Yes & No. (Depending on the product) Our honeycomb range Nidagravel 129, 130 & 140 gravel stabilisation grids all have a membrane attached to the underside of the grid or sheet. The membrane is thermally bonded to the bottom of the honeycomb cells in production using a hot glue process and extends on two sides (1 long side and 1 short side) so that it forms an overlap. When installing Nidagravel grids the overlaps of the membrane are laid flat and the adjoining gravel grids are then laid on top of the overlap when butting sheets together during installation. This ensures the continuity of the membrane across all joints.

Why is it important that our honeycomb gravel grids have a membrane?

Having a membrane attached to the underside of our gravel grids is important for several reasons as follows:

1. The membrane prevents gravel from moving underneath the grids and ensures the gravel stays in the individual hexagonal cells.
2. The membrane adds extra stability to both the gravel grids themselves and the installation generally.
3. The membrane helps inhibit weed growth. Making it harder for weed roots to establish themselves in your path or driveway.

Our heavy-duty gravel grid NG040 does not have a membrane attached the the underside as these grids are manufactured differently from our honeycomb grids (Nidagravel 129, 130 and 140) and the base has of NG040 has a plastic matrix for strength and support instead.

In our OCity range of permeable paving grids, OCity NGR65 does not have a membrane attached to the bottom. Again this gravel grid is manufactured differently from our honeycomb grids and it is a dual-purpose grid for use with gravel and grass surface finishes.

Partly. Nidagravel does not prevent weed growth completely, but it does inhibit weed growth, which is slightly different. Unfortunately, there is no way to completely prevent some wind blown seeds from germinating in a gravel surface, that's just nature. But Nidagravel does inhibit and help reduce weed growth in the following ways:

The membrane on the underside of Nidagravel 129, 130 and 140 gravel grids helps prevent any weed growth emerging from the sub-base or sub-grade. There should not really be any weed growth growing from under the sub-base. When installing a sub-base it is best practice to lay a heavy-duty, porous membrane underneath.

The membrane on the underside of Nidagravel 129, 130 and 140 gravel girds also helps to deter deep-rooted perennial weeds from penetrating the sub-base and becoming fully established.

Any weeds that do manage to establish themselves should have a small root structure. The growth of any weed roots are restricted to an individual cell. The weeds cannot penetrate the plastic side walls of the cell and the membrane beneath inhibits the roots penetrating the sub-base. As Nidagravel grids are 100% water permeable, during hot dry periods in the summer, many weeds will soon suffer from a lack of water and eventually dry out and die.

Any weed that does appear through wind-blown seed or bird droppings is unable to anchor in the gravel within the Nidagravel honeycomb and can easily be removed.

A Nidagravel gravel grid surface, whether it's a gravel garden path, a gravel driveway, or a gravel car park, should be maintained in the same way as any outdoor space. When it comes to weeds, these can either be removed simply by hand or sprayed off with a suitable chemical weed killer.

This depends on which of our gravel grids you choose. We recommend the following gravel sizes for use with our gravel stabilisation grid range:

Nidagravel 129 Gravel Grids
Maximum gravel size approx 10/12mm
Minimum gravel size approx 4/6mm
If using a mixed-size gravel then a gravel type with a size range of 4 - 14mm is acceptable to use.

Nidagravel 130 Gravel Grids
Maximum gravel size approx 10 /12mm
Minimum gravel size approx 4/6mm
If using a mixed-size gravel then a gravel type with a size range of 4 - 14mm is acceptable to use.

Nidagravel 140 Gravel Grids
Maximum gravel size approx 18/20mm
Minimum gravel size approx 4/6mm
If using a mixed-size gravel then a gravel type with a size range of 4 - 20mm is acceptable to use.

Nidagravel NG040 Gravel Grids
Maximum gravel size approx 14mm
Minimum gravel size approx 4/6mm
If using a mixed-size gravel then a gravel type with a size range of 4 - 14mm is acceptable to use.

OCity NGR65 Gravel Grids
Maximum gravel size approx 14mm
Minimum gravel size approx 4/6mm
If using a mixed-size gravel then a gravel type with a size range of 4 - 14mm is acceptable to use.

We recommend the above gravel sizes, as these sizes of gravel fill the individual cells of the Nidagravel grids nicely and allows the gravel to compact well within each cell with minimal void spaces. This ensures the cell walls are supported giving Nidagravel a very high compressive strength. Using this size of gravel also means that Nidagravel grids are 100% rainwater permeable and free draining across the total area of the installation.

Whatever gravel you choose, we recommend that you use angular gravel, chippings, or decorative aggregates. Angular or irregularly shaped gravels will naturally interlock well and when angular gravels are used in combination with Nidagravel grids, this gives maximum surface stability and makes for an extremely stable and strong surface.

Yes, we certainly can!

Choosing the right gravel grid
Nidagravel UK is the 'Home of Gravel Grids!' We manufacture a wide range of gravel grids to suit different sizes and types of gravel stabilisation projects and our gravel grids come in a range of grid sizes, thicknesses and colours. If you need help selecting the right gravel grid for your project please contact the team who will be happy to help and advise you on the right gravel grid for you.

Bespoke gravel grids manufactured to order
For larger projects we can manufacture a bespoke batch of gravel stabilisation grids to suit your project. This can only done for larger projects as the production team has to set up a special production run in the factory and therefore there is a minimum order quantity. We can manufacture our gravel grids in a range of standard and non-standard colours to suit your requirements. If this is of interest please contact us to discuss your project and see what is possible.

