Project posted by Till Kurz

Haus K18

View south east
View south east
detail of the facade west
detail of the facade west
view south west
view south west
detail of the facade south west
detail of the facade south west
detail mailbox
detail mailbox
View north west
View north west
View south west
View south west
View south east
View south east
View west
View west
living room view to the north
living room view to the north
living room view to the south
living room view to the south
guest toilet
guest toilet
Core ground floor
Core ground floor
eat-in kitchen view to the south
eat-in kitchen view to the south
eat-in kitchen view to the north
eat-in kitchen view to the north
eat-in kitchen view to the west
eat-in kitchen view to the west
eat-in kitchen detail
eat-in kitchen detail

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From Till Kurz


The single-family house at Katzengasse 18 is located on the left bank of the Rhine in the former farmer and fishing village of Cologne Niehl.

It replaces a single-storey fisherman's house from the middle of the 19th century, which could not meet today's requirements for a single-family house.

In contrast to its predecessor, the house was set back by about 4 metres from the northern boundary of the property.

This creates a small courtyard that mediates between the house and the alley.

The urban reorganization in terms of location and eaves height will strengthen the "urban space" of Katzengasse

During the dismantling of the previous building by hand by the architect, about 10,000 old field fire stones were cleaned and later reinstalled as facing shells in the new building.

The approximately 170-year-old material was transferred to the new building according to the "cradle to cradle" principle in order to create a strong connection to the history of the place and thus transform the past in a sustainable way.

The K18 house, with its precisely designed spatial sequences, which are preceded by deliberate theories of spatial experience, prototypically demonstrates how a residential building with small dimensions and areas appears generous through the inclusion of outdoor space and a clear concept

The house K18 is geothermally heated with a brine-water heat pump. A fresh water station with a buffer tank is used for hot water heating, which preheats the hot water with the heating water via a heat exchanger.

Architect: Till Robin Kurz, Architect BDA


Instagram: haus_k18

Location: Cologne Germany, Katzengasse

Type: detached house

Structural engineer: Ertl Tragwerk GmbH & Co.KG, Bonn Germany

Photography: Robinson Tilly

Construction year: 2021

Client: Analena Schwarz

Plot: 136 sqm

Living area: 92 sqm

Additional usable area basement 10 sqm.

BRI: 488 cbm

Energy standard: KFW 55 = low energy house


2022 Appointment to the Association of German Architects, BDA

2018 – 2020 Lectureship at the university of applied sciences, Cologne, Germany

2014 Own office in Cologne Germany

2003 - 2013 Employed by USARCH as Project Lead Architect, Bonn, Germany

2000 – 2003 Freelancer at USARCH, Bonn, Germany

1995 – 2002 Studies at the university of applied sciences, Cologne, Germany

1999 Student assistant at ASTOC Architects and Planners, Cologne, Germany

1993 – 1995 Community service in the university clinics, Bonn Germany

1980 – 1993 Schooling in Stuttgart and Bonn, Germany

1973 Born in Stuttgart

Table of contents

01.0 Urban developement situation

02.0 Urban development reaction

03.0 Predecessor

04.0 Fifteen theses on the design of the building

05.0 Architectural order

05.1 Achsial order

05.2 House as a whole

06.0 Space/Room sequences on the ground floor

06.1 Entrance courtyard

06.2 Livingroom

06.3 Corridor

06.4 Guest toilet

06.5 Kitchen-living room

07.0 Rooms upstairs

08.0 Rooms in the attic

08.1 Bathroom

09.0 Material

10.0 Proportions

11.0 Energetic concept

12.0 Sustainability


The urban development Situation

In the immeditate vicinity there are flat-covered houses, one storey outbuildings with desk roofs, houses with hipped roofs, and gabled roof houses.

The single-family house in Katzengasse 18 is located in the left Rhine district of cologne Niehl. In a pure residental area north of the harbour of Niehl, about 6.5 km from the Center of Cologne. The Katzengasse with its small plots is a very narrow road without sidewalks in the former farmers´s and fishing village of Niehl.

The urban environment of the Haus Katzengasse 18 seems very heterogeneous. More randomly than planned. This impression is created by the diffferent floor heights and the roof shapes, by gable and trusty houses and the irregular evidences of houses, which reflect the history of the original village structure. In the immediate vicinity you will find flatly covered houses, one storey outbuildings with desk roofs, houses with hipped roofs and gabled roofs,


Urban Development Reaction

Unlike its predecessor, the two-storey single-family house is moved off the northern property border by about four metres.

