Permeable Paving FAQs

Permeable paving is a hard landscaping SuDs (sustainable drainage systems) solution. These paving products are designed to allow water to pass through joints between paving materials whilst providing a stable, load bearing surface.

Tobermore’s Hydropave paving products reduce the risk of flooding and pollution by allowing water to pass through joint filling material in gaps between concrete paving blocks or slabs into the underlying permeable subbase. A properly installed permeable sub base is crucial.

For more guidance on permeable sub bases, read our ‘choosing the correct aggregate for permeable paving’ blog. If you need a fully indemnified permeable paving design for your project, use our permeable paving design service.

A core-drilled layer of Dense Bitumen Macadam (DBM) can be used to strengthen the pavement sub base. Alternatively, Hydraulically Bound Coarse Graded aggregate can also be used. Guidance on this can be found in BS 7533 Part 13 or by contacting Tobermore for more details.

For more guidance on permeable sub bases, read our ‘choosing the correct aggregate for permeable paving‘ blog.

If you need a fully indemnified permeable paving design for your project, use our permeable paving design service.

The depth of sub base required for permeable paving depends on the loading category, the CBR, the infiltration rate of the ground and, how much water needs to be stored.

For more information on Hydropave loading categories, read our blog: What are the traffic categories for permeable paving? If you need a fully indemnified permeable paving design for your project, use our permeable paving design service.

A 4/20mm coarse graded aggregate to BS EN13242:2002 / BS 7533 Part 13 should be used. For more guidance on permeable sub bases, read our ‘choosing the correct aggregate for permeable paving’ blog.

If you need a fully indemnified permeable paving design for your project, use our permeable paving design service.

No, Hydropave permeable paving systems require a different installation method to non-permeable paving. Hydropave is installed using a method with different sub base and jointing aggregates to allow for infiltration and storage of water.

Hydropave permeable paving requires a careful, professional installation to ensure it functions efficiently in sustainable drainage systems (SuDS). Proper installation of the permeable aggregate sub base is crucial.

Tobermore offers a permeable paving design service where the company’s civil engineer partners will provide a fully indemnified permeable paving design. We also provide detailed guidelines for the installation of Tobermore Hydropave permeable paving.

Ideally, services should not be placed beneath areas of permeable paving.  Best design practice is to place them under areas of conventional paving. This avoids the need to excavate areas of permeable paving to maintain these services.

Access our guidelines for the installation of Tobermore Hydropave permeable paving for comprehensive installation instructions. For fully indemnified permeable paving design drawings, use our permeable paving design service.

Research studies carried out in some of the coldest climates in the USA have shown that permeable paving sub bases are not affected by cold temperatures. There have been no cases of frost heave damaging Hydropave Permeable Pavements in the UK. When the correct aggregates are used in the sub base, they have a high void space ratio which means they drain quickly.

Access our guidelines for the installation of Tobermore Hydropave permeable paving for comprehensive installation instructions. For fully indemnified permeable paving design drawings, use our permeable paving design service.

For optimum permeable paving performance, we recommend that paving is cleaned twice a year.

The maintenance schedule should be:

1. Routine visual inspection

2. Remedial maintenance for ponding

3. Structural maintenance

4. Maintenance for aesthetics of the joints

5. Maintenance for aesthetics of the paving blocks

6. Weed control

7. Maintenance during the winter months.

Access our Hydropave permeable paving maintenance guidelines for more detailed information.

Yes, this can be done by installing a geotextile on top of the geocellular storage boxes. The bedding layer of grit is then installed on top of the geotextile.

Access our guidelines for the installation of Tobermore Hydropave permeable paving for comprehensive installation instructions. For fully indemnified permeable paving design drawings, use our permeable paving design service.

A 6 – 2.3mm clean grit to BS EN 13242 should be used ensuring that the joints are completely filled. Joints should be topped up if necessary after use.

Access our guidelines for the installation of Tobermore Hydropave permeable paving for comprehensive installation instructions. For fully indemnified permeable paving design drawings, use our permeable paving design service.

Yes, all of Tobermore’s Hydropave block paving and Hydropave slab paving products have individual slip/skid results, as verified by independent testing. For the individual results for each product, please access the specification sheets on the downloads section of our website.

For Hydropave design assistance, use our permeable paving design service for fully indemnified permeable paving design drawings.

There are different design methods to cope with sloping sites. These include constructing check dams or baffles within the sub base to restrict the flow or increasing the depth of the sub base. The maximum gradient without the need for baffles is usually 1:20.

Access our guidelines for the installation of Tobermore Hydropave permeable paving for comprehensive installation instructions. For Hydropave design assistance, use our permeable paving design service for fully indemnified permeable paving design drawings.

Tobermore offers both permeable block paving options and permeable slab paving options. Products which carry the Hydropave branding constitute our permeable paving range e.g. Hydropave Tegula, Hydropave Artro, Hydropave Braemar etc. Please note that permeability is the result of correct design and installation of an appropriate permeable sub base. Explore the full Hydropave range by visiting our permeable paving page.

To ensure the best possible performance of Hydropave permeable paving in a Sustainable Drainage System (SuDS), it is crucial to avoid soil being washed onto the surface of the permeable paving. Soil, dirt, and general detritus can clog up the joints of our Hydropave permeable paving, hindering the surface water runoff’s ability to infiltrate the permeable aggregate subbase.

