Stabilising gravel on a slope is made easy with Nidagravel® gravel stabilisation grids
Using a decorative gravel surface for a sloping path, driveway or any other sloping gravel surface application can be problematic. The main three problems that arise when gravel has been laid in the traditional way on a slope (ie. a surface dressing laid directly on top of the sub-base material) are as follows:
1. Gravel Migration
What tends to happen in a majority of cases, when gravel is laid directly on a slope without using a stabiliser, is that the gravel migrates towards the bottom or lowest part of the slope after a period of use. This is more of a problem with gravel driveways or slopes which are used by vehicles. The gravel that has migrated to the bottom of the driveway, then becomes harder to drive or walk over as the gravel becomes deeper and less stable. This deep section of gravel then migrates again across adjacent surfaces with more pedestrian and vehicular use. This gravel migration can be made worse by the type and size of gravel used. A larger 20mm rounded river or pea gravel is likely to migrate much further than a smaller 10mm angular gravel or chipping. The entrance to the gravel driveway or start of the slope, is now beginning to look a mess with the loose gravel having spilled out of the entrance. This loose gravel is then either ground into other surfaces, such as a tarmac road surface or crushed under the weight of a vehicle against the road or pavement.
2. Loss of Surface Gravel Dressing
Gravel migration results in loss of gravel from the driveway or slope, which exposes the sub-base material. In order to keep the surface looking as it should, more gravel needs to be added and spread over the surface to replace the lost gravel and the cycle of gravel migration and loss of gravel starts again. This becomes a long term maintenance issue that will keep repeating itself. Ultimately, gravel slopes and driveways can only be topped up so many times, before the whole section needs to be removed and re-installed properly.
3. Ruts and Potholes
The combination of gravel migration, loss of gravel and exposure of the sub-base material can lead to ruts and potholes developing in the sub-base. Rainwater that washes down the slope, especially in heavy downfalls, can start to scour the surface of the sub-base and wash out some of the finer particles and this can also contribute to the formation of ruts and potholes. With vehicles continuing to pass over the same sections of the sloping driveway, the problem is made worse over time. Simply adding more gravel will not cure the problem, the potholes and ruts need to be filled in with more sub-base material, re-graded and compacted, before re-applying the surface dressing of gravel.
The SOLUTION to the problem is to stabilise the gravel using NIDAGRAVEL® gravel stabilisation grids.
Nidagravel® gravel stabilisation grids are large panels of plastic, hexagonal cells, backed with a membrane that hold the gravel in place. Nidagravel® grids are laid over the prepared sub-base and cut to fit the required area. The honeycomb structure of the gravel stabilisation grids, holds the gravel in place permanently within the hexagonal cells. This prevents gravel migrating, prevents loss of gravel and prevents ruts and potholes from developing. In addition to solving the problem of using gravel on a slope - Nidagravel® honeycomb grids provide a much more stable gravel surface that is firm underfoot, making the gravel slope easier to walk across, a gravel surface that is wheelchair friendly and easy to push a pram or bike over. Nidagravel® grids enable a high quality, long lasting gravel surface to be created that is virtually maintenance free.
NIDAGRAVEL® MAXIMUM RECOMMENDED GRADIENT
We recommend using Nidagravel® 129, 130 and 140 to be laid on any gradient up to 15%.On all gradients up to 15% the weight of the gravel fill holds the sheets in place and prevents longitudinal movement.On all gradients up to 15% there will be no movement of gravel within the honeycomb cells and minimal surface migration.On all gradients up to 15% no additional form of mechanical fixing is required.
The graph above shows the maximum recommended gradient of 15% with acceptable gradients shown in green and excessive gradients shown in red.
The graph above shows an easy to read example of the maximum recommended gradient over a 5m run with rise heights shown in centimeters (cm).
NIDAGRAVEL® MAXIMUM RECOMMENDED GRADIENT
Expressed as a Percentage:
Expressed as a Ratio:
1:6.67 or 1 in 6.67
Expressed as a Degree:
Expressed as a Fall (mm):
Expressed as a Fall (cm):
Expressed as a Fall (m):
NIDAGRAVEL® GRADIENT CALCULATOR
Use our simple gradient calculator below to work out the gradient of your slope.
Enter your RISE and RUN figures and the calculator will do the rest.Enter any unit of measurement you like, BUT make sure the RISE and the RUN units of measurement used are both the same.Enter your figures in Meters (M), Centimeters (CM), Millimeters (MM), Feet (FT) or Inches (IN).