Trees don't die, they're killed!
As with all street furniture it is essential to get the specification for tree protection correct. In many instances we see a lot of money being spent on schemes throughout the country, many look very nice on day one, but come back in a year or two and look and you may be surprised.
This guide is designed to help prevent these pitfalls and ensure that you make the right decisions when choosing products for certain applications.
A specification guide for trees
Check what size your tree is going to grow! Look at this illustration, in all cases the products used were unsuitable for the application. The sad thing is that these situations have not happened overnight, and in all cases something should have been done sooner.
The whole point of tree protection is to aid soil stabilisation, stop soil compaction, ensure the easy passage of nutrients to the root system, aid drainage, and to protect the tree during its early development. Careful specification can avoid the this happening.
Care must be taken if comparing prices from differing manufacturers. There are no British Standards to cover this sector, (or many others), therefore products can often be made to varying standards. We at CIS Street Furniture are trying to implement our own standards, a leaf has been taken from the British Standard for Manholes, and consequently all CIS grilles when combined with medium duty frame will withstand a 6.5 tonne slow moving wheel load, (for occasional traffic areas).
This illustration shows a CIS Street Furniture standard cast iron grille c/w medium duty frame. You will note that the grille is a four part casting. The reason for this are that when combined with our easy fit anti vandal system, the grille segments are allowed to articulate within the frame. This helps spread the load throughout the area without breaking frame or grille. Also grilles are very heavy to move about on site and larger two section designs are extremely heavy and are more likely to get damaged during installation.
This illustration shows how other manufacturers may supply medium duty frames and grilles. Invariably the grilles will be in half sections and a simple peripheral steel frame will be used, sometimes not even angle iron. This will not offer support to the middle of the cast segments. If loads are put on the grille and frame fracture will almost certainly occur.
The lack of standards within the industry allows for many interpretations of the word “medium duty” and often inferior products may be used in error. At CIS Street Furniture we do not even offer a lightweight version of our tree grille frames, as we believe that it will not be a long term benefit to our clients or the tree itself.
Correct installation is very important. It may be many years by the time you realise that the products were not installed in the correct manner. This illustration shows how to install our grilles and frames. A small amount of concretehaunchingis required to stabilise the grille and frame. This should give a firm bedding and stop the grille and frame sinking at a later date.
Another important aspect is thegeotextilemembrane. This relatively inexpensive piece of material will, stop the pea shingle mixing with the planting mixture, aid the passage of air and water born nutrients to the root system, aid drainage, and finally prevent the deep rooting of weeds. Thus what weeds do root will be easy to remove.
If you have concerns about the build up of weed growth and rubbish beneath the grille castings why not specify our hinged grilles and frames. Litter and weed removal will never have been so easy and there is no need for an anti vandal system, as the grilles and frames are tied together integrally with hinges.
This illustration shows what happens when corners are cut and grilles have been supplied without a frame. There becomes little or no way of securing the grille segments. The weight of the castings will also compact the soil surrounding the tree pit, leading to a gradualsinkageof the tree pit itself. In this situation grille segments may be lost, weighed in at the local scrap metal merchant, or simply thrown through a shop window!
This photograph shows a concrete grille used without a frame. Just look at the soil compaction within the tree pit. We can also see from the weedy look of the tree that, ultimately, the development of the tree is being inhibited.
This photograph shows trees in an urban environment. There is little that can be done about this as the surrounding development has almost certainly grown into the trees territory. The roots undergo secondary thickening and start to break up the paving.
However if you are planning for trees to be placed within an urban environment why not consider using a root director. This will allow the roots to establish themselves deeper, which will be better for the tree and the paving!
This grille and frame have been used without anti vandal bolts. This may reduce the initial cost slightly but will lead to premature damage of the tree, the grille, and the tree pit. It will not be long before the grille sections mysteriously disappear!
Specifying is not always as easy as it may seem, it is a lot easier to get it wrong than right. We hope that this will help you make informed and useful decisions about what products to specify and where.
We are able to offer further advice and assistance regarding any street furniture related product. This is, of course without obligation. Please feel free to give us a call.