For decades, impervious surfaces have been considered one of the main causes of urban heat islands, groundwater depletion, and flood risks. Eco-paving—that is, permeable or green paving systems—promises to address precisely these problems: They are designed to allow precipitation to infiltrate, reduce heat islands, and at the same time provide surfaces suitable for vehicle or pedestrian traffic. Understanding the pros and cons of eco-paving allows for an informed decision on where these systems make sense, where they reach their limits, and what planning requirements must be met for a system to function effectively over the long term.

• What eco-paving is, what types exist, and how they differ from one another
• What hydrological, ecological, and urban climate benefits water-permeable paving systems offer
• What disadvantages, limitations, and risks are associated with the use of eco-paving
• What requirements must be met regarding the subgrade, base course, and drainage design
• How eco-paving is properly installed and which standards and regulations apply
• For which uses and locations eco-paving is suitable and where it fails
• What maintenance requirements arise and how long-term functionality is ensured
• How eco-paving is integrated into the overall blue-green infrastructure concept

What is eco-paving? Definition, types, and distinctions

The term “eco-paving” is not a standardized product designation, but rather a collective term for paving systems that offer improved water permeability, vegetation, or both, compared to conventional fully sealed pavements. In technical terminology, these systems are often referred to as water-permeable pavements, permeable paving, or grass paving systems. What they all have in common is the goal of at least partially maintaining the natural water cycle on paved surfaces and thereby mitigating the hydrological and ecological consequences of soil sealing.

Several types can be distinguished within this group. Grass pavers, also known as lawn pavers, are large-format concrete elements with open chambers or recesses that can be filled with soil or gravel and planted with grass. Gravel turf is not paving in the strict sense, but rather a combination of a coarse-grained mineral mixture and a grass sod that does not require solid STEINS. Jointed paving—that is, conventional paving with intentionally open, water-permeable joints—represents another variant: Here, it is not the paving stone itself but the joint material that allows water to seep through. Finally, there are fully porous paving stones made of water-permeable concrete or other materials, through which water passes directly through the STEIN itself. Each of these types has a specific performance profile that significantly determines the pros and cons of eco-paving in a specific application.

Advantages and Disadvantages of Eco-Paving: The Hydrological and Ecological Benefits

The most important advantage of eco-paving lies in its ability to allow stormwater to infiltrate on-site rather than diverting it into the sewer system. On fully impervious surfaces, up to ninety percent of precipitation runs off the surface during heavy rainfall events. Eco-paving systems can significantly reduce this proportion, provided the subsoil is permeable and the system has been properly designed. On-site infiltration contributes to groundwater recharge, relieves the combined sewer system, and reduces the risk of urban flooding. At a time when municipalities are facing growing pressure from heavy rainfall events, this is a relevant consideration in planning.

Green variants such as grass pavers or gravel lawns also contribute to evaporative cooling. Plant surfaces release water into the atmosphere through transpiration, thereby cooling the immediate surroundings. Although this effect is less pronounced than with fully vegetated areas, it is measurably greater than with impervious surfaces. For the urban climate, which is characterized by the so-called heat island effect, widespread use of eco-paving can have a noticeable cumulative impact. Individual parking spaces or driveway entrances have a limited effect on their own; however, the effects add up at the neighborhood level.

Ecologically, green paving systems provide habitat for soil fauna, insects, and low-growing plant communities. Even though the biodiversity impact of grass pavers cannot be compared to that of a near-natural meadow plant system, it is still significantly more positive than that of an asphalted or concrete surface. This added benefit is particularly valuable in planning contexts, especially in dense urban areas where every space must serve multiple purposes. For municipalities that must demonstrate mitigation and compensation measures in accordance with environmental impact regulations, the use of eco-paving on suitable areas may count toward these requirements, provided the competent authority recognizes it.

