CAMBIUM surveys, tests and reports on trees for homes, schools, estates and developers. We don’t sell tree work, so our advice has one interest: the tree, and you.
11,400 trees surveyed since 2012
New case study
A 239-ring oak on a school field, with a decayed heart. Still standing.
0.36t/R — sound wallWhat a tomogram shows
Drag across the section, or keep scrolling. Colours follow the usual tomograph scale: brown is sound wood, green is changing, violet and blue are damaged or gone.
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A walk-round inspection of one tree or a whole site, from the ground and, where it matters, from a climbing line. We record species, size, condition and defects, and give each tree a clear next step.
What we offer
From £180
Get started02
When a tree looks sound but may not be, we look inside without cutting. Sonic tomography maps sound and damaged wood across the stem; a resistance drill confirms the edge of the decay.
What we offer
From £420
Get started
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Surveys and drawings for planning applications near trees: categories, root protection areas, the tree constraints plan, then the impact assessment and method statement your council expects.
What we offer
From £450
Get started04
Management plans for ancient and veteran trees, and help with Tree Preservation Orders and conservation-area notices, so the right work happens with the right permissions.
What we offer
From Quote
Get startedOne tree, read in five steps
From outside
A 107 cm stem, a full crown, and one bracket fungus at the root flare. The first question is what we can’t see.
Twelve sensors
Twelve nails around the stem at one metre. Each sensor is tapped with a small hammer; the others time the sound. Slow paths cross damaged wood.
The tomogram
Sixty-six paths become a map. Brown is sound wood; green, violet and blue are softer, slower and gone: a column of heart rot.
The second opinion
A resistance drill crosses the thin side. The needle meets firm wood, then almost nothing: the edge of the decay, within millimetres of the map.
The answer
Thinnest sound wall 184 mm on a 508 mm radius: t/R 0.36. Above the 0.3 guide. Reduce the crown by 20%, test again in three years.
Numbers from our own survey records, 2012 to 2025.
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trees surveyed
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of “dangerous” trees kept, with work
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tomograms taken
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from visit to report, on average
Try it
Pick a tree and tap the sensor nails. Each tap sends sound to every other sensor; slow paths cross damaged wood. After a few taps a map appears — a simplified version of what the tomograph’s software does.
Tap any numbered nail to start.
fast slow
“They drew us the inside of our oak and then told us how to keep it. That drawing is framed in the staff room.”
Head teacherSouth Bristol primary
“The BS 5837 plan was ready before our architect needed it, and it changed the footprint for the better.”
ArchitectResidential scheme, Bath
“No sales pitch and no chainsaw. Just the facts about the trees, written so a parish council could follow them.”
Parish clerkNorth Somerset
“The drawing of the rings settled an argument that had gone on for two summers.”
Residents’ associationVictorian terrace, Clifton
“Nothing was rushed and nothing was left to guesswork.”
LandownerRural lane, South Gloucestershire
“Precise, unhurried and honest about what the tree needed and didn’t.”
Estate managerCountry-house lawn, Mendip
Fixed prices, written before we visit. VAT included.
Schools, estates and councils: annual inspection programmes on a quote. Ask us.
per visit£180
Book tree checkA consultant visits, looks at the trees that worry you, and writes to you within seven days with what we found and what, if anything, to do.
from£450
Book survey & reportA full survey for a site, a school or a planning application: every tree measured, categorised and drawn, with a report your insurer or council will accept.
per tree£420
Book decay investigationFor one tree that matters: we map the inside with sonic tomography, confirm with a resistance drill, and give you a measured answer rather than an opinion.
Common questions
Law, fungi, planning and what testing does to a tree.
No. CAMBIUM is an independent consultancy: we survey, test, report and specify. We don’t sell tree work, so we never gain from recommending it. If work is needed we write a clear specification you can give to any qualified contractor, and we can check it was done to spec.
It depends on the fungus and the tree. Many fungi on trees are harmless or feed only on dead wood; others, like some soft-rot fungi on beech, can weaken a stem with little outward sign. Identifying the species is the first step, and a tomogram tells us how far it has gone.
Usually you must give the council six weeks’ written notice first (a section 211 notice), unless an exemption applies. If the tree has a Tree Preservation Order you need the council’s consent. We prepare both, with a specification of the work.
The survey British Standard 5837:2012 asks for when trees are on or near a development site. Each tree is measured and categorised (A, B, C or U), and its root protection area is drawn: a circle with a radius of twelve times the stem diameter, capped at about 15 m.
Very little. Tomography uses small nails tapped into the bark and outer wood; resistance drilling leaves a hole about 3 mm across. Both are routine and far less harmful than removing a tree that didn’t need removing.
Active birds’ nests are protected by law at any time of year, and the busiest season runs roughly from March to August. We check before any work we specify, and time it around wildlife where we can.
Why a hollow yew is usually a healthy yew.
Hollowing is how old yews age. What matters is the wall that’s left, not the space in the middle.
What the summer of 1976 wrote into your oak.
Every dry summer leaves a narrow ring. Here is how to read them on a stump, a log or a tomogram.
Reading a BS 5837 report in ten minutes.
Categories, root protection areas and the drawing that matters most to your architect.
Ready when your tree is
Most visits happen within ten working days. Urgent safety calls: same week.
Book a survey See pricing