When installing any of our gravel stabilisation grids for paths and driveways, it is not uncommon to find manhole covers of varying shapes and sizes located where you are installing your gravel grids. One of the most common places to find a manhole cover on your property is on the driveway as drains often exit a property down the driveway where they join up to the main sewerage system. Depending on the age of the property the design and construction of the manhole or inspection chamber will vary along with the size, shape, and type of manhole cover that sits on top. The only way to find out what type of manhole you have is to lift the lid and take a look. Older properties may have a brick-built manhole and a cast iron manhole frame and cover sitting on top. Modern and newly build properties will usually have a plastic circular inspection chamber with a base unit at the bottom and a number of riser sections fitted on top which lead up to the finished ground level and the inspection or manhole cover. Manholes can vary in depth from 400mm to 1m deep or more. Once you have identified the type of manhole you have you can decide how you want to deal with the manhole cover. We will cover the steps required to adjust your manhole cover in the sections below.

Changing Levels - New gravel driveway
You may be changing the levels slightly when installing a new gravel driveway or refurbishing an existing driveway, which means you may have to adjust the height of your manhole chamber before you can change the manhole cover. This might sound like a daunting task, but it is in fact not that difficult to do and a competent DIYer should be able to complete this.

Changing Levels - Refurbishing a concrete or tarmac driveway
Where customers are refurbishing their existing concrete or tarmac driveway with Nidagravel grids to create a gravel driveway surface then manhole covers are usually raised slightly so that they finish flush with the Nidagravel surface that sits on top of the concrete or tarmac. Nidagravel grids are the only way to effectively stabilise gravel on a concrete or tarmac surface. The thickness of our gravel retention system when installed varies slightly depending on the grid used, but manholes are usually raised by 50 to 70mm or in accordance with new site levels where adjustments have been made.

Choosing and changing your manhole cover
Manhole covers come in various shapes, sizes, and colours as we have mentioned before, which means there are plenty of options available when it comes to changing your manhole cover. It is important to remember that a manhole cover is there to allow you to inspect your drains and to allow access for drainage rods that are used to unblock a drain, so the frame and cover need to be installed properly and allow access. When it comes to choosing your manhole cover your first decision to make is - do you want to see a manhole cover or would you prefer to make it blend in with the driveway surface. If you are happy to see the manhole cover, then if your existing manhole cover is in good condition - simply re-use it. It's the quickest and simplest option and you know it will fit onto your chamber. If your manhole cover is old or damaged, you can replace it like for like. If you are doing this you should measure the frame and cover or better still take them will you to your local builder's merchants and find a suitable replacement. You may have a circular, square, or rectangular cover in place.

Adjusting brick-built inspection chambers with cast iron frames and covers
Older properties will probably have a brick-built inspection chamber and the underground pipework is probably salt-glazed pipework, rather than plastic pipework which is used today. Original manhole covers are often made of cast iron and are pretty heavy. You can still purchase cast iron manhole frames and covers today, so there is no problem replacing an old damaged one. Replacing a manhole cover and adjusting the height of the inspection chamber does not interfere with your drains, it is usually a small adjustment to suit the new finished surface level. To reduce the height of a brick-built manhole, you simply need to remove the cover and knock off the frame with a lump hammer and chisel. Then you can knock off one, two, or three courses of bricks to take you down to the required level, taking into account the thickness of your new manhole cover. It is a good idea to put a plastic sheet or similar inside the chamber while removing bricks so that any debris is caught and can be removed (obviously, remove this when you are finished, do not leave it in the drain). You do not want half a brick falling into your drain as it will cause a blockage. It's also a good idea to request that no-one uses and flushes the loo whilst you are working on the manhole chamber or you might get a nasty fright! Once you have reduced your brickwork, simply mortar the new frame and tray into position at the correct level. Point everything up neatly inside and out and you're done.

If the manhole cover is too low. Then it is simply a case of adding extra layers of brickwork to bring the chamber up to the required level and fitting the new manhole frame and cover. Again take precautions to prevent debris from falling into the drains.

Adjsting circular plastic inspection chambers with plastic frames and covers
Modern inspection chambers are often made of plastic. Usually, there is a base section, where the pipe entries are, and then a number of connecting risers that are added on top of the base and lead up to the finished height with a frame and cover on top. The principle of reducing the chamber is the same as a brick chamber, but instead of knocking off courses of brickwork, you will cut down the plastic riser with a saw. The simplest way to do this is 'in situ'. So if you need to reduce the height of the chamber by 150mm, for example, you can dig out around the manhole riser giving yourself approx 30cm clearance all around and to a depth of about 200mm. This will give you access to saw the riser down whilst keeping it in position. There are often lines in the plastic that you can follow to ensure you make a level cut. You may find the manhole has not actually been set level or the riser section has moved a bit over time. When making your cut, you can factor this in and make a correction so that top of the riser becomes level. Then you can simply backfill, compact, and mortar your new frame and tray into position. This technique will work well for medium to deep chambers. If you are working with a particularly shallow chamber then you may have to take a slightly different approach to achieve the same result.

