ArboRadix Root Plate Analysis — Structural Root Assessment
Urban Tree Management carries out ArboRadix sonic root plate analysis for trees where root failure — rather than stem failure — is the primary structural concern. The ArboRadix module is part of the integrated Rinntech diagnostic toolkit and is used alongside the Arbotom sonic tomography system and IML Resistograph to provide a complete assessment of a tree's structural condition both above and below ground.
Completely independent from any tree surgery contractor — our findings are based entirely on the diagnostic data, with no financial interest in the outcome.
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Specialist Tree Decay Detection
What ArboRadix Measures
ArboRadix is based on ground sound analysis. It detects and maps the mechanically active structural roots of a tree — identifying where structurally effective roots run and where the tree is and is not anchored in the soil.
A light tap on the ArboRadix rod generates an impulse wave that spreads spherically through the ground. Where a lignified structural root of sufficient diameter — typically 25mm or more — is present below the tapping point, it absorbs and transmits the vibration to the stem base where the Arbotom sensors detect the arrival and measure the transit time.
Where no signal is received at the stem base there is typically no structurally effective root anchoring the tree in that direction.
The result is a map of mechanically active root directions — showing the extent and distribution of the tree's structural root plate in the soil.
What ArboRadix Cannot Tell You
This is as important as what it can tell you. ArboRadix identifies where mechanically effective roots run — it cannot provide information on root depth or diameter. This distinction is important for report interpretation and management recommendations.
Urban Tree Management will not carry out ArboRadix analysis where results would be unreliable:
Water-saturated or frozen soil — values cannot be reliably evaluated in these conditions. If soil is wet or recently frozen the ArboRadix component will be deferred and the reasons stated in the report.
Asphalt or concrete covering — difficult or impossible to spatially assign signals to root expansion under hard surfaces. A grid pattern approach can be used where root location under hard surfaces is specifically required but results should be treated with caution and clearly qualified.
Rot at root caps or root-stem junction — decay at the junction between structural roots and the stem base can prevent or dampen wave transmission, potentially producing a result that underestimates the extent of structural root anchorage. Urban Tree Management notes this risk in every investigation where basal or root crown decay is present.
Soil conditions are always recorded and stated in every ArboRadix investigation report.
How the Measurement Is Carried Out
The ArboRadix rod is placed in line with a prominent main root collar at the base of the stem. Measurements are taken in one-metre increments working outward from the stem along a radial line from each tapping point through the relevant Arbotom sensor to the trunk centre. Multiple radial lines are measured around the full circumference of the stem — producing a star-shaped measurement pattern that maps the root plate in all directions.
Three targeted taps of consistent strength are applied at each measurement point. The hammer head used depends on ground conditions:
- White side — soft or natural soils, grass, loose ground
- Black side — hard or compacted ground, asphalt, heavily compacted soil — tap lightly to ensure optimal signal transmission
The Colour Scale
The ArboRadix output is displayed as a colour map of the root plate. Urban Tree Management calibrates the colour scale using the RADIX STAT tab for site conditions before finalising every interpretation.
Green to yellow indicates strong coupling — a structurally effective root is likely present in that direction, transmitting the impulse wave from the ground to the stem base.
Red to blue indicates weak coupling — no direct root connection has been detected in that direction, or the signal has been transmitted via soil structures rather than a direct structural root.
The RADIX STAT scale has two zones. The lower zone covers normal ground sound velocities for natural soil conditions. The upper zone covers special cases — hard surfaces such as asphalt or concrete, or direct tapping on strong surface roots where sound velocities are significantly higher.
Urban Tree Management always states which hammer type was used and records the soil conditions at the time of investigation — both of which directly affect the reliability and interpretation of the colour output.
The Anchor Moment Calculation
The most important output of the ArboRadix investigation is the anchor moment — the calculated resistance of the root plate to the overturning force of wind loading.
From the root plate map Urban Tree Management calculates the mechanically active root plate area in square metres and the estimated mean depth of the anchor plate in centimetres. These are combined to give the volume of the anchor plate in cubic metres. Using an estimated average soil density — typically 1500 kg/m³ for normal soils — the anchor weight in kilograms is calculated. Combined with the approximate average radius of the anchor plate this produces the anchor moment, expressed in kilonewton metres.
