A parking roof terrace produced with POLYS BÉTO

The multiplication over the last thirty years of the French car fleet has pushed the legislator and local stakeholders to reconsider a parking policy in the implementation of Urban Displacement Plans (PDU).

Taking into account the high costs of land, town planners and architects have optimized parking areas by developing roof terraces for parking. They freed the roofs from their unique function of "protective cover" to allow them to contribute to the sustainability of the building and its upgrading.

A concrete case

It is with this in mind that one of the buildings of the "Aristide Briand" residence, intended for demolition, was renovated to create parking spaces with 86 underground spaces as well as a roof terrace. with 58 places.

Fabien Jousset from DV Construction, the general contractor in charge of the project, explains the complexity of the site:

“The rehabilitation of an old building into a roof terrace parking lot presents many different problems and very often, the question which arises is that of the existing slope and the problems of drainage on the surface. Indeed, in the event of heavy precipitation on the ground, puddles of water form quickly or the evacuations are blocked by the too rapid descent of the water ”.

It was therefore necessary to give the surface of the parking roof terrace an artificial slope to drain rainwater to the collection devices.

Fabien Jousset specifies“We had to make slope shapes for the water evacuations of a 2200 m² car park, before pouring an asphalt circulatory coating for parking light vehicles”.

It is obvious that the construction of a parking terrace-roof calls on extremely different skills from civil engineering: building and road construction. Taking into account the processes and materials used, the actions they undergo, their thermomechanical behaviors and their degradation is essential for the sustainability of the structure.

Indeed, the level of performance required for a roof on which cars circulate, brake, maneuver and park, is very high.

• to be able to use a light product, - offering the possibility of creating forms of slopes,
• also having the ability to be covered by asphalt, and,
• strong enough for the passage and parking of vehicles.

"The choice of the POLYS BÉTO® solution was a natural one, this process being the only one to benefit from a CSTB Technical Assessment for this type of application with the constraints exposed" testifies Fabien Jousset.

A unique process, validated by CSTB

As specified in the CSTB Technical Notice (Technical Notice 5 + 13 / 11-2242), the POLYS BÉTO® waterproofing support process is perfectly suited to terraces accessible to light vehicles (maximum load 20 kN per axle), with occasional accessibility fire fighting vehicles and moving trucks.

The pressure allowed by the POLYS BÉTO® FORME form is 100 kPa, the coating and / or the additional insulating layer (if any) being able to impose a lower limit.

The light mortars produced with POLYS BÉTO® are an excellent complement of thermal and acoustic insulation for the realization of all supports of ground coverings, insulating racks and under-screeds, adjustments of levels, shapes of slopes, various fillings…

The use of POLYS BÉTO® therefore makes it possible to obtain slopes for receiving sealing systems. * The “POLYS BÉTO® FORME” process for waterproofed roofs is placed:

• above a load-bearing masonry element,
• below a waterproofing system (vapor barrier, insulating panels),
• under a waterproofing coating (asphalt, mixed asphalt coatings, bituminous coatings, synthetic coatings).

 prescribed by standards NF P 10-203-1 and NF P 84-204-1-1 (reference DTU 20.12 - DTU 43.1 P1-1)

The secret of its lightness is the reduction of traditional aggregates in favor of the addition of POLYS BÉTO®. POLYS BÉTO® aggregate completely or partially replaces sand and gravel, traditionally used in the preparation of mortars and concrete. Lightweight mortars produced with POLYS BÉTO® have densities lower than those of traditional concrete, which can range from 500 kg / m³ to 1500 kg / m³. This weight saving therefore allows structures to be lightened.

250 m³ of POLYS BÉTO® were used for the parking lot of the Residence "Aristide Briand". POLYS BÉTO® is very easy to use, its foamy consistency allows a simple and effective application. Rolled with a mixer truck, the process was poured in several times, the form POLYS BÉTO® FORME is poured by layer maximum thickness 0,30 m.

The installation and smoothing were carried out in the manner of a dallagiste's platform. Steep slopes, beyond 10% and up to 20% from the horizontal, are made in successive passes in the horizontal direction, perpendicular to the slopes and starting from the bottom of the slopes.

The direct circulation on the POLYS BÉTO® form was limited for 2 weeks, the drying time. A waterproofing membrane was placed on top of the POLYS BÉTO® form, followed by an asphalt coating.

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