The quick answer is no; pressure washing will not kill the weeds growing in your driveway or patio. A pressure washer will certainly take the heads of the weeds off and most of the body, however, it’s not possible to reach the roots which is how the weed grows. The chemicals used during a clean will certainly damage the weeds roots often killing them and certainly prolongs the regrowth. The best answer for weeds is to apply a weedkiller two weeks before the ground is planned to be cleaned, this will allow time for the weedkiller to kill the weeds down to their roots. Once the surface has been cleaned keep a strict routine maintenance dose of weed killer once you see the weeds have started to regrow. Unfortunately, there is no true answer to prevent weed regrowth, instead they can be managed to keep them under control.