The solution by renowned architectural firm MRLV was to replace the old, ailing roof truss with a steel-free construction. The architect collaborated with the structural engineer Stefan Heidrich from WTM Engineers, and they developed a roof design without any load bearing metal supports or joints.

Any metal joints that can still be seen today only served as an assembly aid, and they remain there without static importance. According to Voss, ”Industrially manufactured, dimensionally stable Kerto® LVL (laminated veneer lumber) helped us to achieve an efficient solution. We were thus able to develop an object-specific design that meets both the static and the economic requirements.”

Minimal thickness, maximum bearing

”Since a traditional timber framework would be too expensive, we chose pre-fabricated cross-bonded Kerto LVL Q wooden trusses,” says Stefan Heidrich. They are constructed of two halves, which are a mirror image of each other. The halves are joined by a round metal bar, which works as a pin in the structure. These built-in metal parts are exposed in the temperature-controlled hall. In this air-conditioned area no condensation is to be expected. The entire roof truss is fully accessible in accordance with safety regulations to ensure the monitoring of the roof’s condition and the easy replacement of parts.
 
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Roof bracing made simple with Kerto LVL Q-panels

Forged drawstrings that are based on historical models, give Kerto® LVL glued trusses in the necessary horizontal bracing. These metal parts add a touch of historical continuity as they are fully visible above the swimming pools. The roof frame covers a span of 27.5 metres. The Kerto roof panels together with the historic masonry walls brace the buildings against horizontal loads from wind and usual structural asymmetries. This was possible with the use of 69-millimetre-thick Kerto LVL Q-panels. The Kerto LVL Q-panels ensured high strength values at a relatively low thickness, with a very high load capacity and dimensional stability. 

New way to preserve the old

Two rows of purlins, one for the roof and second for the ceiling, connect the main trusses with special wooden joints. The purlins were made of slender, high-strength Kerto LVL S-beams, which are ideally suited for this application. The main trusses were drilled for service access in a way that is not visible from the swimming pool due to the suspended ceiling required by the preservation order.