To increase the height of the chamber, you will need to buy a new riser of the correct diameter that will fit onto the risers below. The risers are normally sold in standard heights. So, you may still need to cut the new riser down a bit to finish at the required height when fitted. To fit the new riser, again it is best to dig out around the top of the chamber a bit and clean off the top of the riser you are adding to. Make sure there is no grit or mud left on the rim, so that you get a nice snug fit when you put the new riser on top. Again backfill and compact as required and mortar the new frame and tray into position.

We recommend the use of angular or irregularly shaped gravel to fill our gravel grids because the angular shape naturally interlocks together well and when combined with our gravel grids this gives maximum stability and a very stable gravel surface. Angular-shaped gravels or decorative aggregates are not a special type of gravel. Most types of gravel available to buy in the UK are angular in shape and include gravel types like golden flint, black basalt chippings, granite chippings, limestone, and Cotswold chippings, etc. These types of gravel are widely available from sand and gravel suppliers, builders merchants, and online suppliers across the UK and there is a huge range to choose from with colours varying from white to black and various shades of buff, brown, and grey gravels in between.

Small round pebbles are best avoided. Scottish pebbles are a good example of gravel that is not ideal to use with your gravel grids as they are very smooth and rounded and do not interlock together well.

If you are unsure if the gravel you have chosen is suitable to use with your Nidagravel gravel stabilisation grids please do not hesitate to contact us for advice. Please send us an email with the specifics of the gravel you intend to use and the sales team will be happy to advise you on suitability.

Yes, Nidagravel gravel stabilisation grids are suitable for wheelchairs. Nidagravel grids form a stable and firm gravel surface that is suitable for wheelchair users, mobility scooters, and other users with a disability. Nidagravel grids have been used both in the UK and Europe for a wide range of projects where access for disabled users in wheelchairs is a requirement.

Under the current government building regulations which cover 'Access to and use of Buildings'. There is a section referred to as 'Approved Document M' which ensures that people are able to access and use buildings and their facilities. Set out within this document are a large number of building regulations that cover all aspects of the design of a building, taking into account disabled users. This document covers everything from ramp gradients and path widths to handrail heights and flush thresholds. It also provides some notes on external surfaces for wheelchair users, although the details of what makes a suitable external ground surface for a wheelchair user are, to be honest, a bit vague. The following are some notes regarding external ground surfaces for wheelchair access taken from the current version of the 'Approved Document M':

1. Document reference - 3.45 Private Outdoor Space (Part F, Page 50)
All paved areas have a suitable ground surface

2. Document reference - Appendix A: Key Terms - Suitable Ground Surface Note (Page 53)
The external ground surface is firm, even, and smooth enough to be wheeled over, is not covered with loose-laid materials such as gravel and shingle, and has a maximum cross fall of 1:40

So not a great deal to go on, but Nidagravel gravel stabilisation grids do satisfy the criteria require within the 'Approved Document M' as follows:

1. Nidagravel grids do create a firm, even surface that is smooth enough to be wheeled over.
2. Nidagravel grids contain gravel within a system of honeycomb cells. The surface is not loose gravel or shingle.
3. Nidagravel grids do not require a cross fall for drainage like paving slabs as they are 100% permeable. They can be laid on a perfectly flat and level surface.
4. Nidagravel grids are also referred to as 'Porous Paving' and also fall under the category of paving when dealing with external surfaces.

So, there is no issue using Nidagravel gravel stabilisation grids for projects such as pathways, driveways, and entrances that are going to be used by wheelchair users. It is more a case of using a common-sense approach to the design of the space and dealing with site levels that are the two most important factors in ensuring the project is as suitable as it possibly can be for wheelchair users. Ensuring that there is plenty of space and room for a wheelchair user to maneuver comfortably and wherever possible creating level areas and shallow, gradual slopes and ramps are key to a successful project that is easy for a wheelchair user to access.

Click the link below to download and view the full 'Approved Document M'
Building Regulations - Approved Document M

We recommend that customers use Nidagravel 140 gravel grids for gravel up to 20mm in size. Nidagravel 140 gravel grids are 2m long x 1.2m wide and 40mm thick. The extra depth of the Nidagravel 140 grids can accommodate the use of decorative gravels up to 20mm in size. We recommend that 20mm gravel is the maximum size gravel that can be used with Nidagravel 140. Any gravel larger than this size is not suitable for use with Nidagravel 140 and should not be used.

Our heavy-duty commercial grid Nidagravel NG040 can also accommodate gravel sizes up to 18/20mm.

You can also use smaller gravels, chippings, and decorative aggregates with Nidagravel 140 and Nidagravel NG040 gravel grids. The smallest single-size gravel we would recommend using is 6mm. So there is a wide choice of decorative gravels available to choose from.

Yes, you can. In fact, you can probably park several. When Nidagravel grids are filled with gravel they achieve their full compressive strength. Our gravel stabilisation grids are specifically designed for stabilising gravel. Nidagravel grids are also designed to be lightweight with a very high compressive strength when filled with gravel. All our gravel grids have multi-purpose uses and they can all be used for driveways, the choice of gravel grid for your project will mainly depend on three things, the area of the driveway, the size of gravel being used, and the slope gradient of the driveway. Our range of honeycomb gravel grids, Nidagravel 129, 130, and 140 are normally used for residential driveways. Our heavy-duty commercial gravel grid Nidagravel NG040 is not normally needed for a domestic driveway, but in some circumstances, it can be the appropriate grid to use. For technical advice or to discuss a project please contact us.

