensive and can be dangerous. Many retaining walls need a building permit, and your building surveyor will confirm whether yours does. Where one is needed, it will usually call for engineering.
What drives retaining wall design
- Retained height and slope: the pressure on the wall rises quickly with height and with sloping ground behind it.
- Surcharge: cars, driveways, buildings, pools and stockpiles above the wall all add load.
- Water: most retaining wall problems start with poor drainage. Every design needs free-draining backfill, an agricultural drain and a legal place for the water to go.
- Foundation soil: bearing capacity, sliding resistance and, for taller walls or sloping sites, overall slope stability. Taller walls usually need geotechnical input.
- Boundaries: walls on or near a boundary affect neighbours and may raise additional permit requirements.
Wall types we design
- Reinforced concrete and reinforced blockwork cantilever walls
- Post-and-panel (sleeper) walls with embedded posts
- Gravity walls, where an engineered design is required
- Anchored walls, where site constraints call for them
- Wall footings, drainage details and backfill specifications
- Walls that form part of a building, such as a basement or split-level wall
What you receive
- DrawingsWall layout, sections, reinforcement or post schedules, and drainage details.
- CalculationsStability and structural design calculations for the building surveyor.
- Construction notesBackfill, drainage and inspection requirements.
- Permit supportAnswers to the surveyor's engineering questions, and a certificate of compliance for design where required.
What we need from you
- Where the wall is, and its length and height (a marked-up site plan is ideal)
- Site levels or a feature survey
- What sits above and below the wall: driveways, buildings, pools or boundaries
- A geotechnical report, if available (needed for taller walls)
- Your preferred wall type or material, if you have one
Don't have everything yet? Send what you have. We'll tell you what's missing and whether it affects the proposal.
How it works
- Site informationWe review the location, levels and loads, and tell you if more information is needed.
- ProposalWe confirm the scope, fee and programme.
- DesignWe design the wall, its footing and its drainage.
- Permit and constructionWe support the building permit and can inspect the footing and drainage during construction.
Who does what
MEG provides
- Retaining wall and footing design
- Drainage details within the wall system
- Construction-stage inspections, if engaged
Not included, or by others
- Geotechnical investigation
- Site stormwater design beyond the wall's drainage, unless agreed
- Supply or construction of the wall
Relevant experience
MEG's work includes retaining wall footing design for a residential property in Warragul, with reinforcement schedules and building permit documentation. See project experience.
Questions
Does my retaining wall need a building permit?
It depends on the wall's height, its location and what it supports. Your building surveyor makes that call. If a permit is needed, we'll provide the engineering documentation for it.
Why does drainage matter so much?
Water trapped behind a wall can greatly increase the pressure on it. Many retaining wall failures trace back to blocked or missing drainage rather than a lack of strength.
Can you design a sleeper wall?
Yes. Post-and-panel walls are common in Melbourne. The engineering is mostly about the post size, the embedment and the footing, which depend on the soil and the loads.
My existing wall is leaning. Can you help?
Yes. That's an assessment of an existing structure. See structural assessments.