Resistograph Testing In London

London Tree Surgeons has advanced Resistograph equipment and professional arboricultural consultants ready to provide insured Resistograph Testing in London.

Precision Decay Detection for Safer Trees In London

In a crowded city like London, “maybe” isn’t good enough. If you are managing a large Beech tree next to a playground or a London Plane overhanging a busy street, you need to know exactly what is going on inside. Visual tree assessments are helpful, but they can only tell you what is happening on the surface.

At London Tree Surgeons, we offer Resistograph Testing using a IML Resi PD-500 microdrill to assess what’s happening internally. This advanced diagnostic tool tells us if the wood inside is solid, decaying, or completely hollow, giving you the hard data you need to make informed safety decisions. It is the difference between felling a tree “just in case” and retaining it with confidence.

How Resistograph Testing Works

The Resistograph works on the simple principle of mechanical resistance. The device drives a very fine, long needle (about 3mm in diameter) into the tree at a constant speed. As the needle penetrates the wood, the machine measures the exact amount of resistance it encounters.

• Solid Wood: High resistance. The needle has to work hard to push through.
• Decay or Rot: Low resistance. The needle slides through easily.
• Cavities: Zero resistance. The needle meets no opposition at all.

The Resistograph records data instantly on a graph, creating a precise “density profile” of the tree’s cross-section. It allows our consultants to see exactly where the decay starts and stops, accurate to the millimetre. Because the needle is so thin, the process is very safe and won’t harm the tree.

When Does a Tree Need a Resistograph Test?

While some tests give you a general “map” of the tree, the Resistograph is the tool we use for targeted investigation to identify specific defects. It is particularly effective in these scenarios:

• Basal Decay: Checking the base of the stem for internal rot that could cause the tree to snap at ground level.
• Root Plate Investigation: We can insert a needle into exposed roots to check whether they are structurally sound enough to support the tree.
• Cracks and Seams: If a tree has a visible crack, we use the Resistograph to test the wood behind it and determine whether it is a superficial surface wound or a deep structural fault.
• Cavity Walls: If a tree has a hollow, we can measure the thickness of the remaining healthy wall to calculate if it is still strong enough to support the canopy.

Expert Resistograph Interpretation & Consultancy

A graph is useless without an expert to interpret it. At London Tree Surgeons, our experienced arboricultural consultants don’t just send you a chart; they’ll translate the data into clear, actionable advice.

We analyse the resistance readings in the context of the tree’s height, species, and location. A hollow tree might still be perfectly safe if the remaining wall of wood is thick enough, but dangerous if it’s too thin. We consider all available data, do the maths for you, and provide our expert opinion and recommendations.

Because we carry £2 million in Professional Indemnity insurance, our reports are robust enough to satisfy insurance companies, mortgage lenders, and Local Authority Tree Officers. If we say a tree is safe, we stand by that assessment. If we say it needs to come down, you have the scientific proof to justify the removal.

FAQs About Resistograph Testing

Does the Resistograph drilling hurt the tree?

No. The needle we use is incredibly fine (micro-drilling). The resulting hole is so small that the tree’s natural defence mechanisms seal it up almost immediately. It is far less invasive than older testing methods and causes no long-term harm to the tree’s health.

Can this Resistograph Testing detect Honey Fungus?

It can detect wood decay caused by fungi, such as Honey Fungus, particularly in the lower stem and roots. While it doesn’t identify the fungus species itself, it tells us how much structural damage the fungus has caused, which is the most important factor for safety.

Is a Resistograph Test expensive?

It is a specialist service, but it is often cheaper than removing a large tree unnecessarily. If a Resistograph test proves your tree is safe to keep, it saves you the thousands of pounds it would cost to dismantle it.

Should I choose Resistograph testing or PiCUS testing?

It depends on what we need to find out. Resistograph testing drills a fine needle into a specific point to give a precise density reading along that line, making it ideal for confirming suspected decay in an exact spot, such as behind a fungal bracket or an old wound. PiCUS sonic tomography testing instead maps the entire cross-section of the trunk from the outside, which is better for building a full picture of internal condition. On many London trees we use both: the PiCUS scan to locate areas of concern, then the Resistograph to verify them.

When it comes to tree safety, don’t rely on guesswork. Contact us to book high-precision Resistograph Testing in London today.