Six new apartments with Kerto-Ripa wooden extension  

Extension to a building in Paris

Location 23 Rue de Tlemcen France
Building Year 2014
Architect Lair & Roynette
Products Used Kerto-Ripa, Kerto LVL
Type Residential Buildings And Gardens

Six new apartments made from Kerto LVL roof elements on a 1960s building in Paris

​In the reconstruction  of 23 Rue de Tlemcen in the 20th arrondissement in Paris targets in the renovation were  improved energy performance on the existing seven-floor building and to add six new dwellings on the top of the building.

For the architects Lair & Roynette, who designed the extension, the use of wooden building material was an obvious solution from the architectural, structural and thermal perspectives.
The social tenement house in the Rue de Tlemcen in the 20th arrondissement in Paris had 78 dwellings. Six new apartments, in total 300m², were built from wooden elements on the top of the building.

The architects Lair & Roynette designed the additional floor to fit harmoniously with the existing concrete building. They chose to combine two construction systems made of prefabricated wooden elements. The Leno® wall panels and Kerto® LVL roof elements from Metsä Wood were eventually selected.

The walls of the raised structure are made of 115mm Leno® cross laminated panels with external rock wool insulation. The walls are cladded with larch timber boards. The largest panel measured 3.70m x 9.30m which required the use of a special trailer to transport panels vertically.

The roof complex was designed with 425mm Kerto LVL roof elements, insulated with 400mm of glass wool and closed with a 15mm OSB panel underneath.

Wood: A lightweight solution for additional floors

Metsä Wood’s wood solutions are light, so they minimise the loads on the existing building, while still offering bracing against wind load.

The raised structure could not cover the entire length of the building, due to the chimneys on the roof. The Kerto LVL roof elements provided a made-to-measure solution, because the different widths could be adapted around the existing chimneys.

The Kerto LVL roof elements, with their long span, between the load-bearing walls also increase the interior space, because they do not need any intermediate columns nor beams. 

However three large Kerto LVL beams, measuring 6 to 7m were installed to create a required slope on one side of the building due to limits set in the Paris urban development regulations.

Simple to install and ideal for sites with difficult access

The Rue de Tlemcen site was difficult to access, because it is located in a relatively narrow street in the 20th arrondissement in Paris,  and is surrounded by high buildings.

The solution from Metsä Wood with prefabricated elements enabled rapid, dry construction in addition to other benefits in very dense urban environment and same time technical demands were met.
The wooden structures was delivered to the site already assembled and with the insulation. The openings for the doors and windows were ready in the Leno® wall panels.

In January 2014, a five-man team of carpenters from the company Driollet installed these prefabricated elements - 429m² of Leno® walls and 454m² of Kerto® LVL roof elements - in just 10 working days. The installation of the wooden structures did not require any large machinery, but just a big mobile crane that was folded away every evening.

Thanks to prefabrication, the use of wooden materials also helped to minimize disturbance to the tenants and prevented from the delays in the project.

Energy performance in line with the climate plan

The rehabilitation of the 78 housing units at 23 Rue de Tlemcen and the construction of six new dwellings won the French environment protection and energy management agency’s (ADEME) call for Sustainable Rehabilitation projects. Energy performance requirements were strict.

The thermal and environmental engineering bureau AB Environnement  set the target that the raised structure should be align with the Climate Plan: Primary energy consumption ≈ 50kWh/m². year. The raised structure received New Low-Consumption Building label: Primary energy consumption ≈ 50kWh/m². year.

References related to

extension building

  • De Karel Doorman – 16 floors extension

  • Rakuunantie extension storey

  • Cockfield Windmill – conversion to accommodation using Kerto® LVL

  • Extension to a building in Paris

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