Frequently asked questions about Gravel grids

If you wish to lay gravel surfacing without gravel sheets, you must choose either a coarser type of gravel or gravel with many fine particles.

When using a coarser type of gravel, this will create rutting over time, and the gravel will not stay in place. It is also more difficult to ride through with a bicycle, pram, or trolley. Moreover, the heels on ladies’ shoes sink into the gravel, causing them to get damaged.

You could also choose a finer gravel type to fixate the gravel; however, the use of finer particles (0 - 5 mm or 0 - 15 mm) reduces permeability. This creates puddles, potholes and rutting, and causes the fine particles to stick to the car’s tyres and to one’s shoes.

The use of gravel sheets keeps the gravel in place, and yields a stable and permeable surface without no rutting formation.

Tremendous focus was given to quality during the development of the ECCOgravel sheet. Indeed, ECCOgravel sheets are manufactured from HDPE (High Density Polyethene). By nature, polyethylene - or polyethene - is more flexible than other plastics in the thermoplastic family, such as polypropylene (also called polypropene). In addition, polyethene (contrary to polypropene) withstands freezing temperatures better; the sheet remains flexible even under freezing temperatures, keeping it from breaking or deforming when driven on. The pressure resistance of an ECCOgravel sheet, when filled, goes up to 400 tonnes/m², making it ideally suited for vehicles up to 3.5 tonnes.

Additionally, all ECCOgravel sheets boast synthetic reinforcements between the honeycombs, giving them very high torque resistance. Torque loads are exerted when a car is manoeuvring across the gravel surface (twisting and turning). These reinforcements keep the sheet from deforming.

On top of that, all ECCOgravel grids are equipped with an exceedingly robust anti-rooting mat or geotextile from polyester, which is 100% bonded to the sheet, keeping it from coming loose over time. There is a misconception that a geotextile should have a high density. This is incorrect: a geotextile must be strong, but at the same time water permeable (in other words: it must have an open structure) in order to allow rainwater to permeate into the substrate quickly. Anti-rooting mats that do not have an open structure, as do the ECCOgravel mats, may clog over time, which in turn creates puddles and mud on the gravel surface. If you choose an ECCOgravel sheet equipped with a geotextile that allows for good water permeability, you no longer need to invest in a costly drainage system.

Lastly, ease of use was also considered. Indeed, ECCOgravel sheets are relatively large (120 x 160 cm = 1,92/m² per sheet), but they are bendable to a size of 120 x 80 cm for ease of transport (hence the name “ECCOgravel 30 Double” and “ECCOgravel 40 Double”. This means you can easily transport the mats yourself by car, while still allowing you to install large surfaces at a time.

For instance: a vehicular application (e.g. driveway or parking area) requires more excavation than a non-vehicular application (e.g. walkway or terrace). After all, it is very important to provide a fully structured foundation (otherwise sinking might occur).

Then there is the choice of sheet. For a vehicular application, the ideal choice is a sheet that is 4 cm in thickness (as this provides a better distribution of forces). While for a non-vehicular application, a sheet with a thickness of 3 cm will certainly suffice.

Additionally, there are so many different types of gravel on the market in different price categories (there are gravel types that start at € 2/m², but of course prices vary from type to type, in accordance with your needs and applications). Lastly, the total cost depends on the size of the project.

In short, for a fully accurate price offer, please visit one of our distributors or installers.

As for the choice of the type of gravel, there are four parameters to take into account:

SIZE

We advise against choosing gravel types with a minimum grain size smaller than 4 mm. Finer grain sizes could get stuck in shoes or wedge themselves between car tyre treads. In order to optimally pack the honeycombs, we advise that you limit the maximum diameter of the gravel to 16 mm.

Recommended for applications without cars: 4-8 mm. Recommended for applications with cars: 8-16 mm.

SHAPE

When we speak of round gravel types, we mean pebble. When we talk about broken gravel types we mean gravel. Pebble is nicer for terraces and garden paths, whereas gravel has the advantage that the top layer (this is the layer on top of the honeycomb structure to make the structure invisible) is less likely to shift. Gravel is therefore preferred in places where vehicles will be driving over the surface.

HARDNESS

Hard gravel types are less likely to crumble under moving loads and are less quick to turn green as they retain less water (lower porosity). A soft rock - with a high porosity - on the other hand crumbles easily and dissolves over time. Consequently, soft rock will become water permeable in the long term, leading to puddles and rutting. Moreover, it will turn green on non-sunny sides. Lastly, gravel made from soft rock will produce dust in the summer and stick to one’s shoes in the winter.

