Rooftop parking is a widely-used way of utilising the roofs of large-surface commercial and service buildings such as shopping malls, as well as some residential buildings.
Car park decks are a special type of roof terrace where vehicles of various sizes can move and park on a paved surface.
ADVANTAGES OF INVERTED ROOFS
The main advantages of inverted roofs in flat roofs used for vehicle traffic (eg car park deck) are in:
- mechanical protection of the rainwater proofing membrane
- installation of the waterproofing layer directly on the solid slab
- application of high-strength thermal insulation
The use of high-strength FLOORMATE™ 500-AP and FLOORMATE™ 700-AP boards with high flexible rigidity offers simple, economical structural solutions with long lifespans.
High-performance XPS thermal insulation boards are recommended for flat roofs used for vehicle traffic, irrespective of the order of layers, due to the highly compressive and sliding stresses that arise from the movement of vehicles.
This type of flat roof is usually exposed to higher static and dynamic loads than normal roof terraces, due to the concentrated wheel pressure of vehicles, and the dynamic effects arising from movement.
The production process used in the manufacture of extruded polystyrene (XPS), results in a homogeneous, closed-cell material structure with a smooth surface (called the extrusion skin) which provides:
- consistently high thermal insulation levels
- water and frost resistance
- high strength
- high flexible rigidity
- high resistance to vapour diffusion
All of these characteristics make the XPS thermal insulation material suitable for a car park deck.
INSTALLATION OF CAR PARK DECK
The order of layers and the steps of installation is identical to those of walkable terrace roofs up to the protective layer of waterproofing, but in respect of the loads, the compressive strength of the thermal insulation must be:
- at least 300 kPa in case of load-distribution reinforced concrete slabs
- at least 500 kPa in the case of concrete paving blocks laid into a screed (min. 10-cm thick)
The selection of the type of material should be determined according to size.
The slope of the reinforced concrete top slab or the sloping screed should be determined according to the Roof Insulation Guidelines. A minimum 2% slope is recommended.
It is useful to frame floor gullies and vertical structures with reinforced concrete edges in order to prevent movement.
PAVING SLAB WALKING SURFACE
If a sized concrete screed is prepared, the expected load, sliding stresses arising from vehicle movements, thermal expansions and slope conditions should be taken into account.
Expansion joints are to be used in a raster at least 2.50 x 2.50 m, and the infiltration of rainwater should be counted on despite the persistently flexible joints, so a drainage layer must be installed to act as a vapour pressure relieving layer and a sliding layer as well.
The thickness and rebar needs of the plate and the design of the expansion joints and expansion sections to work together should be prepared based on the instructions of a structural engineer.
When a load distribution reinforced concrete slab is prepared, the dilatation joints need to be sealed.