Nilsson Pflugfelder brings German pre-fab to Cambridge with House R

This new-build on a backland site in central Cambridge was built using a German pre-fab system
Conceived as a ‘compact box’ surrounded by Victorian terraces, House R edges away from its site boundaries to maximise amenity space and minimise overshadowing the neighbouring gardens. The ground floor houses living spaces while the upper floor houses north-facing bedrooms, with fenestration employing frosted glass or projecting fins for privacy.

Baufritz’s system uses timber construction, with closed wall and roof panels that are finished in a production plant and hoisted into place by crane. The waterproof shell is erected in around three days, with construction then taking place within the house.

Architect’s view
For effective production, both in terms of material resourcefulness and cost, the pre-fab construction system favours orthogonal geometries based on a 625mm by 625mm grid. Ceiling heights are standardised and walls, external and internal, have standardised wall thicknesses, all of which makes site wastage negligible.

All details are standard Baufritz details, which makes for cost-effective construction with a minimum of material wastage. Apart from the oriel window, all windows are standardised off-the-shelf types and sizes. The house is clad with a standard timber cladding, consisting of untreated 28mm solid timber. 

As the pre-fab construction system is panel-based, it means that there are certain structural implications. A typical timber frame construction allows for a relatively flexible distribution of loads, whereas the panel system structurally acts like an unstable house-of-cards. The floor plan must therefore inherently provide for lateral bracing. Likewise, large spans and cantilevers are structurally possible, but add cost while making construction overly complicated. As the external walls are delivered as closed walls and fully finished elements, it is not feasible to change the actual walls.

Typically a house pre-fabricated in this way requires only 20 per cent of the energy for space heating compared to a traditional brick built house. The use of large prefabricated elements means that a very high degree of precision is guaranteed, yielding a very high degree of airtightness (exceeding current building regulations by at least 100 per cent), which further reduces the amount of energy required to heat the building. Only non-chemical natural materials and building methods are used throughout. The timber used for construction is logged from certified sustainable forests. The shell is 100 per cent biodegradable and can completely be returned to nature.

Project data
Start on site April 2016
House assembly on site 27 April 2016 - 30 April 2016
Completion August 2016
Gross internal floor area 249m2 
Form of contract or procurement route Design & Build
Construction cost £610,900
Construction cost per m²
Architect Nilsson Pflugfelder, Berlin/London
Client Family R, Cambridge
Structural engineer Baufritz
M&E consultant Baufritz
Quantity surveyor/cost consultant Robert Lumme (Baufritz)
Planning consultant RPS Planning and Development (Paul Derry & Don Proctor)
Landscape Sara Mark
Groundworks Gary Gabriel Associates (Joe O’Donnell & Reiss Rampton)
Project manager Dominik Boehm
Approved building inspector MLM Building Control
Main contractor Baufritz 

Original link - Architects Journal

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