As robotic applications in building processes increase, the majority of studies focus on development of algorithms for object targeting, path planning, and localisation. Very limited attention is given to environmental factors, such as varying luminance and presence of undetected obstacles, that are common on construction sites and can significantly influence the robotic system performance. To address the gap, this work investigates the effects of environmental conditions on robot performance in structural assembly. A series of physical experiments was conducted in a laboratory setting to evaluate the effects of different lighting conditions on the positional accuracy of the robotic arm, the time required to install components, and the overall successful rate of the robotic assembly. The coordinates and orientations of installed AprilTag markers, captured by a red green blue-depth (RGB-D) camera, were then analysed to determine the effects of luminance levels on the accuracy of the positioning robotic system in two different assembly tasks. Furthermore, under constant luminance conditions, obstacles were arranged in various patterns along the path of a mobile robot to evaluate changes in trajectory and alignment disturbances. Differences in robot orientation, installation times, and completion status of the assembly tasks were also recorded to understand the impact of obstacle configurations on the efficiency and adaptability of the robotic system in structural assembly.