Nidagravel 129 Gravel Grids
Compressive Strength, when filled with gravel, is in excess of 300 tonnes per sqm
Suitable for driveways with an area up to 50 SQM (approx.)
Link to Nidagravel 129

Nidagravel 130 Gravel Grids
Compressive Strength, when filled with gravel, is in excess of 300 tonnes per sqm
Suitable for driveways with an area over 50 SQM
Link to Nidagravel 130

Nidagravel 140 Gravel Grids
Compressive Strength, when filled with gravel, is in excess of 400 tonnes per sqm
Suitable for driveways over 50 SQM. Heavier use driveways and steeper sloping driveways.
Link Nidagravel 140

Nidagravel NG040 Gravel Grids
Compressive Strength, when filled with gravel, is in excess of 800 tonnes per sqm
Suitable for heavy-duty commercial driveway and car parks.
Link Nidagravel NG040

View our gravel stabilisation grid driveway projects
Nidagravel Case Studies

The compressive strength tests have been undertaken by the manufacturer Nidaplast using an ISO844 test method. Nidagravel gravel stabilisation grids are made by Nidaplast in France and they specialise in manufacturing honeycomb plastic products for a wide range of applications and industries. In fact, Nidaplast is considered a world leader in the production of honeycomb plastics, so you can be assured of the quality and durability of our gravel grids.

Yes you can. Nidagravel gravel grids can be laid directly against house brickwork without causing any problems to the house brickwork or foundations. Nidagravel grids are 100% permeable and allow rainwater to pass directly through the honeycomb sheets, which will then percolate away through the sub-base and sub-grade. It is important to note that any finished external surfaces that surround a house our building should not breach the DPC (Damp Proof Course) and building regulations currently recommend that finished external surfaces be 150mm below the DPC, which is approximately 2 courses of metric brickwork

You cannot fill Nidagravel 129, 130, and 140 gravel stabilisation grids will soil as they are specifically designed for stabilising gravel surfaces, whether that's a gravel garden path, a gravel driveway or gravel car park. These gravel grids are not designed to be filled with soil.

We have a grass reinforcement grid that is designed to be filled with soil and seeded with grass seed to create grass driveways and parking areas. Nidagrass NG040 grass grids are green in colour to blend in with the grass and are made from 100% recycled plastic. For more information on our grass grids and to order online click the link Nidagrass

No, you do not need to peg down Nidagravel gravel grids and we, therefore, do not supply any pegs or similar products. Pegging down, clipping together, or using any other form of fixing clip is simply not required when installing Nidagravel gravel stabilisation grids. Nidagravel grids are laid out over a prepared sub-base with each sheet butted together. On large projects, we recommend that our gravel grids are laid in rows with a staggered joint. A bit like laying bricks in the standard stretcher bond pattern. This is not absolutely essential, but it is good practice as it offsets the joints between sheets. Once our gravel grids are installed as per our installation guidelines and filled with gravel - the weight of the gravel is more than sufficient to hold the grids in place, even on slopes of up to 15%.

The weight of gravel holding down a single sheet of Nidagravel 130 is approx. 168 - 180 kg (per sheet)

The weight of gravel holding down a single sheet of Nidagravel 140 is approx. 192 - 204 kg (per sheet)

No pegging down is required. Nidagravel grids can be laid on slopes up to 15% or 8.53 degrees and do not require pegging down

No clipping sheets together. Little plastic clips are not required and do not offer additional strength benefits

No. Specialist tools are not required to lay, cut or fill Nidagravel grids. Our gravel stabilisation grids are simple to install and any competent DIYer can install our grids following our installation guidelines. A selection of standard tools are all that is required as follows:

Tools required for laying Nidagravel grids
None required. Both our small grids (Nidagravel 129) and our large grids (Nidagravel 130 and Nidagravel 140) are lightweight and easy to handle. One person can simply pick up a gravel grid and lay one at a time. When laying our grids, you will notice two overlaps of the geotextile membrane on one long side and one short side of the grid. Make sure the long overlap is facing you, which should mean the short overlap is on the right-hand side. This allows you to fold out the overlaps and lay them flat against the sub-base. You can then lay your next sheet against the sheet you have already laid. Laying it on top of the overlap of membrane. This ensures the membrane runs under all the joints. Nidagravel grids do not require pinning in place and do not require any fixing clips. The sheets are butted up to each other and when filled, the weight of the gravel it more than sufficient to hold the grids in place.

Tools required for cutting Nidagravel grids
The simplest way to cut Nidagravel grids is with a small angle grinder. Any size angle grinder is fine to use and a standard masonry or diamond grit cutting disc is suitable. An angler grinder will cut quickly and cleanly straight through the grid and membrane. When installing your Nidagravel grids in rows, when you get to the end of a run, you will inevitable have to cut the grid to fit. You can cut Nidagravel to any shape and cutting grids to follow a curved edge is really easy to do. When cutting Nidagravel to fit, we recommend that the piece to be cut is measured accurately. There is some tolerance or leaway when cutting Nidagravel grids and a gap of 10 - 20mm is acceptable. The grids should not be forced into position or pinched as they need to sit flat against the sub-base. When the grids are filled with gravel, you can also fill in any small gaps around the perimeter of the installation.

