{"id":24490,"date":"2025-11-11T09:28:32","date_gmt":"2025-11-11T09:28:32","guid":{"rendered":"https:\/\/www.tobermore.co.uk\/professional\/?p=24490"},"modified":"2025-11-11T10:29:17","modified_gmt":"2025-11-11T10:29:17","slug":"concrete-permeable-paving-sub-bases-geotextiles-and-how-they-work","status":"publish","type":"post","link":"https:\/\/www.tobermore.co.uk\/professional\/blog\/concrete-permeable-paving-sub-bases-geotextiles-and-how-they-work\/","title":{"rendered":"Concrete permeable paving, sub bases, geotextiles and how they work"},"content":{"rendered":"
Concrete\u00a0<\/span>permeable paving<\/span><\/a>, when combined with appropriate\u00a0sub bases\u00a0and geotextiles, forms an efficient way to control water drainage. This approach helps achieve SuDS compliance. Water that falls upon the surface drains through the joints between the permeable paving blocks. It then passes into the\u00a0sub base\u00a0where it slowly drains through the gaps between the aggregate\u00a0layer. The water then either drains into the ground through a porous geotextile membrane or is\u00a0retained\u00a0by an impermeable membrane.\u00a0<\/span>\u00a0<\/span><\/p>\n The properties of each\u00a0component,\u00a0<\/span>and therefore<\/span>\u00a0the whole design of a permeable paving system, can be adjusted. This allows control over the rate at which water drains\u00a0<\/span>and its<\/span>\u00a0final destination.\u00a0<\/span>\u00a0<\/span><\/p>\n Section 3 of the Flood and Water Management Act 2010 is designed to help with surface water management in urban areas. It was implemented in Wales in 2019 and in 2025 the government has\u00a0stated\u00a0it is strongly committed to requiring standardised SuDS in new developments. Regardless of the legislation, the focus on SuDS is intensifying across the board. Therefore, understanding how geotextile membranes and permeable paving systems manage surface water is more important than ever. This knowledge will help future-proof developments for SuDS compliance and evolving regulatory standards.<\/span>\u00a0<\/span><\/p>\n Concrete permeable paving<\/span><\/a>\u00a0works by allowing surface water to drain through the joints between specially shaped permeable paving blocks. The edges of each block have carefully designed nibs that ensure controlled gaps are always left between installed blocks. These gaps are filled with jointing material that is porous. This allows water to flow off the surface of each permeable paving block, and down through the gaps into the\u00a0sub base\u00a0below.\u00a0<\/span>\u00a0<\/span><\/p>\n In standard paving systems, surface water is taken away through drains and gulleys. By contrast, permeable paving drains the surface water into the ground where it falls. Permeable concrete paving mimics the pattern of natural water absorption. Dealing with the water locally using permeable paving does not increase flood risk. This makes it suitable for use as part of a SuDS (<\/span>Sustainable Drainage<\/span>\u00a0<\/span>Solutions)\u00a0<\/span>system.<\/span>\u00a0<\/span><\/p>\n The\u00a0sub base\u00a0provides a stable base for the traffic loading of a concrete permeable paving area. The permeable nature of the\u00a0sub base\u00a0also provides an area where water can be stored and slowly released. This release can either be into the ground, or into a drainage or storage system.\u00a0<\/span>\u00a0<\/span><\/p>\n The aggregate used for a permeable block paving\u00a0sub base\u00a0consists of angular aggregate. This is typically 4\/20mm coarse graded with no fines. The angular nature of the stones locks the\u00a0sub base\u00a0together to provide stability. This creates pockets where water can be stored.<\/span>\u00a0<\/span><\/p>\n The required thickness of permeable block paving\u00a0sub base\u00a0will depend upon the structural strength needed to support traffic loads. It is also\u00a0determined\u00a0by the volume of water storage needed. The traffic loading thickness is usually the greater of the two. This increases the water holding capacity of the\u00a0sub base\u00a0layer. This is an advantage as it allows the permeable paving surface to drain away the runoff from surrounding impermeable surfaces.