Pres-Lam timber structures are being adopted throughout New Zealand and around the world. This innovative method of timber construction combines the use of large engineered timber members with posttensioning cables/bars. The hybrid version of the Pres-Lam system improves seismic performance through the addition of external or internal steel reinforcing. While the post-tensioning provides re-centering properties, the steel increases energy dissipation from the system as well as increasing moment resistance. The design of these structures is performed to withstand high levels of seismic loading without damage to the structural system. Over time, the post-tensioning force being applied to the structural timber members causes them to reduce in length that has a subsequent impact on the quantity of force being applied. This paper looks at the dynamic characteristics of fundamental period and elastic damping of three recently constructed Pres-Lam buildings, investigating the influence of these losses on the dynamic characteristics. Following this a study of the performance under strong motion is performed. The paper concludes that although the losses in post-tensioning are clear they do not impact on the dynamic characteristics and have only a minor impact on strong motion response.