I was expecting a service throughput issue from the OP's topic
If this only pertains to your household wifi setup, there are numerous ways to tackle dead zones. I normally stay away from using repeaters since they take up bandwith from current wifi signal just to extend, reducing overall wifi throughput.
The homes in DC can be quite close to one another having visited the area numerous times so I would check to make sure if your wifi network is secured from unintentional usage outside the premise. If people are leeching outside, cut them off.
Where is router located? In a 4 story household, you generally want the location of router to be placed in the center of the complex (base of 3rd floor or near ceiling of 2nd floor. Today's wireless router can cover an entire complex with little trouble. If your router is having trouble, I would consider getting signal booster for your router if it happens to be fairly new. Otherwise it wouldn't hurt to upgrade your wireless router as brianiscool