Tools required for filling Nidagravel grids
To fill your Nidagravel grids, a shovel, wheelbarrow and rake are all that is required. Once you have laid your gravel grids it is important not to move any heavy loads onto them, as they do not achieve their full loading bearing strength until filled with gravel. The best way to fill Nidagravel grids with gravel is to start in one corner or along one edge and fill this section with gravel. Using the back of a rake, rake out the gravel to fill the cells, making sure that you over fill the cells by 20 - 25mm as you go. Then working off the section of Nidagravel you have just filled you can continue to fill the grids with gravel until you have covered the full area.

The principles above also apply to installing large areas of Nidagravel.

Nidagravel is specifically designed for stabilising gravel surfaces and to be light in weight with a very high compressive strength when filled with gravel. Nidagravel grids vary in weight depending on the product as follows:

Nidagravel 129 Gravel Grids
Weight 1.25 kg per grid
Weight 1.3 kg per sqm

Nidagravel 130 Gravel Grids
Weight 3.24 kg per grid
Weight 1.35 kg per sqm

Nidagravel 140 Gravel Grids
Weight 4.32 kg per grid
Weight 1.8 kg per sqm

For more details please read the product descriptions for each Nidagravel gravel stabilisation grid. You can also download a technical data sheet for each of our gravel grids, which provides full technical information.

Nidagravel 129, 130 and 140 gravel stabilisation grids are all very easy to cut to size on site. Two methods are commonly used to cut Nidagravel gravel grids. The simplest way to cut Nidagravel grids to shape is with an angle grinder. Most landscaping and building contractors opt to cut sheets using petrol saws or electric angle grinders, as this gives a nice clean cut and is quick to complete. A diamond grit or masonry disc can be used and these discs will cut easily through the polypropylene honeycomb sheets and the geotextile membrane on the underside.

Alternatively if you are a DIYer, then a handsaw can be used, which is still a pretty quick way quick to cut through Nidagravel grids. We recommend using a fine tooth saw with 9 or 10 TPI (teeth per inch) rather than a course saw blade, which can snag on the honeycomb cells. When cutting gravel grids with a handsaw, you will need to measure and mark the piece to be cut first and then place this on something suitable for cutting.

Nidagravel gravel stabilisation grids are simple to cut to fit any shape, size or angle. Whether that's a straight cut, an acute angle or long sweeping curves. This makes Nidagravel a very versatile option for stabilising your gravel surface no matter how complicated the layout or design. Nidagravel grids are frequently used for paths, driveways, and car parks, but have also been used to stabilise gravel in some elaborate garden designs including formal gardens, a maze and some intricate swirling patterns.

Yes, you can. Nidagravel gravel grids are the ideal way to stabilise gravel that is to be laid directly over concrete, tarmac and block paved driveways. In fact, a gravel grid is the only way you can install gravel successfully over a solid slab. It is also probably one of the most cost effective ways to refurbish an existing concrete driveway. Using Nidagravel grids as an overlay to an existing concrete driveway means that you will save on the time, noise, mess and cost of breaking out and removing a large expanse of concrete, which in many cases will need to be replaced with a new sub-base.

When we talk about installing Nidagravel grids, we often talk about a sub-base and compacting it properly. The reason for installing a sub-base is to create a firm, level, stable foundation onto which the surfacing layer can be installed. If you already have a concrete, tarmac or block paved driveway then this is already a firm, stable foundation and Nidagravel grids can be laid on top. When installing Nidagravel grids over a concrete driveway there are a number of points to take into consideration to ensure that you can complete a successful installation, as follows:

Is the concrete base structurally sound?
Your concrete or tarmac base needs to be structurally sound, as you don't want it to start crumbling or subsiding. If your concrete slab has been in situ for years and has previously been used as a driveway, then it's likely to be thick enough and any settlement of the surface will most likely have already happened. There may be settlement cracks in the surface of the concrete, but this is not necessarily a problem if the slab has already settled. If you have any concerns about the stability of your concrete slab, you can seek professional advice from a contractor. You can also cut out a section of the slab to check how thick it is and to see what it is laid on. Once you are happy that your concrete slab is sound, you may need to repair the slab as required to ensure you have a flat surface to work off. This may be as simple as screeding over a sunken area with a strong mortar mix to level up the concrete slab.

Are there any drainage issues with the existing concrete driveway?
As Nidagravel grids are 100% permeable, any rainwater falling on the surface will gradually pass through the gravel grids and make its way along the concrete slab below following any existing falls until it reaches an existing drainage point. The drainage characteristics of the concrete slab will therefore remain the same. If there are any issues with drainage, such as pooling water, etc these will need to be addressed before you install Nidagravel gravel stabilisation grids.

What are the levels of any DPC's of any buildings adjacent to the installation?
When installing Nidagravel grids over an existing concrete driveway, you will of course, be raising the finished surface level slightly. It is therefore important that you do not breach any DPC's (Damp Proof Courses). On new properties, you will usually find the DPC is two courses of brickwork or approx 150mm above finished exterior surfaces. On older properties, the DPC may be in a different position.

