Sealing (floor)

Soil Sealing - Soil sealing refers to the covering of natural soil with water-impermeable materials such as asphalt, concrete, paving, or buildings. It prevents rainwater from infiltrating the ground, hinders gas exchange with the soil, and destroys habitats. In building and planning law, sealing is regulated by the floor area ratio (FAR), and property owners are often required to pay a stormwater fee for sealed areas.

Ecological and Climatic Impacts

Soil sealing is one of the most serious interventions in the natural soil system. Sealed soil cannot absorb rainwater-it runs off the surface and must be managed by the sewer system. During heavy rainfall events, this leads to flooding, as the sewer capacity is quickly exhausted. At the same time, the soil’s natural buffering capacity for groundwater recharge is lost, which impairs the drinking water supply in the long term.

In cities, sealing exacerbates the so-called heat island effect: asphalt and concrete store heat during the day and release it at night, preventing nighttime cooling. In a study on its climate adaptation strategy, Nuremberg found that densely sealed-off neighborhoods such as Gostenhof or the downtown area are several degrees warmer during hot summers than green spaces like Marienberg City Park-with direct health consequences for residents.

For property owners, therefore, soil sealing is not just a matter of building regulations, but also a matter of their property’s climate resilience. Less soil sealing means cooler properties, a lower risk of flooding, and lower wastewater fees.

Building Code Regulations

The Land Use Ordinance (BauNVO) limits permissible soil sealing via the floor area ratio (FAR): It specifies the maximum percentage of the property that may be built upon (sealed). In general residential areas (WA), the GRZ is a maximum of 0.4 (40 percent of the property area); in mixed-use areas (MI), it is 0.6; and in urban areas (MU), it is up to 0.8. With ancillary facilities (garages, driveways, parking spaces), the GRZ may be exceeded by up to 50 percent-meaning a maximum of 0.6 in the WA.

Stricter values may be set in zoning plans; some municipalities also prescribe minimum green space requirements or require a compensatory measure for every new sealed area (e.g., unsealing elsewhere or creating green spaces). The Federal Nature Conservation Act (BNatSchG) generally requires compensation for all new sealing within the framework of building permit procedures.

Exceeding the GRZ without a permit may be considered unauthorized construction and lead to demolition orders. When purchasing property, we therefore recommend comparing the actual impervious area with the approved scope-especially for properties with large terraces, extensive paved areas, or additional carports.

Stormwater Fee

In many municipalities, property owners pay a stormwater fee (split wastewater fee) based on the paved area. In Nuremberg, the fee amounts to approximately 0.80-1.20 euros per square meter of paved area per year. For a typical single-family home with 200 square meters of roof area, 40 square meters of terrace, and 30 square meters of driveway, annual fees amount to around 200 to 300 euros.

If the impervious area is reduced-for example, by removing paving from parking spaces, installing green roofs, or creating infiltration basins-the fee decreases accordingly. Green roofs are calculated in many municipalities using a reduced runoff coefficient (50 to 70 percent instead of 100 percent) because the substrate retains and evaporates part of the rainwater. Owners who implement unsealing measures should report this to the Nuremberg Municipal Drainage Authority to receive the fee reduction.

Unsealing and Funding

The de-sealing of property areas is subsidized in Nuremberg through the municipal climate adaptation program. Eligible measures include the installation of green roofs, the conversion of fully paved areas into water-permeable surfaces (grass pavers, gravel lawns), the creation of infiltration basins, and the greening of facades.

The investment costs for typical unsealing measures: breaking up asphalt and creating a green space approx. 30-60 euros per square meter; replacing solid paving with grass pavers approx. 40-70 euros per square meter; extensive green roof vegetation approx. 50-100 euros per square meter. The payback period is calculated based on the annual savings on the stormwater fee plus any subsidies-for larger areas, the calculation often comes out positive.

Practical Tip for Property Owners in Nuremberg

We recommend that property owners in the Nuremberg metropolitan region check the sealed area of their property and take advantage of opportunities for unsealing. In Nuremberg, the stormwater fee can be reduced through simple measures: grass pavers instead of solid paving for parking spaces, green roofs on garages and outbuildings, and infiltration basins for roof runoff.

For buyers of land and existing properties, we recommend assessing the actual level of sealing and comparing it with the maximum allowed under building codes. Particularly in older residential areas of Nuremberg (Erlenstegen, Mögeldorf, Zerzabelshof), gardens have been gradually built over with terraces, garage driveways, and paved areas over the decades-often exceeding the permitted floor area ratio (FAR). The City of Nuremberg supports soil unsealing measures as part of its climate adaptation program. Contact us-we also advise owners and buyers on building code issues related to land use.

Frequently Asked Questions

What counts as a sealed surface?

The following are considered sealed: building areas (roof projection), asphalt and concrete surfaces, paved areas with joint-tight installation, terrace slabs on mortar, and other water-impermeable surfaces. The following are considered unsealed: lawns, gravel areas, lawn grid pavers, gravel lawns, green roofs (count as partially sealed with a reduced runoff coefficient), and areas with a connected infiltration system. The exact definition varies by municipality-the Nuremberg City Drainage Department provides a calculation tool on its website.

Can I obtain a building permit if the GRZ is exceeded?

Exceeding the GRZ is permitted only within the scope of legally allowed exceptions for ancillary facilities. In addition, an exemption may be applied for under Section 31(2) of the German Building Code (BauGB) if the deviation is justifiable from an urban planning perspective and does not impair the interests of neighbors. In unplanned inner areas (Section 34 of the BauGB), the permissible amount of impervious surface is based on the extent of surrounding development. Exemptions are granted sparingly-do not plan any major impervious surface projects without first submitting a preliminary building inquiry to the Nuremberg City Planning Office.

How much does de-impermeabilization cost?

The costs depend on the scope of the project: Breaking up asphalt or concrete and creating a green space costs approx. 30-60 euros per square meter. Replacing solid paving with grass pavers costs approx. 40-70 euros per square meter. A green roof on a garage: approx. 50-100 euros per square meter for extensive greening. The investment pays for itself through savings on stormwater fees-for 100 square meters of unsealing, you save approximately 80 to 120 euros per year in Nuremberg; in addition, there may be city subsidies that can significantly shorten the payback period.

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