From THE STRAIGHT EDGE, a newsletter by engineer Greg Sethness
TODAY’S SUBJECT: “Grading” and “Watering”
Grading is a term that means to re-shape the surface of the ground. Around buildings it is usually important that the surface water drains away from the foundations, both for flooding and soil
stability (movement) reasons. A good minimum ground slope is 3” of uniform drop in the first 5 linear feet away from the buildings, and then a 2% slope (1” drop every 4 linear feet) throughout the yard to the street or alley. Slopes on hard surfaces like driveways, patios and sidewalks can be a little less, like 1” of drop every 6 lienar feet. Use gutters only where necessary to get the roof water away from the house as they have maintenance issues. The gutter downspouts and air conditioning condensate drain lines emptying in dirt or grassy areas need to be at least 4’ from the house and outside of any planter beds. Don’t use underground drain pipes unless there is no other solution as they can clog and leak undetected.
Soaker hoses are normally used with slab foundations since slabs are relatively shallow and affected more by surface water than deeper, pier foundations. The hoses are placed directly against the lower edges of the slab, especially during dry weather, to try and swell those soils and lift those sides of the foundation. [The soils under the “high side” of the slab have already swelled more and don’t need extra water.] Don’t let the ground get muddy by the soaker hoses. Monitor the inside floor levels every week or so when you are watering the foundation to see when to stop. If you are
watering slowly, you can sometimes let the soaker hoses run for weeks. Unfortuanetly soaker hoses don’t always lift the adjacent foundation.
Remember: The higher sides of a foundation is where you especially need to have good surface water drainage away from the home.
The information provided in this newsletter is general in nature to enlighten the reader on some physical phenomena that can occur. Individual situations must be investigated to determine what their particular cause and effects are. Please feel free to pass this on to your co-workers. To sign up for or cancel the newsletter please send an email to firstname.lastname@example.org or call me at 822-4160.