I am trying to set up a wireless network between my home computers to play lan games. I have a DLINK DI-824VUP+ which has a small inbuilt antenna. I am trying to network with a computer downstairs but the floor is 8inch thick concrete and I cant get a signal. The guys at Computers Online are suggesting I use two directional antennas but before I buy them I want to know if they will actually work. Can anyone tell me from experience if this is going to solve my problem?

I cannot guarantee 100% that it will work, but that is the most obvious solution.

This is all dependent on if there is rebar in the floor, or if it's solid concrete. This will also depend what's driving the signal (how powerful).

The best I can say is... maybe.