De-sealing is the removal of impervious surfaces (asphalt, concrete) to restore soil functions, including infiltration, biological activity, carbon storage, and ecosystem services, particularly in urban environments. De-sealing surfaces involves completely removing any impermeable barriers, foreign materials, and compactions, followed by rebuilding with soils typical of the site to restore natural soil functions as much as possible, or to create a layer of soil that can support roots.

Recommendations for Implementation

The implementation of de-sealing generally involves assessment of existing soil and site conditions, removal of impermeable and artificial layers, restoration and regeneration of soil where necessary, and establishment of an appropriate permeable, vegetated or blue-green surface system. The appropriate intervention depends on the existing soil profile, degree of compaction, permeability, contamination status, groundwater conditions, intended land use and required hydrological functions.

• Before de-sealing, the existing soil and site conditions are assessed (soil profile and degree of compaction, permeability and drainage capacity, groundwater conditions, contamination risks, existing vegetation and surrounding hydrological and ecological networks) to determine whether the site is suitable for full soil restoration, partial de-sealing, permeable surfacing, infiltration measures or a combination of these approaches. This is especially needed for former industrial or heavily developed sites where contamination may constrain infiltration, vegetation establishment or direct reuse of excavated materials.
• Impermeable surfaces and unsuitable artificial layers are be removed and appropriately managed, followed where necessary by the removal of construction artefacts, remediation of contaminated soils, decompaction and restructuring of the underlying soil. Where the original soil profile has been substantially disturbed or removed, soil horizons may need to be reconstructed with constructed soils or amended using suitable materials. Desealing may therefore be combined with demolition, soil decontamination, ecological rehabilitation and soil reconstitution depending on site conditions.
• The new, de-sealed, surface should be selected according to the intended soil functions, land-use requirements and hydrological conditions. Where full restoration is feasible green infrastructure and nature-based solutions such as green spaces, urban meadows, street trees, green strips, micro-urban forests, floodplain meadows, marshes and riparian forests can be used to restore soil, biodiversity, water-regulation and microclimatic functions. Where pedestrian, cycling, parking or other hard-surface functions need to be maintained, partial de-sealing can be achieved through grey structures and permeable materials, including porous asphalt, concrete or plastic grid pavers, wide-joint pavers, resin-bound permeable surfaces, partially vegetated pavements and soil–aggregate mixtures. The choice of surface should consider structural requirements, infiltration capacity, maintenance requirements and accessibility.
• Where stormwater management is a principal objective, de-sealed areas can be combined with water-sensitive practices (like rain gardens, swales, infiltration trenches, infiltration wells, ponds or other stormwater facilities), designed according to local soil conditions.

De-sealing requires site-specific risk assessment because the removal of sealed surfaces and disturbance of underlying soils can mobilise contaminants, expose degraded or compacted soils, alter local drainage and affect surrounding ecosystems. Where contamination is present, remediation or appropriate containment should precede or accompany soil restoration.

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