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Tree Pit Systems for Paving and Hard Landscaping
Tree Pit Systems for Paving and Hard Landscaping works frequently require additional specialist treatment to ensure that the area immediately around the tree is free-draining, yet solid, sound and strong enough to allow inevitable foot traffic. Permeable Resin Bound Surfacing is ideal for these Tree Pit Systems, as it also removes any potential slip or trip hazards, plus this approach also prevents the loss of soil or growing media, and the build-up of rubbish and litter around the trees. It has also been found that with Resin Bound Surfacing Tree Pits, the incidence of dog-fouling is greatly reduced and they can help to prevent other anti-social behaviour, because there is nowhere for any dangerous or hazardous materials to be deposited or hidden.
Tree pit edges are normally finished with a hard paved outer edging and a hard inner ring of hard paving, or another suitable edge that is sufficiently offset from the tree to allow for the tree’s anticipated future growth – especially when tree saplings are being planted.
By using light and colour fast Tree-pit resin mortars over a consolidated base layer, the areas can also be enhanced aesthetically and made to match or contrast with the surrounding paving, according to the Architect and Designers requirements. There are basically two types of these tree-pit systems that can be supplied – those with a factory graded and pre-bagged aggregate mix that is included with the resin binder in a pre-batched unit, or the resin binder alone can be supplied to be mixed with a defined quantity of approved specially prepared kiln dried aggregates, or blends of aggregates and other special materials such as glass beads or pebbles, for the creation of special effects and design solutions.
There are also two types of resin binder that are generally suitable for use in these Tree-pit applications – both are light fast, non-yellowing polyurethane resin based. They are also known as urethanes or urethane polymers, depending on the manufacturer. The first group of these are single pack / one-component, moisture cured polyurethane resin-based materials. The second group are two-component reaction curing polyurethane resin-based materials.
Tree pit systems are normally applied directly onto the firmly compacted soil, in which the tree was preferably planted the specified number of days earlier, and at a nominal thickness of 100mm. This build-up consists of a minimum 60mm base layer that is produced with compacted sand and gravel chippings, or an MOT type-1 sub-base, which is followed by a minimum 40mm layer (for the one component type), or a minimum 30mm (for the two-component type) of the polyurethane resin binder and aggregate mix.
These can be considered in more detail as follows:
- One Component PU Tree Pit Systems
The best single component, moisture cured, polyurethane resin based materials include GftK’s excellent vdw 525 resin binder which is mixed with our graded kiln-dried tree-pit aggregates, or the same binder can be supplied in a pre-batched composite unit - vdw 825, which also contains the pre-weighed aggregates. These one-component materials are the easiest to use for small areas, such as tree pits in any domestic, or non-trafficked areas that are not going to be cleaned with Mechanical Street Cleaning Machines.
The single component polyurethane resin binder is mixed directly with the kiln-dried aggregate component in a suitable large sized, forced action mixer such as Crete angle, Rota mixer Baron or similar. The mixture is then poured out and laid on the prepared compacted base layer, levelled off and trowel finished. The finished tree pits must be left to cure for a suitable length of time, usually a minimum of 12 hours at 20°C for light foot traffic, and around 7 days before the surfaces can be opened for full service and use.
For tree pits in commercial, trafficked and mechanically cleaned areas the tougher, more abrasion and mechanically resistant, two-component polyurethane resin-based binders should always be used to withstand the more frequent exposure to traffic and aggressive cleaning regimes.
The procedure for these materials is outlined in the next section below.
- Two Component PU Tree Pit Systems
Two-component polyurethane resin-based binders should always be used for Tree Pit Systems in commercial, trafficked and mechanically cleaned areas. This is because the two-component material will cure and harden to a tougher and more abrasion and mechanically resistant material.
The two parts (A+B) of the polyurethane resin binder is first mixed with a drill and paddle before being added to the kiln-dried aggregate component (part C), in a suitable large sized, forced action mixer such as Creteangle, Rotamixer or Baron or similar. The mixture is then poured out and laid on the prepared compacted base layer, levelled off and trowel finished; then the tree pits must be left to cure for a suitable length of time, usually about 4-5 hours at 20°C for foot traffic and at least one day for light vehicles.
Pour the Pre-mixed vdw 825 TPS into Place
Smoothing & Finishing the vdw 825 TPS
GftK's vdw 825 Tree Pit System Completed
Tree Pits System ProductsGftK's vdw 520 TPS Binder
Tree Pits Supporting Urban Environment Improvement
Trees are beautiful and improve the appearance of almost any larger paved area; they are home to a variety of wildlife and can create welcome shade and shelter from the elements. Trees are also very effective and efficient at absorbing CO2 from the atmosphere and releasing oxygen into it through their photosynthesis of natural light. Additionally, trees reduce the effects of pollution; they trap, hold and remove particle pollutants (dust, ash, pollen and smoke) that can damage human lungs, Gaseous pollutant particles are also removed by absorption through the pores in the leaf surfaces. The trapped particulates are filtered by the trees leaves, stems and twigs, then taken or washed into the ground by rainfall, which penetrates easily through the permeable tree pit system.
Trees in our urban areas can also significantly help to reduce the "heat-island" effect and reduce temperatures, plus the leaf canopies catch and hold considerable amounts of water during rainfall which in turn can help to reduce flash flooding and overloading of the drainage system. The planting of more trees and the use of these modern resin bound tree pit systems must be a good idea for everybody for all of the advantages and environmental improvements outlined above!
Where required, NCC Streetscape can provide the names of specialist contractors that are experienced in the installation of tree pits in your local area, all around the UK, from our national network of trained professional paving and landscaping contractors.
However, if you are already aware of the tree pit system and product details, plus the application methods and procedures, you can buy your tree pit system products here in our Online shop
Alternatively for help with the use of advanced tree pit systems and planting in your hard landscaping project: please email or call 01257 266 696 for FREE expert advice and assistance – We are confident that we can help you to solve any problems and to save time and money on every single paving job!