BUILDING INSPECTION GUIDE
Tree Roots & Building Movement
Large trees close to a home can influence soil moisture and may contribute to movement in footings and floor slabs. This guide explains the relationship between trees, soil conditions and visible cracking, and how these factors are considered during a building inspection.
UNDERSTANDING THE CAUSE
How Tree Roots Can Affect Buildings
Trees are an important part of the landscape, but large or mature trees located close to residential buildings can sometimes contribute to changes in the ground supporting the structure.
Tree roots naturally seek moisture. In soils that change volume as moisture levels rise and fall, moisture extraction can cause the soil to shrink. Where this occurs unevenly around a building, the support beneath footings or floor slabs can change and building movement may occur.
The roots themselves do not necessarily need to physically lift a footing. In some situations, the more relevant issue is the effect that changing soil moisture has on the ground supporting the building.
COMMON INDICATORS
Signs That May Be Associated With Building Movement
No single symptom establishes the cause. The overall pattern and distribution of visible defects across the property are important.
Cracking through masonry or around openings can be associated with differential movement.
Cracking to walls, cornices and junctions may occur where parts of the building have moved differently.
Movement may alter openings and contribute to doors or windows sticking, binding or becoming misaligned.
Cracked tiles, floor finishes or visible slab cracking may form part of a broader movement pattern.
Gaps around frames, cornice separation and movement at junctions may indicate changes within the building.
Large nearby trees, drainage, dry ground and variations in soil moisture can be relevant to an assessment.
RISK FACTORS
What Can Increase the Risk?
The potential influence of vegetation depends on more than the size of a tree. The distance between the tree and building, root-zone proximity, soil characteristics, tree maturity and local moisture conditions can all be relevant.
Extended dry periods can increase moisture loss from the soil, while poor drainage or significant variations in moisture around a building can also contribute to ground movement.
This is why simply seeing a large tree beside a cracked wall is not enough to determine the cause. The building and surrounding site need to be considered as a whole.
WHAT WE LOOK FOR
Assessing Cracking and Building Movement
A building inspection looks beyond an individual crack. The distribution, direction and extent of visible defects can be considered together with the property and surrounding site.
This helps establish whether the observed conditions appear isolated or form part of a wider pattern that may require further investigation.
EARLY IDENTIFICATION
Why Building Movement Should Be Assessed Properly
Building movement can develop gradually. Understanding the likely contributing factors is important before deciding what monitoring, maintenance or repair work may be appropriate.
Removing or heavily pruning a nearby tree should not automatically be treated as the solution to cracking. Trees, soils and structures can interact in complex ways. The important first step is to understand the visible movement pattern and surrounding site conditions. Where significant movement is suspected, appropriate professional or engineering advice may be required before major changes are made to the site.