How to lay permeable block paving
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.
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. A few key considerations to note for a full infiltration system are:
- 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.
- A free draining 6mm bedding aggregate is laid in place of a normal bedding sand.
- Permeable blocks are restrained in the conventional way with a kerb or edging that provides more than adequate support to traffic.
- A suitable geotextile is a compulsory requirement below the drainage aggregate sub base.
- For a belt and braces approach a further optional layer of the geotextile may be laid between the drainage aggregate and the bedding aggregate.
Step by step guide
Step 1: Excavate and prepare the underlying ground to a suitable depthabove the level of the water table. Any low points should be filled and compacted with a Type 3 material. The finished height of the driveway should be a recommended minimum of 2 courses below DPC.
Step 2: Install a haunched kerb to sides that are not already edged. The haunch to the front of the kerb should be a minimum of 25mm below the
finished level of the base of the paving with a gap left between the kerb and the block for filling with jointing aggregate when completed.
Step 3: Lay a suitable geotextile to the base and sides of the area to be laid. Any joints must be overlapped by a minimum of 300mm.
Step 4: The depth of the sub base will be governed by the strength and type of the underlying ground. Typically you will need to be around 200mm deep on soils of good strength and 500mm in areas of poor soil strength. Add in compacted layers not exceeding 150mm at a time.
Please note: If you opting to lay a further layer of geotextile it should be done after Step 4 and before Step 5 commences.
Step 5: The laying course uses Bradstone Bedding Aggregate, a 6mm angular, open graded material. The laying course should be 50mm thick 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 6: Bradstone 3mm Jointing Aggregate is 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.