Strathtulloh soil: basalt plains clay and why slabs and walls move
Strathtulloh lies on the basalt plains that stretch west from Melbourne. Weathered basalt produces heavy clay soils that take up water and swell after wet weather and then shrink and crack as they dry. Houses on this ground are designed for it, through the site classification in each lot's soil report and a slab engineered to suit, but the design only works when it is built correctly and the ground around the house is kept evenly moist.
Site classification is per lot
AS 2870 classifies sites by how much the ground is expected to move. The class comes from a soil test on your lot, not from the suburb name, so check the report in your contract documents rather than assuming a figure.
Why the slab inspection matters here
A reactive site relies on beams of the designed width and steel at the designed height. Pods that slide during set-up and mesh that sags off its chairs both reduce the slab's stiffness where it is needed most.
Drainage after handover
Water pooling against the slab, or gardens watered heavily on one side only, makes the clay move unevenly. Grading the ground away from the house and connecting downpipes properly are the cheapest protections an owner has.
Cracks that are normal and cracks that are not
Fine plaster cracks in the first year are common as a house settles. The Guide to Standards and Tolerances 2015 sets out when cracking becomes a defect, and measuring it is what settles an argument.
Weep holes and paving
Paths and paving laid too high block weep holes and bridge the damp course. We often find weep holes less than 50mm above the paving at handover.
More about Strathtulloh
- Building a new home in Strathtulloh: the stages that decide how it lasts
- Buying a house in Strathtulloh: estate homes, acreage and what to inspect
- How Strathtulloh is growing: the Toolern plan, the station and the estates
- Building permits, the City of Melton and resolving defects in Strathtulloh
- Termite risk in Strathtulloh: estate homes, acreage and conducive conditions
- The defects we record on Strathtulloh inspections, stage by stage
- Strathtulloh site conditions: wind, grassland fire and planning overlays
Written by our local inspection team from work carried out in Strathtulloh. Licensed building practitioners, Building & Plumbing Commission registration CDB-U 53425.
