By L. Haefner & H. Schnabel (IBH-SE+L+T - Design & Engineering)
Actually, there are a lot of ongoing design and engineering activities here in BERLIN to plan roof top apartments for residential accommodations. Here is the design project for two apartments on existing typical residential building of the period of Wilhelmina time with 4 story built with masonry walls and timber beam ceiling. The two additional stories should be used for new maisonette and 1-room guest apartment. The effective conceptual design is a collaboration of architect, engineer and the building owner community. There should be a large terrace for urban gardening actives of the maisonette owner and enjoying the view to the famous “Potsdam Center”.
To keep the weight of the new story as light as possible a timber roof construction is mandatory. Furthermore, construction time and cost-effective solution requires pre-fabricated large structural elements with advanced wood composite material of high strength laminate veneer lumber (LVL).These timber structural elements of the walls and ceilings needs plates and beams products of type “Kerto®”-Q, -S and -T. The contemporary layout of these new flats, especially for the maisonette, needs effecting glazing elements with nowadays buildings physics properties of modern glass-technology. Obviously, some steel connections parts are required.
Firstly, demolishing of the mono-pitch roof of a building in the center of Berlin follows the strengthening of the existing timber ceiling with thick standard timber beams connected with Kerto-Q plates as a so-called composite construction. The approach increases the load bearing, especially for new columns and walls. The main structural system consists of pre-fabricated column wall elements framed with steel connectors to the Kerto-Ripa floor elements, especially for the first rooftop story. For an effective construction the available masonry walls will be used as bracing elements in addition to new LVL wall elements. These new wall bracing elements consist of Kerto-S and the extremely, effective Kerto-Q plates with transvers veneers.
The top story with a living-, kitchen- and dining-area obtain a roof construction with “Bezier”-shaped curved ceiling. This kind of advanced modern roof shape increase the in height of this apartment area. This roof creates with the additional large windows of contemporary structural glazing a room feeling with great view over the roofs of Berlin. The pre-fabricated large span roof elements consist of layered, three Kerto-Q plates bonded together with transvers ring-stiffeners based on technical approval/EN14374. The kind of roof construction elements comply with approval requirements (single plate t =27mm and minimum radius R > 250t).
Furthermore, there is a circular shaped glass pavilion designed on the rooftop terrace within the urban gardening area. The class cylinder construction requires an effective bracing of the whole floor and can be effective realized with high-strength LVL beam and plate products of Kerto-LVL with some steel elements.
However, for most primary structural elements will be used as LVL products of beam and large plates with advantage of thicknesses of 27mm to 69/75mm and available plate size of 2,50m width and length up to 21m and bonded plates and thicker beams. The external pre-fabricated walls will be built with Kerto-Q plates (27mm and 33m) and Kerto-S respectively Kerto-T studs with an increased static load bearing capacity. Between the two wall plates will be cellulose insulation as a diffusion and air-tight construction. The internal walls are cross-laminated timber (CLT) with gypsum cover boards. The solid wood elements of Kerto-Q, -S and CLT plates yield with fire boards the requisite fire resistance.
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