I am still not sure how "value" is defined here. If it is about the lending value, then theoretically only sustainable renovations and modernizations are taken into account. How this is calculated varies from bank to bank. Many banks use the valuation software Lora and work according to the BelWertV. In this case, renovation and modernization measures affect the remaining useful life and the equipment. That means, according to BelWertV, the total useful life for a single-family house may be assumed to be a maximum of 80 years – modernizations and renovations can extend the total (remaining) useful life accordingly (maintenance backlog has the opposite effect). Then the "equipment" is assessed; there are clear criteria for the definition, but in everyday practice this is increasingly done by feel. A flat-rate approach of x % of the measures in the lending value is not allowed according to BelWertV – but many banks still assess according to their own schemes, although the Federal Financial Supervisory Authority is increasingly putting a stop to this.
Planned renovations and modernizations are not included in the lending value – they have not yet been carried out. Assuming the bank had to auction the property tomorrow, it would also make no sense to have taken them into account in the value. After the measures have been carried out, the lending value can then increase accordingly. Here, unconscious aesthetic changes such as painting work and new flooring may also be factored in, since the equipment is then better assessed by the appraiser.