Cost consultant and external works quantity surveyor, Colm Kenny explores the issues facing urban trees and the designers and contractors charged with creating them
| Money does not grow on trees, but they certainly generate revenue. From the nurseries that produce them, to the design fees of those who specify them, to the contractors who plant and maintain them and finally the environment and end-users who get to benefit from them, each stage of the process generates a return.
The changing nature of development sites and their increased density mean that tree planting is becoming a more complex operation for landscape contractors. Requirements, specifications, methods and expectation are all evolving and the sector is struggling to keep up. Add to this the increasing percentage of the hard landscape in the form of paths, parking spaces and infrastructure and we have a serious situation to contend with. Tree planting by everybody outside the landscape industry is seen as a box-ticking exercise. Developers, construction contractors and planners are all complicit in a lip service process. As a result, a green circle is drawn over car parking spaces or on the footpath on masterplan drawings indicating the requirement to plant a tree, with little regard for the realities of tree establishment. A green circle and a few Latin names seem to suffice for getting most projects through planning. It’s a sad state of affairs. A few months will pass the following planning consent before the contractor gets to view the landscape proposals. A planting schedule is sent to the nursery for ordering, while a further investigation of the drawings is undertaken, usually revealing a section detail showing you how to plant the tree, customary stake detail and soil depth. Often this is not even included.
Typically, it’ll be glanced at by the contractor. They’re used to the cut and paste approach and have learned not to pay much attention. Written specification documents are usually no better with pages of text unrelated to the project, and in my experience, added through lack of knowledge, inexperience and insecurity. Finally, the day will arrive for the contractor to plant the tree, only the drawing shows the tree in what is now a pavement, or a small hole is left filled with waste and retained with haunching. This situation is nothing new and will be familiar to all. The landscape sector has been getting other disciplines out of holes and covering their tracks for far too long. And now, with tree planting becoming highly complex, the pressure is mounting, as are the costs, timelines and tempers. It’s time we took a breath and started understanding the complexities of modern tree planting methods and considerations. |
THE MODERN TREE PIT
Modular tree pits have been in existence in some shape or form since the early 1990s. The original concepts have not really changed over the years, but our knowledge of requirements and technology has. Suspended pavement systems have evolved in tandem with how production processes have changed, and also as a result of demand. These changes have provided an impetus for research and development and the spawning of a whole range of modular tree pit systems and products.
Modular tree pits present a challenge to both designers and contractors on a number of fronts. From the point of view of the designers, there is a constant battle with other design team members and clients, in trying to justify why such features are required. From a client’s perspective, it’s the cost of constructing the tree pit, while from an engineer’s viewpoint, it’s in relation to incorporating the services within the pit. I have frequently experienced engineers stubbornly refusing to move or adjust services or foundations to accommodate tree pits. I regularly hear, “We don’t usually do that” or “We can’t do that”. It can be very frustrating and harks back to the age-old problem for landscape contractors: we’re just too late to the table. Designers and contractors have the challenge of establishing trees, but they have a bigger challenge in convincing the various stakeholders to get on board. Trees are not a luxury, they are an environmental asset.
For urban trees to succeed, a clear understanding of both the science and practical realities of creating optimum growing conditions is needed. Once these are understood, the design of the pits becomes less daunting. And it should be noted that each site and pit is unique. Please don’t just cut and paste a CAD block issued by the supplier, or worse still, simply download one from the web. Allocate time to understand the key factors and design accordingly, from the depth of excavation, incorporation of site services and soil specification, to the choice of tree.
Time devoted to site-specific designing will produce far better results in the long term. The foundation of this site-specific design is in-depth surveying, akin to the “Measure twice, cut once” adage.
Like designers, the contractor has a number of challenges to overcome. In the first instance, it’s ensuring that when they get the opportunity to quote for the project, they do their due diligence and have a clear understanding of the scope of works involved. The cost of the actual materials is the easy bit. What is most often underestimated in tree pit pricing is the true cost of labour. The process of assembly is straightforward, but it is often at a slower pace than expected. Other impacts on the cost include the unknown elements, which are never indicated on the drawings but slow up progress on site. Items such as site services, pedestrian and traffic management, weather conditions, unloading deliveries on inner city sites or developments where storage of materials is not possible so that everything brought in the gate has to ready to be put into its final place. Do yourself a favour, undertake a comprehensive site inspection prior to price submission.
KNOW YOUR PRODUCTS
There are a number of manufacturers of modular tree pits, but the main supplier for the Irish market is Greenleaf Ireland in Londonderry. They have two main products, StrataCells and RootSpace. Their website is a useful resource for both designers and contractors as they provide CAD details and sample specifications. As each tree pit is a different size and has a unique design, it is difficult to give an accurate typical cost of what a modular tree pit costs but as a rule of thumb, including for the worst case scenario of incorporating services and city centre excavation with all the additional costs it brings to the bottom line, it could cost you in the range of €1,500 to €1,800 plus VAT per m³ of root space.
With the regeneration of towns and cities with retro planting of large trees in existing streetscapes, there is no doubt that modular tree pits and their construction will become more common requirements on landscape schemes. Forward planning will sow the seed of success, but this can only be achieved by co-operation between all. The designers need to harness the knowledge and expertise of the tree growers and contractors in order to ensure these modular tree pits work as intended.
I don’t think I need to tell you the importance of trees in our street. There has been plenty of research carried out to prove their economic, health, social and environmental benefits. For me, it is the historic element that is most attractive. They connect us to the past and also to the future.
“Tree planting by everybody outside the landscape industry is seen as a box-ticking exercise” |
Correctly designed and installed tree pits come with a premium, and one which often doesn’t sit well with the short term investment cycles of modern development. Just like the trees they plant, contemporary designers and contractors have their work cut out. ✽
 COLM KENNY, B Ag. Sc (Land Hort) MSc Quantity Surveying. Colm is a landscape estimating specialist. He provides cost and implementation advice to landscape industry professionals, technical advisors, contractors and facility management companies. He can be contacted on 087 288 5016 or by email info@landscapeqs.ie |
