I'm on a small lot (120' x 120') in northern BC. We get our fair share of rain and a lot of spring melt. In the last five years we've had very minor flooding in our basement (like a few gallons total) during very heavy rainstorms or during spring melt.
Our lawn around 1/2 the house is grass and around the other 1/2 is mostly moss with grass blades growing in it. We'd like to improve drainage in the yard to get a healthier lawn and of course prevent all flooding in the basement as we hope to continue finishing it soon.
Ground level around the house is about 2' higher than street level, and about 4' higher than ground level at the back lane of our house, although our lawn is very uneven and in parts slopes gently toward the house. Finally we are about 200' from a steep hill that starts at our ground level and descends about 60' below that.
So, we are wanting to build a french drain and run out a drain out to the back lane (perhaps one in the front too). I am totally new to doing this type of work and we are going to do everything ourselves (or else we won't do it at all). I'm in search of general advice as well as a few specific questions.
1) How deep should the french drain go, does it have to be right at the base of the foundation, or can it be higher?
2) What minimum slope do we need to use along the drain trenches to maintain good drainage?