Where the Roman city of Nida stood a good 1700 years ago, right next to Ernst May's Roman town of the 1920s, the Frankfurt Heddernheim district expanded in the 1960s. The planners retained the concept of through-routing, but the petty-bourgeois style of the post-war single-family housing estates was not avoided. This is the case in Trajanstrasse, which bears the proud name of the adopted Roman emperor who ruled Rome from 98 to 117.

A row of semi-detached single-family houses shows clear similarities, the signature of a single colleague. Front garden, two storeys with extended roof, garage as boundary development, large glass block windows, concrete canopies, punched windows, pitched roof with dormer. The official requirements of the 1974 development plan only allow limited structural alterations. The 410m² plot could have been used more effectively.

The construction project required considerable structural interventions. The rubble recycling company supplied some of the materials for the construction of the estate in 1961. 50% of the material in the basement had to be replaced, and the concrete ceilings were in no way structurally sound. The investment costs inevitably soar without taking into account the planned energy measures. Building fabric mixed with rubble will often be found in estates from the 1960s.

It is foreseeable that the refurbishment costs will significantly exceed the value of the property. This can only be compensated for by expansion, especially in metropolitan areas. However, this fact does not yet seem to have reached the authorities - old development plans almost always have to be adhered to restrictively.

I am very lucky to have a developer in front of me who - despite the unpredictability - continues to tackle the complex construction task. Despite the increased investment costs, the goal of a renovated residential building to KFW 70 standard is still being pursued.

The floor area of the detached house can be extended by approx. 1/4 to the south-west and the roof raised by 80 cm. The installation of the wheelchair-accessible elevator, which can be accessed from the street, is very important - due to the client's private experience. The result is a wheelchair-accessible three-family home with a 33% increase in living space - despite the installation of the space-consuming elevator.

The façade remains structurally intact: the large glass block window above the front door is replaced by clear glass windows (triple glazing) with a front door, the width is adapted to the punched windows on the left. Their parapets are broken off and visually pulled together over the façade frame that runs around two storeys. This simple measure gives the residential building its updated form, while the old structure remains legible.

The two-storey extension with roof terrace extends the living spaces to the south-west - the terraces on the ground floor and top floor can be reached without thresholds. An internal staircase is installed between the ground floor and the first floor - it can potentially be used for quick access between the disabled person and their carer. The pitched roof has a hipped roof, which - due to the raising of the eaves - is due to the spacing requirements. The roof is set off in an accentuated manner and gives the residential building a "hat". The drainage system, which feeds the 8,000-liter underground cistern in the garden, is routed through the consistently surrounding box gutter.

About the energy concept: in addition to the mineral-based ETICS, the house has underfloor heating down to the foundation level in the new lightweight screed. The basement ceiling will be insulated on the underside and the new roof will be insulated on top of the rafters. Integrated into this are photovoltaic panels on the south-west side and solar panels on the two dormers, which feed the large hot water tank in the basement. The air heat pump - equipped with an additional cooling module - is located in the rear garden and is fed by the photovoltaic system. The necessary ventilation - due to the triple-glazed windows and the low ceiling heights - is provided by simple cross-ventilation via the residents in the spirit of "low-tech". Last but not least, a hybrid stove that burns wood and pellets provides sufficient heat in the transitional period.