Nidagravel 129 Gravel Grids
This gravel grid 29mm thick
Plus depth of overfill gravel of approx 20mm
Total thickness when installed is approx 50mm (on top of concrete slab)

Nidagravel 130 Gravel Grids
This gravel grid 30mm thick
Plus depth of overfill gravel of approx 20mm
Total thickness when installed is approx 50mm (on top of concrete slab)

Nidagravel 140 Gravel Grids
This gravel grid 40mm thick
Plus depth of overfill gravel of approx 20mm
Total thickness when installed is approx 60mm (on top of concrete slab)

How to deal with level changes at the entrance to the driveway or garage
As the finished surface level will be increased by 50 - 60mm dependant of which gravel grids you plan to install. You may need to adjust the driveway entrance so that the Nidagravel grids sit flush behind a kerb or threshold of block paving or stone setts. You may also need to adjust the levels at the entrance to a garage, as the garage door may not open / close due the increase in height of the surface. There may not be an issue with either of these things, but it is a common issue to overcome when laying Nidagravel grids over an concrete surface. Depending on your project there may be a number of solutions, but one solution is to cut the slab back by approx 1.5m at the driveway and garage entrance. The concrete should be broken out and removed. It can then be replaced with sub-base material, which can be graded and compacted to finish flush with the concrete slab and taper down so that it finishes 50 - 60mm lower than the kerb at your driveway entrance or garage floor. The Nidagravel grids can then be installed in the normal way on top of these graded sections and this will ensure that the finished gravel surface is completely flush and at the same level as the original concrete slab. This will ensure that you can drive smoothly onto the gravel grids when entering your driveway and also when driving into your garage.

Nidagravel gravel stabilisation grids are 100% permeable. The full surface area of a Nidagravel gravel path, driveway or car park will be permeable. Any rainwater that falls on to the Nidagravel grid surface will immediately drain through the stabilised gravel surface and percolate (filter gradually through a porous surface) through the sub-base and sub-grade.

Ideally yes, but this can be optional, subject to the application, and is ultimately up to the customer. Where gravel surfaces are stabilised with Nidagravel grids it is certainly a good idea to use some sort of edging to separate your gravel surface from your lawns or borders. Where your Nidagravel grid surface finishes against a boundary wall, house wall, paved or hard surface, it may not be necessary to install an additional edging in these locations. Whatever edging option you decide to install, it must be fit for purpose and robust enough for its intended usage, so that the edging functions correctly over the lifetime of the installation. Below are some edging options that can be used with Nidagravel gravel grids:

Pathway Edgings
Pathways that are only going to have foot traffic can be edged with almost any type of edging material. These include timber edging, metal edging, bricks, stone setts, block pavers, and decorative edgings such as scalloped of victorian edgings. Installation of these types of edgings vary, but they can be pegged into place or concreted into position subject to the type of material being used.

Driveway Edgings
Edgings to driveways must be robust enough for the intended application and installed correctly so that they can withstand being driven over accidentally. We would recommend that all driveway edgings are concreted into position and backed up with a mortar haunch, as required. Thin timber edgings are not really suitable to use for a driveway edging. Treated landscape sleepers, oak sleepers, or reclaimed railway sleepers can be used as driveway edgings as these are sufficiently large pieces of timber for external use. Timber sleepers should still be concreted into position when installed as a driveway edging. Metal edgings can be suitable for driveway edgings provided that the metal edging itself is sufficiently thick and strong enough. Some types of metal edgings are pinned into position, but it is also recommended that when used for driveways, that metal edgings are also concreted into position. Stone and masonry edgings are often suitable to use as driveway edgings and include granite setts, block pavers, concrete kerbs, engineering bricks, clay paviors, and natural stone edgings, etc. This type of edging is usually concreted into position and jointed, as required. Depending on the type and size of the edgings being used, they can either be installed flush (at the same level) with the gravel surface, or in the case of an attractive, decorative edging they can be partially visible so that the edging design can be seen.

The two main reasons to install robust driveway edgings and concrete them into position is firstly to ensure that the edging material itself is strong enough to take the weight of a vehicle without being damaged. Secondly, when driveway edgings are concreted into position, the concrete bedding and haunch, not only ensure the edgings are fixed securely, but it also supports the perimeter edge of the sub-base and prevents any lateral movement or subsidence of this part of the sub-base when the weight of a vehicle is imposed on the very edge of the driveway.

Driveway Entrances
The entrance to a driveway may need be to treated slightly differently to the edgings that are installed to the perimeter of the driveway. It is important that, at the entrance to the driveway, Nidagravel grids are laid flush with the driveway entrance levels, so that any vehicles entering the driveway can drive onto the gravel grids smoothly. This ensures that the gravel grids cannot move laterally and that the leading edge of the gravel girds are protected behind the driveway entrance edgings. It is both good practice and makes for an attractive driveway entrance, to lay a band or threshold of block paving, stone paviors, or setts across the entrance to a driveway. When laying a stone sett or black paver threshold to a driveway entrance, it should cover the full width of the entrance. The depth may vary from 3 - 4 courses of setts or paviors to several meters depending on the design and layout of the driveway entrance.

Commercial Edgings
Where Nidagravel gravel grids are installed in any commercial or public setting it is important to install a suitable and robust edging.

No, you will not see the honeycomb gravel grids at all once installed and filled with gravel. Nidagravel 129, 130 and 140 gravel stabilisation grids are specifically to stabilise gravel. They are also designed to be lightweight with a high compressive strength and invisible when installed. When you have installed and cut your Nidagravel grids to fit, you are ready to fill them with gravel.

When filling our honeycomb grids with gravel you fill them to the top of the grid and then overfill them. If you are using 10/12mm max. size gravel then the overfill will be 20 - 25mm thick and if you are using 18/20mm max. size gravel the overfill will be 30-35mm thick. This will ensure that you have good coverage of the overfill layer subject to the gravel size being used. The overfill layer allows for natural settlement and compaction, which will happen after the gravel grids are filled, as the gravel settles down or 'beds in' to the individual cells. The surface covering of gravel also hides the grids from view, so all you will see is a lovely, flat gravel surface.

