Permeable Paving – Meaning

Permeable Paving – Meaning

Permeable paving is a type of paving that allows rainwater to pass through the surface and infiltrate into the ground, rather than collecting as puddles. It is designed to help manage stormwater runoff and reduce the risk of flooding. This concept is commonly associated with Sustainable Drainage Systems (SuDS) regulations, which aim to promote sustainable water management practices. (See SuDS Regulations.) The simplest form of permeable paving is a gravel drive, car park, or hard-standing area. It typically consists of a sub-base layer made of MOT Type 3 (a specific type of crushed stone) that is laid over a non-woven geotextile fabric. The geotextile helps prevent the sub-base fines from mixing with the underlying soil.

For vehicular use, honeycomb-style matting can be used. These mats have a layer of thin geotextile fixed to the bottom and are interlinked together with clips or an over-sail of fabric to lock them together. These mats are then filled with suitable decorative aggregates, such as gravel, to a depth that covers the honeycomb structure. Permeable block pavers are another option for permeable paving. The installation process for these pavers should always follow the manufacturer’s guidelines. These pavers have a similar appearance to grass-grid panels and are also covered with decorative aggregates to ensure the permeability of the surface.

Overall, the goal of permeable paving is to provide paved surfaces that allow water to drain naturally, reducing the need for traditional stormwater drainage systems and promoting sustainable water management. Apart from free-draining shingle surfaces, there are indeed many different types of hard landscaping materials and products that can be used for permeable paving. Some examples include:

1. Open-pored concrete: This is a type of concrete that is designed with open pores to allow water to pass through it. It can be used for driveways, walkways, and other paved areas.
2. Blockpavers: Permeableblockpaversarespeciallydesignedblockswithgapsbetweenthem that allow water to pass through. These pavers are often used in driveways and pathways.
3. Tarmacadam: Tarmacadam, commonly known as tarmac, can be used as a permeable paving option. It can be finished with an open-pore wearing coat or a layer of resin-bound aggregate, which allows water to pass through the surface.
4. Non-porous paving slabs: While non-porous paving slabs are not permeable themselves, their porosity relies on the sub-base and jointing compound. Water can pass freely through the joints, laying bed, and foundations. Proper sub-base construction and jointing are crucial for their permeability. In this instance a proprietary permeable bedding mortar is recommended.

With all the above surfaces mentioned above, base material should always be used such as MOT type 3 to ensure water is not trapped within the layers of the paved surface.

When installing permeable paving, it is important to carry out a percolation test beforehand to determine the suitability of the site’s ground conditions for drainage. This includes using a proprietary permeable bedding mortar for mortar beds and a non-woven geotextile membrane to support the base/sub-base, prevent fines migration in to the sub-grade and prevent water from being trapped. Starting from 2024, Sustainable Drainage Systems (SuDS) will be mandatory for all new developments in the UK. SuDS regulations aim to promote sustainable water management and the use of permeable paving is encouraged as a part of these regulations. It is important to note that this restriction will be applied firmly to the landscaping industry.