<\/span>\u00a0<\/span><\/p>\n Where extra strength and stability is\u00a0required, a layer of Dense Bitumen Macadam (DBM) can be installed. This can reduce the depth of the\u00a0sub base\u00a0and save on excavation and aggregate costs.<\/span>\u00a0<\/span><\/p>\n DBM can also be used to protect the\u00a0sub base\u00a0from damage and clogging on site access roads that will eventually be finished with concrete permeable paving. When the time comes to lay the permeable paving, the DBM is cored. Then the laying course and permeable paving can be installed.\u00a0<\/span>\u00a0<\/span><\/p>\n Geotextile membranes are permeable materials that are used to separate layers within a permeable paving system. They are typically used to separate the\u00a0sub base\u00a0and the ground. In some instances, they can also be positioned between the laying course and the\u00a0sub base.<\/span>\u00a0<\/span><\/p>\n Geotextile membranes are positioned between the\u00a0sub base\u00a0and the sub-grade soil. This\u00a0contains\u00a0and prevents the\u00a0sub base\u00a0from sinking into the soil. Geotextile membranes allow the water to pass through the\u00a0sub base\u00a0into the ground while\u00a0retaining\u00a0the aggregate layer in position. They also prevent finer particles from the soil from entering the\u00a0sub base. This helps to\u00a0maintain\u00a0its water retention capacity.<\/span>\u00a0<\/span><\/p>\n The geotextile membrane layer can be used to separate the fine aggregate of the laying course from the larger aggregate layer of the\u00a0sub base. This helps prevent smaller particles of the laying course from settling into the\u00a0sub base\u00a0layer and hampering effective drainage. However, the use of geotextile membranes in this position is often regarded as optional. If the aggregate sizes of the laying course and\u00a0sub base\u00a0are within specification, water drainage should not be disadvantaged.<\/span>\u00a0<\/span><\/p>\n Impermeable alternatives to geotextile membranes are\u00a0required\u00a0when the\u00a0sub base\u00a0acts as a water tank. Impermeable layers are usually made of plastic. They line the entire section\u00a0containing\u00a0the\u00a0sub base\u00a0to act as a tanking layer. The contained water is then discharged to other drainage systems rather than being allowed to drain directly into the ground. This is referred to as a tanked (no infiltration) system.<\/span>\u00a0<\/span><\/p>\n Water stored in the\u00a0sub base\u00a0underneath concrete permeable paving \u2013 lined with geotextile membrane \u2013 can be released at different infiltration rates. These rates depend on the specific design of the system and need to consider the infiltration rate of the ground.\u00a0<\/span>\u00a0<\/span><\/p>\n There are three main types:<\/span>\u00a0<\/span><\/p>\n The choice of system\u00a0largely depends\u00a0on the permeability of the sub-grade beneath the permeable paving. High permeability rates will allow a total infiltration system to be utilised. As ground permeability rates decline, either partial or no-infiltration systems will be\u00a0required.\u00a0<\/span>\u00a0<\/span><\/p>\n The exception to this is where total capture of water is\u00a0required\u00a0for re-use or water treatment purposes. In these cases, tanked systems will be specified.\u00a0<\/span>\u00a0<\/span><\/p>\n We will look at the design of each of these in turn.<\/span>\u00a0<\/span><\/p>\n In this system, the water passing through the permeable paving is collected and temporality stored within the\u00a0<\/span>sub base<\/span>\u00a0lined with geotextile membrane. Eventually, all the water will drain through the geotextile membrane into the ground.<\/span><\/span>\u00a0<\/span><\/p>\n \n If the permeability of the ground is insufficient to drain the water from the\u00a0<\/span>sub base<\/span>\u00a0at the required rate, a perforated collector pipe is introduced into the system design<\/span>.\u00a0\u00a0<\/span>When the\u00a0<\/span>sub base<\/span>\u00a0below becomes full, the pipe will remove excess water to a different part of the drainage system. This ensures that the permeable system always has sufficient capacity to meet local water management requirements.