Structural Engineering for Difficult Sites

The Australian landscape is a broad mix of difficult building site types — sandstone escarpments, cliff-edge locations, steep gullies, reactive coastal soils and sites with complex coastal engineering and geotechnical profiles. These are the projects that require a structural engineer with genuine experience in challenging terrain, not just standard residential calculation experience.

Thitchener Consulting has engineered structures on difficult sites across this region for over four decades. We understand what councils require, what certifiers look for, and — most importantly — what actually works in the ground.

Site Types We Regularly Engineer

Steep Sloping Sites

Sites with grades exceeding 1:4 require structural solutions that account for differential settlement, lateral soil pressure, construction access constraints and, often, waterproofing complexity. We design footing systems and lower-level structures that perform over the long term on these sites.

Cliff-Edge and Escarpment Locations

Buildings near cliff edges and sandstone escarpments introduce specific structural risks — differential foundation conditions, potential for rock movement, and wind loading conditions that differ from standard residential sites. We assess these conditions carefully and design structural systems that respond to the specific risk profile.

Reactive and Expansive Soils

Many coastal and low-lying areas have highly reactive soils — particularly clay-rich profiles — that move seasonally with moisture content. Foundation design on these sites requires careful classification (Class P to Class E under AS2870) and a footing system calibrated to the site conditions.

Rock and Mixed Ground Conditions

Sandstone rock sits close to the surface across much of the NSW. Where footing into rock is required, or where a building bridges between rock and soil bearing conditions, the structural design must accommodate differential foundation capacity. We have experience designing for these conditions and working with excavation contractors where required.

Filled Ground and Variable Subsurface Conditions

Sites with uncontrolled fill, historical fill of unknown composition, or highly variable subsurface conditions require foundation design that accounts for differential settlement and variable bearing capacity. We design foundation systems appropriate to the fill characteristics and consolidation behavior, often requiring deeper foundations or ground improvement strategies where conventional footings are unsuitable.

Mine Subsidence Districts

Properties within proclaimed mine subsidence districts require structural design that accommodates potential ground movement from historical underground mining. We design buildings in accordance with Mine Subsidence Board requirements, using foundation systems and structural articulation appropriate to the subsidence risk classification for the specific location.

Flood-Prone and Inundation-Affected Sites

Sites below flood planning levels or subject to overland flow require structural design that accounts for hydrostatic pressure, hydrodynamic forces, buoyancy, scour, and debris impact. We design foundation systems and lower-level structures to meet flood load requirements under AS1170.2 and council flood planning controls.

Sites Adjacent to Retaining Walls or Neighboring Excavations

Building near existing retaining structures or where excavation affects neighboring properties requires assessment of surcharge loads, lateral earth pressure changes, and potential undermining. We provide structural engineering advice on foundation design, underpinning requirements where necessary, and temporary works during construction to ensure both new and existing structures remain stable.

Our Approach to Difficult Sites

We begin with a thorough site assessment, reviewing any available geotechnical reports, council flood and contamination data, and site topography. Where geotechnical investigation is required, we can advise on the appropriate scope and work with a preferred geotechnical consultant to interpret results and calibrate our structural response.

Our documentation for difficult sites is detailed and complete — we know from experience that under-documented structural engineering on a complex site creates problems at certification, during construction, and sometimes years later.