Construction of the security post at the Montreuil hospital (93): a wooden cube dressed in red glass

The extension to the east of line 11 of the Parisian metro is an asset for the Center Hospitalier Intercommunal André Grégoire de Montreuil (93) which will be served by a new station, just in front of the establishment. But, among the counterparts, before the start of work on the metro in mid-2016, the hospital had to relocate its fire and anti-malware safety post located in the right of way of the site and build a new one.

Winner of the architectural competition launched during the first quarter of 2014, the SCP Truelle Architectes agency is experienced in construction and renovation projects in the medico-social sector which it has made its specialty: most of its activity relates to social housing, hospitals, retirement homes ...

Building in a dry sector

“For this small building of about 150 m2 we chose the simple shape of a cube, describes Elisa Bellec, associate architect of the Truelle agency. What guided our reflections, in addition to responding as best as possible to the expectations of the hospital, was to design a clearly visible access building, spotted from afar, clearly identifying the entrance to the hospital. This cube is extended by a portico which connects to an existing building. The new construction is made even more visible by tinting red.

From the competition phase, the option of building in a dry sector is favored in order to reduce the duration of intervention on the site as well as the site nuisance. The choice is a wood frame with a low carbon footprint in cross laminated timber panels (CLT cross laminated timber). This two-storey prefabricated structure will be placed on the concrete foundations by the company Paris Charpente in just three days, using a mobile crane.

The facade will be covered with a shiny, robust and quality material. From the outset, Elisa Bellec turned to Sto, whose StoVentec Glass façade system she appreciated. This ventilated cladding with invisible fixings is made up of 6 mm thick enamelled glass panels glued to an aggregate mortar plate made of recycled glass. The panels are implemented by interlocking aluminum staple rails on a network of horizontal aluminum rails.

To animate the simple form of the building, the architect chooses from the range of colors offered by Sto three shades of red (RAL 3016, 3020, 3013) and one orange (RAL 2000) for the portico. The panels of different sizes and colors are distributed randomly on the facade. In total, 227 panels, all different, will be delivered by Sto.

A first on a wooden frame

The holder of the Cladding lot is Socateb, an experienced company that is familiar with Sto products. A chance for this first application of StoVentec Glass on a wooden support. In fact, the Technical Assessment for the system only admitted masonry or poured concrete supports.

"To adapt the implementation of StoVentec Glass on a CLT timber structure, we discussed with the Scientific and Technical Center for Building (CSTB), the control office and the technical service of Sto", explains Antoine Monnot, head of the cladding and cladding department at Socateb.

The technique developed on this site is now included in the Technical Assessment of the system.

From a freestanding tubular scaffolding, which has no attachment to the wooden structure, a rain screen is first installed which surrounds the entire building. It prevents the migration of moisture into the wood. Rafters of 188 mm x 75 mm are then fixed vertically with a center distance of 60 cm using through screws.

"These imposing dimensions are necessary to respect an air gap of 2 cm", justifies Antoine Monnot.

In fact, 16 cm thick glass wool panels are slid between these uprights and held using Dentifix claws (Etanco), thus avoiding perforating the rain screen. The front face of the rafters is protected by an EPDM strip.

The aluminum rails supporting the facing can then be screwed onto the vertical rafter structure, according to the center distance defined by Sto according to the specificities of the site. Finally, it remains to staple the 227 enamelled glass panels, scrupulously respecting the layout and reserving 8 mm open joints between panels. After adjusting the horizontality of the support rail, each panel is adjusted by adjusting screws and is locked with pins.

“The most complicated thing was the adjustment of the panels in the plane, because the wooden uprights fixed directly to the OSB framework leave no margin, observes Antoine Monnot. Sometimes we had to plan or shim to ensure perfect alignment. "

The window frames are dressed in red or orange lacquered aluminum sheet, like the parapet covers.

The 295 m2 facade was completed in one month by three companions from the Socateb company.

After four years, the occupants of the security post say they are very satisfied with the thermal comfort of their new workplace. The combination of timber construction and StoVentec Glass cladding is effective.