Zhang, L. Castagna, J.C. Holmes, M. R. JACoW Publishing Geneva, Switzerland The key features of LCLS-II upgrade are the high repetition rate up to 1 MHz, and two variable-gap undulators (SXR and HXR). To take the advantages of this major upgrade, LCLS, SLAC is designing and building new soft and tender X-ray beamlines (TMO, TXI, RIXS, XPP). The laser pump FEL probe, or SXR FEL pump HXR probe experiments need sub-micron stability in a time range from 5 ms to a few hours. Dynamically bendable KB mirror can focus X-ray beam down to 300 nm. The overlap of the pump laser (or FEL), probe FEL beam and sample is challenging. Some measurements on vibration and long term stability have been carried out on the floor in the Near Experimental Hall (NEH) to host the new beamlines. The vibration displacement in the frequency range of 1 to 200 Hz is at the level of 25 nm. The floor deformation over hours and days measured by HLS and interferometer, however, show tens micro-meters displacement variation. This huge floor deformation is incompatible with the stability requirement. In this paper, we will present the simulation of the whole NEH building, comparison with measurement results, describe mitigation plan and predict the performance.