Know what the ground will carry.
Soil testing across Christchurch and Canterbury. Bearing capacity and soil classification measured on site, not assumed.
Testing turns a guess into a number.
The ground under two houses on the same street can carry very different loads. Soil testing measures what is actually there, so the foundation is sized to a number instead of an assumption. On soft or filled ground, the testing finds the trouble before the footings do. The results feed straight into the geotechnical report and the foundation design, which is why it happens before the plans are locked rather than after.
Geotechnical EngineeringThe tests we run.
Shallow to deep, matched to the site and the load it has to carry.
Hand augers
Shallow sampling to 3.0m, with each layer described and logged as the auger comes up.
Shear vane
The undrained shear strength of cohesive soils, measured in place rather than estimated from a chart.
Scala Penetrometer
A fast index of shallow ground strength to 3.0m, taken at close spacing so a soft pocket cannot hide between holes.
Cone Penetrometer Test
CPT pushed to a minimum of 15m below ground level, giving a continuous strength profile rather than samples at intervals.
Machine borehole
Where CPT cannot be undertaken, drilled and sampled deeper, with the recovered material logged the whole way down.
Groundwater observation
The water level recorded in the holes, because where the water sits changes what the ground above it will do.
Testing across the footprint
Positions set out where the building will actually sit, not where the ground is easiest to get at.
How it runs.
From the site visit to the numbers the design needs.
- 01
Visit and set out
We set the test positions off your plans before a rig is booked, and check what the machine can physically reach while we are there. Testing commences within two to three weeks of confirmation.
- 02
Shallow testing
The shallow holes go down first, so the ground near the surface is described and logged before anything deeper is pushed. What the first few metres return often decides how much deeper the rest has to go.
- 03
Deep testing
Where the loads or the ground call for it, the testing carries on well below the shallow limit, on the same visit. One mobilisation covers both, so nobody pays to bring a rig back a second time.
- 04
Log the ground
The log is written in the field as the holes go down, not reconstructed afterwards, and every position is fixed on a site plan before the crew leaves.
- 05
Classify and report
The field results are written up and checked, and the report is issued two to three weeks after the testing. Urgent jobs can be run start to finish in four weeks, testing included.
Reading the ground.
Testing reads the ground the way a bore log does, top-down, layer by layer, with the strength of each one recorded against its depth. What decides the foundation is rarely a single number. It is where the changes fall, because a soft layer sitting under a firm one is the case a footing has to be designed around. The profile below is indicative, not a specific site.
What the testing tells you.
The numbers the design is built on, and the record that shows where they came from.
Soil classification
What each layer is and how thick it runs, from the topsoil down to the layer that will carry the load.
Bearing capacity
The load the ground will carry at founding depth, as a number the foundation design can be sized against.
Site category
TC1, TC2 or TC3, the technical category the council will want confirmed before it grants consent.
TC1 to TC3 explainedLiquefaction potential
Whether the sands below could lose strength in a large earthquake. Sites prone to it need detailed investigation.
TC1 to TC3 explainedGroundwater
The depth to the water table, which sets how much of the excavation sits below it and what the drainage under the building has to deal with.
Soil logs and a site plan
What was found and exactly where it was found, recorded so another engineer could check the work.
Further testing, where it is needed
A recommendation for deeper work or slope stability modelling where the ground calls for it, rather than a shrug.
What a geotechnical report contains
What soil testing looks like.
Testing and ground works, frame by frame, from the rig on site to the fill it signs off.
Assume the ground, pay for the assumption.
Skip the testing and the foundation is sized on a guess, which is fine until it is not. The bill for an assumption arrives late, as settlement, as cracking, as a repair that costs more than the testing ever would. A day of testing is the cheapest certainty on the whole build.
Test before you build.
Send the site address and the plans. We will say how many tests the footprint needs and how deep they have to go, before anyone books a rig.