Get a Ubiquiti NanoStation Loco M2 and install it on the outside of the shop.  Set it up as a "Station" with a static IP on the same network as your router and disable WDS.  Connect it to your house wifi.  On the inside of the shop install a Ubiquiti AirGateway and set it up as a bridge (not Router or SOHO Router).  Give it the same SSID and encryption as your home network.  With this setup you'll be able to move between house and shop and not worry about managing multiple wireless networks.  Should be able to do it for about $100 in hardware.