Abstract: A self-adjustable stair construction wherein the treads of the stair are supported by spacers between parallel upper and lower stringers in a truss assemblage. The rise and run and nosing are simultaneously adjusted for each tread with the adjustments being cumulative for each stair flight total run while maintaining the treads level. Each tread is located in a right angle relationship with each spacer. The treads, spacers and stringers are pivotally connected together with an elongated slot formed in each spacer to permit the adjusting movement. The slots are inclined and may be either curved or straight with the slope of either being in substantial alignment with the direction of the adjusting movement. The minimum number of repeated parts to produce the whole stair may be two.