Disadvantages and Limitations: Where Eco-Paving Reaches Its Limits

As convincing as the advantages may sound, the disadvantages and limitations must be clearly identified. The most significant disadvantage of eco-paving is its dependence on a suitable subgrade. Permeable pavements function hydrologically only if the underlying soil is sufficiently permeable. On cohesive soils such as clay or silt, which absorb very little water, the water does not infiltrate into the subsoil but instead accumulates in the base layer. The result is a permanently saturated gravel layer that compromises the pavement’s load-bearing capacity and can lead to frost damage in winter. Without a soil analysis, it is impossible to make an informed decision for or against eco-paving.

Another drawback concerns susceptibility to clogging. Open joints and voids tend to fill up with fine material, leaves, algae, and moss. This clogging process—that is, the blockage of pores by fine sediment—significantly reduces water permeability over time. Studies show that the infiltration capacity of permeable paving can drop to a fraction of its original value within a few years without regular maintenance. Anyone planning to install eco-paving must incorporate a maintenance plan from the outset that includes regular cleaning, refilling of joint material, and, if necessary, high-pressure cleaning.

Eco-paving is only suitable to a limited extent for heavily used areas. On surfaces with heavy vehicle traffic—such as streets with regular bus service, heavy-duty access roads, or frequently used fire department access roads—grass pavers and gravel-covered lawns may not always meet the required load-bearing capacity standards. Pedestrian comfort is also limited with some systems: grass pavers with vegetation are more difficult for wheelchairs, strollers, and older adults to navigate than smooth surfaces. Accessibility in accordance with DIN 18040 generally cannot be achieved on such surfaces, which excludes or at least limits their use in public areas with corresponding requirements.

Finally, the issue of pollutant contamination must be considered. On surfaces that may come into contact with fuels, oils, or other environmentally hazardous substances—such as gas stations, workshop forecourts, or areas where hazardous materials are transported—the direct infiltration of stormwater is problematic or prohibited under water law. The infiltration of contaminated water into the ground would endanger the groundwater. In such cases, stormwater must be collected, treated, and discharged in a controlled manner, which negates the advantage of on-site infiltration.

Planning and Installation: Requirements, Standards, and Layer Structure

Proper planning of eco-paving begins with a site analysis. In addition to a soil test to determine the kf value (hydraulic conductivity of the soil), groundwater conditions, the distance to the highest groundwater level, and any protected areas must be assessed. The Water Resources Act (WHG) and state water laws regulate the conditions under which stormwater may be infiltrated. In many federal states, the infiltration of stormwater from roof and yard areas does not require a permit, provided there is no contamination and the required distance from the groundwater table is maintained. Nevertheless, early consultation with the responsible water authority is recommended.

The layered structure of a permeable paving system follows a clear principle. A filter layer is placed on top of the natural soil to retain fine sediment and protect the subsoil. Above this is a base layer of coarse-grained, unbound mineral mix that serves as a water reservoir and buffer. The thickness of this layer depends on the expected traffic load and the infiltration capacity of the subsoil. On top of the base course lies the bedding material, into which the paving stones are embedded. For interlocking pavers and grass pavers, the joints and chambers must be filled with a water-permeable material that does not impede infiltration. Bound joint materials—that is, cement-bound joint mortar—prevent infiltration and must not be used with eco-paving.

The governing set of regulations for the superstructure of traffic areas is the RStO (Guidelines for the Standardization of the Superstructure of Traffic Areas), which defines load classes and layer thicknesses. For permeable pavements, the technical bulletins of the Research Association for Roads and Transportation (FGSV) and the worksheets of the German Association for Water Management, Wastewater, and Waste (DWA), in particular DWA Worksheet A 138, which governs the planning, construction, and operation of facilities for the infiltration of stormwater. For gardening and landscaping, the Supplementary Technical Contract Conditions and Guidelines for Landscaping Work (ZTV La-StB) as well as the FLL regulations are relevant.

During installation, ensure a uniform slope of at least one to two percent to allow for controlled drainage of water when the system is overloaded. After installation, lawn grid blocks are filled with a substrate suitable for the intended vegetation. For turf establishment, lean, well-drained substrates with a low proportion of fine particles are suitable; substrates that are too nutrient-rich promote lush growth, which quickly clogs the chambers and reduces load-bearing capacity. Seeding or planting should be done with species that are resistant to trampling and drought stress, as these areas are typically exposed to periodic stress and dry conditions.

