[kat]

I don't know that the detergent is necessary. For years we've used a mix of salt & vinegar to keep the weeds at bay in the bricks that surround my front garden.

Just be careful that you don't let it sit if it's in a really sunny place. I have a few bricks that were bleached by the vinegar drying in the sun so, if that's a concern, try to use this stuff at night or when the area isn't hit by direct sunlight.