This creates a small forecourt that mediates between the house and the alley and allows the building to be developed from the gabled side. The predecessor building was suddenly developed from its wedding side by the narrow Katzengasse.


The one-storey existing house in Katzengasse 18 was completely dismantled by the builder because it did not meet today´s requirements for a single-family house with its low room heights of 2.19 m on the ground floor, the small living space of about 60 square metres.

An upgrade and expansion in connection with energy rehabilitation was out of question, as the house had serious shortcomings in its building structure and technical building equipment.

The former fisherman´s house from the centre of the 19th century was a nonhistoric massive building. The outer walls and foundations consisted of 36.5/24,0 cm of masonry. The saddle roof was constructed of coniferous wood and covered with red concrete roof stones.

The floor on the ground floor, as well as the floor ceiling between the ground floor and the attic, consisted of a wood-beamed ceiling filled with clay and straw and a floorboard. An existing partial basement as a brick vaulted cellar was partly preserved. In order to gain room height for the new building technology cellar, the vault was cancelled. The enclosure walls were concreted up to the lower edge of the base plate.

During the decommissioning by hand, the old field fire bricks were stored and cleaned so that they could later be reused as an attachement shell during new construction.


Fifteen essential theses on the design of the new building

The house´s draft is preceded by the conviction that an architectural design can only be as good as the questions to which he tries to formulate an answer or just as well as the preceding theses, which can be derived from the questons.


The new date roof house with small living space is supposed to develop a generous spatial effect despite small rooms.

The building is to be enrolled in different, specific spatial experiences.

The aim is to design spatial intentions that make the house for a family a home and a place in the world that touches and inspires you every day.

The building is to be developed with the very own means of the discipline of architecture in such a way that a sphere of the metaphsical can unfold in it.

The design is intended to create a high spatial complexity despite of a radically simple building cubature.

The design aims to find a coherent relationship between uniqueness and ambivalence of spatial boundaries and conturs within the building organisation in order to take into account an overarching idea of buildings.

A common form of a house like perhaps a child would draw should be superimposed with spatial elements, so that something profound emerges from the simple and ordinary.

In connection with a kitchen-living room as centre of life of the family in the house, monumentality should become an architectural theme in a positive sense. This should be brought into effect both inside as an impression of the room and externally as an expression of the building.

On the ground floor with the public rooms of the family, a room sequence is to be organised that connnects two antithetic rooms and includes the respective outdoor area in front of each other. The goal is a sequence of rooms that creates an unmistakeable and exciting spatial effect and that is more than the sum of its individual parts.

The relationships and interactions of the rooms offered with each other are of the utmost importance and must be deliberately organised.

The draft should see the house as a coherent whole. He is supposed to submit to a system and a overarching building idea. Ideally, everything refers to everything and nothing can be added and nothing taken away because everything has found its right place.

The design is supposed to be based on a reduced material cannon with the intention of reducing the rooms to the essentials in favour of the overarching idea.

The draft should not refer to meanings or symbols located outside the discipline of archtecture. It´s not about semantic connotations in any way, but exclusively about pure architecture.

The mission statement for the design is a treasure trove full of inspiring rooms. On the one hand, they should reflect the life draft in the draft house and, on the other hand, build on collective spatial experience.

The clear proportions of the entire structural facility, the rooms in detail, up to openings and components, must be deliberately designed and put at the service of spatial effect.

05.0 Architectural order

Achsial order

The architectural order in house Katzengasse 18 is based on the system of two axes. A north-south axis from gable to gable and an East West axis from eaves to eaves. The north-south axis as the main axis follows the direction of the house and allows the entire length of the house to be perceived on each level. This extension of the house in the lenght corresponds to the lateral extension of all the main rooms, which occupy the entire width of the house. Thus, the house can be experienced in every main room and on every floor as a whole and a coherent one. The east-west axis in the centre of the house, which runs symmetrically with the main axis, is designed as a side axis. The staircase is organised along this axis to the east. On the ground floor and in the attic there are adjoining rooms on the west side. On the upper floor, the side axis of the building in the gallery room is emphasised. A room-sized, frameless opening visually extends the axis into the street space.

The house as a whole

The whole of the house as an organism is based on a spatial systemic idea. A system of organisation with repetetive architectural, spatial motifs and sequences, as well as coordinated proportions, lead to a complete whole. A reduced material cannon with a few good ingredients supports the idea of building unit as not composed additively, but as a homogeneous coherent beeing.


