My house is a wireless nightmare.
Some of my walls/ceilings are plaster applied on top of drywall with steel lathing in the corners (working on replacing that over the years).
Steel door frames (now I know the origin of "stand in a doorway during an earthquake").
Hardwood flooring that was top nailed in a 1x6 inch grid pattern.
Foil backed insulation.
Wire run everywhere in the walls (partly my doing).
Every room in my house is almost a faraday cage. About the only thing more wireless signal resistant is the inner ring of the pentagon. Until the last couple of years (after some remodeling) I couldn't even get cell phone signal in parts of my house, and I live in the city.