The objective of this study was to determine the impact of joint rigidity on results of skeleton furniture construction optimisation expressed by the function of minimum material volume. The performed experiments proved that joint rigidity exerts a significant effect on optimisation results both with regard to the difference of individual dimensions of element cross-sections and total construction volume. Gradient optimisation allowed reducing the volume of skeleton constructions by 72 – 76% of their initial volume within the time of less than 1.4 hours.