Not quite lead, Balix, lesser materials have a significant effect.
Every wall or floor reduces the signal strength, especially if the signal has to pass through at an angle, in which case the wall or floor appears thicker to the signal.
The blurb that came with my gear quotes 100m range in ideal conditions, which is outdoor line of sight. Indoors, every wall and floor reduces that and further reduces with the density of material.
Brick, stone, marble etc will reduce signal more than plasterboard. Plasterboard walls with rolled steel frames (becoming common here - beats the termites) are notably influential.
I tested my gear - the uninterrupted line of sight test got close to 100m. Then I put my wireless router in its cubby under my desk. Signal had to pass through desk partitions and drawers, plasterboard internal wall, timber frame then brick cladding. Range is about 50m.
Most times you will get a workable wireless network with basic equipment in a private house - the signal may not be at its strongest, but it will work ok.
Ancient stone castles, computers in dungeons etc may require special consideration, such as high gain antennas, etc.
AA