It depends ...
WiFi like all radio waves have trouble going through certain materials, like glass, metal and stone. So in a way this problem is fighting physics but there are options.
Increasing the power is may be an option but need to remember there are two sides to the equation, that's the power of your router and the power of your devices. And it's your devices that are the constraint.
However, the wall can actually work in your favour.
Normally your existing router has an access point built in, which limmits what you can do but if you break away to a multi access point solution you can have different access points on either side of your wall, which will actually help clean up the interference from each Access Point and allow you to roam between them.