Monitoring the displacements of structures caused by slight or big seismic shakings and landslides the irrespective of observation points by simply taking the data using a single equipment is useful. GNSS antennas and receivers on the roof of a steel tower to monitor the displacement of the structure caused by the wind etc. has already been reported, but ours is the first study on a low-cost GNSS system attached to the wall of a building to monitor structure deformations. More specifically, this research focuses on real time monitoring for structure deformations using hand-held RTK-GNSS (Real-Time Kinematic Global Navigation Satellite System) receivers installed on building wall. RTK positioning is normally carried out using expensive receivers and antennas compatible with dual frequencies. However, aside from its high cost, this type of equipment is also not easy to procure. This study addresses this problem by using a single-frequency low-cost receiver, with comparable results in centimeter level. The methods presented make use of horizontal spread and statistical values to come up with the positioning results. Our work on the proposed revolutionary monitoring system with a robust RTK improvement method will serve as basic research for monitoring the fluctuations and deformations of structures in the fields of architecture and construction.