Using Nidagravel grids will ensure your gravel surface remains stable, prevents potholes and ruts from developing and makes walking, driving and using the surface generally much, much easier.

Yes, you can use Nidagravel gravel grids on a sloping driveway. In fact, Nidagravel grids are ideal for sloping gravel driveways as they stabilize the gravel surface and help prevent any gravel migration and loss of gravel. Our gravel stabilisation grids work by holding the gravel within honeycomb cells, which prevents the gravel from moving. A surface layer of gravel is laid on top and this interlocks with the gravel that is held within the cells. This results in a very stable surface with minimal movement of gravel. The Nidagravel system is also completely permeable and designed to be invisible.

Nidagravel gravel grids can be used on sloping gravel driveways of any gradient up to 15%. The maximum slope gradient of 15% equates to 8.53 degrees or a ratio of 1:6.67. In simple terms, if describing the maximum gradient as a fall, it would be a fall of approx 15cm per metre. On slopes of up to 15%, the Nidagravel system will perform effectively with very low gravel migration. Whilst Nidagravel could be laid on steeper gradients, we do not recommend this as it may lead to greater movement of the surface layer of gravel over time.

You can find further information about laying Nidagravel grids on a sloping driveway by clicking on the link below. We also have a Gradient Calculator to help customer calculate the gradient of their driveway
Gradient Calculator

For sloping driveways that have a gradient close to 15% we recommend using Nidagravel 140, as this is our highest specification of honeycomb gravel grid and most suited to gradients up to a maximum of 15%. Nidagravel 140 gravel grids are 2m x 1.2m in size, 40mm thick and each sheet covers 2.4 SQM. If the slope gradient is between 10 - 15% we recommend using Nidgravel 140, our most robust honeycomb grid, which holds a greater quantity of gravel making it ideal for containing gravel on a slope.

For heavy use on a sloping gravel driveway that has a 10 - 15% slope gradient, you can also use our commercial-grade grid Nidagravel NG040.

This depends on which Nidagravel gravel stabilistion grid you are using. You will require the following amounts of gravel to fill your Nidagravel sheets:

Nidagravel 129 - Approx. 70 kg of gravel per sqm (Each grid covers 0.96 sqm and requires approx. 67 kg of gravel to fill)

Nidagravel 130 - Approx. 70 kg of gravel per sqm (Each grid covers 2.4 sqm and requires approx. 168 kg of gravel to fill)

Nidagravel 140 - Approx. 80 kg of gravel per sqm (Each grid covers 2.4 sqm and requires approx. 192 kg of gravel to fill)

Nidagravel NG040 - Approx. 80 kg of gravel per sqm (Each grid covers 0.25 sqm and requires approx. 20 kg of gravel to fill)

When filling your Nidagravel honeycomb gravel grids you should fill the grids to the top with gravel and then overfill the grids by approx. 20 - 25mm. (subject to gravel size used) The gravel overfill allows for some natural settlement and compaction of the gravel as it settles into the honeycomb cells after installation. After any initial settlement, there should be a layer of gravel approx. 15mm thick on top of your gravel grids. The above gravel calculations take into account overfilling the grids. This surface layer of gravel hides the grids, so all you will see if nice, flat and level gravel surface. We recommend that the surface is inspected visually, 2 - 3 weeks after installation. If any areas have overly compacted and the Nidagravel grids are visible, simply top up with more gravel. Also, if there are any high spots / areas of deep gravel on top of the grids, these should be raked out accordingly. Once the gravel fill as settled in over the first 2 - 3 weeks after installation there should be no further movement.

For gravel driveways, we recommend using angular gravels, chippings or decorative aggregates as these naturally interlock well and when combined with Nidagravel grids create a particularly stable and hard wearing gravel driveway surface. In addition to this, we recommend choosing a naturally hard stone, which can take the weight of regular use by cars and other vehicles without crushing over time. Some examples of hard stone include flint, granite, and quartz-based decorative aggregates. Some softer gravels and chippings are prone to be gradually crushed over time when driven over regularly and are best avoided.

Finally, we recommend that customers use a 10 - 12mm maximum size gravel with our Nidagravel 129 and Nidagravel 130 grids and a maximum size gravel of 20mm with our Nidagravel 140 grids. You can use smaller sized gravels with all our grids, but we would recommend that the smallest size gravel be approx. 6mm. There is a wide selection of decorative gravels available in the UK that can be used with the Nidagravel gravel grid system and these include gravels like Golden Flint Gravel, Staffordshire Pink Gravel, Black Basalt Chippings, Silver Granite Chippings and many more. There are also a wide range of gravel suppliers around the UK including local quarries, garden and landscaping centres and builders merchants.

