BUILDING INSPECTION GUIDE
Clay Soils & Building Movement
Changes in soil moisture can cause some clay soils to expand and contract. Where this movement occurs beneath or around a building, it can contribute to cracking, distortion and movement within the structure.
UNDERSTANDING SOIL MOVEMENT
How Clay Soils Can Affect a Building
Clay soils can react to changes in moisture content. As moisture increases, some clay soils expand. During prolonged dry conditions, moisture loss can cause the soil to contract.
If these changes occur evenly beneath a building, the effects may be limited. Problems can arise where one part of the supporting ground moves differently from another, creating differential movement beneath footings or floor slabs.
The amount of movement can depend on the soil characteristics, seasonal conditions, drainage, vegetation, leaking services and the design and construction of the building.
COMMON INDICATORS
Signs That May Be Associated With Soil Movement
Building movement can present in different ways. Inspecting the overall pattern helps provide context to individual defects.
Cracking following masonry joints can occur where sections of a wall have moved differently.
Diagonal cracking around windows, doors and other openings may form part of a movement pattern.
Cracking to plasterboard, cornices and wall junctions can occur as parts of the building move.
Frames can become distorted, causing doors or windows to bind, stick or become difficult to operate.
Changes in floor level, cracked finishes or slab cracking may be relevant when considered with other defects.
Separation at walls, ceilings, frames, skirtings or other junctions can sometimes accompany movement.
CONTRIBUTING FACTORS
Why Soil Moisture Can Change Around a Home
Seasonal weather is only one influence on soil moisture. Drainage around a building, leaking pipes, garden watering and nearby vegetation can create different moisture conditions around the perimeter of a property.
Large trees and established vegetation can draw substantial moisture from surrounding ground. Conversely, leaking plumbing or poorly managed stormwater can introduce additional moisture into localised areas.
These variations matter because uneven changes in the supporting soil can contribute to differential movement rather than uniform movement across the whole building.
WHAT WE CHECK
Building Movement During an Inspection
Where signs of movement are visible, we consider the defects in the context of the building and surrounding site rather than treating each crack in isolation.
The purpose is to identify visible patterns, contributing conditions and whether the findings indicate that further specialist assessment may be appropriate.
PUTTING THE FINDINGS IN CONTEXT
Movement Needs to Be Considered as a Pattern
A single crack may provide limited information. A combination of cracking, distortion, floor movement, drainage conditions and surrounding site factors can provide a much clearer picture of what may be occurring.
Where significant or unusual movement is identified, further investigation by an appropriately qualified structural engineer or other relevant specialist may be required. The appropriate response depends on the nature, extent and apparent progression of the observed defects.