29 November 2021
RTC safety surfaces can be laid onto a variety of sub-bases, the most common of these being Type 1 MOT stone, tarmac or concrete, but RTC can also lay the surface onto other sub-bases.
The sub-base can determine the depth of safety surface laid, for example the minimum depth of surface which can be laid onto a type 1 MOT stone sub-base is 40mm. We will be happy to advise you on any aspects of sub-base or edging detail required. Below are specifications for the most common forms of sub-base.
RTC can prepare a sub-base for you if you require, please contact our office for pricing.
1. Existing sub-bases – tarmac or concrete
RTC safety surfaces can be installed onto most existing surfaces which are in reasonable condition - this can prove to be a cost-effective method, eliminating the need for groundwork preparation.
The sub-base should be solid, in good condition and free of any weeds or moss. It is important to ensure that there is sufficient drainage. There may be a requirement to drill holes into the surface in a grid pattern to provide appropriate drainage, particularly if there is no existing drains. Please discuss this further with us if you are in doubt.
2. New base preparation for an RTC safety surface depth of less than 40mm
For surfaces less than 40mm it is necessary to lay a 50mm open textured macadam surface for the rubber to be laid onto. This should be laid onto a type 1 MOT stone sub-base. A concrete kerb edging 150 x 50mm should be installed around the perimeter of the area and set to the appropriate height above the macadam to allow the rubber to finish flush with the edge. The macadam sub-base should have deviations no greater than 7mm under a 3m straight edge.
It may be more cost-effective to lay a surface which is 40mm in depth or greater as this will remove the requirement for the macadam layer as the surface can be laid directly onto a compacted type 1 MOT stone base.
It is important to ensure that the sub-base is solid and free-draining to ensure maximum longevity of the surface.
3. New base preparation for an RTC safety surface depth of greater than 40mm
For surfaces greater than 40mm it is possible to lay directly onto a type 1 MOT stone sub-base. The existing ground should be excavated to accommodate a base of between 100mm and 300mm depending on site conditions, plus the depth of the safety surface required.
A concrete kerb edging of 150 x 50mm should be installed around the perimeter of the specified area which is then filled with the MOT stone layer and compacted. This will then leave the correct depth below the top of the kerb to accommodate the required thickness of RTC safety surface.
The MOT stone layer should be compacted to a tolerance giving local deviations no greater than 7mm under a 3m straight edge in any direction.
It is possible to substitute the concrete edging for a tannelised, pressure-treated timber edge, however this may reduce the longevity of the surface - please contact us to discuss this option further.
Should you have any queries regarding base preparation please do not hesitate to contact our office where we will be happy to advise you or provide you with a costing for preparing the sub-base.