Tree protection fencing and the construction exclusion zone

Tree protection fencing fails on site for two reasons, and neither is the drawing. It goes up in the wrong place, or it comes down in week three because a delivery could not get past it. The condition then sits undischarged, the arboricultural officer visits, and the whole job stops while somebody works out whether roots were damaged.

The construction exclusion zone is the thing the fence defines. Get the zone right first and the fence follows from it.

What the exclusion zone is

The exclusion zone is the area around a retained tree that nothing enters during construction. It is normally set to match the root protection area calculated in the arboricultural survey, which BS 5837:2012 derives from stem diameter: a radius of 12 times the diameter measured at 1.5 metres above ground, giving an area capped at 707 square metres for a single-stem tree.

That circle is then adjusted. Soil conditions, the presence of a building or a road on one side, and the tree's tolerance all shift the shape, so the protected area on the plan is often offset rather than circular, with the same total area maintained. The arboriculturist makes that call, not the site manager.

The zone covers soil as well as roots. Compaction from a single loaded telehandler pass across an unprotected root protection area can do damage that shows as crown dieback three summers later, by which time nobody connects the two events. That delay is why councils treat the fence as non-negotiable.

The default barrier

The default in BS 5837:2012 is not a hire-shop fence. It is a scaffold framework: vertical scaffold tubes driven into the ground, at spacings close enough to resist a knock, with horizontal rails top and bottom, braced, and weldmesh panels wired securely to the frame. Uprights are driven a minimum depth into the ground so the structure cannot be shoved aside, and the whole thing stands around two metres high.

The point is that it should be difficult to move. A barrier that one person can drag out of the way at eight in the morning will be dragged out of the way.

Specify it properly in the arboricultural method statement, with a detail drawing, and show its exact line on the tree protection plan. The relationship between the two documents is covered in the note on tree protection plans and fencing specification.

Where Heras panels sit

Free-standing panels on rubber or concrete feet are the fence most sites actually erect, and they are not the standard's default specification. They are acceptable where the arboricultural method statement says so and justifies it, usually on hard surfaces where driving uprights is impossible, and usually with additional bracing, pinning or a continuous coupled run to stop individual panels being lifted out.

Do not substitute them on your own initiative. If the approved drawing shows a driven scaffold barrier and the site erects panels on feet, the condition is not discharged, however tidy the result looks.

Ground protection instead of exclusion

Sometimes access through part of a root protection area is unavoidable, for scaffolding, for a crane pad or for a site route with no alternative. The standard allows this where the surface is protected so that loads spread and compaction is prevented.

For pedestrian movement, a scaffold board layer over a compressible support on a geotextile is usually enough. For wheeled or tracked plant, the system needs designing: a geotextile separation layer, a granular or cellular layer of specified thickness, and proprietary protection boards or a reinforced surface, with the design signed off by an engineer working with the arboriculturist.

Ground protection is a concession, not a default. It is laid before the first vehicle goes near the tree, and it stays until the work in that area finishes.

Signage and responsibility on site

Fix signs to the barrier at intervals, facing outwards, saying what the area is and that access is prohibited. Weatherproof, and legible from a distance, because the audience is a driver reversing rather than someone reading at arm's length.

Name a responsible person in the method statement, with a role rather than an individual so the document survives staff changes. That person inducts every subcontractor on the exclusion zone, checks the barrier at an agreed frequency, and is the one who contacts the arboriculturist if anything changes.

Put the tree protection plan on the site notice board next to the induction paperwork. Most incursions are ignorance rather than defiance.

Moving the barrier lawfully

The condition normally requires the barrier to remain in place until the development is complete, and moving it without consent breaches the condition even where no tree is harmed.

The route is straightforward. Ask the arboriculturist whether the change is acceptable, get a written variation to the method statement if it is, and send it to the council's arboricultural officer for written agreement before anything moves. Where the change is more than trivial, the council may require a formal application to vary the condition.

Keep the correspondence. A written agreement from the officer is what you produce at the final inspection when someone asks why the fence line differs from the approved drawing.

Photographs, supervision and discharge

Most tree protection conditions have to be satisfied before any work starts, which means the fence goes up before anything else happens on site and evidence of it reaches the council first.

Photograph the erected barrier from several positions, with something in frame that establishes location, and date the images. Repeat the exercise at each stage the method statement identifies. Where the method statement requires arboricultural supervision, book those visits into the programme, and make sure the site diary records them, because a supervision schedule with no record of visits reads as a schedule that was never followed.

The survey that started the whole process, set out in the tree survey, is the reference document for all of this, and the categories it assigned drive which trees get protected and to what standard.

When the fencing comes down early

Councils treat this seriously because the harm is usually invisible on the day and irreversible afterwards. A breach of condition notice can be served, with no right of appeal against it, and non-compliance with that notice is an offence. Where the tree is protected by a preservation order or stands in a conservation area, separate offences apply, and the penalties for damaging a protected tree run to substantial fines with the value of any benefit gained taken into account.

Practically, the more common outcome is a stop on the relevant part of the works while an arboriculturist investigates, sometimes with root excavation to establish what was severed. That costs weeks.

The same reasoning applies before an application is even made, which is why clearing a site in advance so often damages the case it was meant to help.

This is general guidance, not legal advice. Tree protection requirements are set by the approved method statement and the conditions on your permission, so check both with your local planning authority or arboriculturist before altering anything on site.

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