We strongly recommend smart detailing of your soft landscaping, especially where it encounters permeable paved areas. Flowerbeds and lawns should be planted/installed in a manner that prevents soil being washed into Hydropave’s joints. For more information on how to maintain your permeable paving solution, please read our 7 simple steps to maintaining permeable paving blog or access our permeable paving maintenance guidelines document.

When whole life costs are considered, permeable paving systems can be more cost-effective when compared to traditional pavements. When designing and constructing permeable pavements, there is a reduction in the requirement for gullies, drainage pipes, manholes etc. Further savings can be made due to the fact that oil interceptors are often not required when using permeable paving due to it’s ability to clean the water.

Access our guidelines for the installation of Tobermore Hydropave permeable paving for comprehensive installation instructions. For Hydropave design assistance, use our permeable paving design service for fully indemnified permeable paving design drawings.

Climate change in the UK means we are getting more rainfall events and the intensity of these events is increasing. Traditional drainage techniques are unable to cope with the extra surface water run-off. To help combat these issues, the UK Government has introduced The Floods and Water Management Act 2010 (England and Wales). This act aims to replace the traditional methods of handling surface water run-off with SuDs solutions (Sustainable Drainage Systems). Permeable pavements are regarded as one of the most cost-effective and usable SuDS methods of storing and infiltrating/filtering surface water.

For a closer look at how to reduce flood risk using permeable hard landscaping, read our flood prevention using Hydropave permeable paving blog. For Hydropave design assistance, use our permeable paving design service for fully indemnified permeable paving design drawings.

Hydropave permeable paving is designed for a 25-year design life, provided the product and the sub base are installed correctly. For guidance, please refer to BS7533 Part 13 Permeable Pavement Materials & Construction.

Access our guidelines for the installation of Tobermore Hydropave permeable paving for comprehensive installation instructions that will ensure a 25-year design life. For Hydropave design assistance, use our permeable paving design service for fully indemnified permeable paving design drawings.

Hydropave permeable paving should be laid on 6-2.3mm clean grit to BS EN 13242. The depth of this layer should be 50mm.

For a more in-depth look at the importance of the sub base when laying Hydropave products, please read our choosing the correct aggregate for permeable paving: why it matters blog. For Hydropave design assistance, use our permeable paving design service for fully indemnified permeable paving design drawings.

The number of local authorities in England, Scotland & Wales that are adopting permeable pavements is increasing as they see the benefits of using it and understand that they are cost-effective to maintain.

For comprehensive public project guidance, download our considerations for designing hard landscaping for public projects eBook.

For all our local authority support, access our dedicated local authorities landing page.

Permeable pavements mimic natural water behaviour of undeveloped sites by allowing rainfall to infiltrate through the joints in the paving.  Depending on the site conditions, rain is allowed to either drain into the ground or attenuated and released slowly to secondary drainage systems. Typical flow rates for water exiting a permeable pavement are 2 to 7 l/s/ha (litres/second/hectare).

For a closer look at how permeable hard landscaping reduces surface water run-off in a SuDS system, read our flood prevention using Hydropave permeable paving blog.

Worldwide research has shown that permeable paving systems are very effective at cleaning and improving the quality of water entering them. A report by CIRIA (Construction Industry Research and Information Association) demonstrated that permeable paving can remove 60 – 95% of suspended solids and 70 – 90% of hydrocarbons.

To view all the products available in Tobermore’s Hydropave range, please visit our permeable paving page.

It is very important to ensure that permeable paving is not contaminated during the construction process. Therefore, it may be more practical to leave installation of the bedding material and paving blocks until most of the construction on the site is complete.

The solution to this is to install the sub base material and then overlay this with Dense Bitumen Macadam (DBM) to form a temporary site access road. Site traffic can then use this road for access during the construction phase. Once access by construction traffic is no longer needed, the DBM layer can remain in place. The layer is firstly cleaned and then 75mm diameter holes are cored through to allow water to drain through to the sub base aggregate. The 75mm diameter holes should be cored through on a 750 mm grid and filled with 6 – 2.3mm grit. The required thickness of the DBM layer required will be dependent on the amount of construction traffic using it.

Access our guidelines for the installation of Tobermore Hydropave permeable paving for comprehensive installation instructions. For Hydropave design assistance, use our permeable paving design service for fully indemnified permeable paving design drawings.

No, they actually require very little maintenance compared to the sometimes onerous maintenance required for traditional drainage systems which require gulley cleaning on a regular basis. Tobermore Hydropave products ensure a high joint void width percentage to accommodate the correct grit grading, reducing maintenance and maximising drainage flow rates.

For detailed guidance on maintaining Tobermore’s Hydropave permeable paving, access our Hydropave permeable paving maintenance guidelines.

Whilst car parking is one of the most popular areas where Hydropave Permeable Paving is used, designed correctly to BS 7533 Part 13 it can also be used on areas with heavy traffic such as bus stations and roads.

For an in-depth guide to the appropriate traffic loading categories for permeable paving, read our blog: what are the traffic categories for permeable paving? For fully indemnified permeable paving design drawings that are suitable for car parking or trafficked areas, use our permeable paving design service.