Old San Francisco Housing A Bane To Wi-Fi
It's something that San Francisco resident Galen Pewtherer discovered. His old Edwardian house and wi-fi just didn't get along. The reason: before drywall became a popular in the 1950s, walls were made out of plaster applied to lath. In Victorian and Edwardian-era homes, lath was often was made of wood stapled to chicken wire. Unfortunately, this creates an almost perfect Faraday Cage, doing a great job of blocking wireless signals.

It does point out that Google was probably best served when it dropped its plans for free municipal wi-fi in San Francisco. One can only imagine the problems the company would have had getting wi-fi to work in The City.
In terms of fixes, one can always knock out the walls and put up drywall, but there's an obvious alternative: running Ethernet cable through the walls. Truth be told, nothing beats wired Ethernet cabling for speed, security, and less error loss. However, in the case of Pewtherer, the walls also blocked out cellular signals as well. He's since moved.