The race to the highest timber building is ongoing. More and more tall timber buildings are built all over the world. The vertical load-carrying elements (columns and walls) in such high-rise buildings are subject to high permanent loads. Special attention has to be paid to the load-deformation behaviour of these elements, especially during the construction process when the load is incrementally increased with each new storey. The time dependent load-deformation behaviour of the materials timber and concrete is modelled by a chain of Kelvin-Voigt elements. The deformation of the elements of the buildings are modelled during each building phase. The models are evaluated by measurements from a fibre optic system in the columns and cores of two high-rise timber buildings in Switzerland.