<\/span><\/span>\u00a0<\/span><\/p>\n In this system, the\u00a0sub base\u00a0is lined with an impermeable lining rather than a geotextile membrane. This\u00a0contains\u00a0all the water collected within the\u00a0sub base, so none is discharged into the ground. The water is taken away to secondary drainage or storage systems by outlet pipes. The diameter of the pipes will be dependent on drainage rates\u00a0determined\u00a0by specific site conditions.\u00a0<\/span>\u00a0<\/span><\/p>\n This system is used when the ground has insufficient permeability and could be destabilised by exposure to water. It is also used where water is\u00a0required\u00a0for re-use or because it\u00a0contains\u00a0pollutants. The outlet pipes can then direct the collected water to be stored or treated as\u00a0required.<\/span>\u00a0<\/span><\/p>\n Selecting the\u00a0<\/span>appropriate permeable<\/span>\u00a0system for a project can deliver design benefits. It is worth noting that when comparing the\u00a0<\/span>whole system<\/span>\u00a0cost of concrete permeable systems against traditional tarmac systems, the latter tends to be more expensive. This is largely because of the infrastructure\u00a0<\/span>required<\/span>\u00a0to support tarmac systems.<\/span><\/span>\u00a0<\/span><\/span><\/p>\n Where can I learn more about the materials required when designing permeable paving?<\/span><\/b>\u00a0<\/span><\/p>\n Contact<\/span><\/a>\u00a0Tobermore\u2019s\u00a0technical team for advice and guidance when designing\u00a0<\/span>concrete permeable paving<\/span><\/a>. We have in-depth knowledge of the materials\u00a0required\u00a0to deliver successful permeable paving solutions.<\/span>\u00a0<\/span><\/p>\n Concrete permeable paving systems offer a robust,\u00a0attractive\u00a0and economical option to traditional systems such as tarmac when looking to achieve SuDS compliance.<\/span>\u00a0<\/span><\/p>\n Craig McBride,\u00a0Tobermore\u2019s\u00a0Technical and Product Training Manager, comments:<\/span>\u00a0<\/span><\/p>\n \u201cWe have an excellent range of concrete permeable paving products in vibrant long-lasting colours that create robust and attractive hard landscaping for our customers. We pride ourselves on ensuring that all the materials under the paved surface are correctly specified. Our technical team offer our customers a permeable paving design service. This details the materials needed to meet their project\u2019s structural and drainage requirements in a cost-effective manner.\u201d\u00a0<\/span><\/span><\/p>\n<\/blockquote>\n","protected":false},"excerpt":{"rendered":" Concrete\u00a0permeable paving, when combined with appropriate\u00a0sub bases\u00a0and geotextiles, forms an efficient way to control water…<\/p>\n","protected":false},"author":73,"featured_media":24514,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"inline_featured_image":false,"footnotes":""},"categories":[971],"tags":[],"class_list":["post-24490","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-technical","tax_posts_products-permeable-paving"],"acf":[],"yoast_head":"\nHow does concrete permeable paving work?<\/span><\/b>\u00a0<\/span><\/h2>\n
What part does the sub base play in a permeable paving system?<\/span><\/b>\u00a0<\/span><\/h2>\n
<\/p>\nWhat are geotextile membranes used for in permeable paving systems?<\/span><\/b>\u00a0<\/span><\/h2>\n
<\/p>\nGeotextile membranes between the sub base and the ground in permeable paving<\/span><\/b>\u00a0<\/span><\/h3>\n
Geotextile membranes under the laying course of permeable paving<\/span><\/b>\u00a0<\/span><\/h3>\n
When are impermeable alternatives to geotextile membranes required in permeable paving systems?<\/span><\/b>\u00a0<\/span><\/h2>\n
<\/p>\nHow does the infiltration rate of ground affect the choice of permeable paving system?<\/span><\/b>\u00a0<\/span><\/h2>\n
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Full infiltration permeable paving<\/span>\u00a0(<\/span>Type<\/span>\u00a0A)<\/span><\/span>\u00a0<\/span><\/strong><\/h3>\n
<\/p>\nDiscover how to install a Type A full infiltration permeable paving system - step by step<\/h4>\n <\/div>\n <\/div>\n
Partial infiltration permeable paving<\/span>\u00a0(Type B)<\/span><\/span>\u00a0<\/span><\/strong><\/h3>\n
<\/p>\nTanked (no infiltration) permeable paving<\/span>\u00a0(Type C)<\/span><\/span>\u00a0<\/span><\/strong><\/h3>\n
<\/p>\n\n