Metal parts of buildings like metal studs, building materials etc can cause a lot of distortion. I have a Yaesu FT65R which is a VHF/UHF walkie talkie and outside my house I can hit the repeater 9 miles away and talk all over the area. So as far as the radios go, a good quality one with a good quality antenna will transmit well. GMRS is not far outside the UHF ham band and should work unless there are a lot of obstacles. Inside the building may prove to be a challenge but move around a little and see if that makes a difference. You might be able to identify what is causing the signal block.