This anchor moment is then cross-referenced against the wind load bending moment at the stem base — calculated from the ArWiLo wind load analysis — to produce a safety factor expressed as a percentage. This safety factor is the critical output — it tells you whether the root plate is structurally adequate for the tree's current crown loading, and if not, what level of crown reduction would be required to bring the safety factor to an acceptable level.
In simple terms — if the anchor moment is greater than the wind load bending moment the tree is adequately anchored for its current crown. If it is not, the tree requires either crown reduction to reduce wind loading or management to address the root plate compromise.
When ArboRadix Is Used
Urban Tree Management uses ArboRadix in the following situations:
- Root heave or soil movement at the base — where visual tree assessment has identified ground lifting, cracking, or soil disturbance around the root plate suggesting root failure may be in progress.
- Ganoderma or other basal fungal pathogens — where significant fungal attack of structural roots is confirmed or suspected, ArboRadix maps the extent of mechanically active root plate remaining and quantifies the anchor moment.
- Leaning trees — particularly where a lean has developed recently or progressively, ArboRadix can determine whether the root plate is compromised on the tension or compression side.
- Post-storm assessment — where a tree has been subjected to significant wind loading and shows signs of root movement or partial uprooting.
- Construction near root plates — where root severance is proposed or has occurred within the root protection area, ArboRadix can assess the impact on structural anchoring and inform the management recommendation.
- High-consequence locations — where a tree in a high-footfall or high-consequence location requires the most complete structural assessment possible, combining stem condition from the Arbotom and Resistograph with root plate condition from ArboRadix
What the Report Contains
Every ArboRadix investigation report from Urban Tree Management includes:
- Visual tree assessment findings — the context for the investigation
- ArboRadix methodology — measurement pattern, soil conditions, hammer type, tapping protocol, colour scale calibration
- Root plate map — colour diagram of mechanically active root directions
- Anchor moment calculation — full parameter table and calculated safety factor
- Cross-reference with ArboStApp wind load bending moment
- Discussion — whether the root plate is structurally adequate for current crown loading and what this means for the management recommendation
- Management recommendation — specific, proportionate, based entirely on the diagnostic data
- Limitations — all ArboRadix-specific limitations relevant to the investigation including soil conditions at time of survey
The report is suitable for planning authority submission, insurance purposes, legal proceedings, and duty of care documentation.
FAQ
What is the difference between ArboRadix and a standard root investigation?
Standard root investigations typically involve excavation, air spade work, or ground-penetrating radar — all of which physically disturb the ground around the tree. ArboRadix is completely non-invasive. It maps the mechanically active root plate using ground sound analysis from the surface without any excavation or ground disturbance.
Can ArboRadix tell me how deep the roots are?
No — ArboRadix maps the directions in which mechanically effective roots run but cannot provide information on root depth or diameter. This is a fundamental limitation of the current technology and is always stated clearly in the investigation report.
Is ArboRadix reliable in all ground conditions?
No — ArboRadix results are unreliable in water-saturated or frozen soil and difficult to interpret under asphalt or concrete cover. Urban Tree Management records soil conditions at every investigation and will defer the ArboRadix component if ground conditions make the results unreliable.
Do you always use ArboRadix alongside the Arbotom?
Not always — ArboRadix is used specifically where root failure rather than stem failure is the primary concern. Where the investigation is focused on stem decay the Arbotom and Resistograph are typically sufficient without ArboRadix. Urban Tree Management advises on the appropriate combination of instruments before any investigation begins.
Can ArboRadix detect decay in the roots?
ArboRadix can identify sectors where no structurally effective root is transmitting a signal — which may indicate absent, failed, or severely decayed structural roots in that direction. It cannot directly detect decay in the roots themselves. Where basal fungal pathogens such as Ganoderma are present the ArboRadix findings are interpreted alongside the Arbotom basal tomogram and Resistograph data to give the most complete picture of structural root integrity possible.
Can you use ArboRadix for construction impact assessment?
Yes — ArboRadix can be used to map the structural root plate before and after construction works near trees, providing objective evidence of the impact of root severance on structural anchoring. This is particularly useful where roots have been severed within the root protection area and the management implications need to be quantified.
ArboRadix Root Plate Analysis — North West & Nationwide
Urban Tree Management carries out ArboRadix sonic root plate analysis for trees where root failure or stability is the primary concern — providing quantified anchor moment calculations and wind load cross-referencing for a complete, defensible structural assessment.
Get in contact with our highly experienced and personable team of arboricultural consultants today, to discuss your requirements and to obtain your zero obligation quotation.
