National Trust Tree Safety guidance


However, there are risks of injury to staff, volunteers and the public from falling trees and branches. There are also risks of damage to buildings, property and vehicles.

Tree safety management is one aspect of visitor safety management. The Trust’s approach to visitor safety management is based on the guiding principles contained in the booklet ‘Managing Visitor Safety in the Countryside – principles and practice, published by the Visitor Safety in the Countryside Group (vscg.co.uk).

Establishing and mapping usage zones

For a programme of tree inspection and management to be practical, most resources need to be directed to areas where there is greatest risk to people and property. This is initiated by designating each part of the property to one of five Usage Zones. At some properties, all five zones will be applicable; at others, three or four zones may be applicable. Assignment of usage zones is also the responsibility of the Property Manager/General Manager, with assistance from property staff and functional advisers. The Usage Zone is based on how the area is used and consequently the likelihood of people being injured, or buildings and other valued property being damaged in the event of failure of all or part of a tree.

These zones take account of different levels of use and types of activity, reflecting the numbers of people that use a particular area and the time they spend in that area.

The following general factors will have an influence on whether tree failure due to mechanical weaknesses may occur:

  • Wind speeds for the site. Trees adapt their growth to site conditions so that on windy sites the trees are more wind tolerant. The rationale needs to state whether average or maximum gust wind speeds are used as the basis for decision making.
  • Wind direction. Knowledge of prevailing winds will be part of the decision making.
  • The nature of the trees on site is significant. The species, age and size of the tree, together with the rooting substrate and location all have an impact.
  • Other factors. Could include the time of year i.e. are the trees in full leaf or not and is the ground saturated by recent heavy rainfall.
  • Knowledge of the site and a record of weather conditions which relates to damage to trees and restrictions on access will help to inform the rationale. Details of post storm damage to trees should be included as part of Tree Safety Management (TSM).
  • Information from the UK Meteorological Office. The Met Office issues weather reports including severe weather warnings. They also issue information which is very useful in predicting average and maximum gust wind speeds. The rationale should stipulate which report type will be used for decision making on the property. Active monitoring of forecasts will allow a property to be proactive and make a decision in advance.

Tree inspections: Usage Zones

1. Very High Use
For example:

  • Constant very high volume road, rail or visitor use.
  • Very high likelihood of visitors, staff/volunteers staying in the area

Areas close to or used as:

  • Motorways, dual carriageways, major road junctions, main trunk railway lines.
  • Major car parks, camp / caravan sites, adventure play areas, event areas.
  • Very heavily used buildings, e.g. schools, mansions, NT visitor reception / shops / cafes.
  • Residential buildings including tenanted cottages and farm houses, holiday cottages, base camps, neighbouring private dwellings

2. High use
For example:

  • Frequent high volume of road traffic or visitor use.
  • High likelihood of visitors, staff/volunteers staying in the area.

Areas close to or used as:

  • A roads and busy road junctions.
    Busy car parks and adventure play areas.
    Large-scale, but infrequently used event areas.
    Gardens with very high visitor numbers.
    Picnic areas with extensive outside seating.
  • High value structures, e.g. garden statuary, park follies, unique bridges.
  • Heavily used footpaths, bridleways, way-marked trails and avenues.
  • Areas close to heavily used staff working areas, e.g. estate yards, workshops.

3. Medium use
For example:

  • Generally moderate volume of road traffic or visitor use.
  • Visitors tend to disperse rather than gather.

Areas close to or used as:

  • Local roads.
  • Medium / small-scale event areas.
  • Gardens with moderate visitor numbers.
  • Footpaths, bridleways, avenues, way-marked trails.
  • Non residential buildings, e.g. barns.

4. Low use
For example:

  • Generally low volume road traffic or visitor use.
  • Visitors well dispersed.

Areas close to or used as:

  • Minor roads and quiet car parks.
  • Quiet areas of gardens.
  • Footpaths, bridleways, way-marked trails, avenues.
  • Areas restricted for public access, or impeded by natural or planted vegetation.

5. Very low use
For example:

  • Normally very low level of visitor use or infrequently used.

All other areas not classified above. Often this land is arable, park, hill, moor, heath or woodland.

Frequency of inspections

Usage zoneFrequency of inspectionInspection type
1 Very highNormally annually and after severe weather eventsFormal inspection of every tree for defects with binoculars, tapping mallet and probe required to be available for use.
2 HighNormally two years and after severe weather eventsFormal inspection of every tree for defects with binoculars, tapping mallet and probe required to be available for use
3 MediumNormally every three years (with discretion up to 5 years) and after severe weather eventsWalk by inspection of every tree looking for obvious defects
4 LowDuring normal routine visitsInformal observation and awareness of the general condition of trees
5 Very lowNo inspection requiredNo inspection required
Retained treesAt least annually, with additional inspections if appropriateFormal or detailed inspection, often requiring a higher level of expertise
The best time to inspect trees is during September and October, as this is when fungal fruiting bodies can most easily be seen and identified, and deciduous trees still have sufficient foliage to enable their general health to be assessed. However, looking at trees in full leaf during the summer can also be helpful in assessing their general health, while inspecting deciduous trees in winter when leaves have fallen allows any physical defects in the upper tree parts to be observed more easily.