Posted: 07/05/2016 at 09:50
When you say 'vents', do you mean the sink contents empty onto the flower bed and not down a drain?
In normal cases, where the soil is below the damp proof course (which should be around 2 bricks below), then there shouldn't be an issue with rising damp, an the damp proof membrane (DPM) should prevent moister rising and also when rain hits the ground, the splash back up is generally believed to be no more than two bricks.
If you're worried about moister entering the bricks at ground/foundation level, then you could put in what is generally called a French drain, which is essentially a trench dug up against the foundation wall anywhere between 8 inches to two feet below ground level and at least one foot out from the wall (wider the better). At the bottom of the trench your lay washed gravel or small rock, then put in a perforated pipe that redirects the water away from the house, and then cover with more gravel or small rocks. Wider French drains are better because they tend to silt up less. If you also wrap your permeable pipe in permeable landscape cloth, then that will prevent silting up further. You need to have the pipe drain sloping away from the house to the garden and into a land drain or soakaway in the garden that disperses the water into the ground. You shouldn't tap the pipe into the house drainage. Water board would get upset with that. Also, consider rodding points so you can clear the pipe of silt etc, that will build up over the years. Sounds a lot of hard work, but if done properly is a good relatively cheap solution. However, if done incorrectly you could end up with a nice mini moat around your house.