Working out the gradient of your gravel driveway is quite simple to do. In order to calculate the gradient, you will need to know the length of the sloping section of your gravel driveway. We call this measurement the RUN. This is an easy measurement to take, simply use a tape measure or measuring rod, and measure the distance from top to bottom and record your answer. The next measurement you need to take is the difference in height between the top and the bottom of the driveway. We call this measurement the RISE. Depending on how steep and how long your gravel driveway is, this can be a little bit tricky, but you need to know this measurement in order to calculate the gradient. There are a number of ways to obtain the RISE measurement as follows:

1. Use a self-leveling rotational laser level with surveying staff and detector. This is a professional bit of kit which contractors will use on site for setting levels and simple surveying, but if you have access to this bit of equipment it's the quickest way to take an accurate measurement. The laser level sits on a tripod, levels itself, and then projects a laser dot or beam. The detector which attaches to the surveying staff reads the laser beam and emits a beep when it detects the beam. The surveying staff, which is usually telescopic and extends to 5m in height is marked from 1cm to 5m. So once set up, this system is very quick and very accurate.

2. Use a basic laser spirit level mounted on a tripod and a tape measure. The principle is the same as using the professional kit above. The laser spirit level and tripod kit can be purchased from any well known DIY store and this is set up and used to project a level laser dot. The laser dot can be difficult to see in bright sunlight, so it is best to do this on a cloudy day or early evening. Take a piece of white A4 paper and waive this in front of the laser to help you locate the laser dot, then measure from the driveway surface to the dot to get your RISE measurement. You may find that this laser set up is not big enough to take the measurement between the top and bottom of the driveway in one go. If this is the case, you would take a series of measurements up the slope, by measuring and moving the laser tripod set up. Add the results together to get your total RISE measurement.

3. Time to go old school and get the string line out. This is a two-man job (two-person job). When obtaining your RISE measurement this way you will need to hammer a stake or pin into the top of the driveway. Then attach the string line to the stake or pin and ensure that the string line is touching the surface of the driveway. Walk down to the bottom of the sloping driveway reeling out the string line as you go. At the bottom of the driveway attach a simple string line spirit level. A string line spirit level can be purchased from any well known DIY store. It's small, inexpensive, and fits in the palm of your hand. As the name suggests, it's basically a tiny spirit level with two clips to attach it to a string line. Pull the string line as taut as you can, without pulling the stake or pin out and without snapping the line. When the string is taut and level, ask your friend to measure the distance from the string line to the driveway surface. You now have your RISE measurement.

With RUN and RISE measurements you can now calculate the gradient using a mathematical equation, or alternatively go to our Gradient Calculator, enter your measurements and this will calculate the gradient for you.

Firstly, the depth of sub-base required for a Nidagravel gravel stabilisation grid driveway is no different to the depth of sub-base required for a driveway that is to have a block paved, tarmac or concrete surface finish. Whatever surfacing option you choose for your driveway, there will need to be a sub-base underneath. The sub-base is the foundation to the driveway surface and it needs to be of the correct depth and properly compacted. Getting depth and compaction right will mean the sub-base is strong enough for the intended loads to be imposed upon it and that it will not subside or move.

The depth of a sub-base is not an exact science. It can depend on a number of things, which include ground conditions, soil types, height of the water table, weight of vehicles that are going to use the surface, the proximity of mature trees and maybe even the type of sub-base material used. We could get really technical here and start talking about the California Bearing Ratio (CBR) which is a test to evaluate the strength of the sub-grade (the sub-grade is the term for the ground underneath the proposed sub-base or in this case the footprint of the driveway). But we are not going to go too in depth with this aspect in answering this particular question. You may wish to do some research on the CBR if it is of particular interest to you.

If we assume average ground conditions, average drainage, average soil type of sub-grade, etc - it is generally accepted as best practise by most contractors in the UK that a standard residential driveway should have minimum sub-base depth of 150mm or 6 inches. If you wish to install a deeper sub-base up to 250mm in depth that would also be entirely acceptable. It is also considered best practise to lay a geotextile membrane down over the sub-grade first, before you start adding your sub-base material. The geotextile membrane acts as a separating layer between sub-grade and the sub-base. It prevents the sub-base material from being ground into the sub-grade and when loaded with sub-base material it helps to stabilise the ground.

All sub-bases should be properly compacted to ensure the base is well consolidated and will not compress when vehicle weights are applied to the finished surface. When installing a 150mm deep sub-base for a gravel driveway, in order to achieve maximum compaction the sub-base material can be laid in 2 x 75mm layers with the first layer being compacted before the second layer is applied and then compacted. It should also be noted that the sub-base should follow the profile of the driveway surface, should be of an even thickness and should have a tolerance of +/- 10mm. When installing Nidagravel gravel stabilisation grids it is important that the sub-base is properly prepared. Once the sub-base has been compacted the surface should be blinded off with a 10 - 15mm layer of sharp or grit sand and this should also be compacted. You are then ready to lay out your Nidagravel grids to complete the installation. Preparing your sub-base properly will ensure that the underside of the gravel grids are in full contact with the sub-base when laid and when filled with gravel, any loads imposed upon the Nidagravel surface will be transferred through the gravel and the grid to the sub-base below, which provides the foundation and strength for the surface layer above.

In simple terms, the sub-base is the foundation for the surfacing layer and it ultimately provides the load-bearing strength for the installation. Sub-bases are required for all types of paved or stabilised gravel surface, whether that's a simple path, a driveway or a car park. Sub-bases are often made up of a granite or limestone aggregate which contains a range of sizes from large pieces of stone up to approx 40 - 50mm down to smaller particles, called fines. It is the combination of these sizes that enables the sub-base material to bind together and compact. Sub-base material is often referred to as MOT Type 1. This tends to contain material in a size range from 40mm to dust. It compacts well and provides a suitable base for a driveway.