Building near trees, Large Tree, Big Tree

5 things architects need to know about trees

As good architects will know, designing and building near trees can be a complicated and time consuming business. Failure to properly consider the arboricultural implications of a particular design or layout, can often result in planning refusal and costly delays.

Obviously, it is recommend that a tree expert is consulted at the earliest opportunity, as this allows for the development to be designed around the site constraints, rather than having to modify plans to appease the planners. However, this brief list explains some of the fundamental concepts and ideas that an architect should consider when designing near trees.

1. Most of a tree's roots are in the top 60cm of soil...

Tree Root System, Arboriculture, BS5837

It is a common misconception that a trees roots are a mirror image of its canopy, with numerous large roots growing deep in to the earth. In actual fact, 90% of a trees roots are present in the top 60cm of soil. Furthermore, the vast majority of the root system is made up of roots less than 5mm in diameter. These often spread much further than the tree's canopy line.

2. Tree roots need air as well as water...

Tree Root requirements

It is an often overlooked fact that tree roots require oxygen, as well as water. Just like animals, trees require oxygen for cellular respiration. Roots normally get their supply through microscopic air pockets in-between soil particles. Soil compaction via construction traffic or impermeable hard-surfacing can prevent the movement of air within the soil. This can ultimately result in the death of a tree.

3. Its best to avoid building any structures within an RPA...

Foundations, RPA

Where possible, it is always advisable to avoid placing structures within a root protection area (RPA). Failure to do so can increase the complexity and cost of the build, as well as making the planning application more difficult. Upon the advice of an arboricultural consultant, it may be possible to build within a tree's RPA through utilisation of specialist foundation types and the inclusion of important design features; these help ensure the continued health of the site's trees.

4. SuDS can be combined with new plantings...

Sustainable Drainage System, SuDS, Tree Planting

Trees can form part of a Sustainable Drainage System (SuDS), adding to the environmental credentials of a site, as well as the amenity. Trees have been shown to be effective in the filtration of pollutants from stormwater runoff. Drainage systems from new developments can be integrated into specially designed tree pits, providing an effective SuDS system. An added benefit is the reduced aftercare requirements for the new trees.


5. Trees grow...

Large Tree, Big Tree

It may seem obvious, but trees grow, sometimes considerably. When building near trees, it is always a good idea to have a chat with your arboricultural consultant about the growth potential of any nearby trees. Consequences of the failed anticipation of a trees growth can include excessive shading of windows and amenity spaces, physical property damage, and the future occupiers living in constant fear of branch failure.

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