COLOUR

Gravel or pebbles are a natural stone and will retain their colour, even after a long time. For lighter gravel or pebble types the best choice is a white ECCOgravel sheet, while for darker gravel or pebble types one would sooner use a black ECCOgravel sheet.

Because of the flexibility of the sheet, and because the gravel is not bound, frost heaving has no effect on the ECCOgravel® surface.

When designing foundations for asphalt and concrete paving blocks, one must always remember to take into account that no water remains in the zone where frost may occur in the foundation. After all, in the event of frost this could lead to the break-up of the asphalt or concrete surface. This is why the foundation depth for such materials is so large. The depth of the foundation for ECCOgravel® sheets is therefore only determined by the loads the surface will need to endure.

Unlike concrete paving blocks or surfaces, ECCOgravel® requires no minimum slope. Even with very heavy rainfall, the buffering capacity will be sufficient to handle the rainwater.

A quick calculation: the maximum 20-yearly rainfall in Belgium is 270 l/s/ha. For 10 minutes, this corresponds with 16.2 l/m².

The rainwater will immediately flow in between the hollow spaces of the gravel and the underlying foundations. Thus we reduce the risk of a reduction in functionality of the surfacing due to water remaining on the surface. A gravel layer of 5 cm may store up to 10 litres of water. It goes without saying that a minimal gravel foundation will take care of the rest.

The maximum slope or gradient is 20%. This matches with a maximum inclination of about 10°. For a slope we recommend that you choose a broken gravel type, as the gravel will “grab hold” as it were, helping to better keep it in place. It is also important to lay the sheets in a half-brick bond.

The 3 cm and 4 cm ECCOgravel® sheets have similar properties (torque resistance, pressure resistance, flexibility, …). However, the distribution of forces (from cars, …) into the foundation is better with a 4 cm plate than with a 3 cm plate.

Example

1. Place a sheet of paper on your hand and hit it with a hammer.
2. Place a phone book on your hand and hit it with a hammer.

Conclusion: the distribution of forces is better in the second case. If we apply this logic to ECCOgravel® sheets, then we may conclude that the foundation will endure reduced stresses when the sheet is thicker.

Summary: you can use ECCOgravel 30 Double plates for vehicular applications, on condition that the foundations put in place are very sturdy. The added cost for this additional reinforcement does not always outweigh the costs saved by choosing a thinner sheet. Moreover, Belgian dealers can also store ECCOgravel 40 Double in larger quantities, so this product is always in stock.

When placing gravel sheets, it is important to provide a solid foundation for the following reasons:

Water permeability: in the event of rainfall, the rainwater must be able to quickly permeate into the substrate. When no levelling layer (and sub-foundation in case of cars) is provided, there are no hollow spaces where this rainwater may accumulate, so you run the risk that the water will remain standing on the gravel. This is why we always advise that you provide a levelling layer (and sub-foundation).

Sturdiness: when you drive over gravel sheets, you are exerting a certain amount of force on the substrate. A large portion of these loads are borne by the sheet. In order to counter sinking in the long term, it is important that you provide a sub-foundation in a coarse rubble (0-32 mm or 0-40 mm), so that these stones may bear the loads. Earth alone cannot withstand these loads, and will start to sink over time.

In short, to allow you to enjoy your gravel surfacing for a long time, we always advise that you provide sufficiently developed foundations. For more information on this matter, visit “placing gravel sheets”.

No, gravel sheets are not suitable for grass. For this purpose it is best to use a grass grid, such as ECCOdal.

The reason is that gravel sheets have a tighter mesh than grass grids, making it more difficult to sow grass into them. Also, gravel sheets come with a geotextile that also serves as an anti-rooting mat (to counter weeds), making it more difficult for plants and grasses to attack to them. This keeps your gravel surfacing free of weeds for longer. With grass grids, a synthetic base is provided with specific properties that are conducive to the sowing of grasses.

All surfaces, whether dealing with gravel sheets, grass grids, pavement stones, tiles, or wood will always require - minimal – maintenance. With ECCOgravel sheets, this maintenance is limited. Maintenance can be subdivided in 4 groups:

SURFACE LAYER

Occasional inspection is advisable depending on the traffic volume and how the surface is used. It is recommended that you cover the honeycomb sheet again in places where it is exposed.

LEAVES

Preferably clear any leaves once a year by raking, blowing, or vacuuming. Tests have shown that the minimum fraction of your gravel can never be less than 4 mm if you wish to avoid gravel pulverisation.

SOIL | MANURE

If soil or manure ends up on the surface, this is best removed with a shovel down to the honeycomb structure. A new layer of gravel (± 1 cm) on top of the honeycomb structure is sufficient to recreate a perfect surface. The soil or manure that has washed into the hollow spaces of the honeycomb structure will have no effect on water permeability.

