Bad Range with XBee S2D


wanted to ask if anybody get better ranges with the XBee ZigBee S2D module with integrated antenna and +8 dBm output power.
I get only 13 meters through 2 small (15 cm) walls and only 22 meters at line of sight. At one brick wall there are only 10 meters between the devices with best LQI of 255 and no noice at the channel ZigBee used.