Greater consideration should be given to trees in rights to light assessments, says Daniel Wade, rights to light director at Trident Building Consultancy.
As another winter descends on us, we often become more aware of how important access to daylight is. Cold, grey days can make us feel miserable. Not having access to natural daylight is damaging to our circadian rhythm and is linked to many conditions including vitamin D deficiency and seasonal affective disorder.
Therefore, having access to daylight and sunlight is important to us. That’s why right to light (RTL) assessments are undertaken on so many buildings – to assess whether that access is going to be compromised.
Often when we think of what can obstruct this light, we think of other buildings. But what if trees are also a problem?
Trees are a beautiful part of our environment and a natural solution for locking in carbon and improving air quality. But are trees next to buildings actually doing us harm by blocking essential daylight?
Biophilia and built environment
It is a difficult balance. The principles behind biophilic design promote a green, leafy and human-centred approach which brings many health and wellbeing
benefits. Being surrounded by nature is pleasant for all of us, hence the huge rise in plants and trees being installed in and around offices. It’s also why people enjoy being out in their gardens as much as they can.
But the need for new buildings to cater for our ever-expanding population is one that cannot be ignored or come to a standstill in favour of trees, even if they were here first.
Now I am certainly not advocating cutting down mature trees or stopping the planting of them. But we need to think about this more carefully and be prepared to work through some complex decisions. After all, issues around daylight and sunlight and RTL don’t have a history of being straightforward.
Right to light assessments
Daylight and sunlight assessments are treated as a planning matter, while RTL is a completely separate process.
RTL covers common law, so a scenario could arise where a development proposal has planning consent but can still injure a neighbouring owner’s easement to natural light over and above their own land.
Hence why any new development should also consider an RTL assessment.
Guidance is available for including trees as part of daylight assessment. The BRE paper Site Layout Planning for Daylight and Sunlight: A Guide to Good Practice points out the difference in shade between a deciduous tree and an evergreen, such as hedges, referring to evergreens as casting shade “more like that of a building or wall”.
It also explains that most deciduous trees are ignored when assessing new buildings. This is because it is normally the crown of the tree that causes the biggest issue and as daylight is scarcest in the winter, deciduous trees will have shed their leaves at that time, causing less of an obstruction.
But it is important to note that trees come in different shapes and sizes. Some can be very large, with certain species, such as the English oak, blocking up to 80% light in full leaf during the summer months and 55% when bare during the winter.
RTL calculations would assume the winter month figures. Transmittance tests are used to try to assess the dappled light and the effect this will have on a building.
Would previous cases have resulted in a different outcome if trees had been considered within the RTL assessment? Take the high-profile case of HRUK II (CHC) Ltd v Heaney [2010] EWHC 2245 (Ch); [2010] 3 EGLR 15, where the court imposed an injunction requiring the partial demolition of an already-completed development (the construction of two additional floors) that infringed a landowner’s RTL.
Recent images of the site in Leeds show a band of silver maple trees on the servient owner’s land. Could it have been argued that they masked the majority of the RTL effect of the additional sixth and seventh floors?
Consideration of trees
While there is some legislation on the issue, it is mostly related to evergreen hedges under the Anti-social Behaviour Act 2003, relevant to just residential properties. Dr Peter Defoe, a postdoctoral researcher and author, published a white paper, The Consideration of Trees in Rights of Light Cases: Part 2, in June this year, exploring whether more consideration should be given to trees in RTL assessments.
Defoe covers both side of the argument. Trees and hedges are, after all, unpredictable and each one is unique. While average growth rates can give some indication of the likely impact of a tree or hedge, they are living things and do not take much notice of growth charts.
He also explains how cases involving trees are mostly anecdotal. As most RTL cases are settled outside court it makes it hard for others to learn from those cases, or even to see whether or not trees were an issue. On balance, Defoe recommends including trees in RTL assessments, particularly where there is a stand of trees.
Interestingly, modern technology may well change how assessing trees works in the future. Point cloud surveys could be key to providing an accurate model, predicting the impact of a tree on a building over time. But, whether surveyors will go to these lengths is hard to predict – it is not really happening now.
Are RTL practitioners not taking trees into consideration because it is extra work? Or because of the complexity of additional variables or because no relevant case has been tested in court? Until such a case is presented that ends up in court, I am sure the debate will continue.
