In 2015 we blogged about the cost of tree planting with cellular pits in hard landscape, and advised that the cost of a large high water demand tree, such as an
oak, could be well over £10,000. Even the smallest tree can cost more than £2,500 per pit, and no-one budgets for that – we know!
We have posted the blog again, so go-scare yourselves all over again – those are the industry figures we were supplied.
Recently, some clients have omitted trees in hard landscape when the cost was known, or reverted to a standard tree pit, contrary to the approved plans – and have been exposed by the LPA and forced to retro-fit, which is even more costly.
On future schemes, ACD propose to review the initial layouts and advise if there are proposed tree locations where hard landscape pits will be required. It’s a simple calculation for the smallest tree – 4m3 of topsoil, which means a tree should be planted in a soft landscape zone with a surface area of 4m2 minimum. Less than that, and there is the risk that the LPA will demand a cellular tree pit, installed prior to the hard landscape being installed. So narrow landscape strips just wont work.
Blog entry from 2015:
Tree Pits in Hard Landscape
We are encouraged to plant trees in urban locations and the ‘greening’ of cities is widely accepted to have environmental, as well as social benefits. Unfortunately, many situations require load-bearing paving surrounding the trees and the pre-preparation of the pits as a result, with various proprietary planting cells being utilised. The opportunity to provide adequate rooting area in soft landscape is difficult to achieve in urban locations and the new BS 8545:2014 recognises this.
ACD has recognised that many clients do not adequately understand (or accept) the budget implications of this development – put simply, many are missing a zero off the budget figure… a client was recently shocked to find that they had to budget £500,000 for a scheme with 85 trees and the imperative to provide trees in hard landscape areas is often avoided as a result of the budget implications.
BS 8545:2014 Trees: from nursery to independence in the landscape. Recommendations
Produced in response to the knowledge that a significant proportion of newly planted trees fail to survive to maturity and die soon after being planted in an urban environment, BS 8545 has been produced to inform the Industry a little better. The Trees in towns II report commissioned by the Department of Communities and Local Government highlighted that as much as 25% of all planting undertaken in the public sector fails. It is very likely that trees in the private sector have a similar failure rates.
The BS deals with many aspects of production and transplanting and recommends changes to standard tree pit specification, which renders many standard details outdated and inappropriate. Furthermore, with the development of cellular systems to increase soil volumes in urban and hard landscape locations, tree pit design has developed rapidly, with many LPA Officers now demanding the volumetric calculation for trees to be demonstrated.
We asked a major landscape supplier to indicate some likely budgets for the provision of three different tree sizes from small to large. The dimensions they used were based on the Hillier’s Designers guide.
- Quercus robur – Large with an 8m dia canopy spread after 25 years
- Betula pendula – Medium with a 5m canopy spread after 25 years
- Carpinus betulus ‘Fastigiata’ – Small with a 3m canopy spread after 25 years
Using the formula of canopy area (calculated based on the canopy being a circle) multiplied by 0.6, they calculated the soil volume requirements as follows:
- Small Hornbeam = 4m3
- Medium Birch = 12m3
- Large Oak = 30m3
With the soil volumes indicated above and their planting cell, costs were indicated as follows:
- Small £894.72
- Medium £2684.16
- Large £6710.40
They added in a tree grille (1200mm sq), RootDirector, Irrigation, aeration and underground guying this totals approx £995. They allowed £200 for a tree, topsoil fill for the planting cells at say £40/m3 giving totals of:
- Small £2,249.72
- Medium £4,359.19
- Large £9,105.40
That equated to a known scheme in Manchester city centre, where street tree planting is budgeted at £5000 per tree. The soil volumes would be fairly small as the tree species are often small.
Price includes a nominal tree at £200.
We accepted that the tree pit excavation and construction would vary hugely from site to site, but following excavation, two people could assemble a medium size tree pit ready for backfill and surfacing in about 3 hours, a large in approx 8 hours, so we need to allow £1000-£1500 for installation. That assumes easy excavation, but in our experience, in urban locations, the excavations can be problematic and time consuming.
In many situations, there will be a desire for immediate effect and it is likely a semi-mature tree would be favoured over a smaller tree and the cost would rise accordingly, to between £500 and £1,000.
We try to design for adequate soil volumes in soft landscape areas that are cost effective, but often layouts dictate that a cell-solution is the only appropriate method of achieving tree planting in paved areas. The conclusion would be that a package for a large tree could be well over £10k, even for a Standard tree – that’s a tough sell!