Room sequences on the ground floor

Entrance courtyard

The small forecourt that frees the house to Katzengasse in the north is intended as a start to room sequence that leads via the living room to a centre zone with vertical closure and the guest toilet into the eat-kitchen and finally into the fenced open space to the garden terrace. The courtyard is intended as an outdoor room. Complemented by the development of the neighbourhood, it is bordered on three sides.


Various uses overlap in the living room. The room addition includes hallway, cloakroom and storage space, seat and lying surface in a padded wall niche. The living room as an intimate parlour with flanking furniture is a space with horizontal character that is directed along the ridge. This spatial effect is caused by the U-shaped overthrow, which identifies the partially filled room niches and the horizontal opening of the front door system as the only lying format in the facade of the entire house, as well as the relatively low ceiling height. The niche in the built-in cabinet also has a horizontal orientation and the deep seat over the entire length of the room also contributes to this spatial effect. The living room opens through frameless solid glazing on the side in the escape of the walls. The interior thus connects directly via the lateral room escapes with the exterior of the courtyard.

The courtard space is bordered in the north by a brick niche wall. The seating area has the same height and width as the opening of the front door system, thus strengthening the spatial connection between the living room and the courtard.



A narrow, short hallway closes to the living room. He gathers the staircase and the adjoining rooms, guests toilet and storage room. The spatial intention of the narrow passage is figuratively that of a compression. It precedes the spatial expansion in the kitchen´s high hall room and initiates the spatial development into the vertical as a caesura.


Guest toilet

In the guest toilet, different funnctions overlap like in the living room. In a wall niche as a room extension, there is a washing dryer and additional storage space in a built-in cupboard. The upper end of the guest toilet through a gabled roof emphasises its longtudinal orientation and makes a significant contribution to the spatial identity.


Kitchen-living room

The kitchen-living room is intended as an antithetic room in relation to the horizontal living room.

Here, the vertical spatial figure dominates with the two-storey height. The high and slim openings of the room to the south emphasise this orientation. As the living room, the escape from the room is transferred into the outdoor area through frames embedded in the masonry with solid glazing.

The room rises as a hall with monumental order and connects with the gallery on the upper floor.

In contrast to the living room, the room is aligned across the longitudinal axis of the house. The large window of the gallery indirectly exposes the kitchen-living room from the west. The room sequence on the ground floor living room-floor-living kitchen allows two different readings. On the one hand, they can be regarded as a sequence of individual rooms, because the rooms are strong enough contoured for this, on the other hand, they can be described as room continuum, because the rooms are not separated from each other by falls. The underview of the ceiling between the living room and the hallway runs through, just as the ceiling of the kitchen-living room extends into the gallery room. Spatial ambivalence generally pursues the intention to create the spatial experience more complex and, in particular, to make the spatial structure appear more generous.

07.0 Rooms upstairs
Upstairs there is a bedroom and a small gallery that opens into the airspace of the kitchen and connects both floors. The bedroom is accessible from the gallery via a floor-to-ceiling sliding door. With the door open, the room sequence of kitchen-gallery-enclosure combines to form a room continuum with achsial eye-creat through the entire house as a recurring design pattern. Analogous to the room structure on the ground floor.

Rooms in the attic

The attic contains two mirrorbalanced rooms. In between is the bathroom. The room structure follows the logic of the ground floor, with the difference that there is a clearly lowered development room in front of the rooms, which accomodates the open door so that they do not appear in the main room. The door-room allowes built-in wardrobes that can be opened up to the hallway as additional storage space. The heights between the centre zone and the rooms on this floor level have a spatial effect as well as the height differentiation on the ground floor between the hallway and the kitchen. The contrast between narrow and wide and the increased spatial expansion in the rooms is the intention of the room experience and the same motif.



The bathroom is developed in the centre axis of the house. It includes a washbasin over the entire depth of the room, a toilet area, and a cylindrical room for showering, which closes upwards with a dome. Due to a fall and a threshold, as well as deep jourges spatially removed from the bathroom, a narrow and low passage into the shower makes the independence of the room tangible. In this room, too, the interplay of spatial compression and expansion is the architectural theme.

The underlying spatial experience is the physical feeling of being completely inside a holowed-out volume.



The essential materials for the house inside are: oak, clay plaster, natural stone, cement floors and on the outside: Masonry, precast concrete and aluminium.

Oak wood for the windows and part of the built-in furniture.

Mud plaster plaster with luminous coating for walls and ceilings inside in light and dark design.

