Internal decay is not always visible from the outside. A tree may appear healthy, but have structural deterioration is developing within the stem or buttress roots. When trees stand near buildings, highways or public access areas, uncertainty about internal condition requires more than a visual inspection alone.

Our Tree Decay Service provides advanced diagnostic testing to assess structural integrity with accuracy and clarity. Using specialist equipment, we evaluate internal wood condition and provide evidence-based findings to support responsible management decisions.

Why Internal Decay Assessment Matters

Fungal fruiting bodies, cavities, cracks, historic wounds and pronounced lean can all indicate possible internal degradation. However, the extent and severity of decay cannot be reliably judged by appearance alone.

Accurate diagnosis helps:

Determine the proportion of sound wood remaining
Identify internal cavities or hollow sections
Map areas of compromised structural timber
Support proportionate risk management decisions
Provide defensible evidence where trees are retained

Our approach reduces speculation and replaces assumption with measured data.

PiCUS 3 Sonic Tomography System

We utilise the PiCUS 3 Sonic Tomography System, a non-invasive diagnostic tool designed to assess the internal condition of tree stems and buttresses.

Small sensors are positioned around the circumference of the stem. Gentle sound impulses are transmitted between the sensors, and the speed of sound travel through the wood is recorded. This data is converted into a colour-coded tomogram that represents a cross-section of the tree.

Dense, sound wood transmits sound quickly
Decayed or hollow wood slows sound transmission

The resulting image allows us to visualise internal decay patterns without causing damage to the tree. PiCUS is particularly appropriate where trees are located in high-use environments or where removal decisions require strong supporting evidence.

IML PD400 Resistance Drill (Resistograph)

For targeted confirmation, we use the IML PD400 Resistance Drill. This semi-invasive tool measures the resistance encountered by a fine drill needle as it passes through the timber.

The needle, typically around 3mm in diameter, causes negligible damage. Variations in resistance are recorded graphically, allowing us to identify:

Decayed or softened wood
Internal voids and cavities
Transitions between sound and compromised timber

Resistance drilling is often used to verify tomography findings or investigate defects in greater detail.

A Combined, Evidence-Based Approach

In many cases, both systems are used together. Sonic tomography provides a broad, non-invasive overview of internal condition. Resistance drilling then confirms decay depth and remaining wall thickness at critical points. This layered approach verifies findings are robust and defensible.

Professional, Independent Evaluation

Our Tree Decay Service is designed for situations where certainty matters. Whether assessing a tree near a property, within a development site, or adjacent to public space, we provide clear reporting based on measurable data.

If you require a detailed internal decay assessment or specialist investigation, contact Down to Earth Trees to arrange an evaluation.