Question
Hello,
  Can I plant the Thuga next to a fence for screening? Will the root system grow and disturb the neighbors concrete wall on the other side? Also can I plant them in the middle of a Sacramento summer?

Answer
Plant them 5 feet apart for a screen this means 5 feet from the fence also. Any closer the branches will damage the fence. No the root system will not damage the wall --thugas roots are not prone to damaging walls driveways or foundations.
They should be planted in the spring. Planting in the summer is too much of a shock to plants. The main concern in the summer is the hot dry weather.
I would wait until next spring. The survival rate will be much better.