Natural stone:
Light „Kehlheimer Auerkalk“ for the kitchen countertop and dark „Kirchheimer Muschelkalk“ for the washbasin in the bathroom.

Cement floors:

The main rooms of the house as an open space sequence have a seamless white floor covering on a cementic basis. In the closed adjoining rooms, the floor is seamlessly black coated.

The roof cover with double is made of white-grey coated corrugated iron.

Barred masonry:
The facades is made of field fire bricks. During the dismantling of the former fishermen´s house, the approx. 170- year old bricks were removed from mortar residues and cleaned with the steel brush to be reused as a attachement shell during new construction. The old material was transferred to the new house according to the principle of „cradle to cradle“ in order to make a strong reference to the history of the place. The material question of the outer building layer was thus answered by the local situation itself.

Precast concrete:

For the window sills and falls of the openings, as well as a bench in the niche of the entrance courtyard, precast concrete made of white concrete have been inserted into the masonry. The „mailbox throwin“ and the bell sign are also prefabricated moulded stones made of white fairfaced concrete.


The cubature of the house is essentially characterised by three integer proportions of floor plan, longitudinal tear, and gable tear.

The house rises on a double square 1:2, the longitudinal facade has the proportion of 2:3

And the gable facade has measured the aspect ratios from 3:4 to the height of the eaves.

These three geometrically clear proportions have proved to be consistent in the design for the building site with very limited dimensions, the construction legal framework conditions, and the spatial program.

The opening proportions of the facades are based on masonry dimensions (a multiple of 12.5 cm). The pillars or wall discs of the monumental order over two floors in the south have a distance of 2.25 (intercolumnium) in relation to the pillar as the basic module.

This ratio of 1:2.25 was also the intercolumnium favoured by Palladio. It's based on Vitruv, which distinguished five intercolumni with different aesthetic effects.

It has the name Eustylos translated „beautiful columnar“.

The goal of proportionalisation in the design process was not to create a dogmatic search for the absolute figures, but to create the simple building cubature with identity.

From higher-level building volumes to subordinate building structures, all proportions of the house are designed in such a way that an organising bond is created with the intention of strengthening the idea of the house as a whole also on this design level.

When the house is only built and its time begins, all these analytical considerations that were necessary may take back into the background.

Energy concept:

The house K18 is heated with a brine-water heat pump in the building technology cellar in combination with underfloor heating on all floors. For this purpose, four holes of 20 metres deep were carried out and equipped with earth probes. A fresh water station with a buffer tank is used for water heating, which prehears the hot water with the heating water via a heat exchanger. The system technology with a high proportion of renewable energy in connection with a very well insulated outer shell of the building and triple glazed windows enables a low-energy house eligible for funding with the KFW 55 standard.



In order to meet the demands of a sustainable building, an energy concept with a high proportion of renewable energies was realised on the one hand, and on the other hand, predominantly resource-efficient building materials were used.
For the massive 49 cm thick outer wall of the building, it is from the inside to the outside:

1. Masonry of the supporting shell:
Lightweight concrete masonry (KLB climate light block)

2. Core insulation, masonry and roof insulation:
Mineral wool and roof insulation in glass wool.

16 cm (In the roof + 6 cm wood fibre insulation panel)

3. Field fire bricks (recycled brickwork)
11.5-13.0 cm Thickness, 6,5 – 8,0 cm Stone height

1. Supporting shell made of lightweight concrete masonry:
The masonry is made of highly insulating pumice. This was created during the eruption of the Laach volcanos 12,000 years ago. The natural foaming of the liquid lava has

created a grain of rock that has many air inclusions and is now being removed from one of the largest pumice mining areas in Europe in the new basin.

The rock grain is mixed with water and binders, filled in steel moulds, and then solidified by vibration.

After removal from the moulds, the stones dry in the air and cure completely without being fired, which contributes to a very good life cycle assessment of the material.

Another resource-efficient aspect is the extremely short transport distances from mining to further processing of the product.

2. Core insulation, masonry and roof insulation:
The mineral wool is made from natural raw materials and is produced waste-free and sustainably.

Stone wool is made from the mixture of limestone, basalt, dolomite, diabas, waste glass and a residual proportion of organic raw materials of o,5-5% with a low energy consumption and thus has an excellent life cycle assessment. The starting material is melted and then blown out to the fibre material with compressed air and mixed with binders. The glass wool is made of 70% waste glass and is produced in the same way.

3. Field fire bricks (recycled brickwork)
11.5-13.0 cm

The attachment bowl made of field fire bricks comes from the previous building and is therefore 100% reused material.