WEEDS

Consider the following points in preventing weed growth.

Do not use gravel types that have a high porosity. High porosity = water is retained longer = more weeds.

Do not use gravel types with high lime content, as this promotes weed growth.

Create a foundation that has no nutritive constituents and that drains water well.

Any remaining weeds (from seed already present in the soil initially) can be prevented from growing by the geotextile (anti-rooting mat) at the bottom of the ECCOgravel® grids. The weeds can be removed easily by hand, as the roots are concentrated in the honeycomb structure. It is also possible to remove the weeds using hot air or burners. These solutions are preferable to chemical weed killers.

Absolutely, thanks to the open structure of the geotextile (anti-rooting mat) of all our ECCOgravel grids.

In order to guarantee an open and water-permeable structure, it is best not to choose gravel fractions finer than 4 mm. After installation, the gravel will compact, but water permeability will be guaranteed in the long term if you avoid the use of a fine fraction.

If fine particles (e.g. dust, sand, earth, remnants of leaves, …) wash onto the surface over time, this will not affect the water permeability. These fine materials will fill the voids without continuing to be compacted there. The gravel will continue to distribute the load. Due to the presence of the anti-rooting mat at the bottom of the honeycomb structure, fine fractions (e.g. dust) will not wash into the underlying foundations. This guarantees the water buffering properties of the foundations in the long term.

Either too little gravel was used during the placement, or the wrong kind of gravel was chosen. If gravel compaction is significant after placement (this is especially the case if the minimum and maximum fractions show strong variation), this is in itself problematic. This will only manifest itself during the first few weeks after placement. Once compaction is completed, the gravel will not sink any further. The anti-rooting mat underneath the ECCOgravel® sheet helps to ensure this. We strongly advise against the mechanical compaction of the gravel after the installation of the gravel sheets, for instance with the use of a vibrating plate.

For ECCOgravel 40 Double, about 80 kg of gravel per m² is provided, for ECCOgravel 30 Double about 65 kg of gravel per m². The surface layer must be about 1 to 2 cm (depending on the type of gravel).

The gravel in the honeycombs forms a rough surface onto which the loose gravel grabs hold. Because of this, the top layer will show only minimal shifting. Covering the honeycombs with a layer of gravel not only produces the best aesthetic effect, but also maximises the protection of the honeycombs. However, this top layer cannot be too thick, or the effect of gravel stabilisation is lost. The ideal thickness for the top layer is 1 to 2 cm.

Of course you can, if the foundation structure is sufficiently solid. For more information on placement, see here.

In areas where vehicles are parked, an ECCOgravel® sheet system is the perfect solution. The foundation for ECCOgravel® sheets can be designed in such a way as to cope with water from the roadways as well.

With such a foundation, ECCOgravel® can handle the occasional heavy traffic as well. ECCOgravel is therefore ideally suited for parking areas, fire accesses, driveways, etc. A tight reversal manoeuvre of a tractor-trailer combination should be avoided at all times. ECCOgravel is not suited for forklift trucks (due to the tight turning circle these vehicles have).

In places with very intense traffic and speeds over 10 km/h, we recommend that these areas receive a bound surface (asphalt/concrete).

No, for the sale of all our products we work with a network of certified distributors. Our distributors buy our products in large quantities, allowing the consumer (both contractor and private persons) to get the best prices. Moreover, our distributors assist you with technical advice regarding your project.

Yes, but keep in mind the following matters:

Never use more than 150 kg cement/m³. If you use more, the foundation will no longer be water permeable.

Do not use stabilised sand if the soil type has low water permeability. If this is the case, we advise that you use a gravel foundation.

Yes, by doing the following:

Firstly it is important that the depth of the manhole reaches to the rainwater reservoir. As for placement, the pavement stone cover must always be just below the finished surface level. The pavement stone cover must therefore be positioned no higher than the bottom of the ECCOgravel sheets.

We advise against the use of stabilised sand in this setting, as you would need to break it open every time you wanted to reach the rainwater reservoir/water well. As a solution, we propose a concrete block placed on heavy-duty plastic (allowing you to pull out the concrete block with relative ease whenever necessary). You can then place the ECCOgravel on this concrete cover. In this scenario, we advise that you cut the sheets to the size of the pavement stone cover (same size or at the most 5 cm larger), so that you do not need to move a large surface in sheets and more importantly gravel every time.

Lastly, it is important to mark the location of the cover in order to find the rainwater reservoir, for instance by applying markings to a wall. One alternative is to indicate the corners of the ECCOgravel covering the rainwater reservoir with a different colour of gravel.