Suitable Locations and Typical Applications

Eco-paving is most effectively used in areas where the surface is rarely or moderately used and the subsoil has sufficient permeability. Car parking lots, parking spaces in residential areas, infrequently used fire department access roads, driveway entrances, cemetery paths, and event areas are classic applications. On such surfaces, eco-paving can significantly reduce soil sealing compared to conventional paving materials without compromising usage requirements.

In municipal open spaces, eco-paving is gaining importance as part of climate adaptation strategies. Many cities and municipalities have incorporated goals for the de-sealing or partial de-sealing of surfaces into their climate adaptation plans or heavy rain risk management plans. Eco-paving in public parking lots, schoolyards, or market squares can contribute to these goals. Funding programs at the federal and state levels—such as those for urban development or federal funding for energy-efficient buildings—can provide financial support for such measures.

Eco-paving is less suitable for areas with heavy pedestrian traffic, in areas with accessibility requirements, on sites with elevated levels of pollutants, and on heavily trafficked streets. In areas with very high groundwater levels or in Zone I and II water protection areas, water law requirements are so strict that infiltration is not possible—or is only permitted under special conditions. Careful consideration during the planning process is essential in these cases.

Maintenance and Long-Term Performance: What Keeps Eco-Paving Functioning Effectively Over Time

The long-term functionality of eco-paving depends entirely on maintenance. The clogging process mentioned earlier is the most common cause of loss of functionality. Fine dust, tire abrasion, fallen leaves, and biological growth clog the joints and chambers. Regular cleaning with high-pressure water or special brush-equipped vehicles can restore infiltration capacity, provided the clogging is not too advanced. For heavily clogged areas, it is necessary to completely mill out and refill the joints, which involves considerable effort.

Green systems such as grass pavers also require regular mowing. The mowing height should be set so that the grass does not overgrow the chambers and does not compromise the surface’s load-bearing capacity. During dry periods, irrigation may be necessary to maintain the vegetation. On areas that are rarely driven on, the vegetation tends to become overgrown with shrubs, which ultimately negates its function as a paved surface in the long term. A maintenance plan specifying mowing intervals, cleaning cycles, and inspection of the joint material must be established for every eco-paving area from the outset and factored into operating costs.

The costs of eco-paving are generally higher than those of conventional paving materials, both in terms of production and operation. Grass pavers and gravel turf are more labor-intensive to install and maintain compared to asphalt or concrete pavers. This additional expense must be weighed against the benefits: savings on sewer connection fees, avoided mitigation measures, contributions to climate adaptation, and potential subsidies can shift the balance. A comprehensive life-cycle analysis that includes manufacturing, operational, and disposal costs is essential for a robust economic assessment.

Eco-paving in the Context of Blue-Green Infrastructure and Climate Adaptation

Eco-paving is not a panacea, but it is a useful element in a broader system of blue-green infrastructure. Blue-green infrastructure refers to the interconnection of green and water elements within the urban fabric with the aim of providing ecosystem services such as water retention, cooling, biodiversity, and quality of life. Within this system, eco-paving can serve to integrate paved areas into the water cycle that would otherwise be completely excluded from the natural cycle.

Eco-paving is particularly effective when combined with other elements: trough-and-swale systems that collect and temporarily store infiltrated water, tree plantings in permeable tree pits that utilize the water, and retention areas that serve as buffers during periods of overload together form a robust system. In the planning of neighborhoods and districts designed according to the principles of the “sponge city,” eco-paving in parking lots, access roads, and courtyards is an element that should be considered as a matter of course.

Ultimately, the pros and cons of eco-paving cannot be evaluated in isolation from the planning context. A grass paver in a parking lot with permeable sandy soil, infrequent use, and consistent maintenance is a compelling solution. The same STEIN on cohesive subsoil, without a maintenance plan, in an area with high pedestrian traffic, would be a poor investment. The quality of the decision depends on the thoroughness of the site analysis, the precision of the layer structure, and the consistency of operational management. Those who consider these three aspects together can use eco-paving for what it is when applied correctly: an effective tool for designing a more climate-resilient city.