Trees and construction logistics – foreseeing the challenges

There is a growing desire, as enshrined in planning policy at all spatial scales within England, to retain trees that are considered to be of a ‘good’ value (just look at the emerging London Plan). The value of trees may be determined through the lens of BS5837 or instead on the grounds of public visibility, and the contribution of the trees to the public realm and the character of the local landscape (especially, if within a Conservation Area). Therefore, what usually happens is that such trees are considered for retention as a baseline principle, subject perhaps to some losses (with mitigation) to enable the placement of new built structures comprising buildings and surfaces (and services that feed into and out from these places). The situation is of course much more nuanced than this, with an expectation at least within the design team that a project has to be economically viable for it to be worth pursuing – if trees stunt any ability to generate a profit after deductions, it’s not worth investing the time and more importantly the money. With this in mind, it’s also usually the case that a larger massing (often from a large floorspace) can provide a greater return on investment, as land values are quite high in some areas of England (London and the home counties, especially). Thus, what we may end up seeing is a maximised floorspace up to the areas where trees of value constrain further expansions. Let’s now run with this, into the following discussion.

From the above information, we can assume that the site has been designed for redevelopment in a manner that maximises use and utility (thus return on investment – i.e. profit, in some measure), up to the point where the trees stop further development. Great, you’d think, when looking at this on paper – the designs accommodate the trees and there’s a juxtaposition that in overarchingly harmonious. Maybe, it’s a little tight, but it’s all viable stuff in principle. A decision notice granting consent is therein issued, with the consultees being in agreement, subject to various conditions including the requirement for some pre-commencement arboricultural information (a method statement, at this stage, based on the RIBA Stage 4 details).

This is where things can sometimes get interesting.

Enter the main contractor (or consultants producing construction method statements) and a lens for construction traffic routeing (including material management and storage). The build process needs to be in accordance with health and safety laws, best practice, and planning policy – it needs to be logistically safe and fully functional. Now, it may be the case that areas directly under trees are where heavy vehicles need to be positioned or tracked through, be it for delivery, removal of materials, or any other reason. Perhaps a large piling rig needs to pass through into the site, below a tree (and maybe a piling mat set up where a tree is rooting) – or maybe a tower crane needs to be set up and tree crowns are directly impeding the effective use of the tower crane. Further, don’t forget about scaffolding and site huts, including welfare facilities (notably, on larger sites). These details were probably not considered before, as there wasn’t an investigation into construction logistics – instead, the focus was on securing good designs to fit the brief of the client and fit with the relevant expectations of planning policies and guidance documents.

surface tree roots construction site
If you need to track vehicles through this area, were the surface roots ever considered appropriately? They may have a major impact upon how a temporary access road could be constructed.

Now, it may be that the trees that previously and on paper looked like they could easily be retained are under pressure. It may be that some high value trees (e.g. Category A, as per BS5837) are needing to be pruned or even felled. It’s unlikely that the Local Planning Authority is going to appreciate this turn of events, as it could reek of a bait-and-switch act. Moreover, the decision could have been a contentious one that was called into committee and was a subject of hot debate. In any event, it is optically undesirable and can make matters all too bittersweet. Perhaps, pre-commencement conditions cannot get discharged, with the project becoming a non-starter after a lot of work has been invested – this is unlikely but could happen.

In short, without trying to drive things home by repeating myself, it really needs to be the case that the viability of a development (in terms of construction viability) is explored, at the earliest stage possible. Logistics of getting something built are key and it needs to be considered early on – effectively, before a full (or householder, outline, or hybrid) planning application is submitted. The details may not all be there; however, there needs to be enough confidence that areas where retained trees are to constrain access during development are not going to be placed under pressure, due to changes when conditions are being dealt with.

Think ahead and aim to stress test construction logistics at an early stage and how these sit up against retained trees – ask the right questions of the right people, progressing with as few unknowns as possible (at least, in an ideal world). Some detail is better than none.

Trees and construction logistics – foreseeing the challenges