Maintaining Gravel Surfaces to Improve Performance

Gravel surfaces are usually designed for light vehicles and  pedestrians to use.

A gravel path will normally comprise of several layers of material.   The bottom layer will usually be a semi-permeable membrane.  This  prevents mud and weeds from coming up through the compacted surface into the top layer,  while still allowing water to drain away.

The middle layer will usually be a compacted base of hard-core.  This layer provides a solid base that keeps its shape when traffic  or pedestrians use the surface.   It can also be porous, allowing water to drain easily, or not porous, allowing the water to run off into a drainage system.  

The third layer is the gravel itself; which provides a grippy surface for people to walk or drive over. This is also designed to look smart and allow water to drain easily.  When maintaining this surface we need to consider all the  functions that the surface performs and look to maximize its ability to do so.

Picture Credit; https://www.externalworksindex.co.uk/

Surface Compaction is caused by a mixture of traffic on the surface and rain washing mud into the top gravel layer. Surface compaction means that water cannot drain through the surface properly, so symptoms will include puddles and the surface becoming uneven. If left untreated it will lead to potholes and Flooding of the surface.

To prevent surface compaction is simple, we only need to rake the gravel on a regular basis in order to keep the surface loose and even. This will allow it to drain and support traffic correctly.  When the surface has become too compacted for a rake to penetrate this will result in Flooding/puddling whenever it rains. We need to use a mechanical tool to de‐compact the gravel. Kersten offer such a machine, called a gravel path renovator. The knives in the tool will loosen even heavily compacted gravel surfaces allowing them to drain again.

Detritus is usually a mixture of organic material such as leaves and twigs falling from trees, grass cuttings and animal droppings. Gravel is a great catchment area for small pieces of detritus. Eventually this detritus rots down and forms a layer of soil in the gravel. At first this will add to your surface drainage problems, but it also provides a nutrient rich growth environment for moss and weeds to establish themselves in the gravel surface - on top of the semi-permeable membrane. Eventually this will result in a jungle of weeds growing in your gravel .

Detritus build up requires us to look at several things. First is reducing the volume of detritus falling into the surface in the first place. For example you can prune dead branches on nearby trees and collect grass clippings on the border of the gravel. However, detritus will invariably find it’s way into the surface no matter how effective you are at these measures, so you must regularly remove it from the surface. This can be done with a blower or a rake. Harrowing is most effective and can be carried out at relatively low cost (Svensson & Schroeder, 1992; Tvedt et al., 2000). In Denmark, the use of chemicals was banned on churchyards in 1992 and harrowing the gravel surfaces to remove loose organic material and help loosen the surface has been the most used weed control method in these areas (Tvedt et al., 2000).

Once substantial detritus has been allowed to build up and rot down in the surface, weeds and moss will grow.  These need to be removed along with the soil and detritus in the surface. We offer a heavy duty tool for accomplishing this. The gravel path renovator mentioned before has specially shaped knives which cut under the roots of the moss and most weeds,  lifting them to the surface. Once on the surface they can be raked or blown away.  Weed Burning can also be useful on gravel, and other surfaces as spot treatment once the bulk of the detritus and weeds have been removed. Note; As much detritus and soil must be removed as possible so not to allow a possible growing environment for unwanted plants.

Gravel is a loose material, and therefore the traffic driving or walking over the surface will move the surface filling around. Where traffic is heavy the material will become displaced and it will build up in areas with less traffic. This will make the surface uneven and if left untreated will lead to potholes or ditches in the surface, making it difficult to travel over.

Once again this is an easy fix. The displaced material can be raked back into low spots to leave an even surface. Traffic can also be directed a certain way to minimize displacement. Excess surface displacement on its own is still best remedied by a rake, although in our experience this doesn't usually occur in  isolation, and the gravel path renovator can handle this job at the same same as de-compacting the gravel and lifting the weeds to the surface.   

Like this Blog? Find out more by reading our surface maintenance handbook;