Permegrid PG40 Design Guidelines
We have two Design Guides available:
1. Permegrid PG40 Gravel Design Guidelines
2. Permegrid PG40 Grass Design Guidelines
Permegrid PG40 Gravel Design Guidelines
All the design guidelines are written with best practice in mind. It is strongly advised that any questions raised from the guidelines are directed to our technical team.
When Permegrid PG40 is installed correctly to suit site conditions, they should provide source control within Sustainable Urban Drainage Systems. Drainage must be a consideration when designing a construction profile to ensure that flood alleviation and water run-off is properly considered where natural filtration may be incapable of withstanding all eventualities.
When installing Permegrid PG40 the following should be considered:
1. a) Does the proposed installation area drain well already?
b) Is there planned to be a slight fall to be built into the design to perhaps aid drainage if aid is needed?
c) Is the drainage capability of the soils the same at the surface and at 200 to 500mm below the surface?
d) Has there been previous issues with drainage on site?
e) Has disposal of any excess water been considered?
f) Are there SUDS requirements to be considered?
2) If Permegrid is being considered as part of the construction profile please ensure that at least 25% of the particle size of the sub-base is bigger than the mesh size used to ensure good locking.
3) Sub-base particle size should not ideally exceed 60mm and should be less than 5% fines material of content of the whole. Please ask for technical guidance if unsure.
4) Please refer to tables 1 and 2 for guidelines to depth of sub-base for specific design profile to suit site needs. Please note if Permegrid is omitted 50% of the depth of sub-base needs to be added to calculated depth with Permegrid. For example, 100mm with Permegrid would become 150mm without. For detailed guidance please contact our technical team.
5) It is always good practice to confine Permegrid PG40 plastic pavers on the site edges. This could be as strong as 150 x 150mm concrete kerbs or a simple barrier like treated timber. The type of vehicles, frequency of traffic and circulation routes should all be considered when choosing the confinement method for Permegrid PG40 in the design.
6) Permegrid PG40 has been designed to work within stated guidelines to a slope of 5% or less. The Permegrid PG40 can be used on steeper slopes in some cases
7) Ideally the sub-base should extend out further than the surface area of Permegrid PG40. This is so lateral pressure caused by the traffic loading does not displace the Permegrid PG40 on the edge. The extension of sub-base outwards should be the same as the depth of the sub-base.
8) The aggregate for the bedding layer should ideally be a 5-10mm angular clean aggregate laid to a maximum depth of 20mm. For the finishing layer, the filling of the cells should ideally be specified as 10mm to 14mm sharp angular gravel to BS EN13242. This gives the best results for providing a long term, very low maintenance wearing surface. The gravel pieces interlock with each other and, more importantly with the specially designed PG40 plastic paver. Smaller angular gravel/particles fill the voids providing a secure, stable and sustainable finish. Rounded gravel/pea shingle is not recommended.
Note on drainage
Any sub-base used in the construction profile should be permeable – for example MOT Type 3 or MOT Type X. It should be predominantly fines free material and able to compact well without losing integrity, stability and permeability/porosity. MOT type 1 can be used but drainage channels need to be considered – please see schematic.
For any detail on specification for design not covered in above please contact our technical team.
Sub-base Thickness
Use the following charts to confirm the sub-base thickness that is required, based on vehicle load, frequency of use and Soil Strength (CBR %).
Permegrid PG40 Grass Design Guidelines
All the design guidelines are written with best practice in mind. It is strongly advised that any questions raised from the guidelines are directed to our technical team.
When Permegrid PG40 porous pavers are installed correctly to suit site conditions, they should provide source control within Sustainable Urban Drainage Systems. Drainage must be a consideration when designing a construction profile to ensure that flood alleviation and water run-off is properly considered where natural filtration may be incapable of withstanding all eventualities.
When installing Permegrid PG40 the following should be considered:
1. a) Does the proposed installation area drain well already?
b) Is there planned to be a slight fall to be built into the design to perhaps aid drainage if aid is needed?
c) Is the drainage capability of the soils the same at the surface and at 200 to 500mm below the surface?
d) Has there been previous issues with drainage on site?
e) Has disposal of any excess water been considered?
f) Are there SUDS requirements to be considered?
2. If a geogrid is being considered as part of the construction profile please ensure that at least 25% of the particle size of the sub-base is bigger than the mesh size used to ensure good locking.
3. Sub-base particle size should not ideally exceed 60mm and should be less than 5% fines material of content of the whole.
4. Please refer to tables 1 and 2 for guidelines to depth of sub-base for specific design profile to suit site needs. Please note if Permegrid is omitted 50% of the depth of sub-base needs to be added to calculated depth with a Permegrid. For example, 100mm with Permegrid would become 150mm without. For detailed guidance please contact our technical team.
5. It is always good practice to confine Permegrid PG40 plastic pavers on the site edges. This could be as strong as 150 x 150mm concrete kerbs or a simple barrier like treated timber. The type of vehicles, frequency of traffic and circulation routes should all be considered when choosing the confinement method for Permegrid PG40 in the design.
6. Permegrid PG40 has been designed to work within stated guidelines to a slope of 5% or less. The Permegrid PG40 can be used on steeper slopes in some cases.
7. Ideally the sub-base should extend out further than the surface area of Permegrid PG40. This is so lateral pressure caused by the traffic loading does not displace the Permegrid PG40 on the edge. The extension of sub-base outwards should be the same as the depth of the sub-base.
8. Root zone 60/40 should be used for the bedding and filling of the cells of the Permegrid PG40 grass pavers.
Using soils won onsite/reused from excavation are very likely NOT to have any medium to long term success due to poor nutrition and drainage properties. Mixing soils on site is also not advised.
Note on drainage
Any sub-base used in the construction profile should be permeable – for example MOT Type 3. It should be predominantly fines free material and able to compact well without losing integrity, stability and permeability/porosity. MOT type 1 can be used but drainage channels need to be considered – please see schematic.
Sub-base Thickness
Use the following charts to confirm the sub-base thickness that is required, based on vehicle load, frequency of use and Soil Strength (CBR %).
