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This underground parking garage extends under these two new buildings and connects them to each other. On top of the underground garage, an inner courtyard will later be built between the buildings. We start on the back side, where we have to take down the bored pile wall. In order for this to be possible, the slope must first be braced with precast concrete retaining panels. There is already a video on my channel about this. This slope can only be reached via the roof of the underground garage. The roofer has already glued on the first three sheets of waterproofing, so that we can start with the angular retaining panels. Here is our material for the new retaining wall. We protect the waterproofing with protection mats and then start to mortar, apply and compact the filling material. The first row of angular panels can then be placed on top of it. The pieces are set with an excavator and here and there the excavator driver has to use his special skills to set them right. Behind the wall there is a drainage package consisting of a drain pipe, gravel and fleece fabric around it. Then it can be backfilled and compacted. Then a secondary retaining wall is added, because the slope is relatively steep. Between the two walls, greenery will be planted later. While the roofers work hard to seal the entire underground parking garage with root resistant waterproofing membrane, we can start dismantling the bored pile wall. This was delayed due to the bad weather. But without a roof membrane, no green roof. And with the roofing finally finished, we can start with the layering construction of the green roof. First of all, a white protective fleece fabric is applied to the cleaned membrane. This is very important to prevent damage to the waterproofing. The fleece is 500 g/m² and will also continue up the sides. For this construction, a so-called slip layer of PE sheet is placed next. Over time horizontal forces can occur and this slip layer is supposed to absorb these tensions. Because of this sheet, the entire roof structure can slide on the fleece, if necessary. We now place the FKD drainage and water storage elements from Optigreen. Here we have to lay two different FKD elements, which at first glance look exactly the same. They are available with holes at the top and holes at the bottom. The elements with drilled holes at the top are laid in the area of the subsequent greening. The holes at the top ensures an accumulation of water of approx. 23l per m². In the area where it will later be paved, the FKDs with drilled holes at the bottom must be laid, so that quick and good drainage can take place. The large elements can be laid relatively quickly. The drain water later runs under the FKD elements to this drain, which leads the water down through the underground garage. When all elements are laid and cut to size, they are filled with a lava draining material. This drainage fill is light, resilient and drains water well. It is delivered with this truck and blown onto the surface through a hose. It can therefore be applied quickly and easily without driving over the FKD elements with a wheel loader. All compartments of the elements must be filled up to the top. A special and expensive building material is used for the next construction layer. This is foam glass gravel. The foam glass is delivered loose and brought to the roof with the small Schäffer wheel loader. This material is used here to keep the weight down. Otherwise the total structure of about 50 cm in thickness would have too high of a load on the underground garage ceiling. We use the material Optipor 10 to 75 mm. It’s about 20 cm thick and this glass foam layer is covered with a separation layer, a thin fleece. Now, in the area of the paved surfaces, mineral gravel 0 to 32 mm is laid out, levelled and compacted. Simultaneously, we also continue to work on dismantling the bored pile wall. Here you can clearly see where the walkway will be later. A light substrate is being used in the remaining areas. This draining vegetation substrate ensures good water drainage and a sufficient supply of nutrients to the plants. Now we can already start with the paving work. The main entrances to the residential buildings are accessible from the roof of the underground car garage. In addition, these lawn grid slabs will also be used. They are made of plastic and save you some weight compared to concrete lawn grids. The mineral gravel is covered with a 3cm bedding of mineral sand 2-8 mm. The lawn grid is laid in order to provide a stable surface for fire trucks. The pathways are finished and the grid plates have been filled with substrate. Now there are still some fixtures to be installed, like gratings in front of the entrances and bicycle stands. And so the roof construction is finished.
#construction #greenroof #howto