Bulk Volume Calculation

Gross Floor Area Calculation - The gross floor area calculation determines the volume of a building based on its exterior dimensions (gross floor area, GFA) by calculating the cubic volume from the surface areas of the enclosing structural elements. The GFA is determined in accordance with DIN 277 and expressed in cubic meters (m³). In real estate valuation, the gross floor area calculation serves as the basis for determining construction costs in the asset value method - the GFA multiplied by the standard construction costs per cubic meter yields the building’s construction value.

Calculation according to DIN 277

The gross floor area (GFA) is calculated according to DIN 277-1 as the volume of the building structure enclosed by the outer boundary surfaces. This includes: all floors, including the basement and attic (if converted), exterior walls at full thickness, roof surfaces up to the upper edge of the roof deck, and the floor slab. Not included are: roof overhangs without usable floor area, light wells, freestanding balconies without a roof, and exterior staircases. For attics, the GFA is measured up to the roof deck-not just the usable area with sufficient ceiling height. For flat roofs, the calculation corresponds to a simple length × width × height.

Correct delineation often poses difficulties in practice, particularly with: Bay windows and canopies - whether these are included depends on the structural design. Conservatories - unheated, glass-enclosed extensions are only partially included. Underground garages - underground garages are included in the gross floor area (BRI) but valued using their own standard construction costs. Existing buildings - for existing buildings without current plans, measurements must be taken on-site, which can be time-consuming for complex floor plans.

Significance in Real Estate Valuation

In the asset value method according to ImmoWertV, the gross floor area (BRI) forms the basis for calculating construction costs: BRI × standard construction costs (NHK) per m³ = building construction costs. The NHK are differentiated according to the Asset Value Guideline (SW-RL) based on building type, year of construction, and standard of finish. For a detached single-family home of medium standard, the NHK currently stands at approximately 350-500 euros/m³ GFA. An incorrect gross floor area calculation distorts the entire asset value-a 10% deviation in the GFA leads to a corresponding deviation in the building value.

In addition to pure volume, the building’s fit-out class is factored into the valuation. The Property Value Guidelines distinguish five fit-out classes (basic, basic-medium, medium, medium-upscale, upscale), which have a significant impact on the assessed NHK. A high-quality single-family home with underfloor heating, designer bathrooms, and a built-in kitchen is classified in a higher category than a standard construction-even with the same BRI, the building value can thus be 20-30% higher.

Floor Area Calculation and Age-Related Depreciation

The building construction value (BRI × NHK) is then reduced by the age-related depreciation. This is calculated based on the ratio of the building’s current useful life to its total useful life. A 30-year-old single-family home with a total useful life of 80 years has an age-related depreciation of 37.5%. Renovation measures can extend the remaining useful life and thus reduce the age-related depreciation-which is directly reflected in the property value. Proper documentation of completed renovations is therefore also relevant for calculating floor space and determining property value.

The building’s real value determined in this way is finally multiplied by a market adjustment factor (real value factor), which reflects local market conditions. In metropolitan areas such as Nuremberg, these factors typically exceed 1.0-the market values real estate higher than its calculated construction costs. In structurally weak rural regions, it can fall below 1.0.

Practical Tip for Property Owners in Nuremberg

We recommend that property owners in the Nuremberg metropolitan area who need a property valuation using the asset value method (e.g., for inheritance, divorce, or tax purposes) have the gross floor area calculation performed by a certified appraiser. Current building plans or measurements are required for the calculation. For older Nuremberg buildings (especially Wilhelminian-style buildings in the Südstadt or older structures in Gostenhof), the original plans often no longer match the actual condition-additions, story extensions, or attic conversions were not always recorded in the plans. A current survey costs approx. 500-1,500 euros but prevents significant valuation errors.

For inheritance and gift tax purposes, the tax office determines the property value according to its own procedures (determination of the required value under the Property Valuation Act). These values do not always correspond to the property valuation report-but may be lower or higher. An independent expert appraisal can serve as proof of a lower market value to the tax office and reduce the tax burden (Section 198 of the Property Valuation Act). Contact us-we connect you with certified experts in the region who can provide both volume calculations and comprehensive market value appraisals.

Frequently Asked Questions

What is the difference between gross floor area (BRI) and living space?

The gross floor area (BRI) measures the volume of the entire building in cubic meters-including walls, basements, and unusable attic areas. Living space measures the usable floor area in square meters-in accordance with the German Residential Space Ordinance (WoFlV), taking into account ceiling heights, sloped ceilings, and balconies. Living space typically accounts for only 30-40% of the volume described by the GRC. The GRC is used for cost calculations in the asset value method, while living space is used for calculating rent and purchase prices per square meter.

Is the basement included in the gross floor area calculation?

Yes, the basement is fully included in the BRI, even if it is not considered living space. In the asset value method, however, the construction costs for the basement are assessed using separate NHK values, which are lower than those for residential floors (approx. 200-350 euros/m³). An unfinished basement therefore contributes less to the building’s value than a residential floor with the same volume.

Can I perform the volume calculation myself?

In principle, yes, if you have current construction plans. However, the calculation according to DIN 277 requires expert knowledge regarding the correct delineation (what is included, what is not?) and the calculation of sloped ceilings, bay windows, and irregular floor plans. For a rough estimate, a simplified calculation (floor area × height × number of stories) is sufficient. For a legally binding expert opinion, the calculation must be performed by an expert in accordance with DIN 277.

What documents does the expert need for the floor area calculation?

Ideally, the expert needs: floor plans of all floors (basement, ground floor, upper floors, attic) with dimensions, section drawings to determine floor heights, elevations for the roof geometry, and external dimensions of the building. If no current plans are available, the expert will conduct their own on-site measurement. For larger buildings (apartment buildings, commercial properties), the measurement can take half a day to a full day. Digital measuring devices (laser scanners) significantly speed up the process and increase accuracy.

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