How to lay permeable block paving

Our useful how to concrete block permeable paving laying guide gives you all the information you need to install our range permeable block paving products, if you choose to do-it-yourself.

Ensure you read our advice before beginning work on your new design project - this will mean you are fully prepared and have everything to hand, ready to complete your perfect garden.

Concrete block permeable paving differs from conventional block paving as it allows rainwater to filter through gaps between the blocks into a stone sub­ base below where there is enough space to store the water for a short time. It can then either soak into the ground or into drains to collect the water for re­use. 

DESIGN CONSIDERATIONS

When assessing the design of a permeable paved driveway considerations should be given to levels, soil permeability and soil strength.

Infilta block paving is laid in a similar way to normal block paving

  • In free draining applications, a suitable geotextile should be placed at formation level (overlapping joints by 300mm), below the drainage aggregate sub­base.
  • Conventional MOT Type 1 is not used for the sub base as it is not free draining, the Bradstone 20mm open graded Drainage Aggregate is used.
  • It is best to prevent vehicles running on the sub base during construction if possible, as they will cause rutting in the loose surface.
  • The blocks are restrained in the conventional way using a kerb or edging. This provides more than adequate support to traffic.

Step by step guide

Step 1: The depth of the sub­base will be governed by the strength and type of the underlying ground.The depth is determined by the results of the permeability test. Typically you will need around 200mm deep of 20mm open graded aggregate, such as Bradstone Drainage Aggregate, on soils of good strength and 500mm in areas of poor soil strength.

Step 2: Using a concrete mixer, mix 1 part cement and 6 parts ballast to create the concrete foundation, which should be 100mm thick in depth. The kerb unit or edge restraint will sit on top of this at the required level. This should be done using a string line and spirit level. Mortar the kerb units or edge restraints to the foundation using a trowel and rubber mallet. Once the kerbs are in position, haunch the back of the units so that the concrete reaches half way up the rear of the kerb.

Step 3: The laying course uses Bradstone Bedding Aggregate, a 6mm angular, open graded material. Unlike normal bedding sand, it is free draining and therefore it does not require any control on moisture content.

The laying course should be 50mm thick, rather than 30mm for conventional paving and it is not compacted before the blocks are laid.

Once laid, and prior to jointing, a light pass over with a whacker plate with a rubber mat is required.

Step 4: Bradstone Infilta blocks have a nominal joint width of 5mm which is greater than normal block paving

Step 5: Bradstone 3mm Jointing Aggregate should be used for joint filling. Brush in and after ensuring there is not loose aggregate on the surface that could mark the blocks, another pass with the whacker is required.

Finally, brush in more aggregate to fill voids as required.