Ideal sensor placement for Wireless IDS differs from that for Location Tracking.
You have a small office of 10,000 sq. ft. For Wireless IDS/IPS you would only need 1 sensor; to maximize the coverage it makes sense to place the sensor in the center of the building. When location tracking is need in this same scenario, a minimum of 3 sensors for each floor plan would be required, and recommended placement is at the corners.
You have a multi-floor building with 3 floors. Depending on floor construction the RF may travel through each floor. If only Wireless IDS/IPS is required, you may be able to leverage detection through the floor and ceiling and place sensors on every other floor. Depending on the floor characteristics, you may need a sensor on each floor, however it may make sense to off-set each sensor on each floor and take advantage of the detection through the floor and ceiling. If location tracking is needed, the same 3 sensors for each floor plan would be required and the recommended